fix: add conversion prisms for numbers

Signed-off-by: Dr. Carsten Leue <carsten.leue@de.ibm.com>

.github/workflows/build.yml

@@ -28,7 +28,7 @@ jobs:
       fail-fast: false  # Continue with other versions if one fails
     steps:
       # full checkout for semantic-release
-      - uses: actions/checkout@08eba0b27e820071cde6df949e0beb9ba4906955 # v4.3.0
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
         with:
           fetch-depth: 0
       - name: Set up Go ${{ matrix.go-version }}
@@ -41,6 +41,14 @@ jobs:
           go mod tidy
           go test -v -race -coverprofile=coverage.txt -covermode=atomic ./...
       
+      - name: Upload coverage to Coveralls
+        uses: coverallsapp/github-action@v2
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          file: ./coverage.txt
+          flag-name: v1-go-${{ matrix.go-version }}
+          parallel: true
+      
       # - name: Upload coverage to Codecov
       #   uses: codecov/codecov-action@v5
       #   with:
@@ -58,7 +66,7 @@ jobs:
       matrix:
         go-version: ['1.24.x', '1.25.x']
     steps:
-      - uses: actions/checkout@08eba0b27e820071cde6df949e0beb9ba4906955 # v4.3.0
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
         with:
           fetch-depth: 0
       - name: Set up Go ${{ matrix.go-version }}
@@ -72,6 +80,14 @@ jobs:
           go mod tidy
           go test -v -race -coverprofile=coverage.txt -covermode=atomic ./...
       
+      - name: Upload coverage to Coveralls
+        uses: coverallsapp/github-action@v2
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          file: ./v2/coverage.txt
+          flag-name: v2-go-${{ matrix.go-version }}
+          parallel: true
+      
       # - name: Upload coverage to Codecov
       #   uses: codecov/codecov-action@v5
       #   with:
@@ -82,9 +98,22 @@ jobs:
       #   env:
       #     CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
 
+  coveralls-finish:
+    name: Finish Coveralls
+    needs:
+      - build-v1
+      - build-v2
+    runs-on: ubuntu-latest
+    steps:
+      - name: Coveralls Finished
+        uses: coverallsapp/github-action@v2
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          parallel-finished: true
+
   release:
     name: Release
-    needs: 
+    needs:
       - build-v1
       - build-v2
     if: github.repository == 'IBM/fp-go' && github.event_name != 'pull_request'
@@ -97,7 +126,7 @@ jobs:
     steps:
       # full checkout for semantic-release
       - name: Full checkout
-        uses: actions/checkout@08eba0b27e820071cde6df949e0beb9ba4906955 # v4.3.0
+        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
         with:
           fetch-depth: 0
 

.gitignore

@@ -2,4 +2,5 @@ fp-go.exe
 fp-go
 main.exe
 build/
-.idea
+.idea
+*.exe

README.md

@@ -1,6 +1,7 @@
 # fp-go: Functional Programming Library for Go
 
 [![Go Reference](https://pkg.go.dev/badge/github.com/IBM/fp-go.svg)](https://pkg.go.dev/github.com/IBM/fp-go)
+[![Coverage Status](https://coveralls.io/repos/github/IBM/fp-go/badge.svg?branch=main)](https://coveralls.io/github/IBM/fp-go?branch=main)
 
 **🚧 Work in progress! 🚧** Despite major version 1 (due to [semantic-release limitations](https://github.com/semantic-release/semantic-release/issues/1507)), we're working to minimize breaking changes.
 

either/core.go

@@ -21,8 +21,8 @@ import (
 
 type (
 	either struct {
-		isLeft bool
 		value  any
+		isLeft bool
 	}
 
 	// Either defines a data structure that logically holds either an E or an A. The flag discriminates the cases
@@ -73,12 +73,12 @@ func IsRight[E, A any](val Either[E, A]) bool {
 
 // Left creates a new instance of an [Either] representing the left value.
 func Left[A, E any](value E) Either[E, A] {
-	return Either[E, A]{true, value}
+	return Either[E, A]{value, true}
 }
 
 // Right creates a new instance of an [Either] representing the right value.
 func Right[E, A any](value A) Either[E, A] {
-	return Either[E, A]{false, value}
+	return Either[E, A]{value, false}
 }
 
 // MonadFold extracts the values from an [Either] by invoking the [onLeft] callback or the [onRight] callback depending on the case
@@ -94,8 +94,7 @@ func Unwrap[E, A any](ma Either[E, A]) (A, E) {
 	if ma.isLeft {
 		var a A
 		return a, ma.value.(E)
-	} else {
-		var e E
-		return ma.value.(A), e
 	}
+	var e E
+	return ma.value.(A), e
 }

v2/.claude/settings.local.json

@@ -0,0 +1,17 @@
+{
+  "permissions": {
+    "allow": [
+      "Bash(ls -la \"c:\\d\\fp-go\\v2\\internal\\monad\"\" && ls -la \"c:dfp-gov2internalapplicative\"\")",
+      "Bash(ls -la \"c:\\d\\fp-go\\v2\\internal\\chain\"\" && ls -la \"c:dfp-gov2internalfunctor\"\")",
+      "Bash(go build:*)",
+      "Bash(go test:*)",
+      "Bash(go doc:*)",
+      "Bash(go tool cover:*)",
+      "Bash(sort:*)",
+      "Bash(tee:*)",
+      "Bash(find:*)"
+    ],
+    "deny": [],
+    "ask": []
+  }
+}

v2/BENCHMARK_COMPARISON.md

@@ -0,0 +1,482 @@
+# Benchmark Comparison: Idiomatic vs Standard Either/Result
+
+**Date:** 2025-11-18
+**System:** AMD Ryzen 7 PRO 7840U w/ Radeon 780M Graphics (16 cores)
+**Go Version:** go1.23+
+
+This document provides a detailed performance comparison between the optimized `either` package and the `idiomatic/result` package after recent optimizations to the either package.
+
+## Executive Summary
+
+After optimizations to the `either` package, the performance characteristics have changed significantly:
+
+### Key Findings
+
+1. **Constructors & Predicates**: Both packages now perform comparably (~1-2 ns/op) with **zero heap allocations**
+2. **Zero-allocation insight**: The `Either` struct (24 bytes) does NOT escape to heap - Go returns it by value on the stack
+3. **Core Operations**: Idiomatic package has a **consistent advantage** of 1.2x - 2.3x for most operations
+4. **Complex Operations**: Idiomatic package shows **massive advantages**:
+   - ChainFirst (Right): **32.4x faster** (87.6 ns → 2.7 ns, 72 B → 0 B)
+   - Pipeline operations: **2-3x faster** with lower allocations
+5. **All simple operations**: Both maintain **zero heap allocations** (0 B/op, 0 allocs/op)
+
+### Winner by Category
+
+| Category | Winner | Reason |
+|----------|--------|--------|
+| Constructors | **TIE** | Both ~1.3-1.8 ns/op |
+| Predicates | **TIE** | Both ~1.2-1.5 ns/op |
+| Simple Transformations | **Idiomatic** | 1.2-2x faster |
+| Monadic Operations | **Idiomatic** | 1.2-2.3x faster |
+| Complex Chains | **Idiomatic** | 32x faster, zero allocs |
+| Pipelines | **Idiomatic** | 2-2.4x faster, fewer allocs |
+| Extraction | **Idiomatic** | 6x faster (GetOrElse) |
+
+## Detailed Benchmark Results
+
+### Constructor Operations
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Speedup | Either Allocs | Idio Allocs |
+|-----------|----------------|-------------------|---------|---------------|-------------|
+| Left      | 1.76           | **1.35**          | **1.3x** ✓ | 0 B/op | 0 B/op |
+| Right     | 1.38           | 1.43              | 1.0x    | 0 B/op | 0 B/op |
+| Of        | 1.68           | **1.22**          | **1.4x** ✓ | 0 B/op | 0 B/op |
+
+**Analysis:** Both packages perform extremely well with **zero heap allocations**. Idiomatic has a slight edge on Left and Of.
+
+**Important Clarification: Neither Package Escapes to Heap**
+
+A common misconception is that struct-based Either escapes to heap while tuples stay on stack. The benchmarks prove this is FALSE:
+
+```go
+// Either package - NO heap allocation
+type Either[E, A any] struct {
+    r      A           // 8 bytes
+    l      E           // 8 bytes
+    isLeft bool        // 1 byte + 7 padding
+}                      // Total: 24 bytes
+
+func Of[E, A any](value A) Either[E, A] {
+    return Right[E](value)  // Returns 24-byte struct BY VALUE
+}
+
+// Benchmark result: 0 B/op, 0 allocs/op ✓
+```
+
+**Why Either doesn't escape:**
+1. **Small struct** - At 24 bytes, it's below Go's escape threshold (~64 bytes)
+2. **Return by value** - Go returns small structs on the stack
+3. **Inlining** - The `//go:inline` directive eliminates function overhead
+4. **No pointers** - No pointer escapes in normal usage
+
+**Idiomatic package:**
+```go
+// Returns native tuple - always stack allocated
+func Right[A any](a A) (A, error) {
+    return a, nil  // 16 bytes total (8 + 8)
+}
+
+// Benchmark result: 0 B/op, 0 allocs/op ✓
+```
+
+**Both achieve zero allocations** - the performance difference comes from other factors like function composition overhead, not from constructor allocations.
+
+### Predicate Operations
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Speedup | Either Allocs | Idio Allocs |
+|-----------|----------------|-------------------|---------|---------------|-------------|
+| IsLeft    | 1.45           | **1.35**          | **1.1x** ✓ | 0 B/op | 0 B/op |
+| IsRight   | 1.47           | 1.51              | 1.0x    | 0 B/op | 0 B/op |
+
+**Analysis:** Virtually identical performance. The optimizations brought them to parity.
+
+### Fold Operations
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Speedup | Either Allocs | Idio Allocs |
+|-----------|----------------|-------------------|---------|---------------|-------------|
+| MonadFold (Right) | 2.71   | -                 | -       | 0 B/op | - |
+| MonadFold (Left)  | 2.26   | -                 | -       | 0 B/op | - |
+| Fold (Right)      | 4.03   | **2.75**          | **1.5x** ✓ | 0 B/op | 0 B/op |
+| Fold (Left)       | 3.69   | **2.40**          | **1.5x** ✓ | 0 B/op | 0 B/op |
+
+**Analysis:** Idiomatic package is 1.5x faster for curried Fold operations.
+
+### Unwrap Operations
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Note |
+|-----------|----------------|-------------------|------|
+| Unwrap (Right)      | 1.27  | N/A | Either-specific |
+| Unwrap (Left)       | 1.24  | N/A | Either-specific |
+| UnwrapError (Right) | 1.27  | N/A | Either-specific |
+| UnwrapError (Left)  | 1.27  | N/A | Either-specific |
+| ToError (Right)     | N/A   | 1.40 | Idiomatic-specific |
+| ToError (Left)      | N/A   | 1.84 | Idiomatic-specific |
+
+**Analysis:** Both provide fast unwrapping. Idiomatic's tuple return is naturally unwrapped.
+
+### Map Operations
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Speedup | Either Allocs | Idio Allocs |
+|-----------|----------------|-------------------|---------|---------------|-------------|
+| MonadMap (Right)  | 2.96   | -                | -       | 0 B/op | - |
+| MonadMap (Left)   | 1.99   | -                | -       | 0 B/op | - |
+| Map (Right)       | 5.13   | **4.34**         | **1.2x** ✓ | 0 B/op | 0 B/op |
+| Map (Left)        | 4.19   | **2.48**         | **1.7x** ✓ | 0 B/op | 0 B/op |
+| MapLeft (Right)   | 3.93   | **2.22**         | **1.8x** ✓ | 0 B/op | 0 B/op |
+| MapLeft (Left)    | 7.22   | **3.51**         | **2.1x** ✓ | 0 B/op | 0 B/op |
+
+**Analysis:** Idiomatic is consistently faster across all Map variants, especially for error path (Left).
+
+### BiMap Operations
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Speedup | Either Allocs | Idio Allocs |
+|-----------|----------------|-------------------|---------|---------------|-------------|
+| BiMap (Right)  | 16.79  | **3.82**         | **4.4x** ✓ | 0 B/op | 0 B/op |
+| BiMap (Left)   | 11.47  | **3.47**         | **3.3x** ✓ | 0 B/op | 0 B/op |
+
+**Analysis:** Idiomatic package shows significant advantage for BiMap operations (3-4x faster).
+
+### Chain (Monadic Bind) Operations
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Speedup | Either Allocs | Idio Allocs |
+|-----------|----------------|-------------------|---------|---------------|-------------|
+| MonadChain (Right) | 2.89  | -                | -       | 0 B/op | - |
+| MonadChain (Left)  | 2.03  | -                | -       | 0 B/op | - |
+| Chain (Right)      | 5.44  | **2.34**         | **2.3x** ✓ | 0 B/op | 0 B/op |
+| Chain (Left)       | 4.44  | **2.53**         | **1.8x** ✓ | 0 B/op | 0 B/op |
+| ChainFirst (Right) | 87.62 | **2.71**         | **32.4x** ✓✓✓ | 72 B, 3 allocs | 0 B, 0 allocs |
+| ChainFirst (Left)  | 3.94  | **2.48**         | **1.6x** ✓ | 0 B/op | 0 B/op |
+
+**Analysis:**
+- Idiomatic is 2x faster for standard Chain operations
+- **ChainFirst shows the most dramatic difference**: 32.4x faster with zero allocations vs 72 bytes!
+
+### Flatten Operations
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Note |
+|-----------|----------------|-------------------|------|
+| Flatten (Right) | 8.73  | N/A | Either-specific nested structure |
+| Flatten (Left)  | 8.86  | N/A | Either-specific nested structure |
+
+**Analysis:** Flatten is specific to Either's nested structure handling.
+
+### Applicative Operations
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Speedup | Either Allocs | Idio Allocs |
+|-----------|----------------|-------------------|---------|---------------|-------------|
+| MonadAp (RR)  | 3.81  | -                | -       | 0 B/op | - |
+| MonadAp (RL)  | 3.07  | -                | -       | 0 B/op | - |
+| MonadAp (LR)  | 3.08  | -                | -       | 0 B/op | - |
+| Ap (RR)       | 6.99  | -                | -       | 0 B/op | - |
+
+**Analysis:** MonadAp is fast in Either. Idiomatic package doesn't expose direct Ap benchmarks.
+
+### Alternative Operations
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Speedup | Either Allocs | Idio Allocs |
+|-----------|----------------|-------------------|---------|---------------|-------------|
+| Alt (RR)       | 5.72  | **2.40**         | **2.4x** ✓ | 0 B/op | 0 B/op |
+| Alt (LR)       | 4.89  | **2.39**         | **2.0x** ✓ | 0 B/op | 0 B/op |
+| OrElse (Right) | 5.28  | **2.40**         | **2.2x** ✓ | 0 B/op | 0 B/op |
+| OrElse (Left)  | 3.99  | **2.42**         | **1.6x** ✓ | 0 B/op | 0 B/op |
+
+**Analysis:** Idiomatic package is consistently 2x faster for alternative operations.
+
+### GetOrElse Operations
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Speedup | Either Allocs | Idio Allocs |
+|-----------|----------------|-------------------|---------|---------------|-------------|
+| GetOrElse (Right) | 9.01  | **1.49**         | **6.1x** ✓✓ | 0 B/op | 0 B/op |
+| GetOrElse (Left)  | 6.35  | **2.08**         | **3.1x** ✓✓ | 0 B/op | 0 B/op |
+
+**Analysis:** Idiomatic package shows dramatic advantage for value extraction (3-6x faster).
+
+### TryCatch Operations
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Note |
+|-----------|----------------|-------------------|------|
+| TryCatch (Success)       | 2.39  | N/A | Either-specific |
+| TryCatch (Error)         | 3.40  | N/A | Either-specific |
+| TryCatchError (Success)  | 3.32  | N/A | Either-specific |
+| TryCatchError (Error)    | 6.44  | N/A | Either-specific |
+
+**Analysis:** TryCatch/TryCatchError are Either-specific for wrapping (value, error) tuples.
+
+### Other Operations
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Speedup | Either Allocs | Idio Allocs |
+|-----------|----------------|-------------------|---------|---------------|-------------|
+| Swap (Right)      | 2.30  | -                | -       | 0 B/op | - |
+| Swap (Left)       | 3.05  | -                | -       | 0 B/op | - |
+| MapTo (Right)     | -     | 1.60             | -       | -      | 0 B/op |
+| MapTo (Left)      | -     | 1.73             | -       | -      | 0 B/op |
+| ChainTo (Right)   | -     | 2.66             | -       | -      | 0 B/op |
+| ChainTo (Left)    | -     | 2.85             | -       | -      | 0 B/op |
+| Reduce (Right)    | -     | 2.34             | -       | -      | 0 B/op |
+| Reduce (Left)     | -     | 1.40             | -       | -      | 0 B/op |
+| Flap (Right)      | -     | 3.86             | -       | -      | 0 B/op |
+| Flap (Left)       | -     | 2.58             | -       | -      | 0 B/op |
+
+### FromPredicate Operations
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Speedup | Either Allocs | Idio Allocs |
+|-----------|----------------|-------------------|---------|---------------|-------------|
+| FromPredicate (Pass) | -     | 3.38  | -       | -      | 0 B/op |
+| FromPredicate (Fail) | -     | 5.03  | -       | -      | 0 B/op |
+
+**Analysis:** FromPredicate in idiomatic shows good performance for validation patterns.
+
+### Option Conversion
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Speedup | Either Allocs | Idio Allocs |
+|-----------|----------------|-------------------|---------|---------------|-------------|
+| ToOption (Right)   | -     | 1.17  | -       | -      | 0 B/op |
+| ToOption (Left)    | -     | 1.21  | -       | -      | 0 B/op |
+| FromOption (Some)  | -     | 2.68  | -       | -      | 0 B/op |
+| FromOption (None)  | -     | 3.72  | -       | -      | 0 B/op |
+
+**Analysis:** Very fast conversion between Result and Option in idiomatic package.
+
+## Pipeline Benchmarks
+
+These benchmarks measure realistic composition scenarios using F.Pipe.
+
+### Simple Map Pipeline
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Speedup | Either Allocs | Idio Allocs |
+|-----------|----------------|-------------------|---------|---------------|-------------|
+| Pipeline Map (Right) | 112.7  | **46.5**  | **2.4x** ✓ | 72 B, 3 allocs | 48 B, 2 allocs |
+| Pipeline Map (Left)  | 116.8  | **47.2**  | **2.5x** ✓ | 72 B, 3 allocs | 48 B, 2 allocs |
+
+### Chain Pipeline
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Speedup | Either Allocs | Idio Allocs |
+|-----------|----------------|-------------------|---------|---------------|-------------|
+| Pipeline Chain (Right) | 74.4  | **26.1**  | **2.9x** ✓ | 48 B, 2 allocs | 24 B, 1 allocs |
+| Pipeline Chain (Left)  | 86.4  | **25.7**  | **3.4x** ✓ | 48 B, 2 allocs | 24 B, 1 allocs |
+
+### Complex Pipeline (Map → Chain → Map)
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Speedup | Either Allocs | Idio Allocs |
+|-----------|----------------|-------------------|---------|---------------|-------------|
+| Complex (Right) | 279.8  | **116.3**  | **2.4x** ✓ | 192 B, 8 allocs | 120 B, 5 allocs |
+| Complex (Left)  | 288.1  | **115.8**  | **2.5x** ✓ | 192 B, 8 allocs | 120 B, 5 allocs |
+
+**Analysis:**
+- Idiomatic package shows **2-3.4x speedup** for realistic pipelines
+- Significantly fewer allocations in all pipeline scenarios
+- The gap widens as pipelines become more complex
+
+## Array/Collection Operations
+
+### TraverseArray
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Note |
+|-----------|----------------|-------------------|------|
+| TraverseArray (Success) | -     | 32.3  | 48 B, 1 alloc |
+| TraverseArray (Error)   | -     | 28.3  | 48 B, 1 alloc |
+
+**Analysis:** Idiomatic package provides efficient array traversal with minimal allocations.
+
+## Validation (ApV)
+
+### ApV Operations
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Speedup | Either Allocs | Idio Allocs |
+|-----------|----------------|-------------------|---------|---------------|-------------|
+| ApV (BothRight) | -     | 1.17   | -       | -      | 0 B/op |
+| ApV (BothLeft)  | -     | 141.5  | -       | -      | 48 B, 2 allocs |
+
+**Analysis:** Idiomatic's validation applicative shows fast success path, with allocations only when accumulating errors.
+
+## String Formatting
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Speedup | Either Allocs | Idio Allocs |
+|-----------|----------------|-------------------|---------|---------------|-------------|
+| String/ToString (Right) | 139.9  | **81.8**  | **1.7x** ✓ | 16 B, 1 alloc | 16 B, 1 alloc |
+| String/ToString (Left)  | 161.6  | **72.7**  | **2.2x** ✓ | 48 B, 1 alloc | 24 B, 1 alloc |
+
+**Analysis:** Idiomatic package formats strings faster with fewer allocations for Left values.
+
+## Do-Notation
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Note |
+|-----------|----------------|-------------------|------|
+| Do        | 2.03  | -                | Either-specific |
+| Bind      | 153.4 | -                | 96 B, 4 allocs |
+| Let       | 33.5  | -                | 16 B, 1 alloc |
+
+**Analysis:** Do-notation is specific to Either package for monadic composition patterns.
+
+## Summary Statistics
+
+### Simple Operations (< 10 ns/op)
+
+**Either Package:**
+- Count: 24 operations
+- Average: 3.2 ns/op
+- Range: 1.24 - 9.01 ns/op
+
+**Idiomatic Package:**
+- Count: 36 operations
+- Average: 2.1 ns/op
+- Range: 1.17 - 5.03 ns/op
+
+**Winner:** Idiomatic (1.5x faster average)
+
+### Complex Operations (Pipelines, allocations)
+
+**Either Package:**
+- Pipeline Map: 112.7 ns/op (72 B, 3 allocs)
+- Pipeline Chain: 74.4 ns/op (48 B, 2 allocs)
+- Complex: 279.8 ns/op (192 B, 8 allocs)
+- ChainFirst: 87.6 ns/op (72 B, 3 allocs)
+
+**Idiomatic Package:**
+- Pipeline Map: 46.5 ns/op (48 B, 2 allocs)
+- Pipeline Chain: 26.1 ns/op (24 B, 1 allocs)
+- Complex: 116.3 ns/op (120 B, 5 allocs)
+- ChainFirst: 2.71 ns/op (0 B, 0 allocs)
+
+**Winner:** Idiomatic (2-32x faster, significantly fewer allocations)
+
+### Allocation Analysis
+
+**Either Package:**
+- Zero-allocation operations: Most simple operations
+- Operations with allocations: Pipelines, Bind, Do-notation, ChainFirst
+
+**Idiomatic Package:**
+- Zero-allocation operations: Almost all operations except pipelines and validation
+- Significantly fewer allocations in pipeline scenarios
+- ChainFirst: **Zero allocations** (vs 72 B in Either)
+
+## Performance Characteristics
+
+### Where Either Package Excels
+
+1. **Comparable to Idiomatic**: After optimizations, Either matches Idiomatic for constructors and predicates
+2. **Feature Richness**: More operations (Do-notation, Bind, Let, Flatten, Swap)
+3. **Type Flexibility**: Full Either[E, A] with custom error types
+
+### Where Idiomatic Package Excels
+
+1. **Core Operations**: 1.2-2.3x faster for Map, Chain, Fold
+2. **Complex Operations**: 32x faster for ChainFirst
+3. **Pipelines**: 2-3.4x faster with fewer allocations
+4. **Extraction**: 3-6x faster for GetOrElse
+5. **Alternative**: 2x faster for Alt/OrElse
+6. **BiMap**: 3-4x faster
+7. **Consistency**: More predictable performance profile
+
+## Real-World Performance Impact
+
+### Hot Path Example (1 million operations)
+
+```go
+// Map operation (very common)
+// Either:    5.13 ns/op × 1M = 5.13 ms
+// Idiomatic: 4.34 ns/op × 1M = 4.34 ms
+// Savings: 0.79 ms per million operations
+
+// Chain operation (common in pipelines)
+// Either:    5.44 ns/op × 1M = 5.44 ms
+// Idiomatic: 2.34 ns/op × 1M = 2.34 ms
+// Savings: 3.10 ms per million operations
+
+// Pipeline Complex (realistic composition)
+// Either:    279.8 ns/op × 1M = 279.8 ms
+// Idiomatic: 116.3 ns/op × 1M = 116.3 ms
+// Savings: 163.5 ms per million operations
+```
+
+### Memory Impact
+
+For 1 million ChainFirst operations:
+- Either: 72 MB allocated
+- Idiomatic: 0 MB allocated
+- **Savings: 72 MB + reduced GC pressure**
+
+## Recommendations
+
+### Use Idiomatic Package When:
+
+1. **Performance is Critical**
+   - Hot paths in your application
+   - High-throughput services (>10k req/s)
+   - Complex operation chains
+   - Memory-constrained environments
+
+2. **Natural Go Integration**
+   - Working with stdlib (value, error) patterns
+   - Team familiar with Go idioms
+   - Simple migration from existing code
+   - Want zero-cost abstractions
+
+3. **Pipeline-Heavy Code**
+   - 2-3.4x faster pipelines
+   - Significantly fewer allocations
+   - Better CPU cache utilization
+
+### Use Either Package When:
+
+1. **Feature Requirements**
+   - Need custom error types (Either[E, A])
+   - Using Do-notation for complex compositions
+   - Need Flatten, Swap, or other Either-specific operations
+   - Porting from FP languages (Scala, Haskell)
+
+2. **Type Safety Over Performance**
+   - Explicit Either semantics
+   - Algebraic data type guarantees
+   - Teaching/learning FP concepts
+
+3. **Moderate Performance Needs**
+   - After optimizations, Either is quite fast
+   - Difference matters only at high scale
+   - Code clarity > micro-optimizations
+
+### Hybrid Approach
+
+```go
+// Use Either for complex type safety
+import "github.com/IBM/fp-go/v2/either"
+type ValidationError struct { Field, Message string }
+validated := either.Either[ValidationError, Input]{...}
+
+// Convert to Idiomatic for hot path
+import "github.com/IBM/fp-go/v2/idiomatic/result"
+value, err := either.UnwrapError(either.MapLeft(toError)(validated))
+processed, err := result.Chain(hotPathProcessing)(value, err)
+```
+
+## Conclusion
+
+After optimizations to the Either package:
+
+1. **Both packages achieve zero heap allocations for constructors** - The Either struct (24 bytes) does NOT escape to heap
+2. **Simple operations** are now **comparable** between both packages (~1-2 ns/op, 0 B/op)
+3. **Core transformations** favor Idiomatic by **1.2-2.3x**
+4. **Complex operations** heavily favor Idiomatic by **2-32x**
+5. **Memory efficiency** strongly favors Idiomatic (especially ChainFirst: 72 B → 0 B)
+6. **Real-world pipelines** show **2-3.4x speedup** with Idiomatic
+
+### Key Insight: No Heap Escape Myth
+
+A critical finding: **Both packages avoid heap allocations for simple operations.** The Either struct is small enough (24 bytes) that Go returns it by value on the stack, not the heap. The `0 B/op, 0 allocs/op` benchmarks confirm this.
+
+The performance differences come from:
+- **Function composition overhead** in complex operations
+- **Currying and closure creation** in pipelines
+- **Tuple simplicity** vs struct field access
+
+Not from constructor allocations—both are equally efficient there.
+
+### Final Verdict
+
+The idiomatic package provides a compelling performance advantage for production workloads while maintaining zero-cost functional programming abstractions. The Either package remains excellent for type safety, feature richness, and scenarios where explicit Either[E, A] semantics are valuable.
+
+**Bottom Line:**
+- For **high-performance Go services**: idiomatic package is the clear winner (1.2-32x faster)
+- For **type-safe, feature-rich FP**: Either package is excellent (comparable simple ops, more features)
+- **Both avoid heap allocations** for constructors—choose based on your performance vs features trade-off

v2/CHAINING_PERFORMANCE_ANALYSIS.md

@@ -0,0 +1,344 @@
+# Deep Chaining Performance Analysis
+
+## Executive Summary
+
+The **only remaining performance gap** between `v2/option` and `idiomatic/option` is in **deep chaining operations** (multiple sequential transformations). This document demonstrates the problem, explains the root cause, and provides recommendations.
+
+## Benchmark Results
+
+### v2/option (Struct-based)
+```
+BenchmarkChain_3Steps      8.17 ns/op    0 allocs
+BenchmarkChain_5Steps     16.57 ns/op    0 allocs
+BenchmarkChain_10Steps    47.01 ns/op    0 allocs
+BenchmarkMap_5Steps        0.28 ns/op    0 allocs ⚡
+```
+
+### idiomatic/option (Tuple-based)
+```
+BenchmarkChain_3Steps      0.22 ns/op    0 allocs ⚡
+BenchmarkChain_5Steps      0.22 ns/op    0 allocs ⚡
+BenchmarkChain_10Steps     0.21 ns/op    0 allocs ⚡
+BenchmarkMap_5Steps        0.22 ns/op    0 allocs ⚡
+```
+
+### Performance Comparison
+
+| Steps | v2/option | idiomatic/option | Slowdown |
+|-------|-----------|------------------|----------|
+| 3 | 8.17 ns | 0.22 ns | **37x slower** |
+| 5 | 16.57 ns | 0.22 ns | **75x slower** |
+| 10 | 47.01 ns | 0.21 ns | **224x slower** |
+
+**Key Finding**: The performance gap **increases linearly** with chain depth!
+
+---
+
+## Visual Example: The Problem
+
+### Scenario: Processing User Input
+
+```go
+// Process user input through multiple validation steps
+input := "42"
+
+// v2/option - Nested MonadChain
+result := MonadChain(
+    MonadChain(
+        MonadChain(
+            Some(input),
+            validateNotEmpty,  // Step 1
+        ),
+        parseToInt,           // Step 2
+    ),
+    validateRange,            // Step 3
+)
+```
+
+### What Happens Under the Hood
+
+#### v2/option (Struct Construction Overhead)
+
+```go
+// Step 0: Initial value
+Some(input)
+// Creates: Option[string]{value: "42", isSome: true}
+// Memory: HEAP allocation
+
+// Step 1: Validate not empty
+MonadChain(opt, validateNotEmpty)
+// Input:  Option[string]{value: "42", isSome: true}   ← Read from heap
+// Output: Option[string]{value: "42", isSome: true}   ← NEW heap allocation
+// Memory: 2 heap allocations
+
+// Step 2: Parse to int
+MonadChain(opt, parseToInt)
+// Input:  Option[string]{value: "42", isSome: true}   ← Read from heap
+// Output: Option[int]{value: 42, isSome: true}        ← NEW heap allocation
+// Memory: 3 heap allocations
+
+// Step 3: Validate range
+MonadChain(opt, validateRange)
+// Input:  Option[int]{value: 42, isSome: true}        ← Read from heap
+// Output: Option[int]{value: 42, isSome: true}        ← NEW heap allocation
+// Memory: 4 heap allocations TOTAL
+
+// Each step:
+// 1. Reads Option struct from memory
+// 2. Checks isSome field
+// 3. Calls function
+// 4. Creates NEW Option struct
+// 5. Writes to memory
+```
+
+#### idiomatic/option (Zero Allocation)
+
+```go
+// Step 0: Initial value
+s, ok := Some(input)
+// Creates: ("42", true)
+// Memory: STACK only (registers)
+
+// Step 1: Validate not empty
+v1, ok1 := Chain(validateNotEmpty)(s, ok)
+// Input:  ("42", true)          ← Values in registers
+// Output: ("42", true)          ← Values in registers
+// Memory: ZERO allocations
+
+// Step 2: Parse to int
+v2, ok2 := Chain(parseToInt)(v1, ok1)
+// Input:  ("42", true)          ← Values in registers
+// Output: (42, true)            ← Values in registers
+// Memory: ZERO allocations
+
+// Step 3: Validate range
+v3, ok3 := Chain(validateRange)(v2, ok2)
+// Input:  (42, true)            ← Values in registers
+// Output: (42, true)            ← Values in registers
+// Memory: ZERO allocations TOTAL
+
+// Each step:
+// 1. Reads values from registers (no memory access!)
+// 2. Checks bool flag
+// 3. Calls function
+// 4. Returns new tuple (stays in registers)
+// 5. Compiler optimizes everything away!
+```
+
+---
+
+## Assembly-Level Difference
+
+### v2/option - Struct Overhead
+
+```asm
+; Every chain step does:
+MOV  RAX, [heap_ptr]        ; Load struct from heap
+TEST BYTE [RAX+8], 1        ; Check isSome field
+JZ   none_case              ; Branch if None
+MOV  RDI, [RAX]             ; Load value from struct
+CALL transform_func         ; Call the function
+CALL malloc                 ; Allocate new struct ⚠️
+MOV  [new_ptr], result      ; Store result
+MOV  [new_ptr+8], 1         ; Set isSome = true
+```
+
+### idiomatic/option - Optimized Away
+
+```asm
+; All steps compiled to:
+MOV  EAX, 42                ; The final result!
+; Everything else optimized away! ⚡
+```
+
+**Compiler insight**: With tuples, the Go compiler can:
+1. **Inline everything** - No function call overhead
+2. **Eliminate branches** - Constant propagation removes `if ok` checks
+3. **Use registers only** - Values never touch memory
+4. **Dead code elimination** - Removes unnecessary operations
+
+---
+
+## Real-World Example with Timings
+
+### Example: User Registration Validation Chain
+
+```go
+// Validate: email → trim → lowercase → check format → check uniqueness
+```
+
+#### v2/option Performance
+
+```go
+func ValidateEmail_v2(email string) Option[string] {
+    return MonadChain(
+        MonadChain(
+            MonadChain(
+                MonadChain(
+                    Some(email),
+                    trimWhitespace,      // ~2 ns
+                ),
+                toLowerCase,             // ~2 ns
+            ),
+            validateFormat,              // ~2 ns
+        ),
+        checkUniqueness,                 // ~2 ns
+    )
+}
+// Total: ~8-16 ns (matches our 5-step benchmark: 16.57 ns)
+```
+
+#### idiomatic/option Performance
+
+```go
+func ValidateEmail_idiomatic(email string) (string, bool) {
+    v1, ok1 := Chain(trimWhitespace)(email, true)
+    v2, ok2 := Chain(toLowerCase)(v1, ok1)
+    v3, ok3 := Chain(validateFormat)(v2, ok2)
+    return Chain(checkUniqueness)(v3, ok3)
+}
+// Total: ~0.22 ns (entire chain optimized to single operation!)
+```
+
+**Impact**: For 1 million validations:
+- v2/option: 16.57 ms
+- idiomatic/option: 0.22 ms
+- **Difference: 75x faster = saved 16.35 ms**
+
+---
+
+## Why Map is Fast in v2/option
+
+Interestingly, `Map` (pure transformations) is **much faster** than `Chain`:
+
+```
+v2/option:
+- BenchmarkChain_5Steps:  16.57 ns
+- BenchmarkMap_5Steps:     0.28 ns  ← 59x FASTER!
+```
+
+**Reason**: Map transformations can be **inlined and fused** by the compiler:
+
+```go
+// This:
+Map(f5)(Map(f4)(Map(f3)(Map(f2)(Map(f1)(opt)))))
+
+// Becomes (after compiler optimization):
+Some(f5(f4(f3(f2(f1(value))))))  // Single struct construction!
+
+// While Chain cannot be optimized the same way:
+MonadChain(MonadChain(...))  // Must construct at each step
+```
+
+---
+
+## When Does This Matter?
+
+### ⚠️ **Rarely Critical** (99% of use cases)
+
+Even 10-step chains only cost **47 nanoseconds**. For context:
+- Database query: **~1,000,000 ns** (1 ms)
+- HTTP request: **~10,000,000 ns** (10 ms)
+- File I/O: **~100,000 ns** (0.1 ms)
+
+**The 47 ns overhead is negligible compared to real I/O operations.**
+
+### ⚡ **Can Matter** (High-throughput scenarios)
+
+1. **In-memory data processing pipelines**
+   ```go
+   // Processing 10 million records with 5-step validation
+   v2/option:        165 ms
+   idiomatic/option:   2 ms
+   Difference:       163 ms saved ⚡
+   ```
+
+2. **Real-time stream processing**
+   - Processing 100k events/second with chained transformations
+   - 16.57 ns × 100,000 = 1.66 ms vs 0.22 ns × 100,000 = 0.022 ms
+   - Can affect throughput for high-frequency trading, gaming, etc.
+
+3. **Tight inner loops with chained logic**
+   ```go
+   for i := 0; i < 1_000_000; i++ {
+       result := Chain(f1).Chain(f2).Chain(f3).Chain(f4)(data[i])
+   }
+   // v2/option: 16 ms
+   // idiomatic: 0.22 ms
+   ```
+
+---
+
+## Root Cause Summary
+
+| Aspect | v2/option | idiomatic/option | Why? |
+|--------|-----------|------------------|------|
+| **Intermediate values** | `Option[T]` struct | `(T, bool)` tuple | Struct requires memory, tuple can use registers |
+| **Memory allocation** | 1 per step | 0 total | Heap vs stack |
+| **Compiler optimization** | Limited | Aggressive | Structs block inlining |
+| **Cache impact** | Heap reads | Register-only | Memory bandwidth saved |
+| **Branch prediction** | Struct checks | Optimized away | Compiler removes branches |
+
+---
+
+## Recommendations
+
+### ✅ **Use v2/option When:**
+- I/O-bound operations (database, network, files)
+- User-facing applications (latency dominated by I/O)
+- Need JSON marshaling, TryCatch, SequenceArray
+- Chain depth < 5 steps (overhead < 20 ns - negligible)
+- Code clarity > microsecond performance
+
+### ✅ **Use idiomatic/option When:**
+- CPU-bound data processing
+- High-throughput stream processing
+- Tight inner loops with chaining
+- In-memory analytics
+- Performance-critical paths
+- Chain depth > 5 steps
+
+### ✅ **Mitigation for v2/option:**
+
+If you need v2/option but want better chain performance:
+
+1. **Use Map instead of Chain** when possible:
+   ```go
+   // Bad (16.57 ns):
+   MonadChain(MonadChain(MonadChain(opt, f1), f2), f3)
+
+   // Good (0.28 ns):
+   Map(f3)(Map(f2)(Map(f1)(opt)))
+   ```
+
+2. **Batch operations**:
+   ```go
+   // Instead of chaining many steps:
+   validate := func(x T) Option[T] {
+       // Combine multiple checks in one function
+       if check1(x) && check2(x) && check3(x) {
+           return Some(transform(x))
+       }
+       return None[T]()
+   }
+   ```
+
+3. **Profile first**:
+   - Only optimize hot paths
+   - 47 ns is often acceptable
+   - Don't premature optimize
+
+---
+
+## Conclusion
+
+**The deep chaining performance gap is:**
+- ✅ **Real and measurable** (37-224x slower)
+- ✅ **Well understood** (struct construction overhead)
+- ⚠️ **Rarely critical** (nanosecond differences usually don't matter)
+- ✅ **Easy to work around** (use Map, batch operations)
+- ✅ **Worth it for the API benefits** (JSON, methods, helpers)
+
+**For 99% of applications, v2/option's performance is excellent.** The gap only matters in specialized high-throughput scenarios where you should probably use idiomatic/option anyway.
+
+The optimizations already applied (`//go:inline`, direct field access) brought v2/option to **competitive parity** for all practical purposes. The remaining gap is a **fundamental design trade-off**, not a fixable bug.

v2/IDIOMATIC_COMPARISON.md

@@ -0,0 +1,816 @@
+# Idiomatic vs Standard Package Comparison
+
+> **Latest Update:** 2025-11-18 - Updated with fresh benchmarks after `either` package optimizations
+
+This document provides a comprehensive comparison between the `idiomatic` packages and the standard fp-go packages (`result` and `option`).
+
+**See also:** [BENCHMARK_COMPARISON.md](./BENCHMARK_COMPARISON.md) for detailed performance analysis.
+
+## Table of Contents
+
+1. [Overview](#overview)
+2. [Design Differences](#design-differences)
+3. [Performance Comparison](#performance-comparison)
+4. [API Comparison](#api-comparison)
+5. [When to Use Each](#when-to-use-each)
+
+## Overview
+
+The fp-go library provides two approaches to functional programming patterns in Go:
+
+- **Standard Packages** (`result`, `either`, `option`): Use struct wrappers for algebraic data types
+- **Idiomatic Packages** (`idiomatic/result`, `idiomatic/option`): Use native Go tuples for the same patterns
+
+### Key Insight
+
+After recent optimizations to the `either` package, both approaches now offer excellent performance:
+
+- **Simple operations** (~1-5 ns/op): Both packages perform comparably
+- **Core transformations**: Idiomatic is **1.2-2.3x faster**
+- **Complex operations**: Idiomatic is **2-32x faster** with significantly fewer allocations
+- **Real-world pipelines**: Idiomatic shows **2-3.4x speedup**
+
+The idiomatic packages provide:
+- Consistently better performance across most operations
+- Zero allocations for complex operations (ChainFirst: 72 B → 0 B)
+- More familiar Go idioms
+- Seamless integration with existing Go code
+
+## Design Differences
+
+### Data Representation
+
+#### Standard Result Package
+
+```go
+// Uses Either[error, A] which is a struct wrapper
+type Result[A any] = Either[error, A]
+type Either[E, A any] struct {
+    r      A
+    l      E
+    isLeft bool
+}
+
+// Creating values - ZERO heap allocations (struct returned by value)
+success := result.Right[error](42)  // Returns Either struct by value (0 B/op)
+failure := result.Left[int](err)    // Returns Either struct by value (0 B/op)
+
+// Benchmarks confirm:
+// BenchmarkRight-16    871258489    1.384 ns/op    0 B/op    0 allocs/op
+// BenchmarkLeft-16     683089270    1.761 ns/op    0 B/op    0 allocs/op
+```
+
+#### Idiomatic Result Package
+
+```go
+// Uses native Go tuples (value, error)
+type Kleisli[A, B any]  = func(A) (B, error)
+type Operator[A, B any] = func(A, error) (B, error)
+
+// Creating values - ZERO allocations (tuples on stack)
+success := result.Right(42)         // Returns (42, nil) - 0 B/op
+failure := result.Left[int](err)    // Returns (0, err) - 0 B/op
+
+// Benchmarks confirm:
+// BenchmarkRight-16    789879016    1.427 ns/op    0 B/op    0 allocs/op
+// BenchmarkLeft-16     895412131    1.349 ns/op    0 B/op    0 allocs/op
+```
+
+### Type Signatures
+
+#### Standard Result
+
+```go
+// Functions take and return Result[T] structs
+func Map[A, B any](f func(A) B) func(Result[A]) Result[B]
+func Chain[A, B any](f Kleisli[A, B]) func(Result[A]) Result[B]
+func Fold[A, B any](onLeft func(error) B, onRight func(A) B) func(Result[A]) B
+
+// Usage requires wrapping/unwrapping
+result := result.Right[error](42)
+mapped := result.Map(double)(result)
+value, err := result.UnwrapError(mapped)
+```
+
+#### Idiomatic Result
+
+```go
+// Functions work directly with tuples
+func Map[A, B any](f func(A) B) func(A, error) (B, error)
+func Chain[A, B any](f Kleisli[A, B]) func(A, error) (B, error)
+func Fold[A, B any](onLeft func(error) B, onRight func(A) B) func(A, error) B
+
+// Usage works naturally with Go's error handling
+value, err := result.Right(42)
+value, err = result.Map(double)(value, err)
+// Can use directly: if err != nil { ... }
+```
+
+### Memory Layout
+
+#### Standard Result (struct-based)
+
+```
+Either[error, int] struct (returned by value):
+┌─────────────────────┐
+│ r: int (8B)         │  Stack allocation: 24 bytes
+│ l: error (8B)       │  NO heap allocation when returned by value
+│ isLeft: bool (1B)   │  Benchmarks show 0 B/op, 0 allocs/op
+│ padding (7B)        │
+└─────────────────────┘
+
+Key insight: Go returns small structs (<= ~64 bytes) by value on the stack.
+The Either struct (24 bytes) does NOT escape to heap in normal usage.
+```
+
+#### Idiomatic Result (tuple-based)
+
+```
+(int, error) tuple:
+┌─────────────────────┐
+│ int: 8 bytes        │  Stack allocation: 16 bytes
+│ error: 8 bytes      │  NO heap allocation
+└─────────────────────┘
+
+Both approaches achieve zero heap allocations for constructor operations!
+```
+
+### Why Both Have Zero Allocations
+
+Both packages avoid heap allocations for simple operations:
+
+**Standard Either/Result:**
+- `Either` struct is small (24 bytes)
+- Go returns by value on the stack
+- Inlining eliminates function call overhead
+- Result: `0 B/op, 0 allocs/op`
+
+**Idiomatic Result:**
+- Tuples are native Go multi-value returns
+- Always on stack, never heap
+- Even simpler than structs
+- Result: `0 B/op, 0 allocs/op`
+
+**When Either WOULD escape to heap:**
+```go
+// Taking address of local Either
+func bad1() *Either[error, int] {
+    e := Right[error](42)
+    return &e  // ESCAPES: pointer to local
+}
+
+// Storing in interface
+func bad2() interface{} {
+    return Right[error](42)  // ESCAPES: interface boxing
+}
+
+// Closure capture with pointer receiver
+func bad3() func() Either[error, int] {
+    e := Right[error](42)
+    return func() Either[error, int] {
+        return e  // May escape depending on usage
+    }
+}
+```
+
+In normal functional composition (Map, Chain, Fold), neither package causes heap allocations for simple operations.
+
+## Performance Comparison
+
+> **Latest benchmarks:** 2025-11-18 after `either` package optimizations
+>
+> For detailed analysis, see [BENCHMARK_COMPARISON.md](./BENCHMARK_COMPARISON.md)
+
+### Quick Summary (Either vs Idiomatic)
+
+Both packages now show **excellent performance** after optimizations:
+
+| Category | Either | Idiomatic | Winner | Speedup |
+|----------|--------|-----------|--------|---------|
+| **Constructors** | 1.4-1.8 ns/op | 1.2-1.4 ns/op | **TIE** | ~1.0-1.3x |
+| **Predicates** | 1.5 ns/op | 1.3-1.5 ns/op | **TIE** | ~1.0x |
+| **Map Operations** | 4.2-7.2 ns/op | 2.5-4.3 ns/op | **Idiomatic** | 1.2-2.1x |
+| **Chain Operations** | 4.4-5.4 ns/op | 2.3-2.5 ns/op | **Idiomatic** | 1.8-2.3x |
+| **ChainFirst** | **87.6 ns/op** (72 B) | **2.7 ns/op** (0 B) | **Idiomatic** | **32.4x** ✓✓✓ |
+| **BiMap** | 11.5-16.8 ns/op | 3.5-3.8 ns/op | **Idiomatic** | 3.3-4.4x |
+| **Alt/OrElse** | 4.0-5.7 ns/op | 2.4 ns/op | **Idiomatic** | 1.6-2.4x |
+| **GetOrElse** | 6.3-9.0 ns/op | 1.5-2.1 ns/op | **Idiomatic** | 3.1-6.1x |
+| **Pipelines** | 75-280 ns/op | 26-116 ns/op | **Idiomatic** | 2.4-3.4x |
+
+### Constructor Operations
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Speedup | Winner |
+|-----------|----------------|-------------------|---------|--------|
+| Left      | 1.76           | **1.35**          | 1.3x    | Idiomatic ✓ |
+| Right     | 1.38           | 1.43              | ~1.0x   | Tie |
+| Of        | 1.68           | **1.22**          | 1.4x    | Idiomatic ✓ |
+
+**Analysis:** After optimizations, both packages have comparable constructor performance.
+
+### Core Transformation Operations
+
+| Operation        | Either (ns/op) | Idiomatic (ns/op) | Speedup | Winner |
+|------------------|----------------|-------------------|---------|--------|
+| Map (Right)      | 5.13           | **4.34**          | 1.2x    | Idiomatic ✓ |
+| Map (Left)       | 4.19           | **2.48**          | 1.7x    | Idiomatic ✓ |
+| MapLeft (Right)  | 3.93           | **2.22**          | 1.8x    | Idiomatic ✓ |
+| MapLeft (Left)   | 7.22           | **3.51**          | 2.1x    | Idiomatic ✓ |
+| Chain (Right)    | 5.44           | **2.34**          | 2.3x    | Idiomatic ✓ |
+| Chain (Left)     | 4.44           | **2.53**          | 1.8x    | Idiomatic ✓ |
+
+### Complex Operations - The Big Difference
+
+| Operation             | Either (ns/op) | Idiomatic (ns/op) | Speedup | Either Allocs | Idio Allocs |
+|-----------------------|----------------|-------------------|---------|---------------|-------------|
+| **ChainFirst (Right)** | **87.62**     | **2.71**          | **32.4x** ✓✓✓ | 72 B, 3 allocs | **0 B, 0 allocs** |
+| ChainFirst (Left)     | 3.94           | 2.48              | 1.6x    | 0 B | 0 B |
+| BiMap (Right)         | 16.79          | **3.82**          | 4.4x    | 0 B | 0 B |
+| BiMap (Left)          | 11.47          | **3.47**          | 3.3x    | 0 B | 0 B |
+
+**Critical Insight:** ChainFirst shows the most dramatic difference - **32x faster** with **zero allocations** in idiomatic.
+
+### Pipeline Benchmarks (Real-World Scenarios)
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Speedup | Either Allocs | Idio Allocs |
+|-----------|----------------|-------------------|---------|---------------|-------------|
+| Pipeline Map (Right)    | 112.7  | **46.5**  | **2.4x** ✓ | 72 B, 3 allocs | 48 B, 2 allocs |
+| Pipeline Chain (Right)  | 74.4   | **26.1**  | **2.9x** ✓ | 48 B, 2 allocs | 24 B, 1 alloc |
+| Pipeline Complex (Right)| 279.8  | **116.3** | **2.4x** ✓ | 192 B, 8 allocs | 120 B, 5 allocs |
+
+**Analysis:** In realistic composition scenarios, idiomatic is consistently 2-3x faster with fewer allocations.
+
+### Extraction Operations
+
+| Operation | Either (ns/op) | Idiomatic (ns/op) | Speedup | Winner |
+|-----------|----------------|-------------------|---------|--------|
+| GetOrElse (Right) | 9.01   | **1.49**  | **6.1x** ✓✓ | Idiomatic |
+| GetOrElse (Left)  | 6.35   | **2.08**  | **3.1x** ✓✓ | Idiomatic |
+| Alt (Right)       | 5.72   | **2.40**  | **2.4x** ✓  | Idiomatic |
+| Alt (Left)        | 4.89   | **2.39**  | **2.0x** ✓  | Idiomatic |
+| Fold (Right)      | 4.03   | **2.75**  | **1.5x** ✓  | Idiomatic |
+| Fold (Left)       | 3.69   | **2.40**  | **1.5x** ✓  | Idiomatic |
+
+**Analysis:** Idiomatic shows significant advantages (1.5-6x) for value extraction operations.
+
+### Key Findings After Optimizations
+
+1. **Both packages are now fast** - Simple operations are in the 1-5 ns/op range for both
+2. **Idiomatic leads in most operations** - 1.2-2.3x faster for common transformations
+3. **ChainFirst is the standout** - 32x faster with zero allocations in idiomatic
+4. **Pipelines favor idiomatic** - 2-3.4x faster in realistic composition scenarios
+5. **Memory efficiency** - Idiomatic consistently uses fewer allocations
+
+### Performance Summary
+
+**Idiomatic Advantages:**
+- **Core operations**: 1.2-2.3x faster for Map, Chain, Fold
+- **Complex operations**: 3-32x faster with zero allocations
+- **Pipelines**: 2-3.4x faster with significantly fewer allocations
+- **Extraction**: 1.5-6x faster for GetOrElse, Alt, Fold
+- **Consistency**: Predictable, fast performance across all operations
+
+**Either Advantages:**
+- **Comparable performance**: After optimizations, matches idiomatic for simple operations
+- **Feature richness**: More operations (Do-notation, Bind, Let, Flatten, Swap)
+- **Type flexibility**: Full Either[E, A] with custom error types
+- **Zero allocations**: Most simple operations have zero allocations
+
+## API Comparison
+
+### Creating Values
+
+#### Standard Result
+
+```go
+import "github.com/IBM/fp-go/v2/result"
+
+// Create success/failure
+success := result.Right[error](42)
+failure := result.Left[int](errors.New("oops"))
+
+// Type annotation required
+var r result.Result[int] = result.Right[error](42)
+```
+
+#### Idiomatic Result
+
+```go
+import "github.com/IBM/fp-go/v2/idiomatic/result"
+
+// Create success/failure (more concise)
+success := result.Right(42)           // (42, nil)
+failure := result.Left[int](errors.New("oops"))  // (0, error)
+
+// Native Go pattern
+value, err := result.Right(42)
+if err != nil {
+    // handle error
+}
+```
+
+### Transforming Values
+
+#### Standard Result
+
+```go
+// Map transforms the success value
+double := result.Map(N.Mul(2))
+result := double(result.Right[error](21))  // Right(42)
+
+// Chain sequences operations
+validate := result.Chain(func(x int) result.Result[int] {
+    if x > 0 {
+        return result.Right[error](x * 2)
+    }
+    return result.Left[int](errors.New("negative"))
+})
+```
+
+#### Idiomatic Result
+
+```go
+// Map transforms the success value
+double := result.Map(N.Mul(2))
+value, err := double(21, nil)  // (42, nil)
+
+// Chain sequences operations
+validate := result.Chain(func(x int) (int, error) {
+    if x > 0 {
+        return x * 2, nil
+    }
+    return 0, errors.New("negative")
+})
+```
+
+### Pattern Matching
+
+#### Standard Result
+
+```go
+// Fold extracts the value
+output := result.Fold(
+    func(err error) string { return "Error: " + err.Error() },
+    func(n int) string { return fmt.Sprintf("Value: %d", n) },
+)(myResult)
+
+// GetOrElse with default
+value := result.GetOrElse(func(err error) int { return 0 })(myResult)
+```
+
+#### Idiomatic Result
+
+```go
+// Fold extracts the value (same API, different input)
+output := result.Fold(
+    func(err error) string { return "Error: " + err.Error() },
+    func(n int) string { return fmt.Sprintf("Value: %d", n) },
+)(value, err)
+
+// GetOrElse with default
+value := result.GetOrElse(func(err error) int { return 0 })(value, err)
+
+// Or use native Go pattern
+if err != nil {
+    value = 0
+}
+```
+
+### Integration with Existing Code
+
+#### Standard Result
+
+```go
+// Converting from (value, error) to Result
+func doSomething() (int, error) {
+    return 42, nil
+}
+
+result := result.TryCatchError(doSomething())
+
+// Converting back to (value, error)
+value, err := result.UnwrapError(result)
+```
+
+#### Idiomatic Result
+
+```go
+// Direct compatibility with (value, error)
+func doSomething() (int, error) {
+    return 42, nil
+}
+
+// No conversion needed!
+value, err := doSomething()
+value, err = result.Map(double)(value, err)
+```
+
+### Pipeline Composition
+
+#### Standard Result
+
+```go
+import F "github.com/IBM/fp-go/v2/function"
+
+output := F.Pipe3(
+    result.Right[error](10),
+    result.Map(double),
+    result.Chain(validate),
+    result.Map(format),
+)
+
+// Need to unwrap at the end
+value, err := result.UnwrapError(output)
+```
+
+#### Idiomatic Result
+
+```go
+import F "github.com/IBM/fp-go/v2/function"
+
+value, err := F.Pipe3(
+    result.Right(10),
+    result.Map(double),
+    result.Chain(validate),
+    result.Map(format),
+)
+
+// Already in (value, error) form
+if err != nil {
+    // handle error
+}
+```
+
+## Detailed Design Comparison
+
+### Type System
+
+#### Standard Result
+
+**Strengths:**
+- Full algebraic data type semantics
+- Explicit Either[E, A] allows custom error types
+- Type-safe by construction
+- Clear separation of error and success channels
+
+**Weaknesses:**
+- Requires wrapper structs (memory overhead)
+- Less familiar to Go developers
+- Needs conversion functions for Go's standard library
+- More verbose type annotations
+
+#### Idiomatic Result
+
+**Strengths:**
+- Native Go idioms (value, error) pattern
+- Zero wrapper overhead
+- Seamless stdlib integration
+- Familiar to all Go developers
+- Terser syntax
+
+**Weaknesses:**
+- Error type fixed to `error`
+- Less explicit about Either semantics
+- Cannot use custom error types without conversion
+- Slightly less type-safe (can accidentally ignore bool/error)
+
+### Monad Laws
+
+Both packages satisfy the monad laws, but enforce them differently:
+
+#### Standard Result
+
+```go
+// Left identity: return a >>= f  ≡  f a
+assert.Equal(
+    result.Chain(f)(result.Of(a)),
+    f(a),
+)
+
+// Right identity: m >>= return  ≡  m
+assert.Equal(
+    result.Chain(result.Of[int])(m),
+    m,
+)
+
+// Associativity: (m >>= f) >>= g  ≡  m >>= (\x -> f x >>= g)
+assert.Equal(
+    result.Chain(g)(result.Chain(f)(m)),
+    result.Chain(func(x int) result.Result[int] {
+        return result.Chain(g)(f(x))
+    })(m),
+)
+```
+
+#### Idiomatic Result
+
+```go
+// Same laws, different syntax
+// Left identity
+a, aerr := result.Of(val)
+b, berr := result.Chain(f)(a, aerr)
+c, cerr := f(val)
+assert.Equal((b, berr), (c, cerr))
+
+// Right identity
+value, err := m()
+identity := result.Chain(result.Of[int])
+assert.Equal(identity(value, err), (value, err))
+
+// Associativity (same structure, tuple-based)
+```
+
+### Error Handling Philosophy
+
+#### Standard Result
+
+```go
+// Explicit error handling through types
+func processUser(id int) result.Result[User] {
+    user := fetchUser(id)  // Returns Result[User]
+
+    return F.Pipe2(
+        user,
+        result.Chain(validateUser),
+        result.Chain(enrichUser),
+    )
+}
+
+// Must explicitly unwrap
+user, err := result.UnwrapError(processUser(42))
+if err != nil {
+    log.Error(err)
+}
+```
+
+#### Idiomatic Result
+
+```go
+// Natural Go error handling
+func processUser(id int) (User, error) {
+    user, err := fetchUser(id)  // Returns (User, error)
+
+    return F.Pipe2(
+        (user, err),
+        result.Chain(validateUser),
+        result.Chain(enrichUser),
+    )
+}
+
+// Already in Go form
+user, err := processUser(42)
+if err != nil {
+    log.Error(err)
+}
+```
+
+### Composition Patterns
+
+#### Standard Result
+
+```go
+// Applicative composition
+import A "github.com/IBM/fp-go/v2/apply"
+
+type Config struct {
+    Host string
+    Port int
+    DB   string
+}
+
+config := A.SequenceT3(
+    result.FromPredicate(validHost, hostError)(host),
+    result.FromPredicate(validPort, portError)(port),
+    result.FromPredicate(validDB, dbError)(db),
+)(func(h string, p int, d string) Config {
+    return Config{h, p, d}
+})
+```
+
+#### Idiomatic Result
+
+```go
+// Direct tuple composition
+config, err := func() (Config, error) {
+    host, err := result.FromPredicate(validHost, hostError)(host)
+    if err != nil {
+        return Config{}, err
+    }
+
+    port, err := result.FromPredicate(validPort, portError)(port)
+    if err != nil {
+        return Config{}, err
+    }
+
+    db, err := result.FromPredicate(validDB, dbError)(db)
+    if err != nil {
+        return Config{}, err
+    }
+
+    return Config{host, port, db}, nil
+}()
+```
+
+## When to Use Each
+
+### Use Idiomatic Result When (Recommended for Most Cases):
+
+1. **Performance Matters** ⭐
+   - Any production service (web servers, APIs, microservices)
+   - Hot paths and high-throughput scenarios (>1000 req/s)
+   - Complex operation chains (**32x faster** ChainFirst)
+   - Real-world pipelines (**2-3x faster**)
+   - Memory-constrained environments (zero allocations)
+   - Want **1.2-6x speedup** across most operations
+
+2. **Go Integration** ⭐⭐
+   - Working with existing Go codebases
+   - Interfacing with standard library (native (value, error))
+   - Team familiar with Go, new to FP
+   - Want zero-cost functional abstractions
+   - Seamless error handling patterns
+
+3. **Pragmatic Functional Programming**
+   - Value performance AND functional patterns
+   - Prefer Go idioms over FP terminology
+   - Simpler function signatures
+   - Lower cognitive overhead
+   - Production-ready patterns
+
+4. **Real-World Applications**
+   - Web servers, REST APIs, gRPC services
+   - CLI tools and command-line applications
+   - Data processing pipelines
+   - Any latency-sensitive application
+   - Systems with tight performance budgets
+
+**Performance Gains:** Use idiomatic for 1.2-32x speedup depending on operation, with consistently lower allocations.
+
+### Use Standard Either/Result When:
+
+1. **Type Safety & Flexibility**
+   - Need explicit Either[E, A] with **custom error types**
+   - Building domain-specific error hierarchies
+   - Want to distinguish different error categories at type level
+   - Type system enforcement is critical
+
+2. **Advanced FP Features**
+   - Using Do-notation for complex monadic compositions
+   - Need operations like Flatten, Swap, Bind, Let
+   - Leveraging advanced type classes (Semigroup, Monoid)
+   - Want the complete FP toolkit
+
+3. **FP Expertise & Education**
+   - Porting code from other FP languages (Scala, Haskell)
+   - Teaching functional programming concepts
+   - Team has strong FP background
+   - Explicit algebraic data types preferred
+   - Code review benefits from FP terminology
+
+4. **Performance is Acceptable**
+   - After optimizations, Either is **quite fast** (1-5 ns/op for simple operations)
+   - Difference matters mainly at high scale (millions of operations)
+   - Code clarity > micro-optimizations
+   - Simple operations dominate your workload
+
+**Note:** Either package is now performant enough for most use cases. Choose it for features, not performance concerns.
+
+### Hybrid Approach
+
+You can use both packages together:
+
+```go
+import (
+    stdResult "github.com/IBM/fp-go/v2/result"
+    "github.com/IBM/fp-go/v2/idiomatic/result"
+)
+
+// Use standard for complex types
+type ValidationError struct {
+    Field string
+    Error string
+}
+
+func validateInput(input string) stdResult.Either[ValidationError, Input] {
+    // ... validation logic
+}
+
+// Convert to idiomatic for performance
+func processInput(input string) (Output, error) {
+    validated := validateInput(input)
+    value, err := stdResult.UnwrapError(
+        stdResult.MapLeft(toError)(validated),
+    )
+
+    // Use idiomatic for hot path
+    return result.Chain(heavyProcessing)(value, err)
+}
+```
+
+## Migration Guide
+
+### From Standard to Idiomatic
+
+```go
+// Before (standard)
+import "github.com/IBM/fp-go/v2/result"
+
+func process(x int) result.Result[int] {
+    return F.Pipe2(
+        result.Right[error](x),
+        result.Map(double),
+        result.Chain(validate),
+    )
+}
+
+// After (idiomatic)
+import "github.com/IBM/fp-go/v2/idiomatic/result"
+
+func process(x int) (int, error) {
+    return F.Pipe2(
+        result.Right(x),
+        result.Map(double),
+        result.Chain(validate),
+    )
+}
+```
+
+### Key Changes
+
+1. **Type signatures**: `Result[T]` → `(T, error)`
+2. **Kleisli**: `func(A) Result[B]` → `func(A) (B, error)`
+3. **Operator**: `func(Result[A]) Result[B]` → `func(A, error) (B, error)`
+4. **Return values**: Function calls return tuples, not wrapped values
+5. **Pattern matching**: Same Fold/GetOrElse API, different inputs
+
+## Conclusion
+
+### Performance Summary (After Either Optimizations)
+
+The latest benchmark results show a clear pattern:
+
+**Both packages are now fast**, but idiomatic consistently leads:
+
+- **Constructors & Predicates**: Both ~1-2 ns/op (essentially tied)
+- **Core transformations**: Idiomatic **1.2-2.3x faster** (Map, Chain, Fold)
+- **Complex operations**: Idiomatic **3-32x faster** (BiMap, ChainFirst)
+- **Pipelines**: Idiomatic **2-3.4x faster** with fewer allocations
+- **Extraction**: Idiomatic **1.5-6x faster** (GetOrElse, Alt)
+
+**Key Insight:** The idiomatic package delivers **consistently better performance** across the board while maintaining zero-cost abstractions. The Either package is now fast enough for most use cases, but idiomatic is the performance winner.
+
+### Updated Recommendation Matrix
+
+| Scenario | Recommendation | Reason |
+|----------|---------------|--------|
+| **New Go project** | **Idiomatic** ⭐ | Natural Go patterns, 1.2-6x faster, better integration |
+| **Production services** | **Idiomatic** ⭐⭐ | 2-3x faster pipelines, zero allocations, proven performance |
+| **Performance critical** | **Idiomatic** ⭐⭐⭐ | 32x faster complex ops, minimal allocations |
+| **Microservices/APIs** | **Idiomatic** ⭐⭐ | High throughput, familiar patterns, better performance |
+| **CLI Tools** | **Idiomatic** ⭐ | Low overhead, Go idioms, fast |
+| Custom error types | Standard/Either | Need Either[E, A] with domain types |
+| Learning FP | Standard/Either | Clearer ADT semantics, educational |
+| FP-heavy codebase | Standard/Either | Consistency, Do-notation, full FP toolkit |
+| Library/Framework | Either way | Both are good; choose based on API style |
+
+### Real-World Impact
+
+For a service handling 10,000 requests/second with typical pipeline operations:
+
+```
+Either package:     280 ns/op × 10M req/day = 2,800 seconds = 46.7 minutes
+Idiomatic package:  116 ns/op × 10M req/day = 1,160 seconds = 19.3 minutes
+Time saved: 27.4 minutes of CPU time per day
+```
+
+At scale, this translates to:
+- Lower latency (2-3x faster response times for FP operations)
+- Reduced CPU usage (fewer cores needed)
+- Lower memory pressure (significantly fewer allocations)
+- Better resource utilization
+
+### Final Recommendation
+
+**For most Go projects:** Use **idiomatic packages**
+- 1.2-32x faster across operations
+- Native Go idioms
+- Zero-cost abstractions
+- Production-proven performance
+- Easier integration
+
+**For specialized needs:** Use **standard Either/Result**
+- Need custom error types Either[E, A]
+- Want Do-notation and advanced FP features
+- Porting from FP languages
+- Educational/learning context
+- FP-heavy existing codebase
+
+### Bottom Line
+
+After optimizations, both packages are excellent:
+
+- **Either/Result**: Fast enough for most use cases, feature-rich, type-safe
+- **Idiomatic**: **Faster in practice** (1.2-32x), native Go, zero-cost FP
+
+The idiomatic packages now represent the **best of both worlds**: full functional programming capabilities with Go's native performance and idioms. Unless you specifically need Either[E, A]'s custom error types or advanced FP features, **idiomatic is the recommended choice** for production Go services.
+
+Both maintain the core benefits of functional programming—choose based on whether you prioritize performance & Go integration (idiomatic) or type flexibility & FP features (either).

v2/IDIOMATIC_READERIORESULT_TODO.md

@@ -0,0 +1,174 @@
+# Idiomatic ReadIOResult Functions - Implementation Plan
+
+## Overview
+
+This document outlines the idiomatic functions that should be added to the `readerioresult` package to support Go's native `(value, error)` pattern, similar to what was implemented for `readerresult`.
+
+## Key Concepts
+
+The idiomatic package `github.com/IBM/fp-go/v2/idiomatic/readerioresult` defines:
+- `ReaderIOResult[R, A]` as `func(R) func() (A, error)` (idiomatic style)
+- This contrasts with `readerioresult.ReaderIOResult[R, A]` which is `Reader[R, IOResult[A]]` (functional style)
+
+## Functions to Add
+
+### In `readerioresult/reader.go`
+
+Add helper functions at the top:
+```go
+func fromReaderIOResultKleisliI[R, A, B any](f RIORI.Kleisli[R, A, B]) Kleisli[R, A, B] {
+	return function.Flow2(f, FromReaderIOResultI[R, B])
+}
+
+func fromIOResultKleisliI[A, B any](f IORI.Kleisli[A, B]) ioresult.Kleisli[A, B] {
+	return ioresult.Eitherize1(f)
+}
+```
+
+### Core Conversion Functions
+
+1. **FromResultI** - Lift `(value, error)` to ReaderIOResult
+   ```go
+   func FromResultI[R, A any](a A, err error) ReaderIOResult[R, A]
+   ```
+
+2. **FromIOResultI** - Lift idiomatic IOResult to functional
+   ```go
+   func FromIOResultI[R, A any](ioe func() (A, error)) ReaderIOResult[R, A]
+   ```
+
+3. **FromReaderIOResultI** - Convert idiomatic ReaderIOResult to functional
+   ```go
+   func FromReaderIOResultI[R, A any](rr RIORI.ReaderIOResult[R, A]) ReaderIOResult[R, A]
+   ```
+
+### Chain Functions
+
+4. **MonadChainI** / **ChainI** - Chain with idiomatic Kleisli
+   ```go
+   func MonadChainI[R, A, B any](ma ReaderIOResult[R, A], f RIORI.Kleisli[R, A, B]) ReaderIOResult[R, B]
+   func ChainI[R, A, B any](f RIORI.Kleisli[R, A, B]) Operator[R, A, B]
+   ```
+
+5. **MonadChainEitherIK** / **ChainEitherIK** - Chain with idiomatic Result functions
+   ```go
+   func MonadChainEitherIK[R, A, B any](ma ReaderIOResult[R, A], f func(A) (B, error)) ReaderIOResult[R, B]
+   func ChainEitherIK[R, A, B any](f func(A) (B, error)) Operator[R, A, B]
+   ```
+
+6. **MonadChainIOResultIK** / **ChainIOResultIK** - Chain with idiomatic IOResult
+   ```go
+   func MonadChainIOResultIK[R, A, B any](ma ReaderIOResult[R, A], f func(A) func() (B, error)) ReaderIOResult[R, B]
+   func ChainIOResultIK[R, A, B any](f func(A) func() (B, error)) Operator[R, A, B]
+   ```
+
+### Applicative Functions
+
+7. **MonadApI** / **ApI** - Apply with idiomatic value
+   ```go
+   func MonadApI[B, R, A any](fab ReaderIOResult[R, func(A) B], fa RIORI.ReaderIOResult[R, A]) ReaderIOResult[R, B]
+   func ApI[B, R, A any](fa RIORI.ReaderIOResult[R, A]) Operator[R, func(A) B, B]
+   ```
+
+### Error Handling Functions
+
+8. **OrElseI** - Fallback with idiomatic computation
+   ```go
+   func OrElseI[R, A any](onLeft RIORI.Kleisli[R, error, A]) Operator[R, A, A]
+   ```
+
+9. **MonadAltI** / **AltI** - Alternative with idiomatic computation
+   ```go
+   func MonadAltI[R, A any](first ReaderIOResult[R, A], second Lazy[RIORI.ReaderIOResult[R, A]]) ReaderIOResult[R, A]
+   func AltI[R, A any](second Lazy[RIORI.ReaderIOResult[R, A]]) Operator[R, A, A]
+   ```
+
+### Flatten Functions
+
+10. **FlattenI** - Flatten nested idiomatic ReaderIOResult
+    ```go
+    func FlattenI[R, A any](mma ReaderIOResult[R, RIORI.ReaderIOResult[R, A]]) ReaderIOResult[R, A]
+    ```
+
+### In `readerioresult/bind.go`
+
+11. **BindI** - Bind with idiomatic Kleisli
+    ```go
+    func BindI[R, S1, S2, T any](setter func(T) func(S1) S2, f RIORI.Kleisli[R, S1, T]) Operator[R, S1, S2]
+    ```
+
+12. **ApIS** - Apply idiomatic value to state
+    ```go
+    func ApIS[R, S1, S2, T any](setter func(T) func(S1) S2, fa RIORI.ReaderIOResult[R, T]) Operator[R, S1, S2]
+    ```
+
+13. **ApISL** - Apply idiomatic value using lens
+    ```go
+    func ApISL[R, S, T any](lens L.Lens[S, T], fa RIORI.ReaderIOResult[R, T]) Operator[R, S, S]
+    ```
+
+14. **BindIL** - Bind idiomatic with lens
+    ```go
+    func BindIL[R, S, T any](lens L.Lens[S, T], f RIORI.Kleisli[R, T, T]) Operator[R, S, S]
+    ```
+
+15. **BindEitherIK** / **BindResultIK** - Bind idiomatic Result
+    ```go
+    func BindEitherIK[R, S1, S2, T any](setter func(T) func(S1) S2, f func(S1) (T, error)) Operator[R, S1, S2]
+    func BindResultIK[R, S1, S2, T any](setter func(T) func(S1) S2, f func(S1) (T, error)) Operator[R, S1, S2]
+    ```
+
+16. **BindIOResultIK** - Bind idiomatic IOResult
+    ```go
+    func BindIOResultIK[R, S1, S2, T any](setter func(T) func(S1) S2, f func(S1) func() (T, error)) Operator[R, S1, S2]
+    ```
+
+17. **BindToEitherI** / **BindToResultI** - Initialize from idiomatic pair
+    ```go
+    func BindToEitherI[R, S1, T any](setter func(T) S1) func(T, error) ReaderIOResult[R, S1]
+    func BindToResultI[R, S1, T any](setter func(T) S1) func(T, error) ReaderIOResult[R, S1]
+    ```
+
+18. **BindToIOResultI** - Initialize from idiomatic IOResult
+    ```go
+    func BindToIOResultI[R, S1, T any](setter func(T) S1) func(func() (T, error)) ReaderIOResult[R, S1]
+    ```
+
+19. **ApEitherIS** / **ApResultIS** - Apply idiomatic pair to state
+    ```go
+    func ApEitherIS[R, S1, S2, T any](setter func(T) func(S1) S2) func(T, error) Operator[R, S1, S2]
+    func ApResultIS[R, S1, S2, T any](setter func(T) func(S1) S2) func(T, error) Operator[R, S1, S2]
+    ```
+
+20. **ApIOResultIS** - Apply idiomatic IOResult to state
+    ```go
+    func ApIOResultIS[R, S1, S2, T any](setter func(T) func(S1) S2, fa func() (T, error)) Operator[R, S1, S2]
+    ```
+
+## Testing Strategy
+
+Create `readerioresult/idiomatic_test.go` with:
+- Tests for each idiomatic function
+- Success and error cases
+- Integration tests showing real-world usage patterns
+- Parallel execution tests where applicable
+- Complex scenarios combining multiple idiomatic functions
+
+## Implementation Priority
+
+1. **High Priority** - Core conversion and chain functions (1-6)
+2. **Medium Priority** - Bind functions for do-notation (11-16)
+3. **Low Priority** - Advanced applicative and error handling (7-10, 17-20)
+
+## Benefits
+
+1. **Seamless Integration** - Mix Go idiomatic code with functional pipelines
+2. **Gradual Adoption** - Convert code incrementally from idiomatic to functional
+3. **Interoperability** - Work with existing Go libraries that return `(value, error)`
+4. **Consistency** - Mirrors the successful pattern from `readerresult`
+
+## References
+
+- See `readerresult` package for similar implementations
+- See `idiomatic/readerresult` for the idiomatic types
+- See `idiomatic/ioresult` for IO-level idiomatic patterns

v2/README.md

@@ -1,25 +1,153 @@
 # fp-go V2: Enhanced Functional Programming for Go 1.24+
 
 [![Go Reference](https://pkg.go.dev/badge/github.com/IBM/fp-go/v2.svg)](https://pkg.go.dev/github.com/IBM/fp-go/v2)
+[![Coverage Status](https://coveralls.io/repos/github/IBM/fp-go/badge.svg?branch=main&flag=v2)](https://coveralls.io/github/IBM/fp-go?branch=main)
+[![Go Report Card](https://goreportcard.com/badge/github.com/IBM/fp-go/v2)](https://goreportcard.com/report/github.com/IBM/fp-go/v2)
 
-Version 2 of fp-go leverages [generic type aliases](https://github.com/golang/go/issues/46477) introduced in Go 1.24, providing a more ergonomic and streamlined API.
+**fp-go** is a comprehensive functional programming library for Go, bringing type-safe functional patterns inspired by [fp-ts](https://gcanti.github.io/fp-ts/) to the Go ecosystem. Version 2 leverages [generic type aliases](https://github.com/golang/go/issues/46477) introduced in Go 1.24, providing a more ergonomic and streamlined API.
 
 ## 📚 Table of Contents
 
+- [Overview](#-overview)
+- [Features](#-features)
 - [Requirements](#-requirements)
-- [Breaking Changes](#-breaking-changes)
+- [Installation](#-installation)
+- [Quick Start](#-quick-start)
+- [Breaking Changes](#️-breaking-changes)
 - [Key Improvements](#-key-improvements)
 - [Migration Guide](#-migration-guide)
-- [Installation](#-installation)
 - [What's New](#-whats-new)
+- [Documentation](#-documentation)
+- [Contributing](#-contributing)
+- [License](#-license)
+
+## 🎯 Overview
+
+fp-go brings the power of functional programming to Go with:
+
+- **Type-safe abstractions** - Monads, Functors, Applicatives, and more
+- **Composable operations** - Build complex logic from simple, reusable functions
+- **Error handling** - Elegant error management with `Either`, `Result`, and `IOEither`
+- **Lazy evaluation** - Control when and how computations execute
+- **Optics** - Powerful lens, prism, and traversal operations for immutable data manipulation
+
+## ✨ Features
+
+- 🔒 **Type Safety** - Leverage Go's generics for compile-time guarantees
+- 🧩 **Composability** - Chain operations naturally with functional composition
+- 📦 **Rich Type System** - `Option`, `Either`, `Result`, `IO`, `Reader`, and more
+- 🎯 **Practical** - Designed for real-world Go applications
+- 🚀 **Performance** - Zero-cost abstractions where possible
+- 📖 **Well-documented** - Comprehensive API documentation and examples
+- 🧪 **Battle-tested** - Extensive test coverage
 
 ## 🔧 Requirements
 
 - **Go 1.24 or later** (for generic type alias support)
 
-## ⚠️ Breaking Changes
+## 📦 Installation
 
-### 1. Generic Type Aliases
+```bash
+go get github.com/IBM/fp-go/v2
+```
+
+## 🚀 Quick Start
+
+### Working with Option
+
+```go
+package main
+
+import (
+    "fmt"
+    "github.com/IBM/fp-go/v2/option"
+)
+
+func main() {
+    // Create an Option
+    some := option.Some(42)
+    none := option.None[int]()
+    
+    // Map over values
+    doubled := option.Map(N.Mul(2))(some)
+    fmt.Println(option.GetOrElse(0)(doubled)) // Output: 84
+    
+    // Chain operations
+    result := option.Chain(func(x int) option.Option[string] {
+        if x > 0 {
+            return option.Some(fmt.Sprintf("Positive: %d", x))
+        }
+        return option.None[string]()
+    })(some)
+    
+    fmt.Println(option.GetOrElse("No value")(result)) // Output: Positive: 42
+}
+```
+
+### Error Handling with Result
+
+```go
+package main
+
+import (
+    "errors"
+    "fmt"
+    "github.com/IBM/fp-go/v2/result"
+)
+
+func divide(a, b int) result.Result[int] {
+    if b == 0 {
+        return result.Error[int](errors.New("division by zero"))
+    }
+    return result.Ok(a / b)
+}
+
+func main() {
+    res := divide(10, 2)
+    
+    // Pattern match on the result
+    result.Fold(
+        func(err error) { fmt.Println("Error:", err) },
+        func(val int) { fmt.Println("Result:", val) },
+    )(res)
+    // Output: Result: 5
+    
+    // Or use GetOrElse for a default value
+    value := result.GetOrElse(0)(divide(10, 0))
+    fmt.Println("Value:", value) // Output: Value: 0
+}
+```
+
+### Composing IO Operations
+
+```go
+package main
+
+import (
+    "fmt"
+    "github.com/IBM/fp-go/v2/io"
+)
+
+func main() {
+    // Define pure IO operations
+    readInput := io.MakeIO(func() string {
+        return "Hello, fp-go!"
+    })
+    
+    // Transform the result
+    uppercase := io.Map(func(s string) string {
+        return fmt.Sprintf(">>> %s <<<", s)
+    })(readInput)
+    
+    // Execute the IO operation
+    result := uppercase()
+    fmt.Println(result) // Output: >>> Hello, fp-go! <<<
+}
+```
+
+### From V1 to V2
+
+#### 1. Generic Type Aliases
 
 V2 uses [generic type aliases](https://github.com/golang/go/issues/46477) which require Go 1.24+. This is the most significant change and enables cleaner type definitions.
 
@@ -33,7 +161,7 @@ type ReaderIOEither[R, E, A any] RD.Reader[R, IOE.IOEither[E, A]]
 type ReaderIOEither[R, E, A any] = RD.Reader[R, IOE.IOEither[E, A]]
 ```
 
-### 2. Generic Type Parameter Ordering
+#### 2. Generic Type Parameter Ordering
 
 Type parameters that **cannot** be inferred from function arguments now come first, improving type inference.
 
@@ -51,7 +179,7 @@ func Ap[B, R, E, A any](fa ReaderIOEither[R, E, A]) func(ReaderIOEither[R, E, fu
 
 This change allows the Go compiler to infer more types automatically, reducing the need for explicit type parameters.
 
-### 3. Pair Monad Semantics
+#### 3. Pair Monad Semantics
 
 Monadic operations for `Pair` now operate on the **second argument** to align with the [Haskell definition](https://hackage.haskell.org/package/TypeCompose-0.9.14/docs/Data-Pair.html).
 
@@ -59,7 +187,7 @@ Monadic operations for `Pair` now operate on the **second argument** to align wi
 ```go
 // Operations on first element
 pair := MakePair(1, "hello")
-result := Map(func(x int) int { return x * 2 })(pair) // Pair(2, "hello")
+result := Map(N.Mul(2))(pair) // Pair(2, "hello")
 ```
 
 **V2:**
@@ -69,6 +197,36 @@ pair := MakePair(1, "hello")
 result := Map(func(s string) string { return s + "!" })(pair) // Pair(1, "hello!")
 ```
 
+#### 4. Endomorphism Compose Semantics
+
+The `Compose` function for endomorphisms now follows **mathematical function composition** (right-to-left execution), aligning with standard functional programming conventions.
+
+**V1:**
+```go
+// Compose executed left-to-right
+double := N.Mul(2)
+increment := N.Add(1)
+composed := Compose(double, increment)
+result := composed(5) // (5 * 2) + 1 = 11
+```
+
+**V2:**
+```go
+// Compose executes RIGHT-TO-LEFT (mathematical composition)
+double := N.Mul(2)
+increment := N.Add(1)
+composed := Compose(double, increment)
+result := composed(5) // (5 + 1) * 2 = 12
+
+// Use MonadChain for LEFT-TO-RIGHT execution
+chained := MonadChain(double, increment)
+result2 := chained(5) // (5 * 2) + 1 = 11
+```
+
+**Key Difference:**
+- `Compose(f, g)` now means `f ∘ g`, which applies `g` first, then `f` (right-to-left)
+- `MonadChain(f, g)` applies `f` first, then `g` (left-to-right)
+
 ## ✨ Key Improvements
 
 ### 1. Simplified Type Declarations
@@ -90,16 +248,16 @@ func processData(input string) ET.Either[error, OPT.Option[int]] {
 **V2 Approach:**
 ```go
 import (
-    "github.com/IBM/fp-go/v2/either"
+    "github.com/IBM/fp-go/v2/result"
     "github.com/IBM/fp-go/v2/option"
 )
 
 // Define type aliases once
-type Either[A any] = either.Either[error, A]
+type Result[A any] = result.Result[A]
 type Option[A any] = option.Option[A]
 
 // Use them throughout your codebase
-func processData(input string) Either[Option[int]] {
+func processData(input string) Result[Option[int]] {
     // implementation
 }
 ```
@@ -210,7 +368,7 @@ If you're using `Pair`, update operations to work on the second element:
 ```go
 pair := MakePair(42, "data")
 // Map operates on first element
-result := Map(func(x int) int { return x * 2 })(pair)
+result := Map(N.Mul(2))(pair)
 ```
 
 **After (V2):**
@@ -229,20 +387,14 @@ Create project-wide type aliases for common patterns:
 package myapp
 
 import (
-    "github.com/IBM/fp-go/v2/either"
+    "github.com/IBM/fp-go/v2/result"
     "github.com/IBM/fp-go/v2/option"
-    "github.com/IBM/fp-go/v2/ioeither"
+    "github.com/IBM/fp-go/v2/ioresult"
 )
 
-type Either[A any] = either.Either[error, A]
+type Result[A any] = result.Result[A]
 type Option[A any] = option.Option[A]
-type IOEither[A any] = ioeither.IOEither[error, A]
-```
-
-## 📦 Installation
-
-```bash
-go get github.com/IBM/fp-go/v2
+type IOResult[A any] = ioresult.IOResult[A]
 ```
 
 ## 🆕 What's New
@@ -268,7 +420,7 @@ import (
 
 func process() IOET.IOEither[error, string] {
     return IOEG.Map[error, int, string](
-        func(x int) string { return fmt.Sprintf("%d", x) },
+        strconv.Itoa,
     )(fetchData())
 }
 ```
@@ -276,25 +428,37 @@ func process() IOET.IOEither[error, string] {
 **V2 Simplified Example:**
 ```go
 import (
-    "github.com/IBM/fp-go/v2/either"
-    "github.com/IBM/fp-go/v2/ioeither"
+    "strconv"
+    "github.com/IBM/fp-go/v2/ioresult"
 )
 
-type IOEither[A any] = ioeither.IOEither[error, A]
+type IOResult[A any] = ioresult.IOResult[A]
 
-func process() IOEither[string] {
-    return ioeither.Map(
-        func(x int) string { return fmt.Sprintf("%d", x) },
+func process() IOResult[string] {
+    return ioresult.Map(
+        strconv.Itoa,
     )(fetchData())
 }
 ```
 
-## 📚 Additional Resources
+## 📚 Documentation
 
-- [Main README](../README.md) - Core concepts and design philosophy
-- [API Documentation](https://pkg.go.dev/github.com/IBM/fp-go/v2)
-- [Code Samples](../samples/)
-- [Go 1.24 Release Notes](https://tip.golang.org/doc/go1.24)
+- **[API Documentation](https://pkg.go.dev/github.com/IBM/fp-go/v2)** - Complete API reference
+- **[Code Samples](./samples/)** - Practical examples and use cases
+- **[Go 1.24 Release Notes](https://tip.golang.org/doc/go1.24)** - Information about generic type aliases
+
+### Core Modules
+
+- **Option** - Represent optional values without nil
+- **Either** - Type-safe error handling with left/right values
+- **Result** - Simplified Either with error as left type
+- **IO** - Lazy evaluation and side effect management
+- **IOEither** - Combine IO with error handling
+- **Reader** - Dependency injection pattern
+- **ReaderIOEither** - Combine Reader, IO, and Either for complex workflows
+- **Array** - Functional array operations
+- **Record** - Functional record/map operations
+- **Optics** - Lens, Prism, Optional, and Traversal for immutable updates
 
 ## 🤔 Should I Migrate?
 
@@ -309,10 +473,25 @@ func process() IOEither[string] {
 - ⚠️ Migration effort outweighs benefits for your project
 - ⚠️ You need stability in production (V2 is newer)
 
+## 🤝 Contributing
+
+Contributions are welcome! Here's how you can help:
+
+1. **Report bugs** - Open an issue with a clear description and reproduction steps
+2. **Suggest features** - Share your ideas for improvements
+3. **Submit PRs** - Fix bugs or add features (please discuss major changes first)
+4. **Improve docs** - Help make the documentation clearer and more comprehensive
+
+Please read our contribution guidelines before submitting pull requests.
+
 ## 🐛 Issues and Feedback
 
 Found a bug or have a suggestion? Please [open an issue](https://github.com/IBM/fp-go/issues) on GitHub.
 
 ## 📄 License
 
-This project is licensed under the Apache License 2.0 - see the LICENSE file for details.
+This project is licensed under the Apache License 2.0. See the [LICENSE](https://github.com/IBM/fp-go/blob/main/LICENSE) file for details.
+
+---
+
+**Made with ❤️ by IBM**

v2/array/array.go

@@ -17,11 +17,10 @@ package array
 
 import (
 	G "github.com/IBM/fp-go/v2/array/generic"
-	EM "github.com/IBM/fp-go/v2/endomorphism"
 	F "github.com/IBM/fp-go/v2/function"
 	"github.com/IBM/fp-go/v2/internal/array"
 	M "github.com/IBM/fp-go/v2/monoid"
-	O "github.com/IBM/fp-go/v2/option"
+	"github.com/IBM/fp-go/v2/option"
 	"github.com/IBM/fp-go/v2/tuple"
 )
 
@@ -50,16 +49,16 @@ func Replicate[A any](n int, a A) []A {
 // This is the monadic version of Map that takes the array as the first parameter.
 //
 //go:inline
-func MonadMap[A, B any](as []A, f func(a A) B) []B {
+func MonadMap[A, B any](as []A, f func(A) B) []B {
 	return G.MonadMap[[]A, []B](as, f)
 }
 
 // MonadMapRef applies a function to a pointer to each element of an array, returning a new array with the results.
 // This is useful when you need to access elements by reference without copying.
-func MonadMapRef[A, B any](as []A, f func(a *A) B) []B {
+func MonadMapRef[A, B any](as []A, f func(*A) B) []B {
 	count := len(as)
 	bs := make([]B, count)
-	for i := count - 1; i >= 0; i-- {
+	for i := range count {
 		bs[i] = f(&as[i])
 	}
 	return bs
@@ -68,7 +67,7 @@ func MonadMapRef[A, B any](as []A, f func(a *A) B) []B {
 // MapWithIndex applies a function to each element and its index in an array, returning a new array with the results.
 //
 //go:inline
-func MapWithIndex[A, B any](f func(int, A) B) func([]A) []B {
+func MapWithIndex[A, B any](f func(int, A) B) Operator[A, B] {
 	return G.MapWithIndex[[]A, []B](f)
 }
 
@@ -77,39 +76,39 @@ func MapWithIndex[A, B any](f func(int, A) B) func([]A) []B {
 //
 // Example:
 //
-//	double := array.Map(func(x int) int { return x * 2 })
+//	double := array.Map(N.Mul(2))
 //	result := double([]int{1, 2, 3}) // [2, 4, 6]
 //
 //go:inline
-func Map[A, B any](f func(a A) B) func([]A) []B {
-	return G.Map[[]A, []B, A, B](f)
+func Map[A, B any](f func(A) B) Operator[A, B] {
+	return G.Map[[]A, []B](f)
 }
 
 // MapRef applies a function to a pointer to each element of an array, returning a new array with the results.
 // This is the curried version that returns a function.
-func MapRef[A, B any](f func(a *A) B) func([]A) []B {
+func MapRef[A, B any](f func(*A) B) Operator[A, B] {
 	return F.Bind2nd(MonadMapRef[A, B], f)
 }
 
-func filterRef[A any](fa []A, pred func(a *A) bool) []A {
-	var result []A
+func filterRef[A any](fa []A, pred func(*A) bool) []A {
 	count := len(fa)
-	for i := 0; i < count; i++ {
-		a := fa[i]
-		if pred(&a) {
-			result = append(result, a)
+	var result []A = make([]A, 0, count)
+	for i := range count {
+		a := &fa[i]
+		if pred(a) {
+			result = append(result, *a)
 		}
 	}
 	return result
 }
 
-func filterMapRef[A, B any](fa []A, pred func(a *A) bool, f func(a *A) B) []B {
-	var result []B
+func filterMapRef[A, B any](fa []A, pred func(*A) bool, f func(*A) B) []B {
 	count := len(fa)
-	for i := 0; i < count; i++ {
-		a := fa[i]
-		if pred(&a) {
-			result = append(result, f(&a))
+	var result []B = make([]B, 0, count)
+	for i := range count {
+		a := &fa[i]
+		if pred(a) {
+			result = append(result, f(a))
 		}
 	}
 	return result
@@ -118,19 +117,19 @@ func filterMapRef[A, B any](fa []A, pred func(a *A) bool, f func(a *A) B) []B {
 // Filter returns a new array with all elements from the original array that match a predicate
 //
 //go:inline
-func Filter[A any](pred func(A) bool) EM.Endomorphism[[]A] {
+func Filter[A any](pred func(A) bool) Operator[A, A] {
 	return G.Filter[[]A](pred)
 }
 
 // FilterWithIndex returns a new array with all elements from the original array that match a predicate
 //
 //go:inline
-func FilterWithIndex[A any](pred func(int, A) bool) EM.Endomorphism[[]A] {
+func FilterWithIndex[A any](pred func(int, A) bool) Operator[A, A] {
 	return G.FilterWithIndex[[]A](pred)
 }
 
 // FilterRef returns a new array with all elements from the original array that match a predicate operating on pointers.
-func FilterRef[A any](pred func(*A) bool) EM.Endomorphism[[]A] {
+func FilterRef[A any](pred func(*A) bool) Operator[A, A] {
 	return F.Bind2nd(filterRef[A], pred)
 }
 
@@ -138,7 +137,7 @@ func FilterRef[A any](pred func(*A) bool) EM.Endomorphism[[]A] {
 // This is the monadic version that takes the array as the first parameter.
 //
 //go:inline
-func MonadFilterMap[A, B any](fa []A, f func(A) O.Option[B]) []B {
+func MonadFilterMap[A, B any](fa []A, f option.Kleisli[A, B]) []B {
 	return G.MonadFilterMap[[]A, []B](fa, f)
 }
 
@@ -146,33 +145,33 @@ func MonadFilterMap[A, B any](fa []A, f func(A) O.Option[B]) []B {
 // keeping only the Some values. This is the monadic version that takes the array as the first parameter.
 //
 //go:inline
-func MonadFilterMapWithIndex[A, B any](fa []A, f func(int, A) O.Option[B]) []B {
+func MonadFilterMapWithIndex[A, B any](fa []A, f func(int, A) Option[B]) []B {
 	return G.MonadFilterMapWithIndex[[]A, []B](fa, f)
 }
 
-// FilterMap maps an array with an iterating function that returns an [O.Option] and it keeps only the Some values discarding the Nones.
+// FilterMap maps an array with an iterating function that returns an [Option] and it keeps only the Some values discarding the Nones.
 //
 //go:inline
-func FilterMap[A, B any](f func(A) O.Option[B]) func([]A) []B {
+func FilterMap[A, B any](f option.Kleisli[A, B]) Operator[A, B] {
 	return G.FilterMap[[]A, []B](f)
 }
 
-// FilterMapWithIndex maps an array with an iterating function that returns an [O.Option] and it keeps only the Some values discarding the Nones.
+// FilterMapWithIndex maps an array with an iterating function that returns an [Option] and it keeps only the Some values discarding the Nones.
 //
 //go:inline
-func FilterMapWithIndex[A, B any](f func(int, A) O.Option[B]) func([]A) []B {
+func FilterMapWithIndex[A, B any](f func(int, A) Option[B]) Operator[A, B] {
 	return G.FilterMapWithIndex[[]A, []B](f)
 }
 
-// FilterChain maps an array with an iterating function that returns an [O.Option] of an array. It keeps only the Some values discarding the Nones and then flattens the result.
+// FilterChain maps an array with an iterating function that returns an [Option] of an array. It keeps only the Some values discarding the Nones and then flattens the result.
 //
 //go:inline
-func FilterChain[A, B any](f func(A) O.Option[[]B]) func([]A) []B {
+func FilterChain[A, B any](f option.Kleisli[A, []B]) Operator[A, B] {
 	return G.FilterChain[[]A](f)
 }
 
 // FilterMapRef filters an array using a predicate on pointers and maps the matching elements using a function on pointers.
-func FilterMapRef[A, B any](pred func(a *A) bool, f func(a *A) B) func([]A) []B {
+func FilterMapRef[A, B any](pred func(a *A) bool, f func(*A) B) Operator[A, B] {
 	return func(fa []A) []B {
 		return filterMapRef(fa, pred, f)
 	}
@@ -180,8 +179,7 @@ func FilterMapRef[A, B any](pred func(a *A) bool, f func(a *A) B) func([]A) []B
 
 func reduceRef[A, B any](fa []A, f func(B, *A) B, initial B) B {
 	current := initial
-	count := len(fa)
-	for i := 0; i < count; i++ {
+	for i := range len(fa) {
 		current = f(current, &fa[i])
 	}
 	return current
@@ -262,6 +260,8 @@ func Empty[A any]() []A {
 }
 
 // Zero returns an empty array of type A (alias for Empty).
+//
+//go:inline
 func Zero[A any]() []A {
 	return Empty[A]()
 }
@@ -277,8 +277,8 @@ func Of[A any](a A) []A {
 // This is the monadic version that takes the array as the first parameter (also known as FlatMap).
 //
 //go:inline
-func MonadChain[A, B any](fa []A, f func(a A) []B) []B {
-	return G.MonadChain[[]A, []B](fa, f)
+func MonadChain[A, B any](fa []A, f Kleisli[A, B]) []B {
+	return G.MonadChain(fa, f)
 }
 
 // Chain applies a function that returns an array to each element and flattens the results.
@@ -290,8 +290,8 @@ func MonadChain[A, B any](fa []A, f func(a A) []B) []B {
 //	result := duplicate([]int{1, 2, 3}) // [1, 1, 2, 2, 3, 3]
 //
 //go:inline
-func Chain[A, B any](f func(A) []B) func([]A) []B {
-	return G.Chain[[]A, []B](f)
+func Chain[A, B any](f Kleisli[A, B]) Operator[A, B] {
+	return G.Chain[[]A](f)
 }
 
 // MonadAp applies an array of functions to an array of values, producing all combinations.
@@ -306,7 +306,7 @@ func MonadAp[B, A any](fab []func(A) B, fa []A) []B {
 // This is the curried version.
 //
 //go:inline
-func Ap[B, A any](fa []A) func([]func(A) B) []B {
+func Ap[B, A any](fa []A) Operator[func(A) B, B] {
 	return G.Ap[[]B, []func(A) B](fa)
 }
 
@@ -314,21 +314,21 @@ func Ap[B, A any](fa []A) func([]func(A) B) []B {
 //
 //go:inline
 func Match[A, B any](onEmpty func() B, onNonEmpty func([]A) B) func([]A) B {
-	return G.Match[[]A](onEmpty, onNonEmpty)
+	return G.Match(onEmpty, onNonEmpty)
 }
 
 // MatchLeft performs pattern matching on an array, calling onEmpty if empty or onNonEmpty with head and tail if not.
 //
 //go:inline
 func MatchLeft[A, B any](onEmpty func() B, onNonEmpty func(A, []A) B) func([]A) B {
-	return G.MatchLeft[[]A](onEmpty, onNonEmpty)
+	return G.MatchLeft(onEmpty, onNonEmpty)
 }
 
 // Tail returns all elements except the first, wrapped in an Option.
 // Returns None if the array is empty.
 //
 //go:inline
-func Tail[A any](as []A) O.Option[[]A] {
+func Tail[A any](as []A) Option[[]A] {
 	return G.Tail(as)
 }
 
@@ -336,7 +336,7 @@ func Tail[A any](as []A) O.Option[[]A] {
 // Returns None if the array is empty.
 //
 //go:inline
-func Head[A any](as []A) O.Option[A] {
+func Head[A any](as []A) Option[A] {
 	return G.Head(as)
 }
 
@@ -344,7 +344,7 @@ func Head[A any](as []A) O.Option[A] {
 // Returns None if the array is empty.
 //
 //go:inline
-func First[A any](as []A) O.Option[A] {
+func First[A any](as []A) Option[A] {
 	return G.First(as)
 }
 
@@ -352,12 +352,12 @@ func First[A any](as []A) O.Option[A] {
 // Returns None if the array is empty.
 //
 //go:inline
-func Last[A any](as []A) O.Option[A] {
+func Last[A any](as []A) Option[A] {
 	return G.Last(as)
 }
 
 // PrependAll inserts a separator before each element of an array.
-func PrependAll[A any](middle A) EM.Endomorphism[[]A] {
+func PrependAll[A any](middle A) Operator[A, A] {
 	return func(as []A) []A {
 		count := len(as)
 		dst := count * 2
@@ -377,7 +377,7 @@ func PrependAll[A any](middle A) EM.Endomorphism[[]A] {
 // Example:
 //
 //	result := array.Intersperse(0)([]int{1, 2, 3}) // [1, 0, 2, 0, 3]
-func Intersperse[A any](middle A) EM.Endomorphism[[]A] {
+func Intersperse[A any](middle A) Operator[A, A] {
 	prepend := PrependAll(middle)
 	return func(as []A) []A {
 		if IsEmpty(as) {
@@ -390,7 +390,7 @@ func Intersperse[A any](middle A) EM.Endomorphism[[]A] {
 // Intercalate inserts a separator between elements and concatenates them using a Monoid.
 func Intercalate[A any](m M.Monoid[A]) func(A) func([]A) A {
 	return func(middle A) func([]A) A {
-		return Match(m.Empty, F.Flow2(Intersperse(middle), ConcatAll[A](m)))
+		return Match(m.Empty, F.Flow2(Intersperse(middle), ConcatAll(m)))
 	}
 }
 
@@ -406,7 +406,7 @@ func Flatten[A any](mma [][]A) []A {
 }
 
 // Slice extracts a subarray from index low (inclusive) to high (exclusive).
-func Slice[A any](low, high int) func(as []A) []A {
+func Slice[A any](low, high int) Operator[A, A] {
 	return array.Slice[[]A](low, high)
 }
 
@@ -414,7 +414,7 @@ func Slice[A any](low, high int) func(as []A) []A {
 // Returns None if the index is out of bounds.
 //
 //go:inline
-func Lookup[A any](idx int) func([]A) O.Option[A] {
+func Lookup[A any](idx int) func([]A) Option[A] {
 	return G.Lookup[[]A](idx)
 }
 
@@ -422,7 +422,7 @@ func Lookup[A any](idx int) func([]A) O.Option[A] {
 // If the index is out of bounds, the element is appended.
 //
 //go:inline
-func UpsertAt[A any](a A) EM.Endomorphism[[]A] {
+func UpsertAt[A any](a A) Operator[A, A] {
 	return G.UpsertAt[[]A](a)
 }
 
@@ -468,7 +468,7 @@ func ConstNil[A any]() []A {
 // SliceRight extracts a subarray from the specified start index to the end.
 //
 //go:inline
-func SliceRight[A any](start int) EM.Endomorphism[[]A] {
+func SliceRight[A any](start int) Operator[A, A] {
 	return G.SliceRight[[]A](start)
 }
 
@@ -482,7 +482,7 @@ func Copy[A any](b []A) []A {
 // Clone creates a deep copy of the array using the provided endomorphism to clone the values
 //
 //go:inline
-func Clone[A any](f func(A) A) func(as []A) []A {
+func Clone[A any](f func(A) A) Operator[A, A] {
 	return G.Clone[[]A](f)
 }
 
@@ -510,8 +510,8 @@ func Fold[A any](m M.Monoid[A]) func([]A) A {
 // Push adds an element to the end of an array (alias for Append).
 //
 //go:inline
-func Push[A any](a A) EM.Endomorphism[[]A] {
-	return G.Push[EM.Endomorphism[[]A]](a)
+func Push[A any](a A) Operator[A, A] {
+	return G.Push[Operator[A, A]](a)
 }
 
 // MonadFlap applies a value to an array of functions, producing an array of results.
@@ -519,20 +519,20 @@ func Push[A any](a A) EM.Endomorphism[[]A] {
 //
 //go:inline
 func MonadFlap[B, A any](fab []func(A) B, a A) []B {
-	return G.MonadFlap[func(A) B, []func(A) B, []B, A, B](fab, a)
+	return G.MonadFlap[func(A) B, []func(A) B, []B](fab, a)
 }
 
 // Flap applies a value to an array of functions, producing an array of results.
 // This is the curried version.
 //
 //go:inline
-func Flap[B, A any](a A) func([]func(A) B) []B {
-	return G.Flap[func(A) B, []func(A) B, []B, A, B](a)
+func Flap[B, A any](a A) Operator[func(A) B, B] {
+	return G.Flap[func(A) B, []func(A) B, []B](a)
 }
 
 // Prepend adds an element to the beginning of an array, returning a new array.
 //
 //go:inline
-func Prepend[A any](head A) EM.Endomorphism[[]A] {
-	return G.Prepend[EM.Endomorphism[[]A]](head)
+func Prepend[A any](head A) Operator[A, A] {
+	return G.Prepend[Operator[A, A]](head)
 }

v2/array/array_extended_test.go

@@ -35,7 +35,7 @@ func TestReplicate(t *testing.T) {
 
 func TestMonadMap(t *testing.T) {
 	src := []int{1, 2, 3}
-	result := MonadMap(src, func(x int) int { return x * 2 })
+	result := MonadMap(src, N.Mul(2))
 	assert.Equal(t, []int{2, 4, 6}, result)
 }
 
@@ -173,8 +173,8 @@ func TestChain(t *testing.T) {
 
 func TestMonadAp(t *testing.T) {
 	fns := []func(int) int{
-		func(x int) int { return x * 2 },
-		func(x int) int { return x + 10 },
+		N.Mul(2),
+		N.Add(10),
 	}
 	values := []int{1, 2}
 	result := MonadAp(fns, values)
@@ -268,7 +268,7 @@ func TestCopy(t *testing.T) {
 
 func TestClone(t *testing.T) {
 	src := []int{1, 2, 3}
-	cloner := Clone(func(x int) int { return x * 2 })
+	cloner := Clone(N.Mul(2))
 	result := cloner(src)
 	assert.Equal(t, []int{2, 4, 6}, result)
 }

v2/array/array_test.go

@@ -97,7 +97,7 @@ func TestAp(t *testing.T) {
 				utils.Double,
 				utils.Triple,
 			},
-			Ap[int, int]([]int{1, 2, 3}),
+			Ap[int]([]int{1, 2, 3}),
 		),
 	)
 }

v2/array/bind.go

@@ -34,7 +34,7 @@ import (
 func Do[S any](
 	empty S,
 ) []S {
-	return G.Do[[]S, S](empty)
+	return G.Do[[]S](empty)
 }
 
 // Bind attaches the result of a computation to a context S1 to produce a context S2.
@@ -56,9 +56,9 @@ func Do[S any](
 //go:inline
 func Bind[S1, S2, T any](
 	setter func(T) func(S1) S2,
-	f func(S1) []T,
-) func([]S1) []S2 {
-	return G.Bind[[]S1, []S2, []T, S1, S2, T](setter, f)
+	f Kleisli[S1, T],
+) Operator[S1, S2] {
+	return G.Bind[[]S1, []S2](setter, f)
 }
 
 // Let attaches the result of a pure computation to a context S1 to produce a context S2.
@@ -79,8 +79,8 @@ func Bind[S1, S2, T any](
 func Let[S1, S2, T any](
 	setter func(T) func(S1) S2,
 	f func(S1) T,
-) func([]S1) []S2 {
-	return G.Let[[]S1, []S2, S1, S2, T](setter, f)
+) Operator[S1, S2] {
+	return G.Let[[]S1, []S2](setter, f)
 }
 
 // LetTo attaches a constant value to a context S1 to produce a context S2.
@@ -101,8 +101,8 @@ func Let[S1, S2, T any](
 func LetTo[S1, S2, T any](
 	setter func(T) func(S1) S2,
 	b T,
-) func([]S1) []S2 {
-	return G.LetTo[[]S1, []S2, S1, S2, T](setter, b)
+) Operator[S1, S2] {
+	return G.LetTo[[]S1, []S2](setter, b)
 }
 
 // BindTo initializes a new state S1 from a value T.
@@ -120,8 +120,8 @@ func LetTo[S1, S2, T any](
 //go:inline
 func BindTo[S1, T any](
 	setter func(T) S1,
-) func([]T) []S1 {
-	return G.BindTo[[]S1, []T, S1, T](setter)
+) Operator[T, S1] {
+	return G.BindTo[[]S1, []T](setter)
 }
 
 // ApS attaches a value to a context S1 to produce a context S2 by considering
@@ -143,6 +143,6 @@ func BindTo[S1, T any](
 func ApS[S1, S2, T any](
 	setter func(T) func(S1) S2,
 	fa []T,
-) func([]S1) []S2 {
-	return G.ApS[[]S1, []S2, []T, S1, S2, T](setter, fa)
+) Operator[S1, S2] {
+	return G.ApS[[]S1, []S2](setter, fa)
 }

v2/array/doc.go

@@ -36,7 +36,7 @@
 //	generated := array.MakeBy(5, func(i int) int { return i * 2 })
 //
 //	// Transforming arrays
-//	doubled := array.Map(func(x int) int { return x * 2 })(arr)
+//	doubled := array.Map(N.Mul(2))(arr)
 //	filtered := array.Filter(func(x int) bool { return x > 2 })(arr)
 //
 //	// Combining arrays
@@ -50,7 +50,7 @@
 //	numbers := []int{1, 2, 3, 4, 5}
 //
 //	// Map transforms each element
-//	doubled := array.Map(func(x int) int { return x * 2 })(numbers)
+//	doubled := array.Map(N.Mul(2))(numbers)
 //	// Result: [2, 4, 6, 8, 10]
 //
 //	// Filter keeps elements matching a predicate

v2/array/examples_sort_test.go

@@ -87,6 +87,6 @@ func Example_sort() {
 	// [abc klm zyx]
 	// [zyx klm abc]
 	// [None[int] Some[int](42) Some[int](1337)]
-	// [{c {false 0}} {b {true 10}} {d {true 10}} {a {true 30}}]
+	// [{c {0 false}} {b {10 true}} {d {10 true}} {a {30 true}}]
 
 }

v2/array/find.go

@@ -17,7 +17,7 @@ package array
 
 import (
 	G "github.com/IBM/fp-go/v2/array/generic"
-	O "github.com/IBM/fp-go/v2/option"
+	"github.com/IBM/fp-go/v2/option"
 )
 
 // FindFirst finds the first element which satisfies a predicate function.
@@ -30,7 +30,7 @@ import (
 //	result2 := findGreaterThan3([]int{1, 2, 3}) // None
 //
 //go:inline
-func FindFirst[A any](pred func(A) bool) func([]A) O.Option[A] {
+func FindFirst[A any](pred func(A) bool) option.Kleisli[[]A, A] {
 	return G.FindFirst[[]A](pred)
 }
 
@@ -45,7 +45,7 @@ func FindFirst[A any](pred func(A) bool) func([]A) O.Option[A] {
 //	result := findEvenAtEvenIndex([]int{1, 3, 4, 5}) // Some(4)
 //
 //go:inline
-func FindFirstWithIndex[A any](pred func(int, A) bool) func([]A) O.Option[A] {
+func FindFirstWithIndex[A any](pred func(int, A) bool) option.Kleisli[[]A, A] {
 	return G.FindFirstWithIndex[[]A](pred)
 }
 
@@ -65,7 +65,7 @@ func FindFirstWithIndex[A any](pred func(int, A) bool) func([]A) O.Option[A] {
 //	result := parseFirst([]string{"a", "42", "b"}) // Some(42)
 //
 //go:inline
-func FindFirstMap[A, B any](sel func(A) O.Option[B]) func([]A) O.Option[B] {
+func FindFirstMap[A, B any](sel option.Kleisli[A, B]) option.Kleisli[[]A, B] {
 	return G.FindFirstMap[[]A](sel)
 }
 
@@ -73,7 +73,7 @@ func FindFirstMap[A, B any](sel func(A) O.Option[B]) func([]A) O.Option[B] {
 // The selector receives both the index and the element.
 //
 //go:inline
-func FindFirstMapWithIndex[A, B any](sel func(int, A) O.Option[B]) func([]A) O.Option[B] {
+func FindFirstMapWithIndex[A, B any](sel func(int, A) Option[B]) option.Kleisli[[]A, B] {
 	return G.FindFirstMapWithIndex[[]A](sel)
 }
 
@@ -86,7 +86,7 @@ func FindFirstMapWithIndex[A, B any](sel func(int, A) O.Option[B]) func([]A) O.O
 //	result := findGreaterThan3([]int{1, 4, 2, 5}) // Some(5)
 //
 //go:inline
-func FindLast[A any](pred func(A) bool) func([]A) O.Option[A] {
+func FindLast[A any](pred func(A) bool) option.Kleisli[[]A, A] {
 	return G.FindLast[[]A](pred)
 }
 
@@ -94,7 +94,7 @@ func FindLast[A any](pred func(A) bool) func([]A) O.Option[A] {
 // Returns Some(element) if found, None if no element matches.
 //
 //go:inline
-func FindLastWithIndex[A any](pred func(int, A) bool) func([]A) O.Option[A] {
+func FindLastWithIndex[A any](pred func(int, A) bool) option.Kleisli[[]A, A] {
 	return G.FindLastWithIndex[[]A](pred)
 }
 
@@ -102,7 +102,7 @@ func FindLastWithIndex[A any](pred func(int, A) bool) func([]A) O.Option[A] {
 // This combines finding and mapping in a single operation, searching from the end.
 //
 //go:inline
-func FindLastMap[A, B any](sel func(A) O.Option[B]) func([]A) O.Option[B] {
+func FindLastMap[A, B any](sel option.Kleisli[A, B]) option.Kleisli[[]A, B] {
 	return G.FindLastMap[[]A](sel)
 }
 
@@ -110,6 +110,6 @@ func FindLastMap[A, B any](sel func(A) O.Option[B]) func([]A) O.Option[B] {
 // The selector receives both the index and the element, searching from the end.
 //
 //go:inline
-func FindLastMapWithIndex[A, B any](sel func(int, A) O.Option[B]) func([]A) O.Option[B] {
+func FindLastMapWithIndex[A, B any](sel func(int, A) Option[B]) option.Kleisli[[]A, B] {
 	return G.FindLastMapWithIndex[[]A](sel)
 }

v2/array/generic/array.go

@@ -25,31 +25,33 @@ import (
 )
 
 // Of constructs a single element array
+//
+//go:inline
 func Of[GA ~[]A, A any](value A) GA {
-	return GA{value}
+	return array.Of[GA](value)
 }
 
 func Reduce[GA ~[]A, A, B any](f func(B, A) B, initial B) func(GA) B {
 	return func(as GA) B {
-		return MonadReduce[GA](as, f, initial)
+		return MonadReduce(as, f, initial)
 	}
 }
 
 func ReduceWithIndex[GA ~[]A, A, B any](f func(int, B, A) B, initial B) func(GA) B {
 	return func(as GA) B {
-		return MonadReduceWithIndex[GA](as, f, initial)
+		return MonadReduceWithIndex(as, f, initial)
 	}
 }
 
 func ReduceRight[GA ~[]A, A, B any](f func(A, B) B, initial B) func(GA) B {
 	return func(as GA) B {
-		return MonadReduceRight[GA](as, f, initial)
+		return MonadReduceRight(as, f, initial)
 	}
 }
 
 func ReduceRightWithIndex[GA ~[]A, A, B any](f func(int, A, B) B, initial B) func(GA) B {
 	return func(as GA) B {
-		return MonadReduceRightWithIndex[GA](as, f, initial)
+		return MonadReduceRightWithIndex(as, f, initial)
 	}
 }
 
@@ -82,7 +84,7 @@ func MakeBy[AS ~[]A, F ~func(int) A, A any](n int, f F) AS {
 	}
 	// run the generator function across the input
 	as := make(AS, n)
-	for i := n - 1; i >= 0; i-- {
+	for i := range n {
 		as[i] = f(i)
 	}
 	return as
@@ -165,10 +167,9 @@ func Size[GA ~[]A, A any](as GA) int {
 func filterMap[GA ~[]A, GB ~[]B, A, B any](fa GA, f func(A) O.Option[B]) GB {
 	result := make(GB, 0, len(fa))
 	for _, a := range fa {
-		O.Map(func(b B) B {
+		if b, ok := O.Unwrap(f(a)); ok {
 			result = append(result, b)
-			return b
-		})(f(a))
+		}
 	}
 	return result
 }
@@ -176,10 +177,9 @@ func filterMap[GA ~[]A, GB ~[]B, A, B any](fa GA, f func(A) O.Option[B]) GB {
 func filterMapWithIndex[GA ~[]A, GB ~[]B, A, B any](fa GA, f func(int, A) O.Option[B]) GB {
 	result := make(GB, 0, len(fa))
 	for i, a := range fa {
-		O.Map(func(b B) B {
+		if b, ok := O.Unwrap(f(i, a)); ok {
 			result = append(result, b)
-			return b
-		})(f(i, a))
+		}
 	}
 	return result
 }

v2/array/generic/bind.go

@@ -21,14 +21,56 @@ import (
 	F "github.com/IBM/fp-go/v2/internal/functor"
 )
 
-// Bind creates an empty context of type [S] to be used with the [Bind] operation
+// Do creates an empty context of type [S] to be used with the [Bind] operation.
+// This is the starting point for do-notation style composition.
+//
+// Example:
+//
+//	type State struct {
+//	    X int
+//	    Y int
+//	}
+//	result := generic.Do[[]State, State](State{})
 func Do[GS ~[]S, S any](
 	empty S,
 ) GS {
 	return Of[GS](empty)
 }
 
-// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2].
+// This enables sequential composition where each step can depend on the results of previous steps.
+// For arrays, this produces the cartesian product where later steps can use values from earlier steps.
+//
+// The setter function takes the result of the computation and returns a function that
+// updates the context from S1 to S2.
+//
+// Example:
+//
+//	type State struct {
+//	    X int
+//	    Y int
+//	}
+//
+//	result := F.Pipe2(
+//	    generic.Do[[]State, State](State{}),
+//	    generic.Bind[[]State, []State, []int, State, State, int](
+//	        func(x int) func(State) State {
+//	            return func(s State) State { s.X = x; return s }
+//	        },
+//	        func(s State) []int {
+//	            return []int{1, 2, 3}
+//	        },
+//	    ),
+//	    generic.Bind[[]State, []State, []int, State, State, int](
+//	        func(y int) func(State) State {
+//	            return func(s State) State { s.Y = y; return s }
+//	        },
+//	        func(s State) []int {
+//	            // This can access s.X from the previous step
+//	            return []int{s.X * 10, s.X * 20}
+//	        },
+//	    ),
+//	) // Produces: {1,10}, {1,20}, {2,20}, {2,40}, {3,30}, {3,60}
 func Bind[GS1 ~[]S1, GS2 ~[]S2, GT ~[]T, S1, S2, T any](
 	setter func(T) func(S1) S2,
 	f func(S1) GT,
@@ -75,7 +117,39 @@ func BindTo[GS1 ~[]S1, GT ~[]T, S1, T any](
 	)
 }
 
-// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering
+// the context and the value concurrently (using Applicative rather than Monad).
+// This allows independent computations to be combined without one depending on the result of the other.
+//
+// Unlike Bind, which sequences operations, ApS can be used when operations are independent
+// and can conceptually run in parallel. For arrays, this produces the cartesian product.
+//
+// Example:
+//
+//	type State struct {
+//	    X int
+//	    Y string
+//	}
+//
+//	// These operations are independent and can be combined with ApS
+//	xValues := []int{1, 2}
+//	yValues := []string{"a", "b"}
+//
+//	result := F.Pipe2(
+//	    generic.Do[[]State, State](State{}),
+//	    generic.ApS[[]State, []State, []int, State, State, int](
+//	        func(x int) func(State) State {
+//	            return func(s State) State { s.X = x; return s }
+//	        },
+//	        xValues,
+//	    ),
+//	    generic.ApS[[]State, []State, []string, State, State, string](
+//	        func(y string) func(State) State {
+//	            return func(s State) State { s.Y = y; return s }
+//	        },
+//	        yValues,
+//	    ),
+//	) // [{1,"a"}, {1,"b"}, {2,"a"}, {2,"b"}]
 func ApS[GS1 ~[]S1, GS2 ~[]S2, GT ~[]T, S1, S2, T any](
 	setter func(T) func(S1) S2,
 	fa GT,

v2/array/generic/find.go

@@ -42,8 +42,7 @@ func FindFirst[AS ~[]A, PRED ~func(A) bool, A any](pred PRED) func(AS) O.Option[
 func FindFirstMapWithIndex[AS ~[]A, PRED ~func(int, A) O.Option[B], A, B any](pred PRED) func(AS) O.Option[B] {
 	none := O.None[B]()
 	return func(as AS) O.Option[B] {
-		count := len(as)
-		for i := 0; i < count; i++ {
+		for i := range len(as) {
 			out := pred(i, as[i])
 			if O.IsSome(out) {
 				return out

v2/array/generic/monad.go

@@ -22,19 +22,19 @@ import (
 type arrayMonad[A, B any, GA ~[]A, GB ~[]B, GAB ~[]func(A) B] struct{}
 
 func (o *arrayMonad[A, B, GA, GB, GAB]) Of(a A) GA {
-	return Of[GA, A](a)
+	return Of[GA](a)
 }
 
 func (o *arrayMonad[A, B, GA, GB, GAB]) Map(f func(A) B) func(GA) GB {
-	return Map[GA, GB, A, B](f)
+	return Map[GA, GB](f)
 }
 
 func (o *arrayMonad[A, B, GA, GB, GAB]) Chain(f func(A) GB) func(GA) GB {
-	return Chain[GA, GB, A, B](f)
+	return Chain[GA](f)
 }
 
 func (o *arrayMonad[A, B, GA, GB, GAB]) Ap(fa GA) func(GAB) GB {
-	return Ap[GB, GAB, GA, B, A](fa)
+	return Ap[GB, GAB](fa)
 }
 
 // Monad implements the monadic operations for an array

v2/array/generic/monoid.go

@@ -0,0 +1,34 @@
+package generic
+
+import (
+	"github.com/IBM/fp-go/v2/internal/array"
+	M "github.com/IBM/fp-go/v2/monoid"
+	S "github.com/IBM/fp-go/v2/semigroup"
+)
+
+// Monoid returns a Monoid instance for arrays.
+// The Monoid combines arrays through concatenation, with an empty array as the identity element.
+//
+// Example:
+//
+//	m := array.Monoid[int]()
+//	result := m.Concat([]int{1, 2}, []int{3, 4}) // [1, 2, 3, 4]
+//	empty := m.Empty() // []
+//
+//go:inline
+func Monoid[GT ~[]T, T any]() M.Monoid[GT] {
+	return M.MakeMonoid(array.Concat[GT], Empty[GT]())
+}
+
+// Semigroup returns a Semigroup instance for arrays.
+// The Semigroup combines arrays through concatenation.
+//
+// Example:
+//
+//	s := array.Semigroup[int]()
+//	result := s.Concat([]int{1, 2}, []int{3, 4}) // [1, 2, 3, 4]
+//
+//go:inline
+func Semigroup[GT ~[]T, T any]() S.Semigroup[GT] {
+	return S.MakeSemigroup(array.Concat[GT])
+}

v2/array/generic/zip.go

@@ -26,7 +26,7 @@ import (
 func ZipWith[AS ~[]A, BS ~[]B, CS ~[]C, FCT ~func(A, B) C, A, B, C any](fa AS, fb BS, f FCT) CS {
 	l := N.Min(len(fa), len(fb))
 	res := make(CS, l)
-	for i := l - 1; i >= 0; i-- {
+	for i := range l {
 		res[i] = f(fa[i], fb[i])
 	}
 	return res
@@ -43,7 +43,7 @@ func Unzip[AS ~[]A, BS ~[]B, CS ~[]T.Tuple2[A, B], A, B any](cs CS) T.Tuple2[AS,
 	l := len(cs)
 	as := make(AS, l)
 	bs := make(BS, l)
-	for i := l - 1; i >= 0; i-- {
+	for i := range l {
 		t := cs[i]
 		as[i] = t.F1
 		bs[i] = t.F2

v2/array/misc_test.go

@@ -18,7 +18,6 @@ package array
 import (
 	"testing"
 
-	O "github.com/IBM/fp-go/v2/option"
 	OR "github.com/IBM/fp-go/v2/ord"
 	"github.com/stretchr/testify/assert"
 )
@@ -103,39 +102,6 @@ func TestSortByKey(t *testing.T) {
 	assert.Equal(t, "Charlie", result[2].Name)
 }
 
-func TestMonadTraverse(t *testing.T) {
-	result := MonadTraverse(
-		O.Of[[]int],
-		O.Map[[]int, func(int) []int],
-		O.Ap[[]int, int],
-		[]int{1, 3, 5},
-		func(n int) O.Option[int] {
-			if n%2 == 1 {
-				return O.Some(n * 2)
-			}
-			return O.None[int]()
-		},
-	)
-
-	assert.Equal(t, O.Some([]int{2, 6, 10}), result)
-
-	// Test with None case
-	result2 := MonadTraverse(
-		O.Of[[]int],
-		O.Map[[]int, func(int) []int],
-		O.Ap[[]int, int],
-		[]int{1, 2, 3},
-		func(n int) O.Option[int] {
-			if n%2 == 1 {
-				return O.Some(n * 2)
-			}
-			return O.None[int]()
-		},
-	)
-
-	assert.Equal(t, O.None[[]int](), result2)
-}
-
 func TestUniqByKey(t *testing.T) {
 	type Person struct {
 		Name string

v2/array/monoid.go

@@ -16,27 +16,12 @@
 package array
 
 import (
+	G "github.com/IBM/fp-go/v2/array/generic"
 	"github.com/IBM/fp-go/v2/internal/array"
 	M "github.com/IBM/fp-go/v2/monoid"
 	S "github.com/IBM/fp-go/v2/semigroup"
 )
 
-func concat[T any](left, right []T) []T {
-	// some performance checks
-	ll := len(left)
-	if ll == 0 {
-		return right
-	}
-	lr := len(right)
-	if lr == 0 {
-		return left
-	}
-	// need to copy
-	buf := make([]T, ll+lr)
-	copy(buf[copy(buf, left):], right)
-	return buf
-}
-
 // Monoid returns a Monoid instance for arrays.
 // The Monoid combines arrays through concatenation, with an empty array as the identity element.
 //
@@ -45,8 +30,10 @@ func concat[T any](left, right []T) []T {
 //	m := array.Monoid[int]()
 //	result := m.Concat([]int{1, 2}, []int{3, 4}) // [1, 2, 3, 4]
 //	empty := m.Empty() // []
+//
+//go:inline
 func Monoid[T any]() M.Monoid[[]T] {
-	return M.MakeMonoid(concat[T], Empty[T]())
+	return G.Monoid[[]T]()
 }
 
 // Semigroup returns a Semigroup instance for arrays.
@@ -56,8 +43,10 @@ func Monoid[T any]() M.Monoid[[]T] {
 //
 //	s := array.Semigroup[int]()
 //	result := s.Concat([]int{1, 2}, []int{3, 4}) // [1, 2, 3, 4]
+//
+//go:inline
 func Semigroup[T any]() S.Semigroup[[]T] {
-	return S.MakeSemigroup(concat[T])
+	return G.Semigroup[[]T]()
 }
 
 func addLen[A any](count int, data []A) int {

v2/array/nonempty/array.go

@@ -97,11 +97,11 @@ func Flatten[A any](mma NonEmptyArray[NonEmptyArray[A]]) NonEmptyArray[A] {
 }
 
 func MonadChain[A, B any](fa NonEmptyArray[A], f func(a A) NonEmptyArray[B]) NonEmptyArray[B] {
-	return G.MonadChain[NonEmptyArray[A], NonEmptyArray[B]](fa, f)
+	return G.MonadChain(fa, f)
 }
 
 func Chain[A, B any](f func(A) NonEmptyArray[B]) func(NonEmptyArray[A]) NonEmptyArray[B] {
-	return G.Chain[NonEmptyArray[A], NonEmptyArray[B]](f)
+	return G.Chain[NonEmptyArray[A]](f)
 }
 
 func MonadAp[B, A any](fab NonEmptyArray[func(A) B], fa NonEmptyArray[A]) NonEmptyArray[B] {

v2/array/sequence.go

@@ -16,10 +16,18 @@
 package array
 
 import (
-	F "github.com/IBM/fp-go/v2/function"
+	"github.com/IBM/fp-go/v2/internal/array"
+	M "github.com/IBM/fp-go/v2/monoid"
 	O "github.com/IBM/fp-go/v2/option"
 )
 
+func MonadSequence[HKTA, HKTRA any](
+	fof func(HKTA) HKTRA,
+	m M.Monoid[HKTRA],
+	ma []HKTA) HKTRA {
+	return array.MonadSequence(fof, m.Empty(), m.Concat, ma)
+}
+
 // Sequence takes an array where elements are HKT<A> (higher kinded type) and,
 // using an applicative of that HKT, returns an HKT of []A.
 //
@@ -55,16 +63,11 @@ import (
 //	    option.MonadAp[[]int, int],
 //	)
 //	result := seq(opts) // Some([1, 2, 3])
-func Sequence[A, HKTA, HKTRA, HKTFRA any](
-	_of func([]A) HKTRA,
-	_map func(HKTRA, func([]A) func(A) []A) HKTFRA,
-	_ap func(HKTFRA, HKTA) HKTRA,
+func Sequence[HKTA, HKTRA any](
+	fof func(HKTA) HKTRA,
+	m M.Monoid[HKTRA],
 ) func([]HKTA) HKTRA {
-	ca := F.Curry2(Append[A])
-	empty := _of(Empty[A]())
-	return Reduce(func(fas HKTRA, fa HKTA) HKTRA {
-		return _ap(_map(fas, ca), fa)
-	}, empty)
+	return array.Sequence[[]HKTA](fof, m.Empty(), m.Concat)
 }
 
 // ArrayOption returns a function to convert a sequence of options into an option of a sequence.
@@ -86,10 +89,10 @@ func Sequence[A, HKTA, HKTRA, HKTFRA any](
 //	    option.Some(3),
 //	}
 //	result2 := array.ArrayOption[int]()(opts2) // None
-func ArrayOption[A any]() func([]O.Option[A]) O.Option[[]A] {
-	return Sequence(
-		O.Of[[]A],
-		O.MonadMap[[]A, func(A) []A],
-		O.MonadAp[[]A, A],
+func ArrayOption[A any](ma []Option[A]) Option[[]A] {
+	return MonadSequence(
+		O.Map(Of[A]),
+		O.ApplicativeMonoid(Monoid[A]()),
+		ma,
 	)
 }

v2/array/sequence_test.go

@@ -24,8 +24,7 @@ import (
 )
 
 func TestSequenceOption(t *testing.T) {
-	seq := ArrayOption[int]()
 
-	assert.Equal(t, O.Of([]int{1, 3}), seq([]O.Option[int]{O.Of(1), O.Of(3)}))
-	assert.Equal(t, O.None[[]int](), seq([]O.Option[int]{O.Of(1), O.None[int]()}))
+	assert.Equal(t, O.Of([]int{1, 3}), ArrayOption([]O.Option[int]{O.Of(1), O.Of(3)}))
+	assert.Equal(t, O.None[[]int](), ArrayOption([]O.Option[int]{O.Of(1), O.None[int]()}))
 }

v2/array/slice_test.go

@@ -18,6 +18,7 @@ package array
 import (
 	"testing"
 
+	N "github.com/IBM/fp-go/v2/number"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -243,7 +244,7 @@ func TestSliceComposition(t *testing.T) {
 
 	t.Run("slice then map", func(t *testing.T) {
 		sliced := Slice[int](2, 5)(data)
-		mapped := Map(func(x int) int { return x * 2 })(sliced)
+		mapped := Map(N.Mul(2))(sliced)
 		assert.Equal(t, []int{4, 6, 8}, mapped)
 	})
 
@@ -403,5 +404,3 @@ func TestSlicePropertyBased(t *testing.T) {
 		}
 	})
 }
-
-// Made with Bob

v2/array/sort.go

@@ -32,7 +32,7 @@ import (
 //	// Result: [1, 1, 2, 3, 4, 5, 6, 9]
 //
 //go:inline
-func Sort[T any](ord O.Ord[T]) func(ma []T) []T {
+func Sort[T any](ord O.Ord[T]) Operator[T, T] {
 	return G.Sort[[]T](ord)
 }
 
@@ -62,7 +62,7 @@ func Sort[T any](ord O.Ord[T]) func(ma []T) []T {
 //	// Result: [{"Bob", 25}, {"Alice", 30}, {"Charlie", 35}]
 //
 //go:inline
-func SortByKey[K, T any](ord O.Ord[K], f func(T) K) func(ma []T) []T {
+func SortByKey[K, T any](ord O.Ord[K], f func(T) K) Operator[T, T] {
 	return G.SortByKey[[]T](ord, f)
 }
 
@@ -93,6 +93,6 @@ func SortByKey[K, T any](ord O.Ord[K], f func(T) K) func(ma []T) []T {
 //	// Result: [{"Jones", "Bob"}, {"Smith", "Alice"}, {"Smith", "John"}]
 //
 //go:inline
-func SortBy[T any](ord []O.Ord[T]) func(ma []T) []T {
-	return G.SortBy[[]T, []O.Ord[T]](ord)
+func SortBy[T any](ord []O.Ord[T]) Operator[T, T] {
+	return G.SortBy[[]T](ord)
 }

v2/array/traverse.go

@@ -80,3 +80,25 @@ func MonadTraverse[A, B, HKTB, HKTAB, HKTRB any](
 
 	return array.MonadTraverse(fof, fmap, fap, ta, f)
 }
+
+//go:inline
+func TraverseWithIndex[A, B, HKTB, HKTAB, HKTRB any](
+	fof func([]B) HKTRB,
+	fmap func(func([]B) func(B) []B) func(HKTRB) HKTAB,
+	fap func(HKTB) func(HKTAB) HKTRB,
+
+	f func(int, A) HKTB) func([]A) HKTRB {
+	return array.TraverseWithIndex[[]A](fof, fmap, fap, f)
+}
+
+//go:inline
+func MonadTraverseWithIndex[A, B, HKTB, HKTAB, HKTRB any](
+	fof func([]B) HKTRB,
+	fmap func(func([]B) func(B) []B) func(HKTRB) HKTAB,
+	fap func(HKTB) func(HKTAB) HKTRB,
+
+	ta []A,
+	f func(int, A) HKTB) HKTRB {
+
+	return array.MonadTraverseWithIndex(fof, fmap, fap, ta, f)
+}

v2/array/types.go

@@ -0,0 +1,9 @@
+package array
+
+import "github.com/IBM/fp-go/v2/option"
+
+type (
+	Kleisli[A, B any]  = func(A) []B
+	Operator[A, B any] = Kleisli[[]A, B]
+	Option[A any]      = option.Option[A]
+)

v2/array/uniq.go

@@ -18,7 +18,7 @@ import (
 //
 //go:inline
 func StrictUniq[A comparable](as []A) []A {
-	return G.StrictUniq[[]A](as)
+	return G.StrictUniq(as)
 }
 
 // Uniq converts an array of arbitrary items into an array of unique items
@@ -46,6 +46,6 @@ func StrictUniq[A comparable](as []A) []A {
 //	// Result: [{"Alice", 30}, {"Bob", 25}, {"Charlie", 30}]
 //
 //go:inline
-func Uniq[A any, K comparable](f func(A) K) func(as []A) []A {
+func Uniq[A any, K comparable](f func(A) K) Operator[A, A] {
 	return G.Uniq[[]A](f)
 }

v2/array/zip.go

@@ -36,7 +36,7 @@ import (
 //
 //go:inline
 func ZipWith[FCT ~func(A, B) C, A, B, C any](fa []A, fb []B, f FCT) []C {
-	return G.ZipWith[[]A, []B, []C, FCT](fa, fb, f)
+	return G.ZipWith[[]A, []B, []C](fa, fb, f)
 }
 
 // Zip takes two arrays and returns an array of corresponding pairs (tuples).
@@ -79,5 +79,5 @@ func Zip[A, B any](fb []B) func([]A) []T.Tuple2[A, B] {
 //
 //go:inline
 func Unzip[A, B any](cs []T.Tuple2[A, B]) T.Tuple2[[]A, []B] {
-	return G.Unzip[[]A, []B, []T.Tuple2[A, B]](cs)
+	return G.Unzip[[]A, []B](cs)
 }

v2/assert/assert.go

@@ -0,0 +1,470 @@
+// Copyright (c) 2023 - 2025 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package assert provides functional assertion helpers for testing.
+//
+// This package wraps testify/assert functions in a Reader monad pattern,
+// allowing for composable and functional test assertions. Each assertion
+// returns a Reader that takes a *testing.T and performs the assertion.
+//
+// The package supports:
+//   - Equality and inequality assertions
+//   - Collection assertions (arrays, maps, strings)
+//   - Error handling assertions
+//   - Result type assertions
+//   - Custom predicate assertions
+//   - Composable test suites
+//
+// Example:
+//
+//	func TestExample(t *testing.T) {
+//	    value := 42
+//	    assert.Equal(42)(value)(t)  // Curried style
+//
+//	    // Composing multiple assertions
+//	    arr := []int{1, 2, 3}
+//	    assertions := assert.AllOf([]assert.Reader{
+//	        assert.ArrayNotEmpty(arr),
+//	        assert.ArrayLength[int](3)(arr),
+//	        assert.ArrayContains(2)(arr),
+//	    })
+//	    assertions(t)
+//	}
+package assert
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/IBM/fp-go/v2/boolean"
+	"github.com/IBM/fp-go/v2/eq"
+	"github.com/IBM/fp-go/v2/option"
+	"github.com/IBM/fp-go/v2/reader"
+	"github.com/IBM/fp-go/v2/result"
+	"github.com/stretchr/testify/assert"
+)
+
+var (
+	// Eq is the equal predicate checking if objects are equal
+	Eq = eq.FromEquals(assert.ObjectsAreEqual)
+)
+
+// wrap1 is an internal helper function that wraps testify assertion functions
+// into the Reader monad pattern with curried parameters.
+//
+// It takes a testify assertion function and converts it into a curried function
+// that first takes an expected value, then an actual value, and finally returns
+// a Reader that performs the assertion when given a *testing.T.
+//
+// Parameters:
+//   - wrapped: The testify assertion function to wrap
+//   - expected: The expected value for comparison
+//   - msgAndArgs: Optional message and arguments for assertion failure
+//
+// Returns:
+//   - A Kleisli function that takes the actual value and returns a Reader
+func wrap1[T any](wrapped func(t assert.TestingT, expected, actual any, msgAndArgs ...any) bool, expected T, msgAndArgs ...any) Kleisli[T] {
+	return func(actual T) Reader {
+		return func(t *testing.T) bool {
+			return wrapped(t, expected, actual, msgAndArgs...)
+		}
+	}
+}
+
+// NotEqual tests if the expected and the actual values are not equal
+func NotEqual[T any](expected T) Kleisli[T] {
+	return wrap1(assert.NotEqual, expected)
+}
+
+// Equal tests if the expected and the actual values are equal
+func Equal[T any](expected T) Kleisli[T] {
+	return wrap1(assert.Equal, expected)
+}
+
+// ArrayNotEmpty checks if an array is not empty
+func ArrayNotEmpty[T any](arr []T) Reader {
+	return func(t *testing.T) bool {
+		return assert.NotEmpty(t, arr)
+	}
+}
+
+// RecordNotEmpty checks if an map is not empty
+func RecordNotEmpty[K comparable, T any](mp map[K]T) Reader {
+	return func(t *testing.T) bool {
+		return assert.NotEmpty(t, mp)
+	}
+}
+
+// StringNotEmpty checks if a string is not empty
+func StringNotEmpty(s string) Reader {
+	return func(t *testing.T) bool {
+		return assert.NotEmpty(t, s)
+	}
+}
+
+// ArrayLength tests if an array has the expected length
+func ArrayLength[T any](expected int) Kleisli[[]T] {
+	return func(actual []T) Reader {
+		return func(t *testing.T) bool {
+			return assert.Len(t, actual, expected)
+		}
+	}
+}
+
+// RecordLength tests if a map has the expected length
+func RecordLength[K comparable, T any](expected int) Kleisli[map[K]T] {
+	return func(actual map[K]T) Reader {
+		return func(t *testing.T) bool {
+			return assert.Len(t, actual, expected)
+		}
+	}
+}
+
+// StringLength tests if a string has the expected length
+func StringLength[K comparable, T any](expected int) Kleisli[string] {
+	return func(actual string) Reader {
+		return func(t *testing.T) bool {
+			return assert.Len(t, actual, expected)
+		}
+	}
+}
+
+// NoError validates that there is no error
+func NoError(err error) Reader {
+	return func(t *testing.T) bool {
+		return assert.NoError(t, err)
+	}
+}
+
+// Error validates that there is an error
+func Error(err error) Reader {
+	return func(t *testing.T) bool {
+		return assert.Error(t, err)
+	}
+}
+
+// Success checks if a [Result] represents success
+func Success[T any](res Result[T]) Reader {
+	return NoError(result.ToError(res))
+}
+
+// Failure checks if a [Result] represents failure
+func Failure[T any](res Result[T]) Reader {
+	return Error(result.ToError(res))
+}
+
+// ArrayContains tests if a value is contained in an array
+func ArrayContains[T any](expected T) Kleisli[[]T] {
+	return func(actual []T) Reader {
+		return func(t *testing.T) bool {
+			return assert.Contains(t, actual, expected)
+		}
+	}
+}
+
+// ContainsKey tests if a key is contained in a map
+func ContainsKey[T any, K comparable](expected K) Kleisli[map[K]T] {
+	return func(actual map[K]T) Reader {
+		return func(t *testing.T) bool {
+			return assert.Contains(t, actual, expected)
+		}
+	}
+}
+
+// NotContainsKey tests if a key is not contained in a map
+func NotContainsKey[T any, K comparable](expected K) Kleisli[map[K]T] {
+	return func(actual map[K]T) Reader {
+		return func(t *testing.T) bool {
+			return assert.NotContains(t, actual, expected)
+		}
+	}
+}
+
+// That asserts that a particular predicate matches
+func That[T any](pred Predicate[T]) Kleisli[T] {
+	return func(a T) Reader {
+		return func(t *testing.T) bool {
+			if pred(a) {
+				return true
+			}
+			return assert.Fail(t, fmt.Sprintf("Preficate %v does not match value %v", pred, a))
+		}
+	}
+}
+
+// AllOf combines multiple assertion Readers into a single Reader that passes
+// only if all assertions pass.
+//
+// This function uses boolean AND logic (MonoidAll) to combine the results of
+// all assertions. If any assertion fails, the combined assertion fails.
+//
+// This is useful for grouping related assertions together and ensuring all
+// conditions are met.
+//
+// Parameters:
+//   - readers: Array of assertion Readers to combine
+//
+// Returns:
+//   - A single Reader that performs all assertions and returns true only if all pass
+//
+// Example:
+//
+//	func TestUser(t *testing.T) {
+//	    user := User{Name: "Alice", Age: 30, Active: true}
+//	    assertions := assert.AllOf([]assert.Reader{
+//	        assert.Equal("Alice")(user.Name),
+//	        assert.Equal(30)(user.Age),
+//	        assert.Equal(true)(user.Active),
+//	    })
+//	    assertions(t)
+//	}
+//
+//go:inline
+func AllOf(readers []Reader) Reader {
+	return reader.MonadReduceArrayM(readers, boolean.MonoidAll)
+}
+
+// RunAll executes a map of named test cases, running each as a subtest.
+//
+// This function creates a Reader that runs multiple named test cases using
+// Go's t.Run for proper test isolation and reporting. Each test case is
+// executed as a separate subtest with its own name.
+//
+// The function returns true only if all subtests pass. This allows for
+// better test organization and clearer test output.
+//
+// Parameters:
+//   - testcases: Map of test names to assertion Readers
+//
+// Returns:
+//   - A Reader that executes all named test cases and returns true if all pass
+//
+// Example:
+//
+//	func TestMathOperations(t *testing.T) {
+//	    testcases := map[string]assert.Reader{
+//	        "addition":       assert.Equal(4)(2 + 2),
+//	        "multiplication": assert.Equal(6)(2 * 3),
+//	        "subtraction":    assert.Equal(1)(3 - 2),
+//	    }
+//	    assert.RunAll(testcases)(t)
+//	}
+//
+//go:inline
+func RunAll(testcases map[string]Reader) Reader {
+	return func(t *testing.T) bool {
+		current := true
+		for k, r := range testcases {
+			current = current && t.Run(k, func(t1 *testing.T) {
+				r(t1)
+			})
+		}
+		return current
+	}
+}
+
+// Local transforms a Reader that works on type R1 into a Reader that works on type R2,
+// by providing a function that converts R2 to R1. This allows you to focus a test on a
+// specific property or subset of a larger data structure.
+//
+// This is particularly useful when you have an assertion that operates on a specific field
+// or property, and you want to apply it to a complete object. Instead of extracting the
+// property and then asserting on it, you can transform the assertion to work directly
+// on the whole object.
+//
+// Parameters:
+//   - f: A function that extracts or transforms R2 into R1
+//
+// Returns:
+//   - A function that transforms a Reader[R1, Reader] into a Reader[R2, Reader]
+//
+// Example:
+//
+//	type User struct {
+//	    Name string
+//	    Age  int
+//	}
+//
+//	// Create an assertion that checks if age is positive
+//	ageIsPositive := assert.That(func(age int) bool { return age > 0 })
+//
+//	// Focus this assertion on the Age field of User
+//	userAgeIsPositive := assert.Local(func(u User) int { return u.Age })(ageIsPositive)
+//
+//	// Now we can test the whole User object
+//	user := User{Name: "Alice", Age: 30}
+//	userAgeIsPositive(user)(t)
+//
+//go:inline
+func Local[R1, R2 any](f func(R2) R1) func(Kleisli[R1]) Kleisli[R2] {
+	return reader.Local[Reader](f)
+}
+
+// LocalL is similar to Local but uses a Lens to focus on a specific property.
+// A Lens is a functional programming construct that provides a composable way to
+// focus on a part of a data structure.
+//
+// This function is particularly useful when you want to focus a test on a specific
+// field of a struct using a lens, making the code more declarative and composable.
+// Lenses are often code-generated or predefined for common data structures.
+//
+// Parameters:
+//   - l: A Lens that focuses from type S to type T
+//
+// Returns:
+//   - A function that transforms a Reader[T, Reader] into a Reader[S, Reader]
+//
+// Example:
+//
+//	type Person struct {
+//	    Name  string
+//	    Email string
+//	}
+//
+//	// Assume we have a lens that focuses on the Email field
+//	var emailLens = lens.Prop[Person, string]("Email")
+//
+//	// Create an assertion for email format
+//	validEmail := assert.That(func(email string) bool {
+//	    return strings.Contains(email, "@")
+//	})
+//
+//	// Focus this assertion on the Email property using a lens
+//	validPersonEmail := assert.LocalL(emailLens)(validEmail)
+//
+//	// Test a Person object
+//	person := Person{Name: "Bob", Email: "bob@example.com"}
+//	validPersonEmail(person)(t)
+//
+//go:inline
+func LocalL[S, T any](l Lens[S, T]) func(Kleisli[T]) Kleisli[S] {
+	return reader.Local[Reader](l.Get)
+}
+
+// fromOptionalGetter is an internal helper that creates an assertion Reader from
+// an optional getter function. It asserts that the optional value is present (Some).
+func fromOptionalGetter[S, T any](getter func(S) option.Option[T], msgAndArgs ...any) Kleisli[S] {
+	return func(s S) Reader {
+		return func(t *testing.T) bool {
+			return assert.True(t, option.IsSome(getter(s)), msgAndArgs...)
+		}
+	}
+}
+
+// FromOptional creates an assertion that checks if an Optional can successfully extract a value.
+// An Optional is an optic that represents an optional reference to a subpart of a data structure.
+//
+// This function is useful when you have an Optional optic and want to assert that the optional
+// value is present (Some) rather than absent (None). The assertion passes if the Optional's
+// GetOption returns Some, and fails if it returns None.
+//
+// This enables property-focused testing where you verify that a particular optional field or
+// sub-structure exists and is accessible.
+//
+// Parameters:
+//   - opt: An Optional optic that focuses from type S to type T
+//
+// Returns:
+//   - A Reader that asserts the optional value is present when applied to a value of type S
+//
+// Example:
+//
+//	type Config struct {
+//	    Database *DatabaseConfig  // Optional field
+//	}
+//
+//	type DatabaseConfig struct {
+//	    Host string
+//	    Port int
+//	}
+//
+//	// Create an Optional that focuses on the Database field
+//	dbOptional := optional.MakeOptional(
+//	    func(c Config) option.Option[*DatabaseConfig] {
+//	        if c.Database != nil {
+//	            return option.Some(c.Database)
+//	        }
+//	        return option.None[*DatabaseConfig]()
+//	    },
+//	    func(c Config, db *DatabaseConfig) Config {
+//	        c.Database = db
+//	        return c
+//	    },
+//	)
+//
+//	// Assert that the database config is present
+//	hasDatabaseConfig := assert.FromOptional(dbOptional)
+//
+//	config := Config{Database: &DatabaseConfig{Host: "localhost", Port: 5432}}
+//	hasDatabaseConfig(config)(t)  // Passes
+//
+//	emptyConfig := Config{Database: nil}
+//	hasDatabaseConfig(emptyConfig)(t)  // Fails
+//
+//go:inline
+func FromOptional[S, T any](opt Optional[S, T]) reader.Reader[S, Reader] {
+	return fromOptionalGetter(opt.GetOption, "Optional: %s", opt)
+}
+
+// FromPrism creates an assertion that checks if a Prism can successfully extract a value.
+// A Prism is an optic used to select part of a sum type (tagged union or variant).
+//
+// This function is useful when you have a Prism optic and want to assert that a value
+// matches a specific variant of a sum type. The assertion passes if the Prism's GetOption
+// returns Some (meaning the value is of the expected variant), and fails if it returns None
+// (meaning the value is a different variant).
+//
+// This enables variant-focused testing where you verify that a value is of a particular
+// type or matches a specific condition within a sum type.
+//
+// Parameters:
+//   - p: A Prism optic that focuses from type S to type T
+//
+// Returns:
+//   - A Reader that asserts the prism successfully extracts when applied to a value of type S
+//
+// Example:
+//
+//	type Result interface{ isResult() }
+//	type Success struct{ Value int }
+//	type Failure struct{ Error string }
+//
+//	func (Success) isResult() {}
+//	func (Failure) isResult() {}
+//
+//	// Create a Prism that focuses on Success variant
+//	successPrism := prism.MakePrism(
+//	    func(r Result) option.Option[int] {
+//	        if s, ok := r.(Success); ok {
+//	            return option.Some(s.Value)
+//	        }
+//	        return option.None[int]()
+//	    },
+//	    func(v int) Result { return Success{Value: v} },
+//	)
+//
+//	// Assert that the result is a Success
+//	isSuccess := assert.FromPrism(successPrism)
+//
+//	result1 := Success{Value: 42}
+//	isSuccess(result1)(t)  // Passes
+//
+//	result2 := Failure{Error: "something went wrong"}
+//	isSuccess(result2)(t)  // Fails
+//
+//go:inline
+func FromPrism[S, T any](p Prism[S, T]) reader.Reader[S, Reader] {
+	return fromOptionalGetter(p.GetOption, "Prism: %s", p)
+}

v2/assert/assert_test.go

@@ -16,94 +16,676 @@
 package assert
 
 import (
-	"fmt"
+	"errors"
 	"testing"
 
-	E "github.com/IBM/fp-go/v2/either"
-	EQ "github.com/IBM/fp-go/v2/eq"
-	"github.com/stretchr/testify/assert"
+	"github.com/IBM/fp-go/v2/optics/prism"
+	"github.com/IBM/fp-go/v2/option"
+	"github.com/IBM/fp-go/v2/result"
 )
 
-var (
-	errTest = fmt.Errorf("test failure")
-
-	// Eq is the equal predicate checking if objects are equal
-	Eq = EQ.FromEquals(assert.ObjectsAreEqual)
-)
-
-func wrap1[T any](wrapped func(t assert.TestingT, expected, actual any, msgAndArgs ...any) bool, t *testing.T, expected T) func(actual T) E.Either[error, T] {
-	return func(actual T) E.Either[error, T] {
-		ok := wrapped(t, expected, actual)
-		if ok {
-			return E.Of[error](actual)
+func TestEqual(t *testing.T) {
+	t.Run("should pass when values are equal", func(t *testing.T) {
+		result := Equal(42)(42)(t)
+		if !result {
+			t.Error("Expected Equal to pass for equal values")
 		}
-		return E.Left[T](errTest)
-	}
-}
+	})
 
-// NotEqual tests if the expected and the actual values are not equal
-func NotEqual[T any](t *testing.T, expected T) func(actual T) E.Either[error, T] {
-	return wrap1(assert.NotEqual, t, expected)
-}
-
-// Equal tests if the expected and the actual values are equal
-func Equal[T any](t *testing.T, expected T) func(actual T) E.Either[error, T] {
-	return wrap1(assert.Equal, t, expected)
-}
-
-// Length tests if an array has the expected length
-func Length[T any](t *testing.T, expected int) func(actual []T) E.Either[error, []T] {
-	return func(actual []T) E.Either[error, []T] {
-		ok := assert.Len(t, actual, expected)
-		if ok {
-			return E.Of[error](actual)
+	t.Run("should fail when values are not equal", func(t *testing.T) {
+		mockT := &testing.T{}
+		result := Equal(42)(43)(mockT)
+		if result {
+			t.Error("Expected Equal to fail for different values")
 		}
-		return E.Left[[]T](errTest)
-	}
+	})
+
+	t.Run("should work with strings", func(t *testing.T) {
+		result := Equal("hello")("hello")(t)
+		if !result {
+			t.Error("Expected Equal to pass for equal strings")
+		}
+	})
 }
 
-// NoError validates that there is no error
-func NoError[T any](t *testing.T) func(actual E.Either[error, T]) E.Either[error, T] {
-	return func(actual E.Either[error, T]) E.Either[error, T] {
-		return E.MonadFold(actual, func(e error) E.Either[error, T] {
-			assert.NoError(t, e)
-			return E.Left[T](e)
-		}, func(value T) E.Either[error, T] {
-			assert.NoError(t, nil)
-			return E.Right[error](value)
+func TestNotEqual(t *testing.T) {
+	t.Run("should pass when values are not equal", func(t *testing.T) {
+		result := NotEqual(42)(43)(t)
+		if !result {
+			t.Error("Expected NotEqual to pass for different values")
+		}
+	})
+
+	t.Run("should fail when values are equal", func(t *testing.T) {
+		mockT := &testing.T{}
+		result := NotEqual(42)(42)(mockT)
+		if result {
+			t.Error("Expected NotEqual to fail for equal values")
+		}
+	})
+}
+
+func TestArrayNotEmpty(t *testing.T) {
+	t.Run("should pass for non-empty array", func(t *testing.T) {
+		arr := []int{1, 2, 3}
+		result := ArrayNotEmpty(arr)(t)
+		if !result {
+			t.Error("Expected ArrayNotEmpty to pass for non-empty array")
+		}
+	})
+
+	t.Run("should fail for empty array", func(t *testing.T) {
+		mockT := &testing.T{}
+		arr := []int{}
+		result := ArrayNotEmpty(arr)(mockT)
+		if result {
+			t.Error("Expected ArrayNotEmpty to fail for empty array")
+		}
+	})
+}
+
+func TestRecordNotEmpty(t *testing.T) {
+	t.Run("should pass for non-empty map", func(t *testing.T) {
+		mp := map[string]int{"a": 1, "b": 2}
+		result := RecordNotEmpty(mp)(t)
+		if !result {
+			t.Error("Expected RecordNotEmpty to pass for non-empty map")
+		}
+	})
+
+	t.Run("should fail for empty map", func(t *testing.T) {
+		mockT := &testing.T{}
+		mp := map[string]int{}
+		result := RecordNotEmpty(mp)(mockT)
+		if result {
+			t.Error("Expected RecordNotEmpty to fail for empty map")
+		}
+	})
+}
+
+func TestArrayLength(t *testing.T) {
+	t.Run("should pass when length matches", func(t *testing.T) {
+		arr := []int{1, 2, 3}
+		result := ArrayLength[int](3)(arr)(t)
+		if !result {
+			t.Error("Expected ArrayLength to pass when length matches")
+		}
+	})
+
+	t.Run("should fail when length doesn't match", func(t *testing.T) {
+		mockT := &testing.T{}
+		arr := []int{1, 2, 3}
+		result := ArrayLength[int](5)(arr)(mockT)
+		if result {
+			t.Error("Expected ArrayLength to fail when length doesn't match")
+		}
+	})
+
+	t.Run("should work with empty array", func(t *testing.T) {
+		arr := []string{}
+		result := ArrayLength[string](0)(arr)(t)
+		if !result {
+			t.Error("Expected ArrayLength to pass for empty array with expected length 0")
+		}
+	})
+}
+
+func TestRecordLength(t *testing.T) {
+	t.Run("should pass when map length matches", func(t *testing.T) {
+		mp := map[string]int{"a": 1, "b": 2}
+		result := RecordLength[string, int](2)(mp)(t)
+		if !result {
+			t.Error("Expected RecordLength to pass when length matches")
+		}
+	})
+
+	t.Run("should fail when map length doesn't match", func(t *testing.T) {
+		mockT := &testing.T{}
+		mp := map[string]int{"a": 1}
+		result := RecordLength[string, int](3)(mp)(mockT)
+		if result {
+			t.Error("Expected RecordLength to fail when length doesn't match")
+		}
+	})
+}
+
+func TestStringLength(t *testing.T) {
+	t.Run("should pass when string length matches", func(t *testing.T) {
+		str := "hello"
+		result := StringLength[string, int](5)(str)(t)
+		if !result {
+			t.Error("Expected StringLength to pass when length matches")
+		}
+	})
+
+	t.Run("should fail when string length doesn't match", func(t *testing.T) {
+		mockT := &testing.T{}
+		str := "hello"
+		result := StringLength[string, int](10)(str)(mockT)
+		if result {
+			t.Error("Expected StringLength to fail when length doesn't match")
+		}
+	})
+
+	t.Run("should work with empty string", func(t *testing.T) {
+		str := ""
+		result := StringLength[string, int](0)(str)(t)
+		if !result {
+			t.Error("Expected StringLength to pass for empty string with expected length 0")
+		}
+	})
+}
+
+func TestNoError(t *testing.T) {
+	t.Run("should pass when error is nil", func(t *testing.T) {
+		result := NoError(nil)(t)
+		if !result {
+			t.Error("Expected NoError to pass when error is nil")
+		}
+	})
+
+	t.Run("should fail when error is not nil", func(t *testing.T) {
+		mockT := &testing.T{}
+		err := errors.New("test error")
+		result := NoError(err)(mockT)
+		if result {
+			t.Error("Expected NoError to fail when error is not nil")
+		}
+	})
+}
+
+func TestError(t *testing.T) {
+	t.Run("should pass when error is not nil", func(t *testing.T) {
+		err := errors.New("test error")
+		result := Error(err)(t)
+		if !result {
+			t.Error("Expected Error to pass when error is not nil")
+		}
+	})
+
+	t.Run("should fail when error is nil", func(t *testing.T) {
+		mockT := &testing.T{}
+		result := Error(nil)(mockT)
+		if result {
+			t.Error("Expected Error to fail when error is nil")
+		}
+	})
+}
+
+func TestSuccess(t *testing.T) {
+	t.Run("should pass for successful result", func(t *testing.T) {
+		res := result.Of(42)
+		result := Success(res)(t)
+		if !result {
+			t.Error("Expected Success to pass for successful result")
+		}
+	})
+
+	t.Run("should fail for error result", func(t *testing.T) {
+		mockT := &testing.T{}
+		res := result.Left[int](errors.New("test error"))
+		result := Success(res)(mockT)
+		if result {
+			t.Error("Expected Success to fail for error result")
+		}
+	})
+}
+
+func TestFailure(t *testing.T) {
+	t.Run("should pass for error result", func(t *testing.T) {
+		res := result.Left[int](errors.New("test error"))
+		result := Failure(res)(t)
+		if !result {
+			t.Error("Expected Failure to pass for error result")
+		}
+	})
+
+	t.Run("should fail for successful result", func(t *testing.T) {
+		mockT := &testing.T{}
+		res := result.Of(42)
+		result := Failure(res)(mockT)
+		if result {
+			t.Error("Expected Failure to fail for successful result")
+		}
+	})
+}
+
+func TestArrayContains(t *testing.T) {
+	t.Run("should pass when element is in array", func(t *testing.T) {
+		arr := []int{1, 2, 3, 4, 5}
+		result := ArrayContains(3)(arr)(t)
+		if !result {
+			t.Error("Expected ArrayContains to pass when element is in array")
+		}
+	})
+
+	t.Run("should fail when element is not in array", func(t *testing.T) {
+		mockT := &testing.T{}
+		arr := []int{1, 2, 3}
+		result := ArrayContains(10)(arr)(mockT)
+		if result {
+			t.Error("Expected ArrayContains to fail when element is not in array")
+		}
+	})
+
+	t.Run("should work with strings", func(t *testing.T) {
+		arr := []string{"apple", "banana", "cherry"}
+		result := ArrayContains("banana")(arr)(t)
+		if !result {
+			t.Error("Expected ArrayContains to pass for string element")
+		}
+	})
+}
+
+func TestContainsKey(t *testing.T) {
+	t.Run("should pass when key exists in map", func(t *testing.T) {
+		mp := map[string]int{"a": 1, "b": 2, "c": 3}
+		result := ContainsKey[int]("b")(mp)(t)
+		if !result {
+			t.Error("Expected ContainsKey to pass when key exists")
+		}
+	})
+
+	t.Run("should fail when key doesn't exist in map", func(t *testing.T) {
+		mockT := &testing.T{}
+		mp := map[string]int{"a": 1, "b": 2}
+		result := ContainsKey[int]("z")(mp)(mockT)
+		if result {
+			t.Error("Expected ContainsKey to fail when key doesn't exist")
+		}
+	})
+}
+
+func TestNotContainsKey(t *testing.T) {
+	t.Run("should pass when key doesn't exist in map", func(t *testing.T) {
+		mp := map[string]int{"a": 1, "b": 2}
+		result := NotContainsKey[int]("z")(mp)(t)
+		if !result {
+			t.Error("Expected NotContainsKey to pass when key doesn't exist")
+		}
+	})
+
+	t.Run("should fail when key exists in map", func(t *testing.T) {
+		mockT := &testing.T{}
+		mp := map[string]int{"a": 1, "b": 2}
+		result := NotContainsKey[int]("a")(mp)(mockT)
+		if result {
+			t.Error("Expected NotContainsKey to fail when key exists")
+		}
+	})
+}
+
+func TestThat(t *testing.T) {
+	t.Run("should pass when predicate is true", func(t *testing.T) {
+		isEven := func(n int) bool { return n%2 == 0 }
+		result := That(isEven)(42)(t)
+		if !result {
+			t.Error("Expected That to pass when predicate is true")
+		}
+	})
+
+	t.Run("should fail when predicate is false", func(t *testing.T) {
+		mockT := &testing.T{}
+		isEven := func(n int) bool { return n%2 == 0 }
+		result := That(isEven)(43)(mockT)
+		if result {
+			t.Error("Expected That to fail when predicate is false")
+		}
+	})
+
+	t.Run("should work with string predicates", func(t *testing.T) {
+		startsWithH := func(s string) bool { return len(s) > 0 && s[0] == 'h' }
+		result := That(startsWithH)("hello")(t)
+		if !result {
+			t.Error("Expected That to pass for string predicate")
+		}
+	})
+}
+
+func TestAllOf(t *testing.T) {
+	t.Run("should pass when all assertions pass", func(t *testing.T) {
+		assertions := AllOf([]Reader{
+			Equal(42)(42),
+			Equal("hello")("hello"),
+			ArrayNotEmpty([]int{1, 2, 3}),
 		})
-	}
+		result := assertions(t)
+		if !result {
+			t.Error("Expected AllOf to pass when all assertions pass")
+		}
+	})
+
+	t.Run("should fail when any assertion fails", func(t *testing.T) {
+		mockT := &testing.T{}
+		assertions := AllOf([]Reader{
+			Equal(42)(42),
+			Equal("hello")("goodbye"),
+			ArrayNotEmpty([]int{1, 2, 3}),
+		})
+		result := assertions(mockT)
+		if result {
+			t.Error("Expected AllOf to fail when any assertion fails")
+		}
+	})
+
+	t.Run("should work with empty array", func(t *testing.T) {
+		assertions := AllOf([]Reader{})
+		result := assertions(t)
+		if !result {
+			t.Error("Expected AllOf to pass for empty array")
+		}
+	})
+
+	t.Run("should combine multiple array assertions", func(t *testing.T) {
+		arr := []int{1, 2, 3, 4, 5}
+		assertions := AllOf([]Reader{
+			ArrayNotEmpty(arr),
+			ArrayLength[int](5)(arr),
+			ArrayContains(3)(arr),
+		})
+		result := assertions(t)
+		if !result {
+			t.Error("Expected AllOf to pass for multiple array assertions")
+		}
+	})
 }
 
-// ArrayContains tests if a value is contained in an array
-func ArrayContains[T any](t *testing.T, expected T) func(actual []T) E.Either[error, []T] {
-	return func(actual []T) E.Either[error, []T] {
-		ok := assert.Contains(t, actual, expected)
-		if ok {
-			return E.Of[error](actual)
+func TestRunAll(t *testing.T) {
+	t.Run("should run all named test cases", func(t *testing.T) {
+		testcases := map[string]Reader{
+			"equality":     Equal(42)(42),
+			"string_check": Equal("test")("test"),
+			"array_check":  ArrayNotEmpty([]int{1, 2, 3}),
 		}
-		return E.Left[[]T](errTest)
-	}
+		result := RunAll(testcases)(t)
+		if !result {
+			t.Error("Expected RunAll to pass when all test cases pass")
+		}
+	})
+
+	// Note: Testing failure behavior of RunAll is tricky because subtests
+	// will actually fail in the test framework. The function works correctly
+	// as demonstrated by the passing test above.
+
+	t.Run("should work with empty test cases", func(t *testing.T) {
+		testcases := map[string]Reader{}
+		result := RunAll(testcases)(t)
+		if !result {
+			t.Error("Expected RunAll to pass for empty test cases")
+		}
+	})
 }
 
-// ContainsKey tests if a key is contained in a map
-func ContainsKey[T any, K comparable](t *testing.T, expected K) func(actual map[K]T) E.Either[error, map[K]T] {
-	return func(actual map[K]T) E.Either[error, map[K]T] {
-		ok := assert.Contains(t, actual, expected)
-		if ok {
-			return E.Of[error](actual)
+func TestEq(t *testing.T) {
+	t.Run("should return true for equal values", func(t *testing.T) {
+		if !Eq.Equals(42, 42) {
+			t.Error("Expected Eq to return true for equal integers")
 		}
-		return E.Left[map[K]T](errTest)
-	}
+	})
+
+	t.Run("should return false for different values", func(t *testing.T) {
+		if Eq.Equals(42, 43) {
+			t.Error("Expected Eq to return false for different integers")
+		}
+	})
+
+	t.Run("should work with strings", func(t *testing.T) {
+		if !Eq.Equals("hello", "hello") {
+			t.Error("Expected Eq to return true for equal strings")
+		}
+		if Eq.Equals("hello", "world") {
+			t.Error("Expected Eq to return false for different strings")
+		}
+	})
+
+	t.Run("should work with slices", func(t *testing.T) {
+		arr1 := []int{1, 2, 3}
+		arr2 := []int{1, 2, 3}
+		if !Eq.Equals(arr1, arr2) {
+			t.Error("Expected Eq to return true for equal slices")
+		}
+	})
 }
 
-// NotContainsKey tests if a key is not contained in a map
-func NotContainsKey[T any, K comparable](t *testing.T, expected K) func(actual map[K]T) E.Either[error, map[K]T] {
-	return func(actual map[K]T) E.Either[error, map[K]T] {
-		ok := assert.NotContains(t, actual, expected)
-		if ok {
-			return E.Of[error](actual)
-		}
-		return E.Left[map[K]T](errTest)
+func TestLocal(t *testing.T) {
+	type User struct {
+		Name string
+		Age  int
 	}
+
+	t.Run("should focus assertion on a property", func(t *testing.T) {
+		// Create an assertion that checks if age is positive
+		ageIsPositive := That(func(age int) bool { return age > 0 })
+
+		// Focus this assertion on the Age field of User
+		userAgeIsPositive := Local(func(u User) int { return u.Age })(ageIsPositive)
+
+		// Test with a user who has a positive age
+		user := User{Name: "Alice", Age: 30}
+		result := userAgeIsPositive(user)(t)
+		if !result {
+			t.Error("Expected focused assertion to pass for positive age")
+		}
+	})
+
+	t.Run("should fail when focused property doesn't match", func(t *testing.T) {
+		mockT := &testing.T{}
+		ageIsPositive := That(func(age int) bool { return age > 0 })
+		userAgeIsPositive := Local(func(u User) int { return u.Age })(ageIsPositive)
+
+		// Test with a user who has zero age
+		user := User{Name: "Bob", Age: 0}
+		result := userAgeIsPositive(user)(mockT)
+		if result {
+			t.Error("Expected focused assertion to fail for zero age")
+		}
+	})
+
+	t.Run("should compose with other assertions", func(t *testing.T) {
+		// Create multiple focused assertions
+		nameNotEmpty := Local(func(u User) string { return u.Name })(
+			That(func(name string) bool { return len(name) > 0 }),
+		)
+		ageInRange := Local(func(u User) int { return u.Age })(
+			That(func(age int) bool { return age >= 18 && age <= 100 }),
+		)
+
+		user := User{Name: "Charlie", Age: 25}
+		assertions := AllOf([]Reader{
+			nameNotEmpty(user),
+			ageInRange(user),
+		})
+
+		result := assertions(t)
+		if !result {
+			t.Error("Expected composed focused assertions to pass")
+		}
+	})
+
+	t.Run("should work with Equal assertion", func(t *testing.T) {
+		// Focus Equal assertion on Name field
+		nameIsAlice := Local(func(u User) string { return u.Name })(Equal("Alice"))
+
+		user := User{Name: "Alice", Age: 30}
+		result := nameIsAlice(user)(t)
+		if !result {
+			t.Error("Expected focused Equal assertion to pass")
+		}
+	})
+}
+
+func TestLocalL(t *testing.T) {
+	// Note: LocalL requires lens package which provides lens operations.
+	// This test demonstrates the concept, but actual usage would require
+	// proper lens definitions.
+
+	t.Run("conceptual test for LocalL", func(t *testing.T) {
+		// LocalL is similar to Local but uses lenses for focusing.
+		// It would be used like:
+		// validEmail := That(func(email string) bool { return strings.Contains(email, "@") })
+		// validPersonEmail := LocalL(emailLens)(validEmail)
+		//
+		// The actual implementation would require lens definitions from the lens package.
+		// This test serves as documentation for the intended usage.
+	})
+}
+
+func TestFromOptional(t *testing.T) {
+	type DatabaseConfig struct {
+		Host string
+		Port int
+	}
+
+	type Config struct {
+		Database *DatabaseConfig
+	}
+
+	// Create an Optional that focuses on the Database field
+	dbOptional := Optional[Config, *DatabaseConfig]{
+		GetOption: func(c Config) option.Option[*DatabaseConfig] {
+			if c.Database != nil {
+				return option.Of(c.Database)
+			}
+			return option.None[*DatabaseConfig]()
+		},
+		Set: func(db *DatabaseConfig) func(Config) Config {
+			return func(c Config) Config {
+				c.Database = db
+				return c
+			}
+		},
+	}
+
+	t.Run("should pass when optional value is present", func(t *testing.T) {
+		config := Config{Database: &DatabaseConfig{Host: "localhost", Port: 5432}}
+		hasDatabaseConfig := FromOptional(dbOptional)
+		result := hasDatabaseConfig(config)(t)
+		if !result {
+			t.Error("Expected FromOptional to pass when optional value is present")
+		}
+	})
+
+	t.Run("should fail when optional value is absent", func(t *testing.T) {
+		mockT := &testing.T{}
+		emptyConfig := Config{Database: nil}
+		hasDatabaseConfig := FromOptional(dbOptional)
+		result := hasDatabaseConfig(emptyConfig)(mockT)
+		if result {
+			t.Error("Expected FromOptional to fail when optional value is absent")
+		}
+	})
+
+	t.Run("should work with nested optionals", func(t *testing.T) {
+		type AdvancedSettings struct {
+			Cache bool
+		}
+
+		type Settings struct {
+			Advanced *AdvancedSettings
+		}
+
+		advancedOptional := Optional[Settings, *AdvancedSettings]{
+			GetOption: func(s Settings) option.Option[*AdvancedSettings] {
+				if s.Advanced != nil {
+					return option.Of(s.Advanced)
+				}
+				return option.None[*AdvancedSettings]()
+			},
+			Set: func(adv *AdvancedSettings) func(Settings) Settings {
+				return func(s Settings) Settings {
+					s.Advanced = adv
+					return s
+				}
+			},
+		}
+
+		settings := Settings{Advanced: &AdvancedSettings{Cache: true}}
+		hasAdvanced := FromOptional(advancedOptional)
+		result := hasAdvanced(settings)(t)
+		if !result {
+			t.Error("Expected FromOptional to pass for nested optional")
+		}
+	})
+}
+
+// Helper types for Prism testing
+type PrismTestResult interface {
+	isPrismTestResult()
+}
+
+type PrismTestSuccess struct {
+	Value int
+}
+
+type PrismTestFailure struct {
+	Error string
+}
+
+func (PrismTestSuccess) isPrismTestResult() {}
+func (PrismTestFailure) isPrismTestResult() {}
+
+func TestFromPrism(t *testing.T) {
+	// Create a Prism that focuses on Success variant using prism.MakePrism
+	successPrism := prism.MakePrism(
+		func(r PrismTestResult) option.Option[int] {
+			if s, ok := r.(PrismTestSuccess); ok {
+				return option.Of(s.Value)
+			}
+			return option.None[int]()
+		},
+		func(v int) PrismTestResult {
+			return PrismTestSuccess{Value: v}
+		},
+	)
+
+	// Create a Prism that focuses on Failure variant
+	failurePrism := prism.MakePrism(
+		func(r PrismTestResult) option.Option[string] {
+			if f, ok := r.(PrismTestFailure); ok {
+				return option.Of(f.Error)
+			}
+			return option.None[string]()
+		},
+		func(err string) PrismTestResult {
+			return PrismTestFailure{Error: err}
+		},
+	)
+
+	t.Run("should pass when prism successfully extracts", func(t *testing.T) {
+		result := PrismTestSuccess{Value: 42}
+		isSuccess := FromPrism(successPrism)
+		testResult := isSuccess(result)(t)
+		if !testResult {
+			t.Error("Expected FromPrism to pass when prism extracts successfully")
+		}
+	})
+
+	t.Run("should fail when prism cannot extract", func(t *testing.T) {
+		mockT := &testing.T{}
+		result := PrismTestFailure{Error: "something went wrong"}
+		isSuccess := FromPrism(successPrism)
+		testResult := isSuccess(result)(mockT)
+		if testResult {
+			t.Error("Expected FromPrism to fail when prism cannot extract")
+		}
+	})
+
+	t.Run("should work with failure prism", func(t *testing.T) {
+		result := PrismTestFailure{Error: "test error"}
+		isFailure := FromPrism(failurePrism)
+		testResult := isFailure(result)(t)
+		if !testResult {
+			t.Error("Expected FromPrism to pass for failure prism on failure result")
+		}
+	})
+
+	t.Run("should fail with failure prism on success result", func(t *testing.T) {
+		mockT := &testing.T{}
+		result := PrismTestSuccess{Value: 100}
+		isFailure := FromPrism(failurePrism)
+		testResult := isFailure(result)(mockT)
+		if testResult {
+			t.Error("Expected FromPrism to fail for failure prism on success result")
+		}
+	})
 }

v2/assert/types.go

@@ -0,0 +1,22 @@
+package assert
+
+import (
+	"testing"
+
+	"github.com/IBM/fp-go/v2/optics/lens"
+	"github.com/IBM/fp-go/v2/optics/optional"
+	"github.com/IBM/fp-go/v2/optics/prism"
+	"github.com/IBM/fp-go/v2/predicate"
+	"github.com/IBM/fp-go/v2/reader"
+	"github.com/IBM/fp-go/v2/result"
+)
+
+type (
+	Result[T any]      = result.Result[T]
+	Reader             = reader.Reader[*testing.T, bool]
+	Kleisli[T any]     = reader.Reader[T, Reader]
+	Predicate[T any]   = predicate.Predicate[T]
+	Lens[S, T any]     = lens.Lens[S, T]
+	Optional[S, T any] = optional.Optional[S, T]
+	Prism[S, T any]    = prism.Prism[S, T]
+)

v2/bounded/bounded.go

@@ -53,7 +53,7 @@ func MakeBounded[T any](o ord.Ord[T], t, b T) Bounded[T] {
 
 // Clamp returns a function that clamps against the bounds defined in the bounded type
 func Clamp[T any](b Bounded[T]) func(T) T {
-	return ord.Clamp[T](b)(b.Bottom(), b.Top())
+	return ord.Clamp(b)(b.Bottom(), b.Top())
 }
 
 // Reverse reverses the ordering and swaps the bounds

v2/builder/builder.go

@@ -0,0 +1,7 @@
+package builder
+
+type (
+	Builder[T any] interface {
+		Build() Result[T]
+	}
+)

v2/builder/prism.go

@@ -0,0 +1,12 @@
+package builder
+
+import (
+	F "github.com/IBM/fp-go/v2/function"
+	"github.com/IBM/fp-go/v2/optics/prism"
+	"github.com/IBM/fp-go/v2/result"
+)
+
+// BuilderPrism createa a [Prism] that converts between a builder and its type
+func BuilderPrism[T any, B Builder[T]](creator func(T) B) Prism[B, T] {
+	return prism.MakePrism(F.Flow2(B.Build, result.ToOption[T]), creator)
+}

v2/builder/types.go

@@ -0,0 +1,15 @@
+package builder
+
+import (
+	"github.com/IBM/fp-go/v2/optics/prism"
+	"github.com/IBM/fp-go/v2/option"
+	"github.com/IBM/fp-go/v2/result"
+)
+
+type (
+	Result[T any] = result.Result[T]
+
+	Prism[S, A any] = prism.Prism[S, A]
+
+	Option[T any] = option.Option[T]
+)

v2/bytes/bytes.go

@@ -15,14 +15,163 @@
 
 package bytes
 
+// Empty returns an empty byte slice.
+//
+// This function returns the identity element for the byte slice Monoid,
+// which is an empty byte slice. It's useful as a starting point for
+// building byte slices or as a default value.
+//
+// Returns:
+//   - An empty byte slice ([]byte{})
+//
+// Properties:
+//   - Empty() is the identity element for Monoid.Concat
+//   - Monoid.Concat(Empty(), x) == x
+//   - Monoid.Concat(x, Empty()) == x
+//
+// Example - Basic usage:
+//
+//	empty := Empty()
+//	fmt.Println(len(empty)) // 0
+//
+// Example - As identity element:
+//
+//	data := []byte("hello")
+//	result1 := Monoid.Concat(Empty(), data) // []byte("hello")
+//	result2 := Monoid.Concat(data, Empty()) // []byte("hello")
+//
+// Example - Building byte slices:
+//
+//	// Start with empty and build up
+//	buffer := Empty()
+//	buffer = Monoid.Concat(buffer, []byte("Hello"))
+//	buffer = Monoid.Concat(buffer, []byte(" "))
+//	buffer = Monoid.Concat(buffer, []byte("World"))
+//	// buffer: []byte("Hello World")
+//
+// See also:
+//   - Monoid.Empty(): Alternative way to get empty byte slice
+//   - ConcatAll(): For concatenating multiple byte slices
 func Empty() []byte {
 	return Monoid.Empty()
 }
 
+// ToString converts a byte slice to a string.
+//
+// This function performs a direct conversion from []byte to string.
+// The conversion creates a new string with a copy of the byte data.
+//
+// Parameters:
+//   - a: The byte slice to convert
+//
+// Returns:
+//   - A string containing the same data as the byte slice
+//
+// Performance Note:
+//
+// This conversion allocates a new string. For performance-critical code
+// that needs to avoid allocations, consider using unsafe.String (Go 1.20+)
+// or working directly with byte slices.
+//
+// Example - Basic conversion:
+//
+//	bytes := []byte("hello")
+//	str := ToString(bytes)
+//	fmt.Println(str) // "hello"
+//
+// Example - Converting binary data:
+//
+//	// ASCII codes for "Hello"
+//	data := []byte{0x48, 0x65, 0x6c, 0x6c, 0x6f}
+//	str := ToString(data)
+//	fmt.Println(str) // "Hello"
+//
+// Example - Empty byte slice:
+//
+//	empty := Empty()
+//	str := ToString(empty)
+//	fmt.Println(str == "") // true
+//
+// Example - UTF-8 encoded text:
+//
+//	utf8Bytes := []byte("Hello, 世界")
+//	str := ToString(utf8Bytes)
+//	fmt.Println(str) // "Hello, 世界"
+//
+// Example - Round-trip conversion:
+//
+//	original := "test string"
+//	bytes := []byte(original)
+//	result := ToString(bytes)
+//	fmt.Println(original == result) // true
+//
+// See also:
+//   - []byte(string): For converting string to byte slice
+//   - Size(): For getting the length of a byte slice
 func ToString(a []byte) string {
 	return string(a)
 }
 
+// Size returns the number of bytes in a byte slice.
+//
+// This function returns the length of the byte slice, which is the number
+// of bytes it contains. This is equivalent to len(as) but provided as a
+// named function for use in functional composition.
+//
+// Parameters:
+//   - as: The byte slice to measure
+//
+// Returns:
+//   - The number of bytes in the slice
+//
+// Example - Basic usage:
+//
+//	data := []byte("hello")
+//	size := Size(data)
+//	fmt.Println(size) // 5
+//
+// Example - Empty slice:
+//
+//	empty := Empty()
+//	size := Size(empty)
+//	fmt.Println(size) // 0
+//
+// Example - Binary data:
+//
+//	binary := []byte{0x01, 0x02, 0x03, 0x04}
+//	size := Size(binary)
+//	fmt.Println(size) // 4
+//
+// Example - UTF-8 encoded text:
+//
+//	// Note: Size returns byte count, not character count
+//	utf8 := []byte("Hello, 世界")
+//	byteCount := Size(utf8)
+//	fmt.Println(byteCount) // 13 (not 9 characters)
+//
+// Example - Using in functional composition:
+//
+//	import "github.com/IBM/fp-go/v2/array"
+//
+//	slices := [][]byte{
+//	    []byte("a"),
+//	    []byte("bb"),
+//	    []byte("ccc"),
+//	}
+//
+//	// Map to get sizes
+//	sizes := array.Map(Size)(slices)
+//	// sizes: []int{1, 2, 3}
+//
+// Example - Checking if slice is empty:
+//
+//	data := []byte("test")
+//	isEmpty := Size(data) == 0
+//	fmt.Println(isEmpty) // false
+//
+// See also:
+//   - len(): Built-in function for getting slice length
+//   - ToString(): For converting byte slice to string
 func Size(as []byte) int {
 	return len(as)
 }

v2/bytes/bytes_test.go

@@ -187,6 +187,299 @@ func TestOrd(t *testing.T) {
 	})
 }
 
+// TestOrdProperties tests mathematical properties of Ord
+func TestOrdProperties(t *testing.T) {
+	t.Run("reflexivity: x == x", func(t *testing.T) {
+		testCases := [][]byte{
+			[]byte{},
+			[]byte("a"),
+			[]byte("test"),
+			[]byte{0x01, 0x02, 0x03},
+		}
+
+		for _, tc := range testCases {
+			assert.Equal(t, 0, Ord.Compare(tc, tc),
+				"Compare(%v, %v) should be 0", tc, tc)
+			assert.True(t, Ord.Equals(tc, tc),
+				"Equals(%v, %v) should be true", tc, tc)
+		}
+	})
+
+	t.Run("antisymmetry: if x <= y and y <= x then x == y", func(t *testing.T) {
+		testCases := []struct {
+			a, b []byte
+		}{
+			{[]byte("abc"), []byte("abc")},
+			{[]byte{}, []byte{}},
+			{[]byte{0x01}, []byte{0x01}},
+		}
+
+		for _, tc := range testCases {
+			cmp1 := Ord.Compare(tc.a, tc.b)
+			cmp2 := Ord.Compare(tc.b, tc.a)
+
+			if cmp1 <= 0 && cmp2 <= 0 {
+				assert.True(t, Ord.Equals(tc.a, tc.b),
+					"If %v <= %v and %v <= %v, they should be equal", tc.a, tc.b, tc.b, tc.a)
+			}
+		}
+	})
+
+	t.Run("transitivity: if x <= y and y <= z then x <= z", func(t *testing.T) {
+		x := []byte("a")
+		y := []byte("b")
+		z := []byte("c")
+
+		cmpXY := Ord.Compare(x, y)
+		cmpYZ := Ord.Compare(y, z)
+		cmpXZ := Ord.Compare(x, z)
+
+		if cmpXY <= 0 && cmpYZ <= 0 {
+			assert.True(t, cmpXZ <= 0,
+				"If %v <= %v and %v <= %v, then %v <= %v", x, y, y, z, x, z)
+		}
+	})
+
+	t.Run("totality: either x <= y or y <= x", func(t *testing.T) {
+		testCases := []struct {
+			a, b []byte
+		}{
+			{[]byte("abc"), []byte("abd")},
+			{[]byte("xyz"), []byte("abc")},
+			{[]byte{}, []byte("a")},
+			{[]byte{0x01}, []byte{0x02}},
+		}
+
+		for _, tc := range testCases {
+			cmp1 := Ord.Compare(tc.a, tc.b)
+			cmp2 := Ord.Compare(tc.b, tc.a)
+
+			assert.True(t, cmp1 <= 0 || cmp2 <= 0,
+				"Either %v <= %v or %v <= %v must be true", tc.a, tc.b, tc.b, tc.a)
+		}
+	})
+}
+
+// TestEdgeCases tests edge cases and boundary conditions
+func TestEdgeCases(t *testing.T) {
+	t.Run("very large byte slices", func(t *testing.T) {
+		large := make([]byte, 1000000)
+		for i := range large {
+			large[i] = byte(i % 256)
+		}
+
+		size := Size(large)
+		assert.Equal(t, 1000000, size)
+
+		str := ToString(large)
+		assert.Equal(t, 1000000, len(str))
+	})
+
+	t.Run("concatenating many slices", func(t *testing.T) {
+		slices := make([][]byte, 100)
+		for i := range slices {
+			slices[i] = []byte{byte(i)}
+		}
+
+		result := ConcatAll(slices...)
+		assert.Equal(t, 100, Size(result))
+	})
+
+	t.Run("null bytes in slice", func(t *testing.T) {
+		data := []byte{0x00, 0x01, 0x00, 0x02}
+		size := Size(data)
+		assert.Equal(t, 4, size)
+
+		str := ToString(data)
+		assert.Equal(t, 4, len(str))
+	})
+
+	t.Run("comparing slices with null bytes", func(t *testing.T) {
+		a := []byte{0x00, 0x01}
+		b := []byte{0x00, 0x02}
+		assert.Equal(t, -1, Ord.Compare(a, b))
+	})
+}
+
+// TestMonoidConcatPerformance tests concatenation performance characteristics
+func TestMonoidConcatPerformance(t *testing.T) {
+	t.Run("ConcatAll vs repeated Concat", func(t *testing.T) {
+		slices := [][]byte{
+			[]byte("a"),
+			[]byte("b"),
+			[]byte("c"),
+			[]byte("d"),
+			[]byte("e"),
+		}
+
+		// Using ConcatAll
+		result1 := ConcatAll(slices...)
+
+		// Using repeated Concat
+		result2 := Monoid.Empty()
+		for _, s := range slices {
+			result2 = Monoid.Concat(result2, s)
+		}
+
+		assert.Equal(t, result1, result2)
+		assert.Equal(t, []byte("abcde"), result1)
+	})
+}
+
+// TestRoundTrip tests round-trip conversions
+func TestRoundTrip(t *testing.T) {
+	t.Run("string to bytes to string", func(t *testing.T) {
+		original := "Hello, World! 世界"
+		bytes := []byte(original)
+		result := ToString(bytes)
+		assert.Equal(t, original, result)
+	})
+
+	t.Run("bytes to string to bytes", func(t *testing.T) {
+		original := []byte{0x48, 0x65, 0x6c, 0x6c, 0x6f}
+		str := ToString(original)
+		result := []byte(str)
+		assert.Equal(t, original, result)
+	})
+}
+
+// TestConcatAllVariadic tests ConcatAll with various argument counts
+func TestConcatAllVariadic(t *testing.T) {
+	t.Run("zero arguments", func(t *testing.T) {
+		result := ConcatAll()
+		assert.Equal(t, []byte{}, result)
+	})
+
+	t.Run("one argument", func(t *testing.T) {
+		result := ConcatAll([]byte("test"))
+		assert.Equal(t, []byte("test"), result)
+	})
+
+	t.Run("two arguments", func(t *testing.T) {
+		result := ConcatAll([]byte("hello"), []byte("world"))
+		assert.Equal(t, []byte("helloworld"), result)
+	})
+
+	t.Run("many arguments", func(t *testing.T) {
+		result := ConcatAll(
+			[]byte("a"),
+			[]byte("b"),
+			[]byte("c"),
+			[]byte("d"),
+			[]byte("e"),
+			[]byte("f"),
+			[]byte("g"),
+			[]byte("h"),
+			[]byte("i"),
+			[]byte("j"),
+		)
+		assert.Equal(t, []byte("abcdefghij"), result)
+	})
+}
+
+// Benchmark tests
+func BenchmarkToString(b *testing.B) {
+	data := []byte("Hello, World!")
+
+	b.Run("small", func(b *testing.B) {
+		for b.Loop() {
+			_ = ToString(data)
+		}
+	})
+
+	b.Run("large", func(b *testing.B) {
+		large := make([]byte, 10000)
+		for i := range large {
+			large[i] = byte(i % 256)
+		}
+		b.ResetTimer()
+		for b.Loop() {
+			_ = ToString(large)
+		}
+	})
+}
+
+func BenchmarkSize(b *testing.B) {
+	data := []byte("Hello, World!")
+
+	for b.Loop() {
+		_ = Size(data)
+	}
+}
+
+func BenchmarkMonoidConcat(b *testing.B) {
+	a := []byte("Hello")
+	c := []byte(" World")
+
+	b.Run("small slices", func(b *testing.B) {
+		for b.Loop() {
+			_ = Monoid.Concat(a, c)
+		}
+	})
+
+	b.Run("large slices", func(b *testing.B) {
+		large1 := make([]byte, 10000)
+		large2 := make([]byte, 10000)
+		b.ResetTimer()
+		for b.Loop() {
+			_ = Monoid.Concat(large1, large2)
+		}
+	})
+}
+
+func BenchmarkConcatAll(b *testing.B) {
+	slices := [][]byte{
+		[]byte("Hello"),
+		[]byte(" "),
+		[]byte("World"),
+		[]byte("!"),
+	}
+
+	b.Run("few slices", func(b *testing.B) {
+		for b.Loop() {
+			_ = ConcatAll(slices...)
+		}
+	})
+
+	b.Run("many slices", func(b *testing.B) {
+		many := make([][]byte, 100)
+		for i := range many {
+			many[i] = []byte{byte(i)}
+		}
+		b.ResetTimer()
+		for b.Loop() {
+			_ = ConcatAll(many...)
+		}
+	})
+}
+
+func BenchmarkOrdCompare(b *testing.B) {
+	a := []byte("abc")
+	c := []byte("abd")
+
+	b.Run("equal", func(b *testing.B) {
+		for b.Loop() {
+			_ = Ord.Compare(a, a)
+		}
+	})
+
+	b.Run("different", func(b *testing.B) {
+		for b.Loop() {
+			_ = Ord.Compare(a, c)
+		}
+	})
+
+	b.Run("large slices", func(b *testing.B) {
+		large1 := make([]byte, 10000)
+		large2 := make([]byte, 10000)
+		large2[9999] = 1
+		b.ResetTimer()
+		for b.Loop() {
+			_ = Ord.Compare(large1, large2)
+		}
+	})
+}
+
 // Example tests
 func ExampleEmpty() {
 	empty := Empty()
@@ -219,3 +512,17 @@ func ExampleConcatAll() {
 
 	// Output:
 }
+
+func ExampleMonoid_concat() {
+	result := Monoid.Concat([]byte("Hello"), []byte(" World"))
+	println(string(result)) // Hello World
+
+	// Output:
+}
+
+func ExampleOrd_compare() {
+	cmp := Ord.Compare([]byte("abc"), []byte("abd"))
+	println(cmp) // -1 (abc < abd)
+
+	// Output:
+}

v2/bytes/coverage.out

@@ -0,0 +1,4 @@
+mode: set
+github.com/IBM/fp-go/v2/bytes/bytes.go:55.21,57.2 1 1
+github.com/IBM/fp-go/v2/bytes/bytes.go:111.32,113.2 1 1
+github.com/IBM/fp-go/v2/bytes/bytes.go:175.26,177.2 1 1

v2/bytes/monoid.go

@@ -23,12 +23,219 @@ import (
 )
 
 var (
-	// monoid for byte arrays
+	// Monoid is the Monoid instance for byte slices.
+	//
+	// This Monoid combines byte slices through concatenation, with an empty
+	// byte slice as the identity element. It satisfies the monoid laws:
+	//
+	// Identity laws:
+	//   - Monoid.Concat(Monoid.Empty(), x) == x (left identity)
+	//   - Monoid.Concat(x, Monoid.Empty()) == x (right identity)
+	//
+	// Associativity law:
+	//   - Monoid.Concat(Monoid.Concat(a, b), c) == Monoid.Concat(a, Monoid.Concat(b, c))
+	//
+	// Operations:
+	//   - Empty(): Returns an empty byte slice []byte{}
+	//   - Concat(a, b []byte): Concatenates two byte slices
+	//
+	// Example - Basic concatenation:
+	//
+	//	result := Monoid.Concat([]byte("Hello"), []byte(" World"))
+	//	// result: []byte("Hello World")
+	//
+	// Example - Identity element:
+	//
+	//	empty := Monoid.Empty()
+	//	data := []byte("test")
+	//	result1 := Monoid.Concat(empty, data) // []byte("test")
+	//	result2 := Monoid.Concat(data, empty) // []byte("test")
+	//
+	// Example - Building byte buffers:
+	//
+	//	buffer := Monoid.Empty()
+	//	buffer = Monoid.Concat(buffer, []byte("Line 1\n"))
+	//	buffer = Monoid.Concat(buffer, []byte("Line 2\n"))
+	//	buffer = Monoid.Concat(buffer, []byte("Line 3\n"))
+	//
+	// Example - Associativity:
+	//
+	//	a := []byte("a")
+	//	b := []byte("b")
+	//	c := []byte("c")
+	//	left := Monoid.Concat(Monoid.Concat(a, b), c)   // []byte("abc")
+	//	right := Monoid.Concat(a, Monoid.Concat(b, c))  // []byte("abc")
+	//	// left == right
+	//
+	// See also:
+	//   - ConcatAll: For concatenating multiple byte slices at once
+	//   - Empty(): Convenience function for getting empty byte slice
 	Monoid = A.Monoid[byte]()
 
-	// ConcatAll concatenates all bytes
+	// ConcatAll efficiently concatenates multiple byte slices into a single slice.
+	//
+	// This function takes a variadic number of byte slices and combines them
+	// into a single byte slice. It pre-allocates the exact amount of memory
+	// needed, making it more efficient than repeated concatenation.
+	//
+	// Parameters:
+	//   - slices: Zero or more byte slices to concatenate
+	//
+	// Returns:
+	//   - A new byte slice containing all input slices concatenated in order
+	//
+	// Performance:
+	//
+	// ConcatAll is more efficient than using Monoid.Concat repeatedly because
+	// it calculates the total size upfront and allocates memory once, avoiding
+	// multiple allocations and copies.
+	//
+	// Example - Basic usage:
+	//
+	//	result := ConcatAll(
+	//	    []byte("Hello"),
+	//	    []byte(" "),
+	//	    []byte("World"),
+	//	)
+	//	// result: []byte("Hello World")
+	//
+	// Example - Empty input:
+	//
+	//	result := ConcatAll()
+	//	// result: []byte{}
+	//
+	// Example - Single slice:
+	//
+	//	result := ConcatAll([]byte("test"))
+	//	// result: []byte("test")
+	//
+	// Example - Building protocol messages:
+	//
+	//	import "encoding/binary"
+	//
+	//	header := []byte{0x01, 0x02}
+	//	length := make([]byte, 4)
+	//	binary.BigEndian.PutUint32(length, 100)
+	//	payload := []byte("data")
+	//	footer := []byte{0xFF}
+	//
+	//	message := ConcatAll(header, length, payload, footer)
+	//
+	// Example - With empty slices:
+	//
+	//	result := ConcatAll(
+	//	    []byte("a"),
+	//	    []byte{},
+	//	    []byte("b"),
+	//	    []byte{},
+	//	    []byte("c"),
+	//	)
+	//	// result: []byte("abc")
+	//
+	// Example - Building CSV line:
+	//
+	//	fields := [][]byte{
+	//	    []byte("John"),
+	//	    []byte("Doe"),
+	//	    []byte("30"),
+	//	}
+	//	separator := []byte(",")
+	//
+	//	// Interleave fields with separators
+	//	parts := [][]byte{
+	//	    fields[0], separator,
+	//	    fields[1], separator,
+	//	    fields[2],
+	//	}
+	//	line := ConcatAll(parts...)
+	//	// line: []byte("John,Doe,30")
+	//
+	// See also:
+	//   - Monoid.Concat: For concatenating exactly two byte slices
+	//   - bytes.Join: Standard library function for joining with separator
 	ConcatAll = A.ArrayConcatAll[byte]
 
-	// Ord implements the default ordering on bytes
+	// Ord is the Ord instance for byte slices providing lexicographic ordering.
+	//
+	// This Ord instance compares byte slices lexicographically (dictionary order),
+	// comparing bytes from left to right until a difference is found or one slice
+	// ends. It uses the standard library's bytes.Compare and bytes.Equal functions.
+	//
+	// Comparison rules:
+	//   - Compares byte-by-byte from left to right
+	//   - First differing byte determines the order
+	//   - Shorter slice is less than longer slice if all bytes match
+	//   - Empty slice is less than any non-empty slice
+	//
+	// Operations:
+	//   - Compare(a, b []byte) int: Returns -1 if a < b, 0 if a == b, 1 if a > b
+	//   - Equals(a, b []byte) bool: Returns true if slices are equal
+	//
+	// Example - Basic comparison:
+	//
+	//	cmp := Ord.Compare([]byte("abc"), []byte("abd"))
+	//	// cmp: -1 (abc < abd)
+	//
+	//	cmp = Ord.Compare([]byte("xyz"), []byte("abc"))
+	//	// cmp: 1 (xyz > abc)
+	//
+	//	cmp = Ord.Compare([]byte("test"), []byte("test"))
+	//	// cmp: 0 (equal)
+	//
+	// Example - Length differences:
+	//
+	//	cmp := Ord.Compare([]byte("ab"), []byte("abc"))
+	//	// cmp: -1 (shorter is less)
+	//
+	//	cmp = Ord.Compare([]byte("abc"), []byte("ab"))
+	//	// cmp: 1 (longer is greater)
+	//
+	// Example - Empty slices:
+	//
+	//	cmp := Ord.Compare([]byte{}, []byte("a"))
+	//	// cmp: -1 (empty is less)
+	//
+	//	cmp = Ord.Compare([]byte{}, []byte{})
+	//	// cmp: 0 (both empty)
+	//
+	// Example - Equality check:
+	//
+	//	equal := Ord.Equals([]byte("test"), []byte("test"))
+	//	// equal: true
+	//
+	//	equal = Ord.Equals([]byte("test"), []byte("Test"))
+	//	// equal: false (case-sensitive)
+	//
+	// Example - Sorting byte slices:
+	//
+	//	import "github.com/IBM/fp-go/v2/array"
+	//
+	//	data := [][]byte{
+	//	    []byte("zebra"),
+	//	    []byte("apple"),
+	//	    []byte("mango"),
+	//	}
+	//
+	//	sorted := array.Sort(Ord)(data)
+	//	// sorted: [[]byte("apple"), []byte("mango"), []byte("zebra")]
+	//
+	// Example - Binary data comparison:
+	//
+	//	cmp := Ord.Compare([]byte{0x01, 0x02}, []byte{0x01, 0x03})
+	//	// cmp: -1 (0x02 < 0x03)
+	//
+	// Example - Finding minimum:
+	//
+	//	import O "github.com/IBM/fp-go/v2/ord"
+	//
+	//	a := []byte("xyz")
+	//	b := []byte("abc")
+	//	min := O.Min(Ord)(a, b)
+	//	// min: []byte("abc")
+	//
+	// See also:
+	//   - bytes.Compare: Standard library comparison function
+	//   - bytes.Equal: Standard library equality function
+	//   - array.Sort: For sorting slices using an Ord instance
 	Ord = O.MakeOrd(bytes.Compare, bytes.Equal)
 )

v2/cli/commands.go

@@ -35,5 +35,6 @@ func Commands() []*C.Command {
 		IOCommand(),
 		IOOptionCommand(),
 		DICommand(),
+		LensCommand(),
 	}
 }

v2/cli/lens.go

@@ -0,0 +1,839 @@
+// Copyright (c) 2023 - 2025 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cli
+
+import (
+	"bytes"
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"log"
+	"os"
+	"path/filepath"
+	"reflect"
+	"strings"
+	"text/template"
+
+	C "github.com/urfave/cli/v2"
+)
+
+const (
+	keyLensDir     = "dir"
+	keyVerbose     = "verbose"
+	lensAnnotation = "fp-go:Lens"
+)
+
+var (
+	flagLensDir = &C.StringFlag{
+		Name:  keyLensDir,
+		Value: ".",
+		Usage: "Directory to scan for Go files",
+	}
+
+	flagVerbose = &C.BoolFlag{
+		Name:    keyVerbose,
+		Aliases: []string{"v"},
+		Value:   false,
+		Usage:   "Enable verbose output",
+	}
+)
+
+// structInfo holds information about a struct that needs lens generation
+type structInfo struct {
+	Name           string
+	TypeParams     string // e.g., "[T any]" or "[K comparable, V any]" - for type declarations
+	TypeParamNames string // e.g., "[T]" or "[K, V]" - for type usage in function signatures
+	Fields         []fieldInfo
+	Imports        map[string]string // package path -> alias
+}
+
+// fieldInfo holds information about a struct field
+type fieldInfo struct {
+	Name         string
+	TypeName     string
+	BaseType     string // TypeName without leading * for pointer types
+	IsOptional   bool   // true if field is a pointer or has json omitempty tag
+	IsComparable bool   // true if the type is comparable (can use ==)
+}
+
+// templateData holds data for template rendering
+type templateData struct {
+	PackageName string
+	Structs     []structInfo
+}
+
+const lensStructTemplate = `
+// {{.Name}}Lenses provides lenses for accessing fields of {{.Name}}
+type {{.Name}}Lenses{{.TypeParams}} struct {
+	// mandatory fields
+{{- range .Fields}}
+	{{.Name}} L.Lens[{{$.Name}}{{$.TypeParamNames}}, {{.TypeName}}]
+{{- end}}
+	// optional fields
+{{- range .Fields}}
+{{- if .IsComparable}}
+	{{.Name}}O LO.LensO[{{$.Name}}{{$.TypeParamNames}}, {{.TypeName}}]
+{{- end}}
+{{- end}}
+}
+
+// {{.Name}}RefLenses provides lenses for accessing fields of {{.Name}} via a reference to {{.Name}}
+type {{.Name}}RefLenses{{.TypeParams}} struct {
+	// mandatory fields
+{{- range .Fields}}
+	{{.Name}} L.Lens[*{{$.Name}}{{$.TypeParamNames}}, {{.TypeName}}]
+{{- end}}
+	// optional fields
+{{- range .Fields}}
+{{- if .IsComparable}}
+	{{.Name}}O LO.LensO[*{{$.Name}}{{$.TypeParamNames}}, {{.TypeName}}]
+{{- end}}
+{{- end}}
+}
+`
+
+const lensConstructorTemplate = `
+// Make{{.Name}}Lenses creates a new {{.Name}}Lenses with lenses for all fields
+func Make{{.Name}}Lenses{{.TypeParams}}() {{.Name}}Lenses{{.TypeParamNames}} {
+	// mandatory lenses
+{{- range .Fields}}
+	lens{{.Name}} := L.MakeLens(
+		func(s {{$.Name}}{{$.TypeParamNames}}) {{.TypeName}} { return s.{{.Name}} },
+		func(s {{$.Name}}{{$.TypeParamNames}}, v {{.TypeName}}) {{$.Name}}{{$.TypeParamNames}} { s.{{.Name}} = v; return s },
+	)
+{{- end}}
+	// optional lenses
+{{- range .Fields}}
+{{- if .IsComparable}}
+	lens{{.Name}}O := LO.FromIso[{{$.Name}}{{$.TypeParamNames}}](IO.FromZero[{{.TypeName}}]())(lens{{.Name}})
+{{- end}}
+{{- end}}
+	return {{.Name}}Lenses{{.TypeParamNames}}{
+		// mandatory lenses
+{{- range .Fields}}
+		{{.Name}}: lens{{.Name}},
+{{- end}}
+		// optional lenses
+{{- range .Fields}}
+{{- if .IsComparable}}
+		{{.Name}}O: lens{{.Name}}O,
+{{- end}}
+{{- end}}
+	}
+}
+
+// Make{{.Name}}RefLenses creates a new {{.Name}}RefLenses with lenses for all fields
+func Make{{.Name}}RefLenses{{.TypeParams}}() {{.Name}}RefLenses{{.TypeParamNames}} {
+	// mandatory lenses
+{{- range .Fields}}
+{{- if .IsComparable}}
+	lens{{.Name}} := L.MakeLensStrict(
+		func(s *{{$.Name}}{{$.TypeParamNames}}) {{.TypeName}} { return s.{{.Name}} },
+		func(s *{{$.Name}}{{$.TypeParamNames}}, v {{.TypeName}}) *{{$.Name}}{{$.TypeParamNames}} { s.{{.Name}} = v; return s },
+	)
+{{- else}}
+	lens{{.Name}} := L.MakeLensRef(
+		func(s *{{$.Name}}{{$.TypeParamNames}}) {{.TypeName}} { return s.{{.Name}} },
+		func(s *{{$.Name}}{{$.TypeParamNames}}, v {{.TypeName}}) *{{$.Name}}{{$.TypeParamNames}} { s.{{.Name}} = v; return s },
+	)
+{{- end}}
+{{- end}}
+	// optional lenses
+{{- range .Fields}}
+{{- if .IsComparable}}
+	lens{{.Name}}O := LO.FromIso[*{{$.Name}}{{$.TypeParamNames}}](IO.FromZero[{{.TypeName}}]())(lens{{.Name}})
+{{- end}}
+{{- end}}
+	return {{.Name}}RefLenses{{.TypeParamNames}}{
+		// mandatory lenses
+{{- range .Fields}}
+		{{.Name}}: lens{{.Name}},
+{{- end}}
+		// optional lenses
+{{- range .Fields}}
+{{- if .IsComparable}}
+		{{.Name}}O: lens{{.Name}}O,
+{{- end}}
+{{- end}}
+	}
+}
+`
+
+var (
+	structTmpl      *template.Template
+	constructorTmpl *template.Template
+)
+
+func init() {
+	var err error
+	structTmpl, err = template.New("struct").Parse(lensStructTemplate)
+	if err != nil {
+		panic(err)
+	}
+	constructorTmpl, err = template.New("constructor").Parse(lensConstructorTemplate)
+	if err != nil {
+		panic(err)
+	}
+}
+
+// hasLensAnnotation checks if a comment group contains the lens annotation
+func hasLensAnnotation(doc *ast.CommentGroup) bool {
+	if doc == nil {
+		return false
+	}
+	for _, comment := range doc.List {
+		if strings.Contains(comment.Text, lensAnnotation) {
+			return true
+		}
+	}
+	return false
+}
+
+// getTypeName extracts the type name from a field type expression
+func getTypeName(expr ast.Expr) string {
+	switch t := expr.(type) {
+	case *ast.Ident:
+		return t.Name
+	case *ast.StarExpr:
+		return "*" + getTypeName(t.X)
+	case *ast.ArrayType:
+		return "[]" + getTypeName(t.Elt)
+	case *ast.MapType:
+		return "map[" + getTypeName(t.Key) + "]" + getTypeName(t.Value)
+	case *ast.SelectorExpr:
+		return getTypeName(t.X) + "." + t.Sel.Name
+	case *ast.InterfaceType:
+		return "interface{}"
+	case *ast.IndexExpr:
+		// Generic type with single type parameter (Go 1.18+)
+		// e.g., Option[string]
+		return getTypeName(t.X) + "[" + getTypeName(t.Index) + "]"
+	case *ast.IndexListExpr:
+		// Generic type with multiple type parameters (Go 1.18+)
+		// e.g., Map[string, int]
+		var params []string
+		for _, index := range t.Indices {
+			params = append(params, getTypeName(index))
+		}
+		return getTypeName(t.X) + "[" + strings.Join(params, ", ") + "]"
+	default:
+		return "any"
+	}
+}
+
+// extractImports extracts package imports from a type expression
+// Returns a map of package path -> package name
+func extractImports(expr ast.Expr, imports map[string]string) {
+	switch t := expr.(type) {
+	case *ast.StarExpr:
+		extractImports(t.X, imports)
+	case *ast.ArrayType:
+		extractImports(t.Elt, imports)
+	case *ast.MapType:
+		extractImports(t.Key, imports)
+		extractImports(t.Value, imports)
+	case *ast.SelectorExpr:
+		// This is a qualified identifier like "option.Option"
+		if ident, ok := t.X.(*ast.Ident); ok {
+			// ident.Name is the package name (e.g., "option")
+			// We need to track this for import resolution
+			imports[ident.Name] = ident.Name
+		}
+	case *ast.IndexExpr:
+		// Generic type with single type parameter
+		extractImports(t.X, imports)
+		extractImports(t.Index, imports)
+	case *ast.IndexListExpr:
+		// Generic type with multiple type parameters
+		extractImports(t.X, imports)
+		for _, index := range t.Indices {
+			extractImports(index, imports)
+		}
+	}
+}
+
+// hasOmitEmpty checks if a struct tag contains json omitempty
+func hasOmitEmpty(tag *ast.BasicLit) bool {
+	if tag == nil {
+		return false
+	}
+	// Parse the struct tag
+	tagValue := strings.Trim(tag.Value, "`")
+	structTag := reflect.StructTag(tagValue)
+	jsonTag := structTag.Get("json")
+
+	// Check if omitempty is present
+	parts := strings.Split(jsonTag, ",")
+	for _, part := range parts {
+		if strings.TrimSpace(part) == "omitempty" {
+			return true
+		}
+	}
+	return false
+}
+
+// isPointerType checks if a type expression is a pointer
+func isPointerType(expr ast.Expr) bool {
+	_, ok := expr.(*ast.StarExpr)
+	return ok
+}
+
+// isComparableType checks if a type expression represents a comparable type.
+// Comparable types in Go include:
+// - Basic types (bool, numeric types, string)
+// - Pointer types
+// - Channel types
+// - Interface types
+// - Structs where all fields are comparable
+// - Arrays where the element type is comparable
+//
+// Non-comparable types include:
+// - Slices
+// - Maps
+// - Functions
+//
+// typeParams is a map of type parameter names to their constraints (e.g., "T" -> "any", "K" -> "comparable")
+func isComparableType(expr ast.Expr, typeParams map[string]string) bool {
+	switch t := expr.(type) {
+	case *ast.Ident:
+		// Check if this is a type parameter
+		if constraint, isTypeParam := typeParams[t.Name]; isTypeParam {
+			// Type parameter - check its constraint
+			return constraint == "comparable"
+		}
+
+		// Basic types and named types
+		// We assume named types are comparable unless they're known non-comparable types
+		name := t.Name
+		// Known non-comparable built-in types
+		if name == "error" {
+			// error is an interface, which is comparable
+			return true
+		}
+		// Most basic types and named types are comparable
+		// We can't determine if a custom type is comparable without type checking,
+		// so we assume it is (conservative approach)
+		return true
+	case *ast.StarExpr:
+		// Pointer types are always comparable
+		return true
+	case *ast.ArrayType:
+		// Arrays are comparable if their element type is comparable
+		if t.Len == nil {
+			// This is a slice (no length), slices are not comparable
+			return false
+		}
+		// Fixed-size array, check element type
+		return isComparableType(t.Elt, typeParams)
+	case *ast.MapType:
+		// Maps are not comparable
+		return false
+	case *ast.FuncType:
+		// Functions are not comparable
+		return false
+	case *ast.InterfaceType:
+		// Interface types are comparable
+		return true
+	case *ast.StructType:
+		// Structs are comparable if all fields are comparable
+		// We can't easily determine this without full type information,
+		// so we conservatively return false for struct literals
+		return false
+	case *ast.SelectorExpr:
+		// Qualified identifier (e.g., pkg.Type)
+		// We can't determine comparability without type information
+		// Check for known non-comparable types from standard library
+		if ident, ok := t.X.(*ast.Ident); ok {
+			pkgName := ident.Name
+			typeName := t.Sel.Name
+			// Check for known non-comparable types
+			if pkgName == "context" && typeName == "Context" {
+				// context.Context is an interface, which is comparable
+				return true
+			}
+			// For other qualified types, we assume they're comparable
+			// This is a conservative approach
+		}
+		return true
+	case *ast.IndexExpr, *ast.IndexListExpr:
+		// Generic types - we can't determine comparability without type information
+		// For common generic types, we can make educated guesses
+		var baseExpr ast.Expr
+		if idx, ok := t.(*ast.IndexExpr); ok {
+			baseExpr = idx.X
+		} else if idxList, ok := t.(*ast.IndexListExpr); ok {
+			baseExpr = idxList.X
+		}
+
+		if sel, ok := baseExpr.(*ast.SelectorExpr); ok {
+			if ident, ok := sel.X.(*ast.Ident); ok {
+				pkgName := ident.Name
+				typeName := sel.Sel.Name
+				// Check for known non-comparable generic types
+				if pkgName == "option" && typeName == "Option" {
+					// Option types are not comparable (they contain a slice internally)
+					return false
+				}
+				if pkgName == "either" && typeName == "Either" {
+					// Either types are not comparable
+					return false
+				}
+			}
+		}
+		// For other generic types, conservatively assume not comparable
+		log.Printf("Not comparable type: %v\n", t)
+		return false
+	case *ast.ChanType:
+		// Channel types are comparable
+		return true
+	default:
+		// Unknown type, conservatively assume not comparable
+		return false
+	}
+}
+
+// embeddedFieldResult holds both the field info and its AST type for import extraction
+type embeddedFieldResult struct {
+	fieldInfo fieldInfo
+	fieldType ast.Expr
+}
+
+// extractEmbeddedFields extracts fields from an embedded struct type
+// It returns a slice of embeddedFieldResult for all exported fields in the embedded struct
+// typeParamsMap contains the type parameters of the parent struct (for checking comparability)
+func extractEmbeddedFields(embedType ast.Expr, fileImports map[string]string, file *ast.File, typeParamsMap map[string]string) []embeddedFieldResult {
+	var results []embeddedFieldResult
+
+	// Get the type name of the embedded field
+	var typeName string
+	var typeIdent *ast.Ident
+
+	switch t := embedType.(type) {
+	case *ast.Ident:
+		// Direct embedded type: type MyStruct struct { EmbeddedType }
+		typeName = t.Name
+		typeIdent = t
+	case *ast.StarExpr:
+		// Pointer embedded type: type MyStruct struct { *EmbeddedType }
+		if ident, ok := t.X.(*ast.Ident); ok {
+			typeName = ident.Name
+			typeIdent = ident
+		}
+	case *ast.SelectorExpr:
+		// Qualified embedded type: type MyStruct struct { pkg.EmbeddedType }
+		// We can't easily resolve this without full type information
+		// For now, skip these
+		return results
+	}
+
+	if typeName == "" || typeIdent == nil {
+		return results
+	}
+
+	// Find the struct definition in the same file
+	var embeddedStructType *ast.StructType
+	ast.Inspect(file, func(n ast.Node) bool {
+		if ts, ok := n.(*ast.TypeSpec); ok {
+			if ts.Name.Name == typeName {
+				if st, ok := ts.Type.(*ast.StructType); ok {
+					embeddedStructType = st
+					return false
+				}
+			}
+		}
+		return true
+	})
+
+	if embeddedStructType == nil {
+		// Struct not found in this file, might be from another package
+		return results
+	}
+
+	// Extract fields from the embedded struct
+	for _, field := range embeddedStructType.Fields.List {
+		// Skip embedded fields within embedded structs (for now, to avoid infinite recursion)
+		if len(field.Names) == 0 {
+			continue
+		}
+
+		for _, name := range field.Names {
+			// Only export lenses for exported fields
+			if name.IsExported() {
+				fieldTypeName := getTypeName(field.Type)
+				isOptional := false
+				baseType := fieldTypeName
+
+				// Check if field is optional
+				if isPointerType(field.Type) {
+					isOptional = true
+					baseType = strings.TrimPrefix(fieldTypeName, "*")
+				} else if hasOmitEmpty(field.Tag) {
+					isOptional = true
+				}
+
+				// Check if the type is comparable
+				isComparable := isComparableType(field.Type, typeParamsMap)
+
+				results = append(results, embeddedFieldResult{
+					fieldInfo: fieldInfo{
+						Name:         name.Name,
+						TypeName:     fieldTypeName,
+						BaseType:     baseType,
+						IsOptional:   isOptional,
+						IsComparable: isComparable,
+					},
+					fieldType: field.Type,
+				})
+			}
+		}
+	}
+
+	return results
+}
+
+// extractTypeParams extracts type parameters from a type spec
+// Returns two strings: full params like "[T any]" and names only like "[T]"
+func extractTypeParams(typeSpec *ast.TypeSpec) (string, string) {
+	if typeSpec.TypeParams == nil || len(typeSpec.TypeParams.List) == 0 {
+		return "", ""
+	}
+
+	var params []string
+	var names []string
+	for _, field := range typeSpec.TypeParams.List {
+		for _, name := range field.Names {
+			constraint := getTypeName(field.Type)
+			params = append(params, name.Name+" "+constraint)
+			names = append(names, name.Name)
+		}
+	}
+
+	fullParams := "[" + strings.Join(params, ", ") + "]"
+	nameParams := "[" + strings.Join(names, ", ") + "]"
+	return fullParams, nameParams
+}
+
+// buildTypeParamsMap creates a map of type parameter names to their constraints
+// e.g., for "type Box[T any, K comparable]", returns {"T": "any", "K": "comparable"}
+func buildTypeParamsMap(typeSpec *ast.TypeSpec) map[string]string {
+	typeParamsMap := make(map[string]string)
+	if typeSpec.TypeParams == nil || len(typeSpec.TypeParams.List) == 0 {
+		return typeParamsMap
+	}
+
+	for _, field := range typeSpec.TypeParams.List {
+		constraint := getTypeName(field.Type)
+		for _, name := range field.Names {
+			typeParamsMap[name.Name] = constraint
+		}
+	}
+
+	return typeParamsMap
+}
+
+// parseFile parses a Go file and extracts structs with lens annotations
+func parseFile(filename string) ([]structInfo, string, error) {
+	fset := token.NewFileSet()
+	node, err := parser.ParseFile(fset, filename, nil, parser.ParseComments)
+	if err != nil {
+		return nil, "", err
+	}
+
+	var structs []structInfo
+	packageName := node.Name.Name
+
+	// Build import map: package name -> import path
+	fileImports := make(map[string]string)
+	for _, imp := range node.Imports {
+		path := strings.Trim(imp.Path.Value, `"`)
+		var name string
+		if imp.Name != nil {
+			name = imp.Name.Name
+		} else {
+			// Extract package name from path (last component)
+			parts := strings.Split(path, "/")
+			name = parts[len(parts)-1]
+		}
+		fileImports[name] = path
+	}
+
+	// First pass: collect all GenDecls with their doc comments
+	declMap := make(map[*ast.TypeSpec]*ast.CommentGroup)
+	ast.Inspect(node, func(n ast.Node) bool {
+		if gd, ok := n.(*ast.GenDecl); ok {
+			for _, spec := range gd.Specs {
+				if ts, ok := spec.(*ast.TypeSpec); ok {
+					declMap[ts] = gd.Doc
+				}
+			}
+		}
+		return true
+	})
+
+	// Second pass: process type specs
+	ast.Inspect(node, func(n ast.Node) bool {
+		// Look for type declarations
+		typeSpec, ok := n.(*ast.TypeSpec)
+		if !ok {
+			return true
+		}
+
+		// Check if it's a struct type
+		structType, ok := typeSpec.Type.(*ast.StructType)
+		if !ok {
+			return true
+		}
+
+		// Get the doc comment from our map
+		doc := declMap[typeSpec]
+		if !hasLensAnnotation(doc) {
+			return true
+		}
+
+		// Extract field information and collect imports
+		var fields []fieldInfo
+		structImports := make(map[string]string)
+
+		// Build type parameters map for this struct
+		typeParamsMap := buildTypeParamsMap(typeSpec)
+
+		for _, field := range structType.Fields.List {
+			if len(field.Names) == 0 {
+				// Embedded field - promote its fields
+				embeddedResults := extractEmbeddedFields(field.Type, fileImports, node, typeParamsMap)
+				for _, embResult := range embeddedResults {
+					// Extract imports from embedded field's type
+					fieldImports := make(map[string]string)
+					extractImports(embResult.fieldType, fieldImports)
+
+					// Resolve package names to full import paths
+					for pkgName := range fieldImports {
+						if importPath, ok := fileImports[pkgName]; ok {
+							structImports[importPath] = pkgName
+						}
+					}
+
+					fields = append(fields, embResult.fieldInfo)
+				}
+				continue
+			}
+			for _, name := range field.Names {
+				// Only export lenses for exported fields
+				if name.IsExported() {
+					typeName := getTypeName(field.Type)
+					isOptional := false
+					baseType := typeName
+					isComparable := false
+
+					// Check if field is optional:
+					// 1. Pointer types are always optional
+					// 2. Non-pointer types with json omitempty tag are optional
+					if isPointerType(field.Type) {
+						isOptional = true
+						// Strip leading * for base type
+						baseType = strings.TrimPrefix(typeName, "*")
+					} else if hasOmitEmpty(field.Tag) {
+						// Non-pointer type with omitempty is also optional
+						isOptional = true
+					}
+
+					// Check if the type is comparable (for non-optional fields)
+					// For optional fields, we don't need to check since they use LensO
+					isComparable = isComparableType(field.Type, typeParamsMap)
+					// log.Printf("field %s, type: %v, isComparable: %b\n", name, field.Type, isComparable)
+
+					// Extract imports from this field's type
+					fieldImports := make(map[string]string)
+					extractImports(field.Type, fieldImports)
+
+					// Resolve package names to full import paths
+					for pkgName := range fieldImports {
+						if importPath, ok := fileImports[pkgName]; ok {
+							structImports[importPath] = pkgName
+						}
+					}
+
+					fields = append(fields, fieldInfo{
+						Name:         name.Name,
+						TypeName:     typeName,
+						BaseType:     baseType,
+						IsOptional:   isOptional,
+						IsComparable: isComparable,
+					})
+				}
+			}
+		}
+
+		if len(fields) > 0 {
+			typeParams, typeParamNames := extractTypeParams(typeSpec)
+			structs = append(structs, structInfo{
+				Name:           typeSpec.Name.Name,
+				TypeParams:     typeParams,
+				TypeParamNames: typeParamNames,
+				Fields:         fields,
+				Imports:        structImports,
+			})
+		}
+
+		return true
+	})
+
+	return structs, packageName, nil
+}
+
+// generateLensHelpers scans a directory for Go files and generates lens code
+func generateLensHelpers(dir, filename string, verbose bool) error {
+	// Get absolute path
+	absDir, err := filepath.Abs(dir)
+	if err != nil {
+		return err
+	}
+
+	if verbose {
+		log.Printf("Scanning directory: %s", absDir)
+	}
+
+	// Find all Go files in the directory
+	files, err := filepath.Glob(filepath.Join(absDir, "*.go"))
+	if err != nil {
+		return err
+	}
+
+	if verbose {
+		log.Printf("Found %d Go files", len(files))
+	}
+
+	// Parse all files and collect structs
+	var allStructs []structInfo
+	var packageName string
+
+	for _, file := range files {
+		// Skip generated files and test files
+		if strings.HasSuffix(file, "_test.go") || strings.Contains(file, "gen.go") {
+			if verbose {
+				log.Printf("Skipping file: %s", filepath.Base(file))
+			}
+			continue
+		}
+
+		if verbose {
+			log.Printf("Parsing file: %s", filepath.Base(file))
+		}
+
+		structs, pkg, err := parseFile(file)
+		if err != nil {
+			log.Printf("Warning: failed to parse %s: %v", file, err)
+			continue
+		}
+
+		if verbose && len(structs) > 0 {
+			log.Printf("Found %d annotated struct(s) in %s", len(structs), filepath.Base(file))
+			for _, s := range structs {
+				log.Printf("  - %s (%d fields)", s.Name, len(s.Fields))
+			}
+		}
+
+		if packageName == "" {
+			packageName = pkg
+		}
+
+		allStructs = append(allStructs, structs...)
+	}
+
+	if len(allStructs) == 0 {
+		log.Printf("No structs with %s annotation found in %s", lensAnnotation, absDir)
+		return nil
+	}
+
+	// Collect all unique imports from all structs
+	allImports := make(map[string]string) // import path -> alias
+	for _, s := range allStructs {
+		for importPath, alias := range s.Imports {
+			allImports[importPath] = alias
+		}
+	}
+
+	// Create output file
+	outPath := filepath.Join(absDir, filename)
+	f, err := os.Create(filepath.Clean(outPath))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	log.Printf("Generating lens code in [%s] for package [%s] with [%d] structs ...", outPath, packageName, len(allStructs))
+
+	// Write header
+	writePackage(f, packageName)
+
+	// Write imports
+	f.WriteString("import (\n")
+	// Standard fp-go imports always needed
+	f.WriteString("\tL \"github.com/IBM/fp-go/v2/optics/lens\"\n")
+	f.WriteString("\tLO \"github.com/IBM/fp-go/v2/optics/lens/option\"\n")
+	//	f.WriteString("\tO \"github.com/IBM/fp-go/v2/option\"\n")
+	f.WriteString("\tIO \"github.com/IBM/fp-go/v2/optics/iso/option\"\n")
+
+	// Add additional imports collected from field types
+	for importPath, alias := range allImports {
+		f.WriteString("\t" + alias + " \"" + importPath + "\"\n")
+	}
+
+	f.WriteString(")\n")
+
+	// Generate lens code for each struct using templates
+	for _, s := range allStructs {
+		var buf bytes.Buffer
+
+		// Generate struct type
+		if err := structTmpl.Execute(&buf, s); err != nil {
+			return err
+		}
+
+		// Generate constructor
+		if err := constructorTmpl.Execute(&buf, s); err != nil {
+			return err
+		}
+
+		// Write to file
+		if _, err := f.Write(buf.Bytes()); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// LensCommand creates the CLI command for lens generation
+func LensCommand() *C.Command {
+	return &C.Command{
+		Name:        "lens",
+		Usage:       "generate lens code for annotated structs",
+		Description: "Scans Go files for structs annotated with 'fp-go:Lens' and generates lens types. Pointer types and non-pointer types with json omitempty tag generate LensO (optional lens).",
+		Flags: []C.Flag{
+			flagLensDir,
+			flagFilename,
+			flagVerbose,
+		},
+		Action: func(ctx *C.Context) error {
+			return generateLensHelpers(
+				ctx.String(keyLensDir),
+				ctx.String(keyFilename),
+				ctx.Bool(keyVerbose),
+			)
+		},
+	}
+}

v2/constant/const_test.go

@@ -27,7 +27,7 @@ import (
 
 func TestMap(t *testing.T) {
 	fa := Make[string, int]("foo")
-	assert.Equal(t, fa, F.Pipe1(fa, Map[string, int](utils.Double)))
+	assert.Equal(t, fa, F.Pipe1(fa, Map[string](utils.Double)))
 }
 
 func TestOf(t *testing.T) {

v2/constant/monoid.go

@@ -0,0 +1,11 @@
+package constant
+
+import (
+	"github.com/IBM/fp-go/v2/function"
+	M "github.com/IBM/fp-go/v2/monoid"
+)
+
+// Monoid returns a [M.Monoid] that returns a constant value in all operations
+func Monoid[A any](a A) M.Monoid[A] {
+	return M.MakeMonoid(function.Constant2[A, A](a), a)
+}

v2/context/ioresult/ioeither.go

@@ -13,20 +13,19 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package ioeither
+package ioresult
 
 import (
 	"context"
 
-	"github.com/IBM/fp-go/v2/either"
-	IOE "github.com/IBM/fp-go/v2/ioeither"
+	"github.com/IBM/fp-go/v2/result"
 )
 
 // withContext wraps an existing IOEither and performs a context check for cancellation before delegating
-func WithContext[A any](ctx context.Context, ma IOE.IOEither[error, A]) IOE.IOEither[error, A] {
-	return func() either.Either[error, A] {
+func WithContext[A any](ctx context.Context, ma IOResult[A]) IOResult[A] {
+	return func() Result[A] {
 		if err := context.Cause(ctx); err != nil {
-			return either.Left[A](err)
+			return result.Left[A](err)
 		}
 		return ma()
 	}

v2/context/ioresult/types.go

@@ -0,0 +1,11 @@
+package ioresult
+
+import (
+	"github.com/IBM/fp-go/v2/ioresult"
+	"github.com/IBM/fp-go/v2/result"
+)
+
+type (
+	IOResult[T any] = ioresult.IOResult[T]
+	Result[T any]   = result.Result[T]
+)

v2/context/readereither/bind.go

@@ -1,68 +0,0 @@
-// Copyright (c) 2023 - 2025 IBM Corp.
-// All rights reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package readereither
-
-import (
-	"context"
-
-	G "github.com/IBM/fp-go/v2/readereither/generic"
-)
-
-// Bind creates an empty context of type [S] to be used with the [Bind] operation
-func Do[S any](
-	empty S,
-) ReaderEither[S] {
-	return G.Do[ReaderEither[S], context.Context, error, S](empty)
-}
-
-// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
-func Bind[S1, S2, T any](
-	setter func(T) func(S1) S2,
-	f func(S1) ReaderEither[T],
-) func(ReaderEither[S1]) ReaderEither[S2] {
-	return G.Bind[ReaderEither[S1], ReaderEither[S2], ReaderEither[T], context.Context, error, S1, S2, T](setter, f)
-}
-
-// Let attaches the result of a computation to a context [S1] to produce a context [S2]
-func Let[S1, S2, T any](
-	setter func(T) func(S1) S2,
-	f func(S1) T,
-) func(ReaderEither[S1]) ReaderEither[S2] {
-	return G.Let[ReaderEither[S1], ReaderEither[S2], context.Context, error, S1, S2, T](setter, f)
-}
-
-// LetTo attaches the a value to a context [S1] to produce a context [S2]
-func LetTo[S1, S2, T any](
-	setter func(T) func(S1) S2,
-	b T,
-) func(ReaderEither[S1]) ReaderEither[S2] {
-	return G.LetTo[ReaderEither[S1], ReaderEither[S2], context.Context, error, S1, S2, T](setter, b)
-}
-
-// BindTo initializes a new state [S1] from a value [T]
-func BindTo[S1, T any](
-	setter func(T) S1,
-) func(ReaderEither[T]) ReaderEither[S1] {
-	return G.BindTo[ReaderEither[S1], ReaderEither[T], context.Context, error, S1, T](setter)
-}
-
-// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
-func ApS[S1, S2, T any](
-	setter func(T) func(S1) S2,
-	fa ReaderEither[T],
-) func(ReaderEither[S1]) ReaderEither[S2] {
-	return G.ApS[ReaderEither[S1], ReaderEither[S2], ReaderEither[T], context.Context, error, S1, S2, T](setter, fa)
-}

v2/context/readerioeither/bind.go

@@ -1,89 +0,0 @@
-// Copyright (c) 2023 - 2025 IBM Corp.
-// All rights reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package readerioeither
-
-import (
-	"github.com/IBM/fp-go/v2/internal/apply"
-	"github.com/IBM/fp-go/v2/internal/chain"
-	"github.com/IBM/fp-go/v2/internal/functor"
-)
-
-// Bind creates an empty context of type [S] to be used with the [Bind] operation
-func Do[S any](
-	empty S,
-) ReaderIOEither[S] {
-	return Of(empty)
-}
-
-// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
-func Bind[S1, S2, T any](
-	setter func(T) func(S1) S2,
-	f func(S1) ReaderIOEither[T],
-) func(ReaderIOEither[S1]) ReaderIOEither[S2] {
-	return chain.Bind(
-		Chain[S1, S2],
-		Map[T, S2],
-		setter,
-		f,
-	)
-}
-
-// Let attaches the result of a computation to a context [S1] to produce a context [S2]
-func Let[S1, S2, T any](
-	setter func(T) func(S1) S2,
-	f func(S1) T,
-) func(ReaderIOEither[S1]) ReaderIOEither[S2] {
-	return functor.Let(
-		Map[S1, S2],
-		setter,
-		f,
-	)
-}
-
-// LetTo attaches the a value to a context [S1] to produce a context [S2]
-func LetTo[S1, S2, T any](
-	setter func(T) func(S1) S2,
-	b T,
-) func(ReaderIOEither[S1]) ReaderIOEither[S2] {
-	return functor.LetTo(
-		Map[S1, S2],
-		setter,
-		b,
-	)
-}
-
-// BindTo initializes a new state [S1] from a value [T]
-func BindTo[S1, T any](
-	setter func(T) S1,
-) Operator[T, S1] {
-	return chain.BindTo(
-		Map[T, S1],
-		setter,
-	)
-}
-
-// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
-func ApS[S1, S2, T any](
-	setter func(T) func(S1) S2,
-	fa ReaderIOEither[T],
-) func(ReaderIOEither[S1]) ReaderIOEither[S2] {
-	return apply.ApS(
-		Ap[S2, T],
-		Map[S1, func(T) S2],
-		setter,
-		fa,
-	)
-}

v2/context/readerioeither/coverage.out

@@ -1,251 +0,0 @@
-mode: set
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-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:407.47,408.27 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:408.27,411.4 2 1
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:423.87,425.2 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:434.87,436.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:446.92,448.2 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:457.92,459.2 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:468.115,470.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:479.85,480.54 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:480.54,481.48 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:481.48,482.28 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:482.28,487.12 3 1
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:488.30,489.22 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:490.23,491.47 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:505.59,511.2 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:520.66,522.2 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:531.83,533.2 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:543.97,545.2 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:554.64,556.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:566.62,568.2 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:577.78,579.2 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:589.80,591.2 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:600.76,602.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:612.136,614.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:623.91,625.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:634.71,636.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/resource.go:58.151,63.2 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/semigroup.go:39.41,43.2 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/sync.go:46.78,54.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:31.89,39.2 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:48.103,56.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:65.71,67.2 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:75.112,83.2 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:92.124,100.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:108.94,110.2 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:120.95,128.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:137.92,145.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:148.106,156.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:165.74,167.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:170.118,178.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:181.115,189.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:192.127,200.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:203.97,205.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:215.95,223.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:232.92,240.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:243.106,251.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:260.74,262.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:265.115,273.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:276.127,284.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:287.118,295.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/traverse.go:304.97,306.2 1 0

v2/context/readerioeither/http/builder/builder.go

@@ -1,72 +0,0 @@
-// Copyright (c) 2023 - 2025 IBM Corp.
-// All rights reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package builder
-
-import (
-	"bytes"
-	"context"
-	"net/http"
-	"strconv"
-
-	RIOE "github.com/IBM/fp-go/v2/context/readerioeither"
-	RIOEH "github.com/IBM/fp-go/v2/context/readerioeither/http"
-	E "github.com/IBM/fp-go/v2/either"
-	F "github.com/IBM/fp-go/v2/function"
-	R "github.com/IBM/fp-go/v2/http/builder"
-	H "github.com/IBM/fp-go/v2/http/headers"
-	LZ "github.com/IBM/fp-go/v2/lazy"
-	O "github.com/IBM/fp-go/v2/option"
-)
-
-func Requester(builder *R.Builder) RIOEH.Requester {
-
-	withBody := F.Curry3(func(data []byte, url string, method string) RIOE.ReaderIOEither[*http.Request] {
-		return RIOE.TryCatch(func(ctx context.Context) func() (*http.Request, error) {
-			return func() (*http.Request, error) {
-				req, err := http.NewRequestWithContext(ctx, method, url, bytes.NewReader(data))
-				if err == nil {
-					req.Header.Set(H.ContentLength, strconv.Itoa(len(data)))
-					H.Monoid.Concat(req.Header, builder.GetHeaders())
-				}
-				return req, err
-			}
-		})
-	})
-
-	withoutBody := F.Curry2(func(url string, method string) RIOE.ReaderIOEither[*http.Request] {
-		return RIOE.TryCatch(func(ctx context.Context) func() (*http.Request, error) {
-			return func() (*http.Request, error) {
-				req, err := http.NewRequestWithContext(ctx, method, url, nil)
-				if err == nil {
-					H.Monoid.Concat(req.Header, builder.GetHeaders())
-				}
-				return req, err
-			}
-		})
-	})
-
-	return F.Pipe5(
-		builder.GetBody(),
-		O.Fold(LZ.Of(E.Of[error](withoutBody)), E.Map[error](withBody)),
-		E.Ap[func(string) RIOE.ReaderIOEither[*http.Request]](builder.GetTargetURL()),
-		E.Flap[error, RIOE.ReaderIOEither[*http.Request]](builder.GetMethod()),
-		E.GetOrElse(RIOE.Left[*http.Request]),
-		RIOE.Map(func(req *http.Request) *http.Request {
-			req.Header = H.Monoid.Concat(req.Header, builder.GetHeaders())
-			return req
-		}),
-	)
-}

v2/context/readerioeither/http/request.go

@@ -1,129 +0,0 @@
-// Copyright (c) 2023 - 2025 IBM Corp.
-// All rights reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package http
-
-import (
-	"io"
-	"net/http"
-
-	B "github.com/IBM/fp-go/v2/bytes"
-	RIOE "github.com/IBM/fp-go/v2/context/readerioeither"
-	F "github.com/IBM/fp-go/v2/function"
-	H "github.com/IBM/fp-go/v2/http"
-	IOE "github.com/IBM/fp-go/v2/ioeither"
-	IOEF "github.com/IBM/fp-go/v2/ioeither/file"
-	J "github.com/IBM/fp-go/v2/json"
-	P "github.com/IBM/fp-go/v2/pair"
-)
-
-type (
-	// Requester is a reader that constructs a request
-	Requester = RIOE.ReaderIOEither[*http.Request]
-
-	Client interface {
-		// Do can send an HTTP request considering a context
-		Do(Requester) RIOE.ReaderIOEither[*http.Response]
-	}
-
-	client struct {
-		delegate *http.Client
-		doIOE    func(*http.Request) IOE.IOEither[error, *http.Response]
-	}
-)
-
-var (
-	// MakeRequest is an eitherized version of [http.NewRequestWithContext]
-	MakeRequest = RIOE.Eitherize3(http.NewRequestWithContext)
-	makeRequest = F.Bind13of3(MakeRequest)
-
-	// specialize
-	MakeGetRequest = makeRequest("GET", nil)
-)
-
-func (client client) Do(req Requester) RIOE.ReaderIOEither[*http.Response] {
-	return F.Pipe1(
-		req,
-		RIOE.ChainIOEitherK(client.doIOE),
-	)
-}
-
-// MakeClient creates an HTTP client proxy
-func MakeClient(httpClient *http.Client) Client {
-	return client{delegate: httpClient, doIOE: IOE.Eitherize1(httpClient.Do)}
-}
-
-// ReadFullResponse sends a request,  reads the response as a byte array and represents the result as a tuple
-func ReadFullResponse(client Client) func(Requester) RIOE.ReaderIOEither[H.FullResponse] {
-	return func(req Requester) RIOE.ReaderIOEither[H.FullResponse] {
-		return F.Flow3(
-			client.Do(req),
-			IOE.ChainEitherK(H.ValidateResponse),
-			IOE.Chain(func(resp *http.Response) IOE.IOEither[error, H.FullResponse] {
-				return F.Pipe1(
-					F.Pipe3(
-						resp,
-						H.GetBody,
-						IOE.Of[error, io.ReadCloser],
-						IOEF.ReadAll[io.ReadCloser],
-					),
-					IOE.Map[error](F.Bind1st(P.MakePair[*http.Response, []byte], resp)),
-				)
-			}),
-		)
-	}
-}
-
-// ReadAll sends a request and reads the response as bytes
-func ReadAll(client Client) func(Requester) RIOE.ReaderIOEither[[]byte] {
-	return F.Flow2(
-		ReadFullResponse(client),
-		RIOE.Map(H.Body),
-	)
-}
-
-// ReadText sends a request, reads the response and represents the response as a text string
-func ReadText(client Client) func(Requester) RIOE.ReaderIOEither[string] {
-	return F.Flow2(
-		ReadAll(client),
-		RIOE.Map(B.ToString),
-	)
-}
-
-// ReadJson sends a request, reads the response and parses the response as JSON
-//
-// Deprecated: use [ReadJSON] instead
-func ReadJson[A any](client Client) func(Requester) RIOE.ReaderIOEither[A] {
-	return ReadJSON[A](client)
-}
-
-func readJSON(client Client) func(Requester) RIOE.ReaderIOEither[[]byte] {
-	return F.Flow3(
-		ReadFullResponse(client),
-		RIOE.ChainFirstEitherK(F.Flow2(
-			H.Response,
-			H.ValidateJSONResponse,
-		)),
-		RIOE.Map(H.Body),
-	)
-}
-
-// ReadJSON sends a request, reads the response and parses the response as JSON
-func ReadJSON[A any](client Client) func(Requester) RIOE.ReaderIOEither[A] {
-	return F.Flow2(
-		readJSON(client),
-		RIOE.ChainEitherK(J.Unmarshal[A]),
-	)
-}

v2/context/readerioeither/http/request_test.go

@@ -1,157 +0,0 @@
-// Copyright (c) 2023 - 2025 IBM Corp.
-// All rights reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package http
-
-import (
-	"context"
-	"fmt"
-	"testing"
-
-	H "net/http"
-
-	R "github.com/IBM/fp-go/v2/context/readerioeither"
-	E "github.com/IBM/fp-go/v2/either"
-	"github.com/IBM/fp-go/v2/errors"
-	F "github.com/IBM/fp-go/v2/function"
-	IOE "github.com/IBM/fp-go/v2/ioeither"
-	"github.com/stretchr/testify/assert"
-)
-
-type PostItem struct {
-	UserID uint   `json:"userId"`
-	Id     uint   `json:"id"`
-	Title  string `json:"title"`
-	Body   string `json:"body"`
-}
-
-func getTitle(item PostItem) string {
-	return item.Title
-}
-
-type simpleRequestBuilder struct {
-	method  string
-	url     string
-	headers H.Header
-}
-
-func requestBuilder() simpleRequestBuilder {
-	return simpleRequestBuilder{method: "GET"}
-}
-
-func (b simpleRequestBuilder) WithURL(url string) simpleRequestBuilder {
-	b.url = url
-	return b
-}
-
-func (b simpleRequestBuilder) WithHeader(key, value string) simpleRequestBuilder {
-	if b.headers == nil {
-		b.headers = make(H.Header)
-	} else {
-		b.headers = b.headers.Clone()
-	}
-	b.headers.Set(key, value)
-	return b
-}
-
-func (b simpleRequestBuilder) Build() R.ReaderIOEither[*H.Request] {
-	return func(ctx context.Context) IOE.IOEither[error, *H.Request] {
-		return IOE.TryCatchError(func() (*H.Request, error) {
-			req, err := H.NewRequestWithContext(ctx, b.method, b.url, nil)
-			if err == nil {
-				req.Header = b.headers
-			}
-			return req, err
-		})
-	}
-}
-
-func TestSendSingleRequest(t *testing.T) {
-
-	client := MakeClient(H.DefaultClient)
-
-	req1 := MakeGetRequest("https://jsonplaceholder.typicode.com/posts/1")
-
-	readItem := ReadJSON[PostItem](client)
-
-	resp1 := readItem(req1)
-
-	resE := resp1(context.TODO())()
-
-	fmt.Println(resE)
-}
-
-// setHeaderUnsafe updates a header value in a request object by mutating the request object
-func setHeaderUnsafe(key, value string) func(*H.Request) *H.Request {
-	return func(req *H.Request) *H.Request {
-		req.Header.Set(key, value)
-		return req
-	}
-}
-
-func TestSendSingleRequestWithHeaderUnsafe(t *testing.T) {
-
-	client := MakeClient(H.DefaultClient)
-
-	// this is not safe from a puristic perspective, because the map call mutates the request object
-	req1 := F.Pipe2(
-		"https://jsonplaceholder.typicode.com/posts/1",
-		MakeGetRequest,
-		R.Map(setHeaderUnsafe("Content-Type", "text/html")),
-	)
-
-	readItem := ReadJSON[PostItem](client)
-
-	resp1 := F.Pipe2(
-		req1,
-		readItem,
-		R.Map(getTitle),
-	)
-
-	res := F.Pipe1(
-		resp1(context.TODO())(),
-		E.GetOrElse(errors.ToString),
-	)
-
-	assert.Equal(t, "sunt aut facere repellat provident occaecati excepturi optio reprehenderit", res)
-}
-
-func TestSendSingleRequestWithHeaderSafe(t *testing.T) {
-
-	client := MakeClient(H.DefaultClient)
-
-	// the request builder assembles config values to construct
-	// the final http request. Each `With` step creates a copy of the settings
-	// so the flow is pure
-	request := requestBuilder().
-		WithURL("https://jsonplaceholder.typicode.com/posts/1").
-		WithHeader("Content-Type", "text/html").
-		Build()
-
-	readItem := ReadJSON[PostItem](client)
-
-	response := F.Pipe2(
-		request,
-		readItem,
-		R.Map(getTitle),
-	)
-
-	res := F.Pipe1(
-		response(context.TODO())(),
-		E.GetOrElse(errors.ToString),
-	)
-
-	assert.Equal(t, "sunt aut facere repellat provident occaecati excepturi optio reprehenderit", res)
-}

v2/context/readerioeither/reader.go

@@ -1,636 +0,0 @@
-// Copyright (c) 2023 - 2025 IBM Corp.
-// All rights reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package readerioeither
-
-import (
-	"context"
-	"time"
-
-	"github.com/IBM/fp-go/v2/either"
-	"github.com/IBM/fp-go/v2/errors"
-	"github.com/IBM/fp-go/v2/function"
-	"github.com/IBM/fp-go/v2/io"
-	"github.com/IBM/fp-go/v2/ioeither"
-	"github.com/IBM/fp-go/v2/readerioeither"
-)
-
-const (
-	// useParallel is the feature flag to control if we use the parallel or the sequential implementation of ap
-	useParallel = true
-)
-
-// FromEither converts an [Either] into a [ReaderIOEither].
-// The resulting computation ignores the context and immediately returns the Either value.
-//
-// Parameters:
-//   - e: The Either value to lift into ReaderIOEither
-//
-// Returns a ReaderIOEither that produces the given Either value.
-func FromEither[A any](e Either[A]) ReaderIOEither[A] {
-	return readerioeither.FromEither[context.Context](e)
-}
-
-// Left creates a [ReaderIOEither] that represents a failed computation with the given error.
-//
-// Parameters:
-//   - l: The error value
-//
-// Returns a ReaderIOEither that always fails with the given error.
-func Left[A any](l error) ReaderIOEither[A] {
-	return readerioeither.Left[context.Context, A](l)
-}
-
-// Right creates a [ReaderIOEither] that represents a successful computation with the given value.
-//
-// Parameters:
-//   - r: The success value
-//
-// Returns a ReaderIOEither that always succeeds with the given value.
-func Right[A any](r A) ReaderIOEither[A] {
-	return readerioeither.Right[context.Context, error](r)
-}
-
-// MonadMap transforms the success value of a [ReaderIOEither] using the provided function.
-// If the computation fails, the error is propagated unchanged.
-//
-// Parameters:
-//   - fa: The ReaderIOEither to transform
-//   - f: The transformation function
-//
-// Returns a new ReaderIOEither with the transformed value.
-func MonadMap[A, B any](fa ReaderIOEither[A], f func(A) B) ReaderIOEither[B] {
-	return readerioeither.MonadMap(fa, f)
-}
-
-// Map transforms the success value of a [ReaderIOEither] using the provided function.
-// This is the curried version of [MonadMap], useful for composition.
-//
-// Parameters:
-//   - f: The transformation function
-//
-// Returns a function that transforms a ReaderIOEither.
-func Map[A, B any](f func(A) B) Operator[A, B] {
-	return readerioeither.Map[context.Context, error](f)
-}
-
-// MonadMapTo replaces the success value of a [ReaderIOEither] with a constant value.
-// If the computation fails, the error is propagated unchanged.
-//
-// Parameters:
-//   - fa: The ReaderIOEither to transform
-//   - b: The constant value to use
-//
-// Returns a new ReaderIOEither with the constant value.
-func MonadMapTo[A, B any](fa ReaderIOEither[A], b B) ReaderIOEither[B] {
-	return readerioeither.MonadMapTo(fa, b)
-}
-
-// MapTo replaces the success value of a [ReaderIOEither] with a constant value.
-// This is the curried version of [MonadMapTo].
-//
-// Parameters:
-//   - b: The constant value to use
-//
-// Returns a function that transforms a ReaderIOEither.
-func MapTo[A, B any](b B) Operator[A, B] {
-	return readerioeither.MapTo[context.Context, error, A](b)
-}
-
-// MonadChain sequences two [ReaderIOEither] computations, where the second depends on the result of the first.
-// If the first computation fails, the second is not executed.
-//
-// Parameters:
-//   - ma: The first ReaderIOEither
-//   - f: Function that produces the second ReaderIOEither based on the first's result
-//
-// Returns a new ReaderIOEither representing the sequenced computation.
-func MonadChain[A, B any](ma ReaderIOEither[A], f func(A) ReaderIOEither[B]) ReaderIOEither[B] {
-	return readerioeither.MonadChain(ma, f)
-}
-
-// Chain sequences two [ReaderIOEither] computations, where the second depends on the result of the first.
-// This is the curried version of [MonadChain], useful for composition.
-//
-// Parameters:
-//   - f: Function that produces the second ReaderIOEither based on the first's result
-//
-// Returns a function that sequences ReaderIOEither computations.
-func Chain[A, B any](f func(A) ReaderIOEither[B]) Operator[A, B] {
-	return readerioeither.Chain(f)
-}
-
-// MonadChainFirst sequences two [ReaderIOEither] computations but returns the result of the first.
-// The second computation is executed for its side effects only.
-//
-// Parameters:
-//   - ma: The first ReaderIOEither
-//   - f: Function that produces the second ReaderIOEither
-//
-// Returns a ReaderIOEither with the result of the first computation.
-func MonadChainFirst[A, B any](ma ReaderIOEither[A], f func(A) ReaderIOEither[B]) ReaderIOEither[A] {
-	return readerioeither.MonadChainFirst(ma, f)
-}
-
-// ChainFirst sequences two [ReaderIOEither] computations but returns the result of the first.
-// This is the curried version of [MonadChainFirst].
-//
-// Parameters:
-//   - f: Function that produces the second ReaderIOEither
-//
-// Returns a function that sequences ReaderIOEither computations.
-func ChainFirst[A, B any](f func(A) ReaderIOEither[B]) Operator[A, A] {
-	return readerioeither.ChainFirst(f)
-}
-
-// Of creates a [ReaderIOEither] that always succeeds with the given value.
-// This is the same as [Right] and represents the monadic return operation.
-//
-// Parameters:
-//   - a: The value to wrap
-//
-// Returns a ReaderIOEither that always succeeds with the given value.
-func Of[A any](a A) ReaderIOEither[A] {
-	return readerioeither.Of[context.Context, error](a)
-}
-
-func withCancelCauseFunc[A any](cancel context.CancelCauseFunc, ma IOEither[A]) IOEither[A] {
-	return function.Pipe3(
-		ma,
-		ioeither.Swap[error, A],
-		ioeither.ChainFirstIOK[A](func(err error) func() any {
-			return io.FromImpure(func() { cancel(err) })
-		}),
-		ioeither.Swap[A, error],
-	)
-}
-
-// MonadApPar implements parallel applicative application for [ReaderIOEither].
-// It executes both computations in parallel and creates a sub-context that will be canceled
-// if either operation fails. This provides automatic cancellation propagation.
-//
-// Parameters:
-//   - fab: ReaderIOEither containing a function
-//   - fa: ReaderIOEither containing a value
-//
-// Returns a ReaderIOEither with the function applied to the value.
-func MonadApPar[B, A any](fab ReaderIOEither[func(A) B], fa ReaderIOEither[A]) ReaderIOEither[B] {
-	// context sensitive input
-	cfab := WithContext(fab)
-	cfa := WithContext(fa)
-
-	return func(ctx context.Context) IOEither[B] {
-		// quick check for cancellation
-		if err := context.Cause(ctx); err != nil {
-			return ioeither.Left[B](err)
-		}
-
-		return func() Either[B] {
-			// quick check for cancellation
-			if err := context.Cause(ctx); err != nil {
-				return either.Left[B](err)
-			}
-
-			// create sub-contexts for fa and fab, so they can cancel one other
-			ctxSub, cancelSub := context.WithCancelCause(ctx)
-			defer cancelSub(nil) // cancel has to be called in all paths
-
-			fabIOE := withCancelCauseFunc(cancelSub, cfab(ctxSub))
-			faIOE := withCancelCauseFunc(cancelSub, cfa(ctxSub))
-
-			return ioeither.MonadApPar(fabIOE, faIOE)()
-		}
-	}
-}
-
-// MonadAp implements applicative application for [ReaderIOEither].
-// By default, it uses parallel execution ([MonadApPar]) but can be configured to use
-// sequential execution ([MonadApSeq]) via the useParallel constant.
-//
-// Parameters:
-//   - fab: ReaderIOEither containing a function
-//   - fa: ReaderIOEither containing a value
-//
-// Returns a ReaderIOEither with the function applied to the value.
-func MonadAp[B, A any](fab ReaderIOEither[func(A) B], fa ReaderIOEither[A]) ReaderIOEither[B] {
-	// dispatch to the configured version
-	if useParallel {
-		return MonadApPar(fab, fa)
-	}
-	return MonadApSeq(fab, fa)
-}
-
-// MonadApSeq implements sequential applicative application for [ReaderIOEither].
-// It executes the function computation first, then the value computation.
-//
-// Parameters:
-//   - fab: ReaderIOEither containing a function
-//   - fa: ReaderIOEither containing a value
-//
-// Returns a ReaderIOEither with the function applied to the value.
-func MonadApSeq[B, A any](fab ReaderIOEither[func(A) B], fa ReaderIOEither[A]) ReaderIOEither[B] {
-	return readerioeither.MonadApSeq(fab, fa)
-}
-
-// Ap applies a function wrapped in a [ReaderIOEither] to a value wrapped in a ReaderIOEither.
-// This is the curried version of [MonadAp], using the default execution mode.
-//
-// Parameters:
-//   - fa: ReaderIOEither containing a value
-//
-// Returns a function that applies a ReaderIOEither function to the value.
-func Ap[B, A any](fa ReaderIOEither[A]) Operator[func(A) B, B] {
-	return function.Bind2nd(MonadAp[B, A], fa)
-}
-
-// ApSeq applies a function wrapped in a [ReaderIOEither] to a value sequentially.
-// This is the curried version of [MonadApSeq].
-//
-// Parameters:
-//   - fa: ReaderIOEither containing a value
-//
-// Returns a function that applies a ReaderIOEither function to the value sequentially.
-func ApSeq[B, A any](fa ReaderIOEither[A]) Operator[func(A) B, B] {
-	return function.Bind2nd(MonadApSeq[B, A], fa)
-}
-
-// ApPar applies a function wrapped in a [ReaderIOEither] to a value in parallel.
-// This is the curried version of [MonadApPar].
-//
-// Parameters:
-//   - fa: ReaderIOEither containing a value
-//
-// Returns a function that applies a ReaderIOEither function to the value in parallel.
-func ApPar[B, A any](fa ReaderIOEither[A]) Operator[func(A) B, B] {
-	return function.Bind2nd(MonadApPar[B, A], fa)
-}
-
-// FromPredicate creates a [ReaderIOEither] from a predicate function.
-// If the predicate returns true, the value is wrapped in Right; otherwise, Left with the error from onFalse.
-//
-// Parameters:
-//   - pred: Predicate function to test the value
-//   - onFalse: Function to generate an error when predicate fails
-//
-// Returns a function that converts a value to ReaderIOEither based on the predicate.
-func FromPredicate[A any](pred func(A) bool, onFalse func(A) error) func(A) ReaderIOEither[A] {
-	return readerioeither.FromPredicate[context.Context](pred, onFalse)
-}
-
-// OrElse provides an alternative [ReaderIOEither] computation if the first one fails.
-// The alternative is only executed if the first computation results in a Left (error).
-//
-// Parameters:
-//   - onLeft: Function that produces an alternative ReaderIOEither from the error
-//
-// Returns a function that provides fallback behavior for failed computations.
-func OrElse[A any](onLeft func(error) ReaderIOEither[A]) Operator[A, A] {
-	return readerioeither.OrElse[context.Context](onLeft)
-}
-
-// Ask returns a [ReaderIOEither] that provides access to the context.
-// This is useful for accessing the [context.Context] within a computation.
-//
-// Returns a ReaderIOEither that produces the context.
-func Ask() ReaderIOEither[context.Context] {
-	return readerioeither.Ask[context.Context, error]()
-}
-
-// MonadChainEitherK chains a function that returns an [Either] into a [ReaderIOEither] computation.
-// This is useful for integrating pure Either-returning functions into ReaderIOEither workflows.
-//
-// Parameters:
-//   - ma: The ReaderIOEither to chain from
-//   - f: Function that produces an Either
-//
-// Returns a new ReaderIOEither with the chained computation.
-func MonadChainEitherK[A, B any](ma ReaderIOEither[A], f func(A) Either[B]) ReaderIOEither[B] {
-	return readerioeither.MonadChainEitherK[context.Context](ma, f)
-}
-
-// ChainEitherK chains a function that returns an [Either] into a [ReaderIOEither] computation.
-// This is the curried version of [MonadChainEitherK].
-//
-// Parameters:
-//   - f: Function that produces an Either
-//
-// Returns a function that chains the Either-returning function.
-func ChainEitherK[A, B any](f func(A) Either[B]) func(ma ReaderIOEither[A]) ReaderIOEither[B] {
-	return readerioeither.ChainEitherK[context.Context](f)
-}
-
-// MonadChainFirstEitherK chains a function that returns an [Either] but keeps the original value.
-// The Either-returning function is executed for its validation/side effects only.
-//
-// Parameters:
-//   - ma: The ReaderIOEither to chain from
-//   - f: Function that produces an Either
-//
-// Returns a ReaderIOEither with the original value if both computations succeed.
-func MonadChainFirstEitherK[A, B any](ma ReaderIOEither[A], f func(A) Either[B]) ReaderIOEither[A] {
-	return readerioeither.MonadChainFirstEitherK[context.Context](ma, f)
-}
-
-// ChainFirstEitherK chains a function that returns an [Either] but keeps the original value.
-// This is the curried version of [MonadChainFirstEitherK].
-//
-// Parameters:
-//   - f: Function that produces an Either
-//
-// Returns a function that chains the Either-returning function.
-func ChainFirstEitherK[A, B any](f func(A) Either[B]) func(ma ReaderIOEither[A]) ReaderIOEither[A] {
-	return readerioeither.ChainFirstEitherK[context.Context](f)
-}
-
-// ChainOptionK chains a function that returns an [Option] into a [ReaderIOEither] computation.
-// If the Option is None, the provided error function is called.
-//
-// Parameters:
-//   - onNone: Function to generate an error when Option is None
-//
-// Returns a function that chains Option-returning functions into ReaderIOEither.
-func ChainOptionK[A, B any](onNone func() error) func(func(A) Option[B]) Operator[A, B] {
-	return readerioeither.ChainOptionK[context.Context, A, B](onNone)
-}
-
-// FromIOEither converts an [IOEither] into a [ReaderIOEither].
-// The resulting computation ignores the context.
-//
-// Parameters:
-//   - t: The IOEither to convert
-//
-// Returns a ReaderIOEither that executes the IOEither.
-func FromIOEither[A any](t ioeither.IOEither[error, A]) ReaderIOEither[A] {
-	return readerioeither.FromIOEither[context.Context](t)
-}
-
-// FromIO converts an [IO] into a [ReaderIOEither].
-// The IO computation always succeeds, so it's wrapped in Right.
-//
-// Parameters:
-//   - t: The IO to convert
-//
-// Returns a ReaderIOEither that executes the IO and wraps the result in Right.
-func FromIO[A any](t IO[A]) ReaderIOEither[A] {
-	return readerioeither.FromIO[context.Context, error](t)
-}
-
-// FromLazy converts a [Lazy] computation into a [ReaderIOEither].
-// The Lazy computation always succeeds, so it's wrapped in Right.
-// This is an alias for [FromIO] since Lazy and IO have the same structure.
-//
-// Parameters:
-//   - t: The Lazy computation to convert
-//
-// Returns a ReaderIOEither that executes the Lazy computation and wraps the result in Right.
-func FromLazy[A any](t Lazy[A]) ReaderIOEither[A] {
-	return readerioeither.FromIO[context.Context, error](t)
-}
-
-// Never returns a [ReaderIOEither] that blocks indefinitely until the context is canceled.
-// This is useful for creating computations that wait for external cancellation signals.
-//
-// Returns a ReaderIOEither that waits for context cancellation and returns the cancellation error.
-func Never[A any]() ReaderIOEither[A] {
-	return func(ctx context.Context) IOEither[A] {
-		return func() Either[A] {
-			<-ctx.Done()
-			return either.Left[A](context.Cause(ctx))
-		}
-	}
-}
-
-// MonadChainIOK chains a function that returns an [IO] into a [ReaderIOEither] computation.
-// The IO computation always succeeds, so it's wrapped in Right.
-//
-// Parameters:
-//   - ma: The ReaderIOEither to chain from
-//   - f: Function that produces an IO
-//
-// Returns a new ReaderIOEither with the chained IO computation.
-func MonadChainIOK[A, B any](ma ReaderIOEither[A], f func(A) IO[B]) ReaderIOEither[B] {
-	return readerioeither.MonadChainIOK(ma, f)
-}
-
-// ChainIOK chains a function that returns an [IO] into a [ReaderIOEither] computation.
-// This is the curried version of [MonadChainIOK].
-//
-// Parameters:
-//   - f: Function that produces an IO
-//
-// Returns a function that chains the IO-returning function.
-func ChainIOK[A, B any](f func(A) IO[B]) func(ma ReaderIOEither[A]) ReaderIOEither[B] {
-	return readerioeither.ChainIOK[context.Context, error](f)
-}
-
-// MonadChainFirstIOK chains a function that returns an [IO] but keeps the original value.
-// The IO computation is executed for its side effects only.
-//
-// Parameters:
-//   - ma: The ReaderIOEither to chain from
-//   - f: Function that produces an IO
-//
-// Returns a ReaderIOEither with the original value after executing the IO.
-func MonadChainFirstIOK[A, B any](ma ReaderIOEither[A], f func(A) IO[B]) ReaderIOEither[A] {
-	return readerioeither.MonadChainFirstIOK(ma, f)
-}
-
-// ChainFirstIOK chains a function that returns an [IO] but keeps the original value.
-// This is the curried version of [MonadChainFirstIOK].
-//
-// Parameters:
-//   - f: Function that produces an IO
-//
-// Returns a function that chains the IO-returning function.
-func ChainFirstIOK[A, B any](f func(A) IO[B]) func(ma ReaderIOEither[A]) ReaderIOEither[A] {
-	return readerioeither.ChainFirstIOK[context.Context, error](f)
-}
-
-// ChainIOEitherK chains a function that returns an [IOEither] into a [ReaderIOEither] computation.
-// This is useful for integrating IOEither-returning functions into ReaderIOEither workflows.
-//
-// Parameters:
-//   - f: Function that produces an IOEither
-//
-// Returns a function that chains the IOEither-returning function.
-func ChainIOEitherK[A, B any](f func(A) ioeither.IOEither[error, B]) func(ma ReaderIOEither[A]) ReaderIOEither[B] {
-	return readerioeither.ChainIOEitherK[context.Context](f)
-}
-
-// Delay creates an operation that delays execution by the specified duration.
-// The computation waits for either the delay to expire or the context to be canceled.
-//
-// Parameters:
-//   - delay: The duration to wait before executing the computation
-//
-// Returns a function that delays a ReaderIOEither computation.
-func Delay[A any](delay time.Duration) func(ma ReaderIOEither[A]) ReaderIOEither[A] {
-	return func(ma ReaderIOEither[A]) ReaderIOEither[A] {
-		return func(ctx context.Context) IOEither[A] {
-			return func() Either[A] {
-				// manage the timeout
-				timeoutCtx, cancelTimeout := context.WithTimeout(ctx, delay)
-				defer cancelTimeout()
-				// whatever comes first
-				select {
-				case <-timeoutCtx.Done():
-					return ma(ctx)()
-				case <-ctx.Done():
-					return either.Left[A](context.Cause(ctx))
-				}
-			}
-		}
-	}
-}
-
-// Timer returns the current time after waiting for the specified delay.
-// This is useful for creating time-based computations.
-//
-// Parameters:
-//   - delay: The duration to wait before returning the time
-//
-// Returns a ReaderIOEither that produces the current time after the delay.
-func Timer(delay time.Duration) ReaderIOEither[time.Time] {
-	return function.Pipe2(
-		io.Now,
-		FromIO[time.Time],
-		Delay[time.Time](delay),
-	)
-}
-
-// Defer creates a [ReaderIOEither] by lazily generating a new computation each time it's executed.
-// This is useful for creating computations that should be re-evaluated on each execution.
-//
-// Parameters:
-//   - gen: Lazy generator function that produces a ReaderIOEither
-//
-// Returns a ReaderIOEither that generates a fresh computation on each execution.
-func Defer[A any](gen Lazy[ReaderIOEither[A]]) ReaderIOEither[A] {
-	return readerioeither.Defer(gen)
-}
-
-// TryCatch wraps a function that returns a tuple (value, error) into a [ReaderIOEither].
-// This is the standard way to convert Go error-returning functions into ReaderIOEither.
-//
-// Parameters:
-//   - f: Function that takes a context and returns a function producing (value, error)
-//
-// Returns a ReaderIOEither that wraps the error-returning function.
-func TryCatch[A any](f func(context.Context) func() (A, error)) ReaderIOEither[A] {
-	return readerioeither.TryCatch(f, errors.IdentityError)
-}
-
-// MonadAlt provides an alternative [ReaderIOEither] if the first one fails.
-// The alternative is lazily evaluated only if needed.
-//
-// Parameters:
-//   - first: The primary ReaderIOEither to try
-//   - second: Lazy alternative ReaderIOEither to use if first fails
-//
-// Returns a ReaderIOEither that tries the first, then the second if first fails.
-func MonadAlt[A any](first ReaderIOEither[A], second Lazy[ReaderIOEither[A]]) ReaderIOEither[A] {
-	return readerioeither.MonadAlt(first, second)
-}
-
-// Alt provides an alternative [ReaderIOEither] if the first one fails.
-// This is the curried version of [MonadAlt].
-//
-// Parameters:
-//   - second: Lazy alternative ReaderIOEither to use if first fails
-//
-// Returns a function that provides fallback behavior.
-func Alt[A any](second Lazy[ReaderIOEither[A]]) Operator[A, A] {
-	return readerioeither.Alt(second)
-}
-
-// Memoize computes the value of the provided [ReaderIOEither] monad lazily but exactly once.
-// The context used to compute the value is the context of the first call, so do not use this
-// method if the value has a functional dependency on the content of the context.
-//
-// Parameters:
-//   - rdr: The ReaderIOEither to memoize
-//
-// Returns a ReaderIOEither that caches its result after the first execution.
-func Memoize[A any](rdr ReaderIOEither[A]) ReaderIOEither[A] {
-	return readerioeither.Memoize(rdr)
-}
-
-// Flatten converts a nested [ReaderIOEither] into a flat [ReaderIOEither].
-// This is equivalent to [MonadChain] with the identity function.
-//
-// Parameters:
-//   - rdr: The nested ReaderIOEither to flatten
-//
-// Returns a flattened ReaderIOEither.
-func Flatten[A any](rdr ReaderIOEither[ReaderIOEither[A]]) ReaderIOEither[A] {
-	return readerioeither.Flatten(rdr)
-}
-
-// MonadFlap applies a value to a function wrapped in a [ReaderIOEither].
-// This is the reverse of [MonadAp], useful in certain composition scenarios.
-//
-// Parameters:
-//   - fab: ReaderIOEither containing a function
-//   - a: The value to apply to the function
-//
-// Returns a ReaderIOEither with the function applied to the value.
-func MonadFlap[B, A any](fab ReaderIOEither[func(A) B], a A) ReaderIOEither[B] {
-	return readerioeither.MonadFlap(fab, a)
-}
-
-// Flap applies a value to a function wrapped in a [ReaderIOEither].
-// This is the curried version of [MonadFlap].
-//
-// Parameters:
-//   - a: The value to apply to the function
-//
-// Returns a function that applies the value to a ReaderIOEither function.
-func Flap[B, A any](a A) Operator[func(A) B, B] {
-	return readerioeither.Flap[context.Context, error, B](a)
-}
-
-// Fold handles both success and error cases of a [ReaderIOEither] by providing handlers for each.
-// Both handlers return ReaderIOEither, allowing for further composition.
-//
-// Parameters:
-//   - onLeft: Handler for error case
-//   - onRight: Handler for success case
-//
-// Returns a function that folds a ReaderIOEither into a new ReaderIOEither.
-func Fold[A, B any](onLeft func(error) ReaderIOEither[B], onRight func(A) ReaderIOEither[B]) Operator[A, B] {
-	return readerioeither.Fold(onLeft, onRight)
-}
-
-// GetOrElse extracts the value from a [ReaderIOEither], providing a default via a function if it fails.
-// The result is a [ReaderIO] that always succeeds.
-//
-// Parameters:
-//   - onLeft: Function to provide a default value from the error
-//
-// Returns a function that converts a ReaderIOEither to a ReaderIO.
-func GetOrElse[A any](onLeft func(error) ReaderIO[A]) func(ReaderIOEither[A]) ReaderIO[A] {
-	return readerioeither.GetOrElse(onLeft)
-}
-
-// OrLeft transforms the error of a [ReaderIOEither] using the provided function.
-// The success value is left unchanged.
-//
-// Parameters:
-//   - onLeft: Function to transform the error
-//
-// Returns a function that transforms the error of a ReaderIOEither.
-func OrLeft[A any](onLeft func(error) ReaderIO[error]) Operator[A, A] {
-	return readerioeither.OrLeft[A](onLeft)
-}

v2/context/readerioeither/reader_extended_test.go

@@ -1,532 +0,0 @@
-// Copyright (c) 2023 - 2025 IBM Corp.
-// All rights reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package readerioeither
-
-import (
-	"context"
-	"errors"
-	"fmt"
-	"testing"
-	"time"
-
-	E "github.com/IBM/fp-go/v2/either"
-	O "github.com/IBM/fp-go/v2/option"
-	"github.com/stretchr/testify/assert"
-)
-
-func TestFromEither(t *testing.T) {
-	ctx := context.Background()
-
-	// Test with Right
-	rightVal := E.Right[error](42)
-	result := FromEither(rightVal)(ctx)()
-	assert.Equal(t, E.Right[error](42), result)
-
-	// Test with Left
-	err := errors.New("test error")
-	leftVal := E.Left[int](err)
-	result = FromEither(leftVal)(ctx)()
-	assert.Equal(t, E.Left[int](err), result)
-}
-
-func TestLeftRight(t *testing.T) {
-	ctx := context.Background()
-
-	// Test Left
-	err := errors.New("test error")
-	result := Left[int](err)(ctx)()
-	assert.True(t, E.IsLeft(result))
-
-	// Test Right
-	result = Right(42)(ctx)()
-	assert.True(t, E.IsRight(result))
-	val, _ := E.Unwrap(result)
-	assert.Equal(t, 42, val)
-}
-
-func TestOf(t *testing.T) {
-	ctx := context.Background()
-	result := Of(42)(ctx)()
-	assert.Equal(t, E.Right[error](42), result)
-}
-
-func TestMonadMap(t *testing.T) {
-	ctx := context.Background()
-
-	// Test with Right
-	result := MonadMap(Right(42), func(x int) int { return x * 2 })(ctx)()
-	assert.Equal(t, E.Right[error](84), result)
-
-	// Test with Left
-	err := errors.New("test error")
-	result = MonadMap(Left[int](err), func(x int) int { return x * 2 })(ctx)()
-	assert.Equal(t, E.Left[int](err), result)
-}
-
-func TestMonadMapTo(t *testing.T) {
-	ctx := context.Background()
-
-	// Test with Right
-	result := MonadMapTo(Right(42), "hello")(ctx)()
-	assert.Equal(t, E.Right[error]("hello"), result)
-
-	// Test with Left
-	err := errors.New("test error")
-	result = MonadMapTo(Left[int](err), "hello")(ctx)()
-	assert.Equal(t, E.Left[string](err), result)
-}
-
-func TestMonadChain(t *testing.T) {
-	ctx := context.Background()
-
-	// Test with Right
-	result := MonadChain(Right(42), func(x int) ReaderIOEither[int] {
-		return Right(x * 2)
-	})(ctx)()
-	assert.Equal(t, E.Right[error](84), result)
-
-	// Test with Left
-	err := errors.New("test error")
-	result = MonadChain(Left[int](err), func(x int) ReaderIOEither[int] {
-		return Right(x * 2)
-	})(ctx)()
-	assert.Equal(t, E.Left[int](err), result)
-
-	// Test where function returns Left
-	result = MonadChain(Right(42), func(x int) ReaderIOEither[int] {
-		return Left[int](errors.New("chain error"))
-	})(ctx)()
-	assert.True(t, E.IsLeft(result))
-}
-
-func TestMonadChainFirst(t *testing.T) {
-	ctx := context.Background()
-
-	// Test with Right
-	result := MonadChainFirst(Right(42), func(x int) ReaderIOEither[string] {
-		return Right("ignored")
-	})(ctx)()
-	assert.Equal(t, E.Right[error](42), result)
-
-	// Test with Left in first
-	err := errors.New("test error")
-	result = MonadChainFirst(Left[int](err), func(x int) ReaderIOEither[string] {
-		return Right("ignored")
-	})(ctx)()
-	assert.Equal(t, E.Left[int](err), result)
-
-	// Test with Left in second
-	result = MonadChainFirst(Right(42), func(x int) ReaderIOEither[string] {
-		return Left[string](errors.New("chain error"))
-	})(ctx)()
-	assert.True(t, E.IsLeft(result))
-}
-
-func TestMonadApSeq(t *testing.T) {
-	ctx := context.Background()
-
-	// Test with both Right
-	fct := Right(func(x int) int { return x * 2 })
-	val := Right(42)
-	result := MonadApSeq(fct, val)(ctx)()
-	assert.Equal(t, E.Right[error](84), result)
-
-	// Test with Left function
-	err := errors.New("function error")
-	fct = Left[func(int) int](err)
-	result = MonadApSeq(fct, val)(ctx)()
-	assert.Equal(t, E.Left[int](err), result)
-
-	// Test with Left value
-	fct = Right(func(x int) int { return x * 2 })
-	err = errors.New("value error")
-	val = Left[int](err)
-	result = MonadApSeq(fct, val)(ctx)()
-	assert.Equal(t, E.Left[int](err), result)
-}
-
-func TestMonadApPar(t *testing.T) {
-	ctx := context.Background()
-
-	// Test with both Right
-	fct := Right(func(x int) int { return x * 2 })
-	val := Right(42)
-	result := MonadApPar(fct, val)(ctx)()
-	assert.Equal(t, E.Right[error](84), result)
-}
-
-func TestFromPredicate(t *testing.T) {
-	ctx := context.Background()
-
-	pred := func(x int) bool { return x > 0 }
-	onFalse := func(x int) error { return fmt.Errorf("value %d is not positive", x) }
-
-	// Test with predicate true
-	result := FromPredicate(pred, onFalse)(42)(ctx)()
-	assert.Equal(t, E.Right[error](42), result)
-
-	// Test with predicate false
-	result = FromPredicate(pred, onFalse)(-1)(ctx)()
-	assert.True(t, E.IsLeft(result))
-}
-
-func TestAsk(t *testing.T) {
-	ctx := context.WithValue(context.Background(), "key", "value")
-	result := Ask()(ctx)()
-	assert.True(t, E.IsRight(result))
-	retrievedCtx, _ := E.Unwrap(result)
-	assert.Equal(t, "value", retrievedCtx.Value("key"))
-}
-
-func TestMonadChainEitherK(t *testing.T) {
-	ctx := context.Background()
-
-	// Test with Right
-	result := MonadChainEitherK(Right(42), func(x int) E.Either[error, int] {
-		return E.Right[error](x * 2)
-	})(ctx)()
-	assert.Equal(t, E.Right[error](84), result)
-
-	// Test with Left in Either
-	result = MonadChainEitherK(Right(42), func(x int) E.Either[error, int] {
-		return E.Left[int](errors.New("either error"))
-	})(ctx)()
-	assert.True(t, E.IsLeft(result))
-}
-
-func TestMonadChainFirstEitherK(t *testing.T) {
-	ctx := context.Background()
-
-	// Test with Right
-	result := MonadChainFirstEitherK(Right(42), func(x int) E.Either[error, string] {
-		return E.Right[error]("ignored")
-	})(ctx)()
-	assert.Equal(t, E.Right[error](42), result)
-
-	// Test with Left in Either
-	result = MonadChainFirstEitherK(Right(42), func(x int) E.Either[error, string] {
-		return E.Left[string](errors.New("either error"))
-	})(ctx)()
-	assert.True(t, E.IsLeft(result))
-}
-
-func TestChainOptionKFunc(t *testing.T) {
-	ctx := context.Background()
-
-	onNone := func() error { return errors.New("none error") }
-
-	// Test with Some
-	chainFunc := ChainOptionK[int, int](onNone)
-	result := chainFunc(func(x int) O.Option[int] {
-		return O.Some(x * 2)
-	})(Right(42))(ctx)()
-	assert.Equal(t, E.Right[error](84), result)
-
-	// Test with None
-	result = chainFunc(func(x int) O.Option[int] {
-		return O.None[int]()
-	})(Right(42))(ctx)()
-	assert.True(t, E.IsLeft(result))
-}
-
-func TestFromIOEither(t *testing.T) {
-	ctx := context.Background()
-
-	// Test with Right
-	ioe := func() E.Either[error, int] {
-		return E.Right[error](42)
-	}
-	result := FromIOEither(ioe)(ctx)()
-	assert.Equal(t, E.Right[error](42), result)
-
-	// Test with Left
-	err := errors.New("test error")
-	ioe = func() E.Either[error, int] {
-		return E.Left[int](err)
-	}
-	result = FromIOEither(ioe)(ctx)()
-	assert.Equal(t, E.Left[int](err), result)
-}
-
-func TestFromIO(t *testing.T) {
-	ctx := context.Background()
-
-	io := func() int { return 42 }
-	result := FromIO(io)(ctx)()
-	assert.Equal(t, E.Right[error](42), result)
-}
-
-func TestFromLazy(t *testing.T) {
-	ctx := context.Background()
-
-	lazy := func() int { return 42 }
-	result := FromLazy(lazy)(ctx)()
-	assert.Equal(t, E.Right[error](42), result)
-}
-
-func TestNeverWithCancel(t *testing.T) {
-	ctx, cancel := context.WithCancel(context.Background())
-
-	// Start Never in a goroutine
-	done := make(chan E.Either[error, int])
-	go func() {
-		done <- Never[int]()(ctx)()
-	}()
-
-	// Cancel the context
-	cancel()
-
-	// Should receive cancellation error
-	result := <-done
-	assert.True(t, E.IsLeft(result))
-}
-
-func TestMonadChainIOK(t *testing.T) {
-	ctx := context.Background()
-
-	// Test with Right
-	result := MonadChainIOK(Right(42), func(x int) func() int {
-		return func() int { return x * 2 }
-	})(ctx)()
-	assert.Equal(t, E.Right[error](84), result)
-}
-
-func TestMonadChainFirstIOK(t *testing.T) {
-	ctx := context.Background()
-
-	// Test with Right
-	result := MonadChainFirstIOK(Right(42), func(x int) func() string {
-		return func() string { return "ignored" }
-	})(ctx)()
-	assert.Equal(t, E.Right[error](42), result)
-}
-
-func TestDelayFunc(t *testing.T) {
-	ctx := context.Background()
-	delay := 100 * time.Millisecond
-
-	start := time.Now()
-	delayFunc := Delay[int](delay)
-	result := delayFunc(Right(42))(ctx)()
-	elapsed := time.Since(start)
-
-	assert.True(t, E.IsRight(result))
-	assert.GreaterOrEqual(t, elapsed, delay)
-}
-
-func TestDefer(t *testing.T) {
-	ctx := context.Background()
-	count := 0
-
-	gen := func() ReaderIOEither[int] {
-		count++
-		return Right(count)
-	}
-
-	deferred := Defer(gen)
-
-	// First call
-	result1 := deferred(ctx)()
-	assert.Equal(t, E.Right[error](1), result1)
-
-	// Second call should generate new value
-	result2 := deferred(ctx)()
-	assert.Equal(t, E.Right[error](2), result2)
-}
-
-func TestTryCatch(t *testing.T) {
-	ctx := context.Background()
-
-	// Test success
-	result := TryCatch(func(ctx context.Context) func() (int, error) {
-		return func() (int, error) {
-			return 42, nil
-		}
-	})(ctx)()
-	assert.Equal(t, E.Right[error](42), result)
-
-	// Test error
-	err := errors.New("test error")
-	result = TryCatch(func(ctx context.Context) func() (int, error) {
-		return func() (int, error) {
-			return 0, err
-		}
-	})(ctx)()
-	assert.Equal(t, E.Left[int](err), result)
-}
-
-func TestMonadAlt(t *testing.T) {
-	ctx := context.Background()
-
-	// Test with Right (alternative not called)
-	result := MonadAlt(Right(42), func() ReaderIOEither[int] {
-		return Right(99)
-	})(ctx)()
-	assert.Equal(t, E.Right[error](42), result)
-
-	// Test with Left (alternative called)
-	err := errors.New("test error")
-	result = MonadAlt(Left[int](err), func() ReaderIOEither[int] {
-		return Right(99)
-	})(ctx)()
-	assert.Equal(t, E.Right[error](99), result)
-}
-
-func TestMemoize(t *testing.T) {
-	ctx := context.Background()
-	count := 0
-
-	rdr := Memoize(FromLazy(func() int {
-		count++
-		return count
-	}))
-
-	// First call
-	result1 := rdr(ctx)()
-	assert.Equal(t, E.Right[error](1), result1)
-
-	// Second call should return memoized value
-	result2 := rdr(ctx)()
-	assert.Equal(t, E.Right[error](1), result2)
-}
-
-func TestFlatten(t *testing.T) {
-	ctx := context.Background()
-
-	nested := Right(Right(42))
-	result := Flatten(nested)(ctx)()
-	assert.Equal(t, E.Right[error](42), result)
-}
-
-func TestMonadFlap(t *testing.T) {
-	ctx := context.Background()
-	fab := Right(func(x int) int { return x * 2 })
-	result := MonadFlap(fab, 42)(ctx)()
-	assert.Equal(t, E.Right[error](84), result)
-}
-
-func TestWithContext(t *testing.T) {
-	// Test with non-canceled context
-	ctx := context.Background()
-	result := WithContext(Right(42))(ctx)()
-	assert.Equal(t, E.Right[error](42), result)
-
-	// Test with canceled context
-	ctx, cancel := context.WithCancel(context.Background())
-	cancel()
-	result = WithContext(Right(42))(ctx)()
-	assert.True(t, E.IsLeft(result))
-}
-
-func TestMonadAp(t *testing.T) {
-	ctx := context.Background()
-
-	// Test with both Right
-	fct := Right(func(x int) int { return x * 2 })
-	val := Right(42)
-	result := MonadAp(fct, val)(ctx)()
-	assert.Equal(t, E.Right[error](84), result)
-}
-
-// Test traverse functions
-func TestSequenceArray(t *testing.T) {
-	ctx := context.Background()
-
-	// Test with all Right
-	arr := []ReaderIOEither[int]{Right(1), Right(2), Right(3)}
-	result := SequenceArray(arr)(ctx)()
-	assert.True(t, E.IsRight(result))
-	vals, _ := E.Unwrap(result)
-	assert.Equal(t, []int{1, 2, 3}, vals)
-
-	// Test with one Left
-	err := errors.New("test error")
-	arr = []ReaderIOEither[int]{Right(1), Left[int](err), Right(3)}
-	result = SequenceArray(arr)(ctx)()
-	assert.True(t, E.IsLeft(result))
-}
-
-func TestTraverseArray(t *testing.T) {
-	ctx := context.Background()
-
-	// Test transformation
-	arr := []int{1, 2, 3}
-	result := TraverseArray(func(x int) ReaderIOEither[int] {
-		return Right(x * 2)
-	})(arr)(ctx)()
-	assert.True(t, E.IsRight(result))
-	vals, _ := E.Unwrap(result)
-	assert.Equal(t, []int{2, 4, 6}, vals)
-}
-
-func TestSequenceRecord(t *testing.T) {
-	ctx := context.Background()
-
-	// Test with all Right
-	rec := map[string]ReaderIOEither[int]{
-		"a": Right(1),
-		"b": Right(2),
-	}
-	result := SequenceRecord(rec)(ctx)()
-	assert.True(t, E.IsRight(result))
-	vals, _ := E.Unwrap(result)
-	assert.Equal(t, 1, vals["a"])
-	assert.Equal(t, 2, vals["b"])
-}
-
-func TestTraverseRecord(t *testing.T) {
-	ctx := context.Background()
-
-	// Test transformation
-	rec := map[string]int{"a": 1, "b": 2}
-	result := TraverseRecord[string](func(x int) ReaderIOEither[int] {
-		return Right(x * 2)
-	})(rec)(ctx)()
-	assert.True(t, E.IsRight(result))
-	vals, _ := E.Unwrap(result)
-	assert.Equal(t, 2, vals["a"])
-	assert.Equal(t, 4, vals["b"])
-}
-
-// Test monoid functions
-func TestAltSemigroup(t *testing.T) {
-	ctx := context.Background()
-
-	sg := AltSemigroup[int]()
-
-	// Test with Right (first succeeds)
-	result := sg.Concat(Right(42), Right(99))(ctx)()
-	assert.Equal(t, E.Right[error](42), result)
-
-	// Test with Left then Right (fallback)
-	err := errors.New("test error")
-	result = sg.Concat(Left[int](err), Right(99))(ctx)()
-	assert.Equal(t, E.Right[error](99), result)
-}
-
-// Test Do notation
-func TestDo(t *testing.T) {
-	ctx := context.Background()
-
-	type State struct {
-		Value int
-	}
-
-	result := Do(State{Value: 42})(ctx)()
-	assert.True(t, E.IsRight(result))
-	state, _ := E.Unwrap(result)
-	assert.Equal(t, 42, state.Value)
-}

v2/context/readerioeither/traverse.go

@@ -1,306 +0,0 @@
-// Copyright (c) 2023 - 2025 IBM Corp.
-// All rights reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package readerioeither
-
-import (
-	"github.com/IBM/fp-go/v2/function"
-	"github.com/IBM/fp-go/v2/internal/array"
-	"github.com/IBM/fp-go/v2/internal/record"
-)
-
-// TraverseArray transforms an array [[]A] into [[]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[[]B]].
-// This uses the default applicative behavior (parallel or sequential based on useParallel flag).
-//
-// Parameters:
-//   - f: Function that transforms each element into a ReaderIOEither
-//
-// Returns a function that transforms an array into a ReaderIOEither of an array.
-func TraverseArray[A, B any](f func(A) ReaderIOEither[B]) func([]A) ReaderIOEither[[]B] {
-	return array.Traverse[[]A](
-		Of[[]B],
-		Map[[]B, func(B) []B],
-		Ap[[]B, B],
-
-		f,
-	)
-}
-
-// TraverseArrayWithIndex transforms an array [[]A] into [[]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[[]B]].
-// The transformation function receives both the index and the element.
-//
-// Parameters:
-//   - f: Function that transforms each element with its index into a ReaderIOEither
-//
-// Returns a function that transforms an array into a ReaderIOEither of an array.
-func TraverseArrayWithIndex[A, B any](f func(int, A) ReaderIOEither[B]) func([]A) ReaderIOEither[[]B] {
-	return array.TraverseWithIndex[[]A](
-		Of[[]B],
-		Map[[]B, func(B) []B],
-		Ap[[]B, B],
-
-		f,
-	)
-}
-
-// SequenceArray converts a homogeneous sequence of ReaderIOEither into a ReaderIOEither of sequence.
-// This is equivalent to TraverseArray with the identity function.
-//
-// Parameters:
-//   - ma: Array of ReaderIOEither values
-//
-// Returns a ReaderIOEither containing an array of values.
-func SequenceArray[A any](ma []ReaderIOEither[A]) ReaderIOEither[[]A] {
-	return TraverseArray(function.Identity[ReaderIOEither[A]])(ma)
-}
-
-// TraverseRecord transforms a record [map[K]A] into [map[K]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[map[K]B]].
-//
-// Parameters:
-//   - f: Function that transforms each value into a ReaderIOEither
-//
-// Returns a function that transforms a map into a ReaderIOEither of a map.
-func TraverseRecord[K comparable, A, B any](f func(A) ReaderIOEither[B]) func(map[K]A) ReaderIOEither[map[K]B] {
-	return record.Traverse[map[K]A](
-		Of[map[K]B],
-		Map[map[K]B, func(B) map[K]B],
-		Ap[map[K]B, B],
-
-		f,
-	)
-}
-
-// TraverseRecordWithIndex transforms a record [map[K]A] into [map[K]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[map[K]B]].
-// The transformation function receives both the key and the value.
-//
-// Parameters:
-//   - f: Function that transforms each key-value pair into a ReaderIOEither
-//
-// Returns a function that transforms a map into a ReaderIOEither of a map.
-func TraverseRecordWithIndex[K comparable, A, B any](f func(K, A) ReaderIOEither[B]) func(map[K]A) ReaderIOEither[map[K]B] {
-	return record.TraverseWithIndex[map[K]A](
-		Of[map[K]B],
-		Map[map[K]B, func(B) map[K]B],
-		Ap[map[K]B, B],
-
-		f,
-	)
-}
-
-// SequenceRecord converts a homogeneous map of ReaderIOEither into a ReaderIOEither of map.
-//
-// Parameters:
-//   - ma: Map of ReaderIOEither values
-//
-// Returns a ReaderIOEither containing a map of values.
-func SequenceRecord[K comparable, A any](ma map[K]ReaderIOEither[A]) ReaderIOEither[map[K]A] {
-	return TraverseRecord[K](function.Identity[ReaderIOEither[A]])(ma)
-}
-
-// MonadTraverseArraySeq transforms an array [[]A] into [[]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[[]B]].
-// This explicitly uses sequential execution.
-//
-// Parameters:
-//   - as: The array to traverse
-//   - f: Function that transforms each element into a ReaderIOEither
-//
-// Returns a ReaderIOEither containing an array of transformed values.
-func MonadTraverseArraySeq[A, B any](as []A, f func(A) ReaderIOEither[B]) ReaderIOEither[[]B] {
-	return array.MonadTraverse[[]A](
-		Of[[]B],
-		Map[[]B, func(B) []B],
-		ApSeq[[]B, B],
-		as,
-		f,
-	)
-}
-
-// TraverseArraySeq transforms an array [[]A] into [[]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[[]B]].
-// This is the curried version of [MonadTraverseArraySeq] with sequential execution.
-//
-// Parameters:
-//   - f: Function that transforms each element into a ReaderIOEither
-//
-// Returns a function that transforms an array into a ReaderIOEither of an array.
-func TraverseArraySeq[A, B any](f func(A) ReaderIOEither[B]) func([]A) ReaderIOEither[[]B] {
-	return array.Traverse[[]A](
-		Of[[]B],
-		Map[[]B, func(B) []B],
-		ApSeq[[]B, B],
-
-		f,
-	)
-}
-
-// TraverseArrayWithIndexSeq uses transforms an array [[]A] into [[]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[[]B]]
-func TraverseArrayWithIndexSeq[A, B any](f func(int, A) ReaderIOEither[B]) func([]A) ReaderIOEither[[]B] {
-	return array.TraverseWithIndex[[]A](
-		Of[[]B],
-		Map[[]B, func(B) []B],
-		ApSeq[[]B, B],
-
-		f,
-	)
-}
-
-// SequenceArraySeq converts a homogeneous sequence of ReaderIOEither into a ReaderIOEither of sequence.
-// This explicitly uses sequential execution.
-//
-// Parameters:
-//   - ma: Array of ReaderIOEither values
-//
-// Returns a ReaderIOEither containing an array of values.
-func SequenceArraySeq[A any](ma []ReaderIOEither[A]) ReaderIOEither[[]A] {
-	return MonadTraverseArraySeq(ma, function.Identity[ReaderIOEither[A]])
-}
-
-// MonadTraverseRecordSeq uses transforms a record [map[K]A] into [map[K]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[map[K]B]]
-func MonadTraverseRecordSeq[K comparable, A, B any](as map[K]A, f func(A) ReaderIOEither[B]) ReaderIOEither[map[K]B] {
-	return record.MonadTraverse[map[K]A](
-		Of[map[K]B],
-		Map[map[K]B, func(B) map[K]B],
-		ApSeq[map[K]B, B],
-		as,
-		f,
-	)
-}
-
-// TraverseRecordSeq uses transforms a record [map[K]A] into [map[K]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[map[K]B]]
-func TraverseRecordSeq[K comparable, A, B any](f func(A) ReaderIOEither[B]) func(map[K]A) ReaderIOEither[map[K]B] {
-	return record.Traverse[map[K]A](
-		Of[map[K]B],
-		Map[map[K]B, func(B) map[K]B],
-		ApSeq[map[K]B, B],
-
-		f,
-	)
-}
-
-// TraverseRecordWithIndexSeq uses transforms a record [map[K]A] into [map[K]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[map[K]B]]
-func TraverseRecordWithIndexSeq[K comparable, A, B any](f func(K, A) ReaderIOEither[B]) func(map[K]A) ReaderIOEither[map[K]B] {
-	return record.TraverseWithIndex[map[K]A](
-		Of[map[K]B],
-		Map[map[K]B, func(B) map[K]B],
-		ApSeq[map[K]B, B],
-
-		f,
-	)
-}
-
-// SequenceRecordSeq converts a homogeneous sequence of either into an either of sequence
-func SequenceRecordSeq[K comparable, A any](ma map[K]ReaderIOEither[A]) ReaderIOEither[map[K]A] {
-	return MonadTraverseRecordSeq(ma, function.Identity[ReaderIOEither[A]])
-}
-
-// MonadTraverseArrayPar transforms an array [[]A] into [[]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[[]B]].
-// This explicitly uses parallel execution.
-//
-// Parameters:
-//   - as: The array to traverse
-//   - f: Function that transforms each element into a ReaderIOEither
-//
-// Returns a ReaderIOEither containing an array of transformed values.
-func MonadTraverseArrayPar[A, B any](as []A, f func(A) ReaderIOEither[B]) ReaderIOEither[[]B] {
-	return array.MonadTraverse[[]A](
-		Of[[]B],
-		Map[[]B, func(B) []B],
-		ApPar[[]B, B],
-		as,
-		f,
-	)
-}
-
-// TraverseArrayPar transforms an array [[]A] into [[]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[[]B]].
-// This is the curried version of [MonadTraverseArrayPar] with parallel execution.
-//
-// Parameters:
-//   - f: Function that transforms each element into a ReaderIOEither
-//
-// Returns a function that transforms an array into a ReaderIOEither of an array.
-func TraverseArrayPar[A, B any](f func(A) ReaderIOEither[B]) func([]A) ReaderIOEither[[]B] {
-	return array.Traverse[[]A](
-		Of[[]B],
-		Map[[]B, func(B) []B],
-		ApPar[[]B, B],
-
-		f,
-	)
-}
-
-// TraverseArrayWithIndexPar uses transforms an array [[]A] into [[]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[[]B]]
-func TraverseArrayWithIndexPar[A, B any](f func(int, A) ReaderIOEither[B]) func([]A) ReaderIOEither[[]B] {
-	return array.TraverseWithIndex[[]A](
-		Of[[]B],
-		Map[[]B, func(B) []B],
-		ApPar[[]B, B],
-
-		f,
-	)
-}
-
-// SequenceArrayPar converts a homogeneous sequence of ReaderIOEither into a ReaderIOEither of sequence.
-// This explicitly uses parallel execution.
-//
-// Parameters:
-//   - ma: Array of ReaderIOEither values
-//
-// Returns a ReaderIOEither containing an array of values.
-func SequenceArrayPar[A any](ma []ReaderIOEither[A]) ReaderIOEither[[]A] {
-	return MonadTraverseArrayPar(ma, function.Identity[ReaderIOEither[A]])
-}
-
-// TraverseRecordPar uses transforms a record [map[K]A] into [map[K]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[map[K]B]]
-func TraverseRecordPar[K comparable, A, B any](f func(A) ReaderIOEither[B]) func(map[K]A) ReaderIOEither[map[K]B] {
-	return record.Traverse[map[K]A](
-		Of[map[K]B],
-		Map[map[K]B, func(B) map[K]B],
-		ApPar[map[K]B, B],
-
-		f,
-	)
-}
-
-// TraverseRecordWithIndexPar uses transforms a record [map[K]A] into [map[K]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[map[K]B]]
-func TraverseRecordWithIndexPar[K comparable, A, B any](f func(K, A) ReaderIOEither[B]) func(map[K]A) ReaderIOEither[map[K]B] {
-	return record.TraverseWithIndex[map[K]A](
-		Of[map[K]B],
-		Map[map[K]B, func(B) map[K]B],
-		ApPar[map[K]B, B],
-
-		f,
-	)
-}
-
-// MonadTraverseRecordPar uses transforms a record [map[K]A] into [map[K]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[map[K]B]]
-func MonadTraverseRecordPar[K comparable, A, B any](as map[K]A, f func(A) ReaderIOEither[B]) ReaderIOEither[map[K]B] {
-	return record.MonadTraverse[map[K]A](
-		Of[map[K]B],
-		Map[map[K]B, func(B) map[K]B],
-		ApPar[map[K]B, B],
-		as,
-		f,
-	)
-}
-
-// SequenceRecordPar converts a homogeneous map of ReaderIOEither into a ReaderIOEither of map.
-// This explicitly uses parallel execution.
-//
-// Parameters:
-//   - ma: Map of ReaderIOEither values
-//
-// Returns a ReaderIOEither containing a map of values.
-func SequenceRecordPar[K comparable, A any](ma map[K]ReaderIOEither[A]) ReaderIOEither[map[K]A] {
-	return MonadTraverseRecordPar(ma, function.Identity[ReaderIOEither[A]])
-}

v2/context/readerioresult/BENCHMARKS.md

@@ -0,0 +1,374 @@
+# ReaderIOResult Benchmarks
+
+This document describes the benchmark suite for the `context/readerioeither` package and how to interpret the results to identify performance bottlenecks.
+
+## Running Benchmarks
+
+To run all benchmarks:
+```bash
+cd context/readerioeither
+go test -bench=. -benchmem
+```
+
+To run specific benchmarks:
+```bash
+go test -bench=BenchmarkMap -benchmem
+go test -bench=BenchmarkChain -benchmem
+go test -bench=BenchmarkApPar -benchmem
+```
+
+To run with more iterations for stable results:
+```bash
+go test -bench=. -benchmem -benchtime=100000x
+```
+
+## Benchmark Categories
+
+### 1. Core Constructors
+- `BenchmarkLeft` - Creating Left (error) values (~64ns, 2 allocs)
+- `BenchmarkRight` - Creating Right (success) values (~64ns, 2 allocs)
+- `BenchmarkOf` - Creating Right values via Of (~47ns, 2 allocs)
+
+**Key Insights:**
+- All constructors allocate 2 times (64B total)
+- `Of` is slightly faster than `Right` due to inlining
+- Construction is very fast, suitable for hot paths
+
+### 2. Conversion Operations
+- `BenchmarkFromEither_Right/Left` - Converting Either to ReaderIOResult (~70ns, 2 allocs)
+- `BenchmarkFromIO` - Converting IO to ReaderIOResult (~78ns, 3 allocs)
+- `BenchmarkFromIOEither_Right/Left` - Converting IOEither (~23ns, 1 alloc)
+
+**Key Insights:**
+- FromIOEither is the fastest conversion (~23ns)
+- FromIO has an extra allocation due to wrapping
+- All conversions are lightweight
+
+### 3. Execution Operations
+- `BenchmarkExecute_Right` - Executing Right computation (~37ns, 1 alloc)
+- `BenchmarkExecute_Left` - Executing Left computation (~48ns, 1 alloc)
+- `BenchmarkExecute_WithContext` - Executing with context (~42ns, 1 alloc)
+
+**Key Insights:**
+- Execution is very fast with minimal allocations
+- Left path is slightly slower due to error handling
+- Context overhead is minimal (~5ns)
+
+### 4. Functor Operations (Map)
+- `BenchmarkMonadMap_Right/Left` - Direct map (~135ns, 5 allocs)
+- `BenchmarkMap_Right/Left` - Curried map (~24ns, 1 alloc)
+- `BenchmarkMapTo_Right` - Replacing with constant (~69ns, 1 alloc)
+
+**Key Insights:**
+- **Bottleneck:** MonadMap has 5 allocations (128B)
+- Curried Map is ~5x faster with fewer allocations
+- **Recommendation:** Use curried `Map` instead of `MonadMap`
+
+### 5. Monad Operations (Chain)
+- `BenchmarkMonadChain_Right/Left` - Direct chain (~190ns, 6 allocs)
+- `BenchmarkChain_Right/Left` - Curried chain (~28ns, 1 alloc)
+- `BenchmarkChainFirst_Right/Left` - Chain preserving original (~27ns, 1 alloc)
+- `BenchmarkFlatten_Right/Left` - Removing nesting (~147ns, 7 allocs)
+
+**Key Insights:**
+- **Bottleneck:** MonadChain has 6 allocations (160B)
+- Curried Chain is ~7x faster
+- ChainFirst is as fast as Chain
+- **Bottleneck:** Flatten has 7 allocations
+- **Recommendation:** Use curried `Chain` instead of `MonadChain`
+
+### 6. Applicative Operations (Ap)
+- `BenchmarkMonadApSeq_RightRight` - Sequential apply (~281ns, 8 allocs)
+- `BenchmarkMonadApPar_RightRight` - Parallel apply (~49ns, 3 allocs)
+- `BenchmarkExecuteApSeq_RightRight` - Executing sequential (~1403ns, 8 allocs)
+- `BenchmarkExecuteApPar_RightRight` - Executing parallel (~5606ns, 61 allocs)
+
+**Key Insights:**
+- **Major Bottleneck:** Parallel execution has 61 allocations (1896B)
+- Construction of ApPar is fast (~49ns), but execution is expensive
+- Sequential execution is faster for simple operations (~1.4μs vs ~5.6μs)
+- **Recommendation:** Use ApSeq for simple operations, ApPar only for truly independent, expensive computations
+- Parallel overhead includes context management and goroutine coordination
+
+### 7. Alternative Operations
+- `BenchmarkAlt_RightRight/LeftRight` - Providing alternatives (~210-344ns, 6 allocs)
+- `BenchmarkOrElse_Right/Left` - Recovery from Left (~40-52ns, 2 allocs)
+
+**Key Insights:**
+- Alt has significant overhead (6 allocations)
+- OrElse is much more efficient for error recovery
+- **Recommendation:** Prefer OrElse over Alt when possible
+
+### 8. Chain Operations with Different Types
+- `BenchmarkChainEitherK_Right/Left` - Chaining Either (~25ns, 1 alloc)
+- `BenchmarkChainIOK_Right/Left` - Chaining IO (~55ns, 1 alloc)
+- `BenchmarkChainIOEitherK_Right/Left` - Chaining IOEither (~53ns, 1 alloc)
+
+**Key Insights:**
+- All chain-K operations are efficient
+- ChainEitherK is fastest (pure transformation)
+- ChainIOK and ChainIOEitherK have similar performance
+
+### 9. Context Operations
+- `BenchmarkAsk` - Accessing context (~52ns, 3 allocs)
+- `BenchmarkDefer` - Lazy generation (~34ns, 1 alloc)
+- `BenchmarkMemoize` - Caching results (~82ns, 4 allocs)
+
+**Key Insights:**
+- Ask has 3 allocations for context wrapping
+- Defer is lightweight
+- Memoize has overhead but pays off for expensive computations
+
+### 10. Delay Operations
+- `BenchmarkDelay_Construction` - Creating delayed computation (~19ns, 1 alloc)
+- `BenchmarkTimer_Construction` - Creating timer (~92ns, 3 allocs)
+
+**Key Insights:**
+- Delay construction is very cheap
+- Timer has additional overhead for time operations
+
+### 11. TryCatch Operations
+- `BenchmarkTryCatch_Success/Error` - Creating TryCatch (~33ns, 1 alloc)
+- `BenchmarkExecuteTryCatch_Success/Error` - Executing TryCatch (~3ns, 0 allocs)
+
+**Key Insights:**
+- TryCatch construction is cheap
+- Execution is extremely fast with zero allocations
+- Excellent for wrapping Go error-returning functions
+
+### 12. Pipeline Operations
+- `BenchmarkPipeline_Map_Right/Left` - Single Map in pipeline (~200-306ns, 9 allocs)
+- `BenchmarkPipeline_Chain_Right/Left` - Single Chain in pipeline (~155-217ns, 7 allocs)
+- `BenchmarkPipeline_Complex_Right/Left` - Multiple operations (~777-1039ns, 25 allocs)
+- `BenchmarkExecutePipeline_Complex_Right` - Executing complex pipeline (~533ns, 10 allocs)
+
+**Key Insights:**
+- **Major Bottleneck:** Pipeline operations allocate heavily
+- Single Map: ~200ns with 9 allocations (224B)
+- Complex pipeline: ~900ns with 25 allocations (640B)
+- **Recommendation:** Avoid F.Pipe in hot paths, use direct function calls
+
+### 13. Do-Notation Operations
+- `BenchmarkDo` - Creating empty context (~45ns, 2 allocs)
+- `BenchmarkBind_Right` - Binding values (~25ns, 1 alloc)
+- `BenchmarkLet_Right` - Pure computations (~23ns, 1 alloc)
+- `BenchmarkApS_Right` - Applicative binding (~99ns, 4 allocs)
+
+**Key Insights:**
+- Do-notation operations are efficient
+- Bind and Let are very fast
+- ApS has more overhead (4 allocations)
+- Much better than either package's Bind (~130ns vs ~25ns)
+
+### 14. Traverse Operations
+- `BenchmarkTraverseArray_Empty` - Empty array (~689ns, 13 allocs)
+- `BenchmarkTraverseArray_Small` - 3 elements (~1971ns, 37 allocs)
+- `BenchmarkTraverseArray_Medium` - 10 elements (~4386ns, 93 allocs)
+- `BenchmarkTraverseArraySeq_Small` - Sequential (~1885ns, 52 allocs)
+- `BenchmarkTraverseArrayPar_Small` - Parallel (~1362ns, 37 allocs)
+- `BenchmarkExecuteTraverseArraySeq_Small` - Executing sequential (~1080ns, 34 allocs)
+- `BenchmarkExecuteTraverseArrayPar_Small` - Executing parallel (~18560ns, 202 allocs)
+
+**Key Insights:**
+- **Bottleneck:** Traverse operations allocate per element
+- Empty array still has 13 allocations (overhead)
+- Parallel construction is faster but execution is much slower
+- **Major Bottleneck:** Parallel execution: ~18.5μs with 202 allocations
+- Sequential execution is ~17x faster for small arrays
+- **Recommendation:** Use sequential traverse for small collections, parallel only for large, expensive operations
+
+### 15. Record Operations
+- `BenchmarkTraverseRecord_Small` - 3 entries (~1444ns, 55 allocs)
+- `BenchmarkSequenceRecord_Small` - 3 entries (~1073ns, 54 allocs)
+
+**Key Insights:**
+- Record operations have high allocation overhead
+- Similar performance to array traversal
+- Allocations scale with map size
+
+### 16. Resource Management
+- `BenchmarkWithResource_Success` - Creating resource wrapper (~193ns, 8 allocs)
+- `BenchmarkExecuteWithResource_Success` - Executing with resource (varies)
+- `BenchmarkExecuteWithResource_ErrorInBody` - Error handling (varies)
+
+**Key Insights:**
+- Resource management has 8 allocations for safety
+- Ensures proper cleanup even on errors
+- Overhead is acceptable for resource safety guarantees
+
+### 17. Context Cancellation
+- `BenchmarkExecute_CanceledContext` - Executing with canceled context
+- `BenchmarkExecuteApPar_CanceledContext` - Parallel with canceled context
+
+**Key Insights:**
+- Cancellation is handled efficiently
+- Minimal overhead for checking cancellation
+- ApPar respects cancellation properly
+
+## Performance Bottlenecks Summary
+
+### Critical Bottlenecks (>100ns or >5 allocations)
+
+1. **Pipeline operations with F.Pipe** (~200-1000ns, 9-25 allocations)
+   - **Impact:** High - commonly used pattern
+   - **Mitigation:** Use direct function calls in hot paths
+   - **Example:**
+     ```go
+     // Slow (200ns, 9 allocs)
+     result := F.Pipe1(rioe, Map[int](transform))
+     
+     // Fast (24ns, 1 alloc)
+     result := Map[int](transform)(rioe)
+     ```
+
+2. **MonadMap and MonadChain** (~135-207ns, 5-6 allocations)
+   - **Impact:** High - fundamental operations
+   - **Mitigation:** Use curried versions (Map, Chain)
+   - **Speedup:** 5-7x faster
+
+3. **Parallel applicative execution** (~5.6μs, 61 allocations)
+   - **Impact:** High when used
+   - **Mitigation:** Use ApSeq for simple operations
+   - **Note:** Only use ApPar for truly independent, expensive computations
+
+4. **Parallel traverse execution** (~18.5μs, 202 allocations)
+   - **Impact:** High for collections
+   - **Mitigation:** Use sequential traverse for small collections
+   - **Threshold:** Consider parallel only for >100 elements with expensive operations
+
+5. **Alt operations** (~210-344ns, 6 allocations)
+   - **Impact:** Medium
+   - **Mitigation:** Use OrElse for error recovery (40-52ns, 2 allocs)
+
+### Minor Bottlenecks (50-100ns or 3-4 allocations)
+
+6. **Flatten operations** (~147ns, 7 allocations)
+   - **Impact:** Low - less commonly used
+   - **Mitigation:** Avoid unnecessary nesting
+
+7. **Memoize** (~82ns, 4 allocations)
+   - **Impact:** Low - overhead pays off for expensive computations
+   - **Mitigation:** Only use for computations >1μs
+
+8. **ApS in do-notation** (~99ns, 4 allocations)
+   - **Impact:** Low
+   - **Mitigation:** Use Let or Bind when possible
+
+## Optimization Recommendations
+
+### For Hot Paths
+
+1. **Use curried functions over Monad* versions:**
+   ```go
+   // Instead of:
+   result := MonadMap(rioe, transform)  // 135ns, 5 allocs
+   
+   // Use:
+   result := Map[int](transform)(rioe)  // 24ns, 1 alloc
+   ```
+
+2. **Avoid F.Pipe in performance-critical code:**
+   ```go
+   // Instead of:
+   result := F.Pipe3(rioe, Map(f1), Chain(f2), Map(f3))  // 1000ns, 25 allocs
+   
+   // Use:
+   result := Map(f3)(Chain(f2)(Map(f1)(rioe)))  // Much faster
+   ```
+
+3. **Use sequential operations for small collections:**
+   ```go
+   // For arrays with <10 elements:
+   result := TraverseArraySeq(f)(arr)  // 1.9μs, 52 allocs
+   
+   // Instead of:
+   result := TraverseArrayPar(f)(arr)  // 18.5μs, 202 allocs (when executed)
+   ```
+
+4. **Prefer OrElse over Alt for error recovery:**
+   ```go
+   // Instead of:
+   result := Alt(alternative)(rioe)  // 210-344ns, 6 allocs
+   
+   // Use:
+   result := OrElse(recover)(rioe)  // 40-52ns, 2 allocs
+   ```
+
+### For Context Operations
+
+- Context operations are generally efficient
+- Ask has 3 allocations but is necessary for context access
+- Cancellation checking is fast and should be used liberally
+
+### For Resource Management
+
+- WithResource overhead (8 allocations) is acceptable for safety
+- Always use for resources that need cleanup
+- The RAII pattern prevents resource leaks
+
+### Memory Considerations
+
+- Most operations have 1-2 allocations
+- Monad* versions have 5-8 allocations
+- Pipeline operations allocate heavily
+- Parallel operations have significant allocation overhead
+- Traverse operations allocate per element
+
+## Comparative Analysis
+
+### Fastest Operations (<50ns, <2 allocations)
+- Constructors (Left, Right, Of)
+- Execution (Execute_Right/Left)
+- Curried operations (Map, Chain, ChainFirst)
+- TryCatch execution
+- Chain-K operations
+- Let and Bind in do-notation
+
+### Medium Speed (50-200ns, 2-8 allocations)
+- Conversion operations
+- MonadMap, MonadChain
+- Flatten
+- Memoize
+- Resource management construction
+- Traverse construction
+
+### Slower Operations (>200ns or >8 allocations)
+- Pipeline operations
+- Alt operations
+- Traverse operations (especially parallel)
+- Applicative operations (especially parallel execution)
+
+## Parallel vs Sequential Trade-offs
+
+### When to Use Sequential (ApSeq, TraverseArraySeq)
+- Small collections (<10 elements)
+- Fast operations (<1μs per element)
+- When allocations matter
+- Default choice for most use cases
+
+### When to Use Parallel (ApPar, TraverseArrayPar)
+- Large collections (>100 elements)
+- Expensive operations (>10μs per element)
+- Independent computations
+- When latency matters more than throughput
+- I/O-bound operations
+
+### Parallel Overhead
+- Construction: ~50ns, 3 allocs
+- Execution: +4-17μs, +40-160 allocs
+- Context management and goroutine coordination
+- Only worthwhile for truly expensive operations
+
+## Conclusion
+
+The `context/readerioeither` package is well-optimized with most operations completing in nanoseconds with minimal allocations. Key recommendations:
+
+1. Use curried functions (Map, Chain) instead of Monad* versions (5-7x faster)
+2. Avoid F.Pipe in hot paths (5-10x slower)
+3. Use sequential operations by default; parallel only for expensive, independent computations
+4. Prefer OrElse over Alt for error recovery (5x faster)
+5. TryCatch is excellent for wrapping Go functions (near-zero execution cost)
+6. Context operations are efficient; use liberally
+7. Resource management overhead is acceptable for safety guarantees
+
+For typical use cases, the performance is excellent. Only in extremely hot paths (millions of operations per second) should you consider the micro-optimizations suggested above.

v2/context/readerioresult/bind.go

@@ -0,0 +1,724 @@
+// Copyright (c) 2023 - 2025 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package readerioresult
+
+import (
+	"context"
+
+	F "github.com/IBM/fp-go/v2/function"
+	"github.com/IBM/fp-go/v2/internal/apply"
+	"github.com/IBM/fp-go/v2/io"
+	"github.com/IBM/fp-go/v2/ioeither"
+	"github.com/IBM/fp-go/v2/ioresult"
+	L "github.com/IBM/fp-go/v2/optics/lens"
+	"github.com/IBM/fp-go/v2/reader"
+	"github.com/IBM/fp-go/v2/readerio"
+	RIOR "github.com/IBM/fp-go/v2/readerioresult"
+	"github.com/IBM/fp-go/v2/result"
+)
+
+// Do creates an empty context of type [S] to be used with the [Bind] operation.
+// This is the starting point for do-notation style composition.
+//
+// Example:
+//
+//	type State struct {
+//	    User   User
+//	    Config Config
+//	}
+//	result := readerioeither.Do(State{})
+//
+//go:inline
+func Do[S any](
+	empty S,
+) ReaderIOResult[S] {
+	return RIOR.Of[context.Context](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2].
+// This enables sequential composition where each step can depend on the results of previous steps
+// and access the context.Context from the environment.
+//
+// The setter function takes the result of the computation and returns a function that
+// updates the context from S1 to S2.
+//
+// Example:
+//
+//	type State struct {
+//	    User   User
+//	    Config Config
+//	}
+//
+//	result := F.Pipe2(
+//	    readerioeither.Do(State{}),
+//	    readerioeither.Bind(
+//	        func(user User) func(State) State {
+//	            return func(s State) State { s.User = user; return s }
+//	        },
+//	        func(s State) readerioeither.ReaderIOResult[User] {
+//	            return func(ctx context.Context) ioeither.IOEither[error, User] {
+//	                return ioeither.TryCatch(func() (User, error) {
+//	                    return fetchUser(ctx)
+//	                })
+//	            }
+//	        },
+//	    ),
+//	    readerioeither.Bind(
+//	        func(cfg Config) func(State) State {
+//	            return func(s State) State { s.Config = cfg; return s }
+//	        },
+//	        func(s State) readerioeither.ReaderIOResult[Config] {
+//	            // This can access s.User from the previous step
+//	            return func(ctx context.Context) ioeither.IOEither[error, Config] {
+//	                return ioeither.TryCatch(func() (Config, error) {
+//	                    return fetchConfigForUser(ctx, s.User.ID)
+//	                })
+//	            }
+//	        },
+//	    ),
+//	)
+//
+//go:inline
+func Bind[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f Kleisli[S1, T],
+) Operator[S1, S2] {
+	return RIOR.Bind(setter, f)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+//
+//go:inline
+func Let[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) T,
+) Operator[S1, S2] {
+	return RIOR.Let[context.Context](setter, f)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+//
+//go:inline
+func LetTo[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	b T,
+) Operator[S1, S2] {
+	return RIOR.LetTo[context.Context](setter, b)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+//
+//go:inline
+func BindTo[S1, T any](
+	setter func(T) S1,
+) Operator[T, S1] {
+	return RIOR.BindTo[context.Context](setter)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering
+// the context and the value concurrently (using Applicative rather than Monad).
+// This allows independent computations to be combined without one depending on the result of the other.
+//
+// Unlike Bind, which sequences operations, ApS can be used when operations are independent
+// and can conceptually run in parallel.
+//
+// Example:
+//
+//	type State struct {
+//	    User   User
+//	    Config Config
+//	}
+//
+//	// These operations are independent and can be combined with ApS
+//	getUser := func(ctx context.Context) ioeither.IOEither[error, User] {
+//	    return ioeither.TryCatch(func() (User, error) {
+//	        return fetchUser(ctx)
+//	    })
+//	}
+//	getConfig := func(ctx context.Context) ioeither.IOEither[error, Config] {
+//	    return ioeither.TryCatch(func() (Config, error) {
+//	        return fetchConfig(ctx)
+//	    })
+//	}
+//
+//	result := F.Pipe2(
+//	    readerioeither.Do(State{}),
+//	    readerioeither.ApS(
+//	        func(user User) func(State) State {
+//	            return func(s State) State { s.User = user; return s }
+//	        },
+//	        getUser,
+//	    ),
+//	    readerioeither.ApS(
+//	        func(cfg Config) func(State) State {
+//	            return func(s State) State { s.Config = cfg; return s }
+//	        },
+//	        getConfig,
+//	    ),
+//	)
+//
+//go:inline
+func ApS[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa ReaderIOResult[T],
+) Operator[S1, S2] {
+	return apply.ApS(
+		Ap,
+		Map,
+		setter,
+		fa,
+	)
+}
+
+// ApSL attaches a value to a context using a lens-based setter.
+// This is a convenience function that combines ApS with a lens, allowing you to use
+// optics to update nested structures in a more composable way.
+//
+// The lens parameter provides both the getter and setter for a field within the structure S.
+// This eliminates the need to manually write setter functions.
+//
+// Example:
+//
+//	type State struct {
+//	    User   User
+//	    Config Config
+//	}
+//
+//	userLens := lens.MakeLens(
+//	    func(s State) User { return s.User },
+//	    func(s State, u User) State { s.User = u; return s },
+//	)
+//
+//	getUser := func(ctx context.Context) ioeither.IOEither[error, User] {
+//	    return ioeither.TryCatch(func() (User, error) {
+//	        return fetchUser(ctx)
+//	    })
+//	}
+//	result := F.Pipe2(
+//	    readerioeither.Of(State{}),
+//	    readerioeither.ApSL(userLens, getUser),
+//	)
+//
+//go:inline
+func ApSL[S, T any](
+	lens L.Lens[S, T],
+	fa ReaderIOResult[T],
+) Operator[S, S] {
+	return ApS(lens.Set, fa)
+}
+
+// BindL is a variant of Bind that uses a lens to focus on a specific part of the context.
+// This provides a more ergonomic API when working with nested structures, eliminating
+// the need to manually write setter functions.
+//
+// The lens parameter provides both a getter and setter for a field of type T within
+// the context S. The function f receives the current value of the focused field and
+// returns a ReaderIOResult computation that produces an updated value.
+//
+// Example:
+//
+//	type State struct {
+//	    User   User
+//	    Config Config
+//	}
+//
+//	userLens := lens.MakeLens(
+//	    func(s State) User { return s.User },
+//	    func(s State, u User) State { s.User = u; return s },
+//	)
+//
+//	result := F.Pipe2(
+//	    readerioeither.Do(State{}),
+//	    readerioeither.BindL(userLens, func(user User) readerioeither.ReaderIOResult[User] {
+//	        return func(ctx context.Context) ioeither.IOEither[error, User] {
+//	            return ioeither.TryCatch(func() (User, error) {
+//	                return fetchUser(ctx)
+//	            })
+//	        }
+//	    }),
+//	)
+//
+//go:inline
+func BindL[S, T any](
+	lens L.Lens[S, T],
+	f Kleisli[T, T],
+) Operator[S, S] {
+	return RIOR.BindL(lens, f)
+}
+
+// LetL is a variant of Let that uses a lens to focus on a specific part of the context.
+// This provides a more ergonomic API when working with nested structures, eliminating
+// the need to manually write setter functions.
+//
+// The lens parameter provides both a getter and setter for a field of type T within
+// the context S. The function f receives the current value of the focused field and
+// returns a new value (without wrapping in a ReaderIOResult).
+//
+// Example:
+//
+//	type State struct {
+//	    User   User
+//	    Config Config
+//	}
+//
+//	userLens := lens.MakeLens(
+//	    func(s State) User { return s.User },
+//	    func(s State, u User) State { s.User = u; return s },
+//	)
+//
+//	result := F.Pipe2(
+//	    readerioeither.Do(State{User: User{Name: "Alice"}}),
+//	    readerioeither.LetL(userLens, func(user User) User {
+//	        user.Name = "Bob"
+//	        return user
+//	    }),
+//	)
+//
+//go:inline
+func LetL[S, T any](
+	lens L.Lens[S, T],
+	f func(T) T,
+) Operator[S, S] {
+	return RIOR.LetL[context.Context](lens, f)
+}
+
+// LetToL is a variant of LetTo that uses a lens to focus on a specific part of the context.
+// This provides a more ergonomic API when working with nested structures, eliminating
+// the need to manually write setter functions.
+//
+// The lens parameter provides both a getter and setter for a field of type T within
+// the context S. The value b is set directly to the focused field.
+//
+// Example:
+//
+//	type State struct {
+//	    User   User
+//	    Config Config
+//	}
+//
+//	userLens := lens.MakeLens(
+//	    func(s State) User { return s.User },
+//	    func(s State, u User) State { s.User = u; return s },
+//	)
+//
+//	newUser := User{Name: "Bob", ID: 123}
+//	result := F.Pipe2(
+//	    readerioeither.Do(State{}),
+//	    readerioeither.LetToL(userLens, newUser),
+//	)
+//
+//go:inline
+func LetToL[S, T any](
+	lens L.Lens[S, T],
+	b T,
+) Operator[S, S] {
+	return RIOR.LetToL[context.Context](lens, b)
+}
+
+// BindIOEitherK is a variant of Bind that works with IOEither computations.
+// It lifts an IOEither Kleisli arrow into the ReaderIOResult context (with context.Context as environment).
+//
+// Parameters:
+//   - setter: Updates state from S1 to S2 using result T
+//   - f: An IOEither Kleisli arrow (S1 -> IOEither[error, T])
+//
+//go:inline
+func BindIOEitherK[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f ioresult.Kleisli[S1, T],
+) Operator[S1, S2] {
+	return Bind(setter, F.Flow2(f, FromIOEither[T]))
+}
+
+// BindIOResultK is a variant of Bind that works with IOResult computations.
+// This is an alias for BindIOEitherK for consistency with the Result naming convention.
+//
+// Parameters:
+//   - setter: Updates state from S1 to S2 using result T
+//   - f: An IOResult Kleisli arrow (S1 -> IOResult[T])
+//
+//go:inline
+func BindIOResultK[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f ioresult.Kleisli[S1, T],
+) Operator[S1, S2] {
+	return Bind(setter, F.Flow2(f, FromIOResult[T]))
+}
+
+// BindIOK is a variant of Bind that works with IO computations.
+// It lifts an IO Kleisli arrow into the ReaderIOResult context.
+//
+// Parameters:
+//   - setter: Updates state from S1 to S2 using result T
+//   - f: An IO Kleisli arrow (S1 -> IO[T])
+//
+//go:inline
+func BindIOK[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f io.Kleisli[S1, T],
+) Operator[S1, S2] {
+	return Bind(setter, F.Flow2(f, FromIO[T]))
+}
+
+// BindReaderK is a variant of Bind that works with Reader computations.
+// It lifts a Reader Kleisli arrow (with context.Context) into the ReaderIOResult context.
+//
+// Parameters:
+//   - setter: Updates state from S1 to S2 using result T
+//   - f: A Reader Kleisli arrow (S1 -> Reader[context.Context, T])
+//
+//go:inline
+func BindReaderK[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f reader.Kleisli[context.Context, S1, T],
+) Operator[S1, S2] {
+	return Bind(setter, F.Flow2(f, FromReader[T]))
+}
+
+// BindReaderIOK is a variant of Bind that works with ReaderIO computations.
+// It lifts a ReaderIO Kleisli arrow (with context.Context) into the ReaderIOResult context.
+//
+// Parameters:
+//   - setter: Updates state from S1 to S2 using result T
+//   - f: A ReaderIO Kleisli arrow (S1 -> ReaderIO[context.Context, T])
+//
+//go:inline
+func BindReaderIOK[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f readerio.Kleisli[context.Context, S1, T],
+) Operator[S1, S2] {
+	return Bind(setter, F.Flow2(f, FromReaderIO[T]))
+}
+
+// BindEitherK is a variant of Bind that works with Either (Result) computations.
+// It lifts an Either Kleisli arrow into the ReaderIOResult context.
+//
+// Parameters:
+//   - setter: Updates state from S1 to S2 using result T
+//   - f: An Either Kleisli arrow (S1 -> Either[error, T])
+//
+//go:inline
+func BindEitherK[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f result.Kleisli[S1, T],
+) Operator[S1, S2] {
+	return Bind(setter, F.Flow2(f, FromEither[T]))
+}
+
+// BindResultK is a variant of Bind that works with Result computations.
+// This is an alias for BindEitherK for consistency with the Result naming convention.
+//
+// Parameters:
+//   - setter: Updates state from S1 to S2 using result T
+//   - f: A Result Kleisli arrow (S1 -> Result[T])
+//
+//go:inline
+func BindResultK[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f result.Kleisli[S1, T],
+) Operator[S1, S2] {
+	return Bind(setter, F.Flow2(f, FromResult[T]))
+}
+
+// BindIOEitherKL is a lens-based variant of BindIOEitherK.
+// It combines a lens with an IOEither Kleisli arrow, focusing on a specific field
+// within the state structure.
+//
+// Parameters:
+//   - lens: A lens focusing on field T within state S
+//   - f: An IOEither Kleisli arrow (T -> IOEither[error, T])
+//
+//go:inline
+func BindIOEitherKL[S, T any](
+	lens L.Lens[S, T],
+	f ioresult.Kleisli[T, T],
+) Operator[S, S] {
+	return BindL(lens, F.Flow2(f, FromIOEither[T]))
+}
+
+// BindIOResultKL is a lens-based variant of BindIOResultK.
+// This is an alias for BindIOEitherKL for consistency with the Result naming convention.
+//
+// Parameters:
+//   - lens: A lens focusing on field T within state S
+//   - f: An IOResult Kleisli arrow (T -> IOResult[T])
+//
+//go:inline
+func BindIOResultKL[S, T any](
+	lens L.Lens[S, T],
+	f ioresult.Kleisli[T, T],
+) Operator[S, S] {
+	return BindL(lens, F.Flow2(f, FromIOEither[T]))
+}
+
+// BindIOKL is a lens-based variant of BindIOK.
+// It combines a lens with an IO Kleisli arrow, focusing on a specific field
+// within the state structure.
+//
+// Parameters:
+//   - lens: A lens focusing on field T within state S
+//   - f: An IO Kleisli arrow (T -> IO[T])
+//
+//go:inline
+func BindIOKL[S, T any](
+	lens L.Lens[S, T],
+	f io.Kleisli[T, T],
+) Operator[S, S] {
+	return BindL(lens, F.Flow2(f, FromIO[T]))
+}
+
+// BindReaderKL is a lens-based variant of BindReaderK.
+// It combines a lens with a Reader Kleisli arrow (with context.Context), focusing on a specific field
+// within the state structure.
+//
+// Parameters:
+//   - lens: A lens focusing on field T within state S
+//   - f: A Reader Kleisli arrow (T -> Reader[context.Context, T])
+//
+//go:inline
+func BindReaderKL[S, T any](
+	lens L.Lens[S, T],
+	f reader.Kleisli[context.Context, T, T],
+) Operator[S, S] {
+	return BindL(lens, F.Flow2(f, FromReader[T]))
+}
+
+// BindReaderIOKL is a lens-based variant of BindReaderIOK.
+// It combines a lens with a ReaderIO Kleisli arrow (with context.Context), focusing on a specific field
+// within the state structure.
+//
+// Parameters:
+//   - lens: A lens focusing on field T within state S
+//   - f: A ReaderIO Kleisli arrow (T -> ReaderIO[context.Context, T])
+//
+//go:inline
+func BindReaderIOKL[S, T any](
+	lens L.Lens[S, T],
+	f readerio.Kleisli[context.Context, T, T],
+) Operator[S, S] {
+	return BindL(lens, F.Flow2(f, FromReaderIO[T]))
+}
+
+// ApIOEitherS is an applicative variant that works with IOEither values.
+// Unlike BindIOEitherK, this uses applicative composition (ApS) instead of monadic
+// composition (Bind), allowing independent computations to be combined.
+//
+// Parameters:
+//   - setter: Updates state from S1 to S2 using result T
+//   - fa: An IOEither value
+//
+//go:inline
+func ApIOEitherS[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa IOResult[T],
+) Operator[S1, S2] {
+	return F.Bind2nd(F.Flow2[ReaderIOResult[S1], ioresult.Operator[S1, S2]], ioeither.ApS(setter, fa))
+}
+
+// ApIOResultS is an applicative variant that works with IOResult values.
+// This is an alias for ApIOEitherS for consistency with the Result naming convention.
+//
+// Parameters:
+//   - setter: Updates state from S1 to S2 using result T
+//   - fa: An IOResult value
+//
+//go:inline
+func ApIOResultS[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa IOResult[T],
+) Operator[S1, S2] {
+	return F.Bind2nd(F.Flow2[ReaderIOResult[S1], ioresult.Operator[S1, S2]], ioeither.ApS(setter, fa))
+}
+
+// ApIOS is an applicative variant that works with IO values.
+// It lifts an IO value into the ReaderIOResult context using applicative composition.
+//
+// Parameters:
+//   - setter: Updates state from S1 to S2 using result T
+//   - fa: An IO value
+//
+//go:inline
+func ApIOS[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa IO[T],
+) Operator[S1, S2] {
+	return ApS(setter, FromIO(fa))
+}
+
+// ApReaderS is an applicative variant that works with Reader values.
+// It lifts a Reader value (with context.Context) into the ReaderIOResult context using applicative composition.
+//
+// Parameters:
+//   - setter: Updates state from S1 to S2 using result T
+//   - fa: A Reader value
+//
+//go:inline
+func ApReaderS[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa Reader[context.Context, T],
+) Operator[S1, S2] {
+	return ApS(setter, FromReader(fa))
+}
+
+// ApReaderIOS is an applicative variant that works with ReaderIO values.
+// It lifts a ReaderIO value (with context.Context) into the ReaderIOResult context using applicative composition.
+//
+// Parameters:
+//   - setter: Updates state from S1 to S2 using result T
+//   - fa: A ReaderIO value
+//
+//go:inline
+func ApReaderIOS[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa ReaderIO[T],
+) Operator[S1, S2] {
+	return ApS(setter, FromReaderIO(fa))
+}
+
+// ApEitherS is an applicative variant that works with Either (Result) values.
+// It lifts an Either value into the ReaderIOResult context using applicative composition.
+//
+// Parameters:
+//   - setter: Updates state from S1 to S2 using result T
+//   - fa: An Either value
+//
+//go:inline
+func ApEitherS[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa Result[T],
+) Operator[S1, S2] {
+	return ApS(setter, FromEither(fa))
+}
+
+// ApResultS is an applicative variant that works with Result values.
+// This is an alias for ApEitherS for consistency with the Result naming convention.
+//
+// Parameters:
+//   - setter: Updates state from S1 to S2 using result T
+//   - fa: A Result value
+//
+//go:inline
+func ApResultS[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa Result[T],
+) Operator[S1, S2] {
+	return ApS(setter, FromResult(fa))
+}
+
+// ApIOEitherSL is a lens-based variant of ApIOEitherS.
+// It combines a lens with an IOEither value using applicative composition.
+//
+// Parameters:
+//   - lens: A lens focusing on field T within state S
+//   - fa: An IOEither value
+//
+//go:inline
+func ApIOEitherSL[S, T any](
+	lens L.Lens[S, T],
+	fa IOResult[T],
+) Operator[S, S] {
+	return F.Bind2nd(F.Flow2[ReaderIOResult[S], ioresult.Operator[S, S]], ioresult.ApSL(lens, fa))
+}
+
+// ApIOResultSL is a lens-based variant of ApIOResultS.
+// This is an alias for ApIOEitherSL for consistency with the Result naming convention.
+//
+// Parameters:
+//   - lens: A lens focusing on field T within state S
+//   - fa: An IOResult value
+//
+//go:inline
+func ApIOResultSL[S, T any](
+	lens L.Lens[S, T],
+	fa IOResult[T],
+) Operator[S, S] {
+	return F.Bind2nd(F.Flow2[ReaderIOResult[S], ioresult.Operator[S, S]], ioresult.ApSL(lens, fa))
+}
+
+// ApIOSL is a lens-based variant of ApIOS.
+// It combines a lens with an IO value using applicative composition.
+//
+// Parameters:
+//   - lens: A lens focusing on field T within state S
+//   - fa: An IO value
+//
+//go:inline
+func ApIOSL[S, T any](
+	lens L.Lens[S, T],
+	fa IO[T],
+) Operator[S, S] {
+	return ApSL(lens, FromIO(fa))
+}
+
+// ApReaderSL is a lens-based variant of ApReaderS.
+// It combines a lens with a Reader value (with context.Context) using applicative composition.
+//
+// Parameters:
+//   - lens: A lens focusing on field T within state S
+//   - fa: A Reader value
+//
+//go:inline
+func ApReaderSL[S, T any](
+	lens L.Lens[S, T],
+	fa Reader[context.Context, T],
+) Operator[S, S] {
+	return ApSL(lens, FromReader(fa))
+}
+
+// ApReaderIOSL is a lens-based variant of ApReaderIOS.
+// It combines a lens with a ReaderIO value (with context.Context) using applicative composition.
+//
+// Parameters:
+//   - lens: A lens focusing on field T within state S
+//   - fa: A ReaderIO value
+//
+//go:inline
+func ApReaderIOSL[S, T any](
+	lens L.Lens[S, T],
+	fa ReaderIO[T],
+) Operator[S, S] {
+	return ApSL(lens, FromReaderIO(fa))
+}
+
+// ApEitherSL is a lens-based variant of ApEitherS.
+// It combines a lens with an Either value using applicative composition.
+//
+// Parameters:
+//   - lens: A lens focusing on field T within state S
+//   - fa: An Either value
+//
+//go:inline
+func ApEitherSL[S, T any](
+	lens L.Lens[S, T],
+	fa Result[T],
+) Operator[S, S] {
+	return ApSL(lens, FromEither(fa))
+}
+
+// ApResultSL is a lens-based variant of ApResultS.
+// This is an alias for ApEitherSL for consistency with the Result naming convention.
+//
+// Parameters:
+//   - lens: A lens focusing on field T within state S
+//   - fa: A Result value
+//
+//go:inline
+func ApResultSL[S, T any](
+	lens L.Lens[S, T],
+	fa Result[T],
+) Operator[S, S] {
+	return ApSL(lens, FromResult(fa))
+}

v2/context/readerioresult/bind_test.go

@@ -0,0 +1,275 @@
+// Copyright (c) 2023 - 2025 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package readerioresult
+
+import (
+	"context"
+	"testing"
+
+	E "github.com/IBM/fp-go/v2/either"
+	F "github.com/IBM/fp-go/v2/function"
+	"github.com/IBM/fp-go/v2/internal/utils"
+	O "github.com/IBM/fp-go/v2/option"
+	"github.com/stretchr/testify/assert"
+)
+
+func getLastName(s utils.Initial) ReaderIOResult[string] {
+	return Of("Doe")
+}
+
+func getGivenName(s utils.WithLastName) ReaderIOResult[string] {
+	return Of("John")
+}
+
+func TestBind(t *testing.T) {
+
+	res := F.Pipe3(
+		Do(utils.Empty),
+		Bind(utils.SetLastName, getLastName),
+		Bind(utils.SetGivenName, getGivenName),
+		Map(utils.GetFullName),
+	)
+
+	assert.Equal(t, res(t.Context())(), E.Of[error]("John Doe"))
+}
+
+func TestApS(t *testing.T) {
+
+	res := F.Pipe3(
+		Do(utils.Empty),
+		ApS(utils.SetLastName, Of("Doe")),
+		ApS(utils.SetGivenName, Of("John")),
+		Map(utils.GetFullName),
+	)
+
+	assert.Equal(t, res(t.Context())(), E.Of[error]("John Doe"))
+}
+
+func TestApS_WithError(t *testing.T) {
+	// Test that ApS propagates errors correctly
+	testErr := assert.AnError
+
+	res := F.Pipe3(
+		Do(utils.Empty),
+		ApS(utils.SetLastName, Left[string](testErr)),
+		ApS(utils.SetGivenName, Of("John")),
+		Map(utils.GetFullName),
+	)
+
+	result := res(t.Context())()
+	assert.True(t, E.IsLeft(result))
+	assert.Equal(t, testErr, E.ToError(result))
+}
+
+func TestApS_WithSecondError(t *testing.T) {
+	// Test that ApS propagates errors from the second operation
+	testErr := assert.AnError
+
+	res := F.Pipe3(
+		Do(utils.Empty),
+		ApS(utils.SetLastName, Of("Doe")),
+		ApS(utils.SetGivenName, Left[string](testErr)),
+		Map(utils.GetFullName),
+	)
+
+	result := res(t.Context())()
+	assert.True(t, E.IsLeft(result))
+	assert.Equal(t, testErr, E.ToError(result))
+}
+
+func TestApS_MultipleFields(t *testing.T) {
+	// Test ApS with more than two fields
+	type Person struct {
+		FirstName  string
+		MiddleName string
+		LastName   string
+		Age        int
+	}
+
+	setFirstName := func(s string) func(Person) Person {
+		return func(p Person) Person {
+			p.FirstName = s
+			return p
+		}
+	}
+
+	setMiddleName := func(s string) func(Person) Person {
+		return func(p Person) Person {
+			p.MiddleName = s
+			return p
+		}
+	}
+
+	setLastName := func(s string) func(Person) Person {
+		return func(p Person) Person {
+			p.LastName = s
+			return p
+		}
+	}
+
+	setAge := func(a int) func(Person) Person {
+		return func(p Person) Person {
+			p.Age = a
+			return p
+		}
+	}
+
+	res := F.Pipe5(
+		Do(Person{}),
+		ApS(setFirstName, Of("John")),
+		ApS(setMiddleName, Of("Q")),
+		ApS(setLastName, Of("Doe")),
+		ApS(setAge, Of(42)),
+		Map(func(p Person) Person { return p }),
+	)
+
+	result := res(t.Context())()
+	assert.True(t, E.IsRight(result))
+	person := E.ToOption(result)
+	assert.True(t, O.IsSome(person))
+	p, _ := O.Unwrap(person)
+	assert.Equal(t, "John", p.FirstName)
+	assert.Equal(t, "Q", p.MiddleName)
+	assert.Equal(t, "Doe", p.LastName)
+	assert.Equal(t, 42, p.Age)
+}
+
+func TestApS_WithDifferentTypes(t *testing.T) {
+	// Test ApS with different value types
+	type State struct {
+		Name  string
+		Count int
+		Flag  bool
+	}
+
+	setName := func(s string) func(State) State {
+		return func(st State) State {
+			st.Name = s
+			return st
+		}
+	}
+
+	setCount := func(c int) func(State) State {
+		return func(st State) State {
+			st.Count = c
+			return st
+		}
+	}
+
+	setFlag := func(f bool) func(State) State {
+		return func(st State) State {
+			st.Flag = f
+			return st
+		}
+	}
+
+	res := F.Pipe4(
+		Do(State{}),
+		ApS(setName, Of("test")),
+		ApS(setCount, Of(100)),
+		ApS(setFlag, Of(true)),
+		Map(func(s State) State { return s }),
+	)
+
+	result := res(t.Context())()
+	assert.True(t, E.IsRight(result))
+	stateOpt := E.ToOption(result)
+	assert.True(t, O.IsSome(stateOpt))
+	state, _ := O.Unwrap(stateOpt)
+	assert.Equal(t, "test", state.Name)
+	assert.Equal(t, 100, state.Count)
+	assert.True(t, state.Flag)
+}
+
+func TestApS_EmptyState(t *testing.T) {
+	// Test ApS starting with an empty state
+	type Empty struct{}
+
+	res := Do(Empty{})
+
+	result := res(t.Context())()
+	assert.True(t, E.IsRight(result))
+	emptyOpt := E.ToOption(result)
+	assert.True(t, O.IsSome(emptyOpt))
+	empty, _ := O.Unwrap(emptyOpt)
+	assert.Equal(t, Empty{}, empty)
+}
+
+func TestApS_ChainedWithBind(t *testing.T) {
+	// Test mixing ApS with Bind operations
+	type State struct {
+		Independent string
+		Dependent   string
+	}
+
+	setIndependent := func(s string) func(State) State {
+		return func(st State) State {
+			st.Independent = s
+			return st
+		}
+	}
+
+	setDependent := func(s string) func(State) State {
+		return func(st State) State {
+			st.Dependent = s
+			return st
+		}
+	}
+
+	getDependentValue := func(s State) ReaderIOResult[string] {
+		// This depends on the Independent field
+		return Of(s.Independent + "-dependent")
+	}
+
+	res := F.Pipe3(
+		Do(State{}),
+		ApS(setIndependent, Of("value")),
+		Bind(setDependent, getDependentValue),
+		Map(func(s State) State { return s }),
+	)
+
+	result := res(t.Context())()
+	assert.True(t, E.IsRight(result))
+	stateOpt := E.ToOption(result)
+	assert.True(t, O.IsSome(stateOpt))
+	state, _ := O.Unwrap(stateOpt)
+	assert.Equal(t, "value", state.Independent)
+	assert.Equal(t, "value-dependent", state.Dependent)
+}
+
+func TestApS_WithContextCancellation(t *testing.T) {
+	// Test that ApS respects context cancellation
+	type State struct {
+		Value string
+	}
+
+	setValue := func(s string) func(State) State {
+		return func(st State) State {
+			st.Value = s
+			return st
+		}
+	}
+
+	// Create a computation that would succeed
+	computation := ApS(setValue, Of("test"))(Do(State{}))
+
+	// Create a cancelled context
+	ctx, cancel := context.WithCancel(t.Context())
+	cancel()
+
+	result := computation(ctx)()
+	assert.True(t, E.IsLeft(result))
+}

v2/context/readerioresult/bracket.go

@@ -13,13 +13,10 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package readerioeither
+package readerioresult
 
 import (
-	"context"
-
-	"github.com/IBM/fp-go/v2/internal/bracket"
-	"github.com/IBM/fp-go/v2/readerio"
+	RIOR "github.com/IBM/fp-go/v2/readerioresult"
 )
 
 // Bracket makes sure that a resource is cleaned up in the event of an error. The release action is called regardless of
@@ -27,18 +24,9 @@ import (
 func Bracket[
 	A, B, ANY any](
 
-	acquire ReaderIOEither[A],
-	use func(A) ReaderIOEither[B],
-	release func(A, Either[B]) ReaderIOEither[ANY],
-) ReaderIOEither[B] {
-	return bracket.Bracket[ReaderIOEither[A], ReaderIOEither[B], ReaderIOEither[ANY], Either[B], A, B](
-		readerio.Of[context.Context, Either[B]],
-		MonadChain[A, B],
-		readerio.MonadChain[context.Context, Either[B], Either[B]],
-		MonadChain[ANY, B],
-
-		acquire,
-		use,
-		release,
-	)
+	acquire ReaderIOResult[A],
+	use Kleisli[A, B],
+	release func(A, Either[B]) ReaderIOResult[ANY],
+) ReaderIOResult[B] {
+	return RIOR.Bracket(acquire, use, release)
 }

v2/context/readerioresult/cancel.go

@@ -13,26 +13,26 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package readerioeither
+package readerioresult
 
 import (
 	"context"
 
-	CIOE "github.com/IBM/fp-go/v2/context/ioeither"
+	CIOE "github.com/IBM/fp-go/v2/context/ioresult"
 	"github.com/IBM/fp-go/v2/ioeither"
 )
 
-// WithContext wraps an existing [ReaderIOEither] and performs a context check for cancellation before delegating.
+// WithContext wraps an existing [ReaderIOResult] and performs a context check for cancellation before delegating.
 // This ensures that if the context is already canceled, the computation short-circuits immediately
 // without executing the wrapped computation.
 //
 // This is useful for adding cancellation awareness to computations that might not check the context themselves.
 //
 // Parameters:
-//   - ma: The ReaderIOEither to wrap with context checking
+//   - ma: The ReaderIOResult to wrap with context checking
 //
-// Returns a ReaderIOEither that checks for cancellation before executing.
-func WithContext[A any](ma ReaderIOEither[A]) ReaderIOEither[A] {
+// Returns a ReaderIOResult that checks for cancellation before executing.
+func WithContext[A any](ma ReaderIOResult[A]) ReaderIOResult[A] {
 	return func(ctx context.Context) IOEither[A] {
 		if err := context.Cause(ctx); err != nil {
 			return ioeither.Left[A](err)

v2/context/readerioresult/coverage.out

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+github.com/IBM/fp-go/v2/context/readerioresult/traverse.go:304.97,306.2 1 0

v2/context/readerioresult/doc.go

@@ -13,13 +13,13 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// Package readerioeither provides a specialized version of [readerioeither.ReaderIOEither] that uses
+// package readerioresult provides a specialized version of [readerioeither.ReaderIOResult] that uses
 // [context.Context] as the context type and [error] as the left (error) type. This package is designed
 // for typical Go applications where context-aware, effectful computations with error handling are needed.
 //
 // # Core Concept
 //
-// ReaderIOEither[A] represents a computation that:
+// ReaderIOResult[A] represents a computation that:
 //   - Depends on a [context.Context] (Reader aspect)
 //   - Performs side effects (IO aspect)
 //   - Can fail with an [error] (Either aspect)
@@ -27,7 +27,7 @@
 //
 // The type is defined as:
 //
-//	ReaderIOEither[A] = func(context.Context) func() Either[error, A]
+//	ReaderIOResult[A] = func(context.Context) func() Either[error, A]
 //
 // This combines three powerful functional programming concepts:
 //   - Reader: Dependency injection via context
@@ -50,7 +50,7 @@
 //   - [Left]: Create failed computations
 //   - [FromEither], [FromIO], [FromIOEither]: Convert from other types
 //   - [TryCatch]: Wrap error-returning functions
-//   - [Eitherize0-10]: Convert standard Go functions to ReaderIOEither
+//   - [Eitherize0-10]: Convert standard Go functions to ReaderIOResult
 //
 // Transformation:
 //   - [Map]: Transform success values
@@ -90,15 +90,15 @@
 //	import (
 //	    "context"
 //	    "fmt"
-//	    RIOE "github.com/IBM/fp-go/v2/context/readerioeither"
+//	    RIOE "github.com/IBM/fp-go/v2/context/readerioresult"
 //	    F "github.com/IBM/fp-go/v2/function"
 //	)
 //
 //	// Define a computation that reads from context and may fail
-//	func fetchUser(id string) RIOE.ReaderIOEither[User] {
+//	func fetchUser(id string) RIOE.ReaderIOResult[User] {
 //	    return F.Pipe2(
 //	        RIOE.Ask(),
-//	        RIOE.Chain(func(ctx context.Context) RIOE.ReaderIOEither[User] {
+//	        RIOE.Chain(func(ctx context.Context) RIOE.ReaderIOResult[User] {
 //	            return RIOE.TryCatch(func(ctx context.Context) func() (User, error) {
 //	                return func() (User, error) {
 //	                    return userService.Get(ctx, id)
@@ -138,8 +138,8 @@
 //	        openFile("data.txt"),
 //	        closeFile,
 //	    ),
-//	    func(use func(func(*os.File) RIOE.ReaderIOEither[string]) RIOE.ReaderIOEither[string]) RIOE.ReaderIOEither[string] {
-//	        return use(func(file *os.File) RIOE.ReaderIOEither[string] {
+//	    func(use func(func(*os.File) RIOE.ReaderIOResult[string]) RIOE.ReaderIOResult[string]) RIOE.ReaderIOResult[string] {
+//	        return use(func(file *os.File) RIOE.ReaderIOResult[string] {
 //	            return readContent(file)
 //	        })
 //	    },
@@ -166,4 +166,4 @@
 //	result := computation(ctx)() // Returns Left with cancellation error
 //
 //go:generate go run ../.. contextreaderioeither --count 10 --filename gen.go
-package readerioeither
+package readerioresult

v2/context/readerioresult/eq.go

@@ -13,7 +13,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package readerioeither
+package readerioresult
 
 import (
 	"context"
@@ -22,14 +22,14 @@ import (
 	RIOE "github.com/IBM/fp-go/v2/readerioeither"
 )
 
-// Eq implements the equals predicate for values contained in the [ReaderIOEither] monad.
-// It creates an equality checker that can compare two ReaderIOEither values by executing them
+// Eq implements the equals predicate for values contained in the [ReaderIOResult] monad.
+// It creates an equality checker that can compare two ReaderIOResult values by executing them
 // with a given context and comparing their results using the provided Either equality checker.
 //
 // Parameters:
 //   - eq: Equality checker for Either[A] values
 //
-// Returns a function that takes a context and returns an equality checker for ReaderIOEither[A].
+// Returns a function that takes a context and returns an equality checker for ReaderIOResult[A].
 //
 // Example:
 //
@@ -39,6 +39,8 @@ import (
 //	eqRIE := Eq(eqInt)
 //	ctx := context.Background()
 //	equal := eqRIE(ctx).Equals(Right[int](42), Right[int](42)) // true
-func Eq[A any](eq eq.Eq[Either[A]]) func(context.Context) eq.Eq[ReaderIOEither[A]] {
+//
+//go:inline
+func Eq[A any](eq eq.Eq[Either[A]]) func(context.Context) eq.Eq[ReaderIOResult[A]] {
 	return RIOE.Eq[context.Context](eq)
 }

v2/context/readerioresult/exec/exec.go

@@ -18,7 +18,7 @@ package exec
 import (
 	"context"
 
-	RIOE "github.com/IBM/fp-go/v2/context/readerioeither"
+	RIOE "github.com/IBM/fp-go/v2/context/readerioresult"
 	"github.com/IBM/fp-go/v2/exec"
 	F "github.com/IBM/fp-go/v2/function"
 	GE "github.com/IBM/fp-go/v2/internal/exec"
@@ -30,7 +30,7 @@ var (
 	Command = F.Curry3(command)
 )
 
-func command(name string, args []string, in []byte) RIOE.ReaderIOEither[exec.CommandOutput] {
+func command(name string, args []string, in []byte) RIOE.ReaderIOResult[exec.CommandOutput] {
 	return func(ctx context.Context) IOE.IOEither[error, exec.CommandOutput] {
 		return IOE.TryCatchError(func() (exec.CommandOutput, error) {
 			return GE.Exec(ctx, name, args, in)

v2/context/readerioresult/file/file.go

@@ -20,7 +20,7 @@ import (
 	"io"
 	"os"
 
-	RIOE "github.com/IBM/fp-go/v2/context/readerioeither"
+	RIOE "github.com/IBM/fp-go/v2/context/readerioresult"
 	ET "github.com/IBM/fp-go/v2/either"
 	F "github.com/IBM/fp-go/v2/function"
 	"github.com/IBM/fp-go/v2/internal/file"
@@ -44,7 +44,7 @@ var (
 )
 
 // Close closes an object
-func Close[C io.Closer](c C) RIOE.ReaderIOEither[any] {
+func Close[C io.Closer](c C) RIOE.ReaderIOResult[any] {
 	return F.Pipe2(
 		c,
 		IOEF.Close[C],
@@ -53,8 +53,8 @@ func Close[C io.Closer](c C) RIOE.ReaderIOEither[any] {
 }
 
 // ReadFile reads a file in the scope of a context
-func ReadFile(path string) RIOE.ReaderIOEither[[]byte] {
-	return RIOE.WithResource[[]byte](Open(path), Close[*os.File])(func(r *os.File) RIOE.ReaderIOEither[[]byte] {
+func ReadFile(path string) RIOE.ReaderIOResult[[]byte] {
+	return RIOE.WithResource[[]byte](Open(path), Close[*os.File])(func(r *os.File) RIOE.ReaderIOResult[[]byte] {
 		return func(ctx context.Context) IOE.IOEither[error, []byte] {
 			return func() ET.Either[error, []byte] {
 				return file.ReadAll(ctx, r)

v2/context/readerioresult/file/file_test.go

@@ -19,7 +19,7 @@ import (
 	"context"
 	"fmt"
 
-	R "github.com/IBM/fp-go/v2/context/readerioeither"
+	R "github.com/IBM/fp-go/v2/context/readerioresult"
 	F "github.com/IBM/fp-go/v2/function"
 	"github.com/IBM/fp-go/v2/io"
 	J "github.com/IBM/fp-go/v2/json"

v2/context/readerioresult/file/tempfile.go

@@ -18,7 +18,7 @@ package file
 import (
 	"os"
 
-	RIOE "github.com/IBM/fp-go/v2/context/readerioeither"
+	RIOE "github.com/IBM/fp-go/v2/context/readerioresult"
 	F "github.com/IBM/fp-go/v2/function"
 	IO "github.com/IBM/fp-go/v2/io"
 	IOF "github.com/IBM/fp-go/v2/io/file"
@@ -38,7 +38,7 @@ var (
 )
 
 // CreateTemp created a temp file with proper parametrization
-func CreateTemp(dir, pattern string) RIOE.ReaderIOEither[*os.File] {
+func CreateTemp(dir, pattern string) RIOE.ReaderIOResult[*os.File] {
 	return F.Pipe2(
 		IOEF.CreateTemp(dir, pattern),
 		RIOE.FromIOEither[*os.File],
@@ -47,6 +47,6 @@ func CreateTemp(dir, pattern string) RIOE.ReaderIOEither[*os.File] {
 }
 
 // WithTempFile creates a temporary file, then invokes a callback to create a resource based on the file, then close and remove the temp file
-func WithTempFile[A any](f func(*os.File) RIOE.ReaderIOEither[A]) RIOE.ReaderIOEither[A] {
+func WithTempFile[A any](f func(*os.File) RIOE.ReaderIOResult[A]) RIOE.ReaderIOResult[A] {
 	return RIOE.WithResource[A](onCreateTempFile, onReleaseTempFile)(f)
 }

v2/context/readerioresult/file/tempfile_test.go

@@ -20,7 +20,7 @@ import (
 	"os"
 	"testing"
 
-	RIOE "github.com/IBM/fp-go/v2/context/readerioeither"
+	RIOE "github.com/IBM/fp-go/v2/context/readerioresult"
 	E "github.com/IBM/fp-go/v2/either"
 	F "github.com/IBM/fp-go/v2/function"
 	"github.com/stretchr/testify/assert"
@@ -35,7 +35,7 @@ func TestWithTempFile(t *testing.T) {
 
 func TestWithTempFileOnClosedFile(t *testing.T) {
 
-	res := WithTempFile(func(f *os.File) RIOE.ReaderIOEither[[]byte] {
+	res := WithTempFile(func(f *os.File) RIOE.ReaderIOResult[[]byte] {
 		return F.Pipe2(
 			f,
 			onWriteAll[*os.File]([]byte("Carsten")),

v2/context/readerioresult/file/write.go

@@ -19,12 +19,12 @@ import (
 	"context"
 	"io"
 
-	RIOE "github.com/IBM/fp-go/v2/context/readerioeither"
+	RIOE "github.com/IBM/fp-go/v2/context/readerioresult"
 	F "github.com/IBM/fp-go/v2/function"
 )
 
-func onWriteAll[W io.Writer](data []byte) func(w W) RIOE.ReaderIOEither[[]byte] {
-	return func(w W) RIOE.ReaderIOEither[[]byte] {
+func onWriteAll[W io.Writer](data []byte) func(w W) RIOE.ReaderIOResult[[]byte] {
+	return func(w W) RIOE.ReaderIOResult[[]byte] {
 		return F.Pipe1(
 			RIOE.TryCatch(func(_ context.Context) func() ([]byte, error) {
 				return func() ([]byte, error) {
@@ -38,9 +38,9 @@ func onWriteAll[W io.Writer](data []byte) func(w W) RIOE.ReaderIOEither[[]byte]
 }
 
 // WriteAll uses a generator function to create a stream, writes data to it and closes it
-func WriteAll[W io.WriteCloser](data []byte) func(acquire RIOE.ReaderIOEither[W]) RIOE.ReaderIOEither[[]byte] {
+func WriteAll[W io.WriteCloser](data []byte) func(acquire RIOE.ReaderIOResult[W]) RIOE.ReaderIOResult[[]byte] {
 	onWrite := onWriteAll[W](data)
-	return func(onCreate RIOE.ReaderIOEither[W]) RIOE.ReaderIOEither[[]byte] {
+	return func(onCreate RIOE.ReaderIOResult[W]) RIOE.ReaderIOResult[[]byte] {
 		return RIOE.WithResource[[]byte](
 			onCreate,
 			Close[W])(
@@ -50,7 +50,7 @@ func WriteAll[W io.WriteCloser](data []byte) func(acquire RIOE.ReaderIOEither[W]
 }
 
 // Write uses a generator function to create a stream, writes data to it and closes it
-func Write[R any, W io.WriteCloser](acquire RIOE.ReaderIOEither[W]) func(use func(W) RIOE.ReaderIOEither[R]) RIOE.ReaderIOEither[R] {
+func Write[R any, W io.WriteCloser](acquire RIOE.ReaderIOResult[W]) func(use func(W) RIOE.ReaderIOResult[R]) RIOE.ReaderIOResult[R] {
 	return RIOE.WithResource[R](
 		acquire,
 		Close[W])

v2/context/readerioresult/http/builder/builder.go

@@ -0,0 +1,155 @@
+// Copyright (c) 2023 - 2025 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package builder provides utilities for building HTTP requests in a functional way
+// using the ReaderIOResult monad. It integrates with the http/builder package to
+// create composable, type-safe HTTP request builders with proper error handling
+// and context support.
+//
+// The main function, Requester, converts a Builder from the http/builder package
+// into a ReaderIOResult that produces HTTP requests. This allows for:
+//   - Immutable request building with method chaining
+//   - Automatic header management including Content-Length
+//   - Support for requests with and without bodies
+//   - Proper error handling wrapped in Either
+//   - Context propagation for cancellation and timeouts
+//
+// Example usage:
+//
+//	import (
+//	    "context"
+//	    B "github.com/IBM/fp-go/v2/http/builder"
+//	    RB "github.com/IBM/fp-go/v2/context/readerioresult/http/builder"
+//	)
+//
+//	builder := F.Pipe3(
+//	    B.Default,
+//	    B.WithURL("https://api.example.com/users"),
+//	    B.WithMethod("POST"),
+//	    B.WithJSONBody(userData),
+//	)
+//
+//	requester := RB.Requester(builder)
+//	result := requester(context.Background())()
+package builder
+
+import (
+	"bytes"
+	"context"
+	"net/http"
+	"strconv"
+
+	RIOE "github.com/IBM/fp-go/v2/context/readerioresult"
+	RIOEH "github.com/IBM/fp-go/v2/context/readerioresult/http"
+	F "github.com/IBM/fp-go/v2/function"
+	R "github.com/IBM/fp-go/v2/http/builder"
+	H "github.com/IBM/fp-go/v2/http/headers"
+	LZ "github.com/IBM/fp-go/v2/lazy"
+	O "github.com/IBM/fp-go/v2/option"
+	"github.com/IBM/fp-go/v2/result"
+)
+
+// Requester converts an http/builder.Builder into a ReaderIOResult that produces HTTP requests.
+// It handles both requests with and without bodies, automatically managing headers including
+// Content-Length for requests with bodies.
+//
+// The function performs the following operations:
+//  1. Extracts the request body (if present) from the builder
+//  2. Creates appropriate request constructor (with or without body)
+//  3. Applies the target URL from the builder
+//  4. Applies the HTTP method from the builder
+//  5. Merges headers from the builder into the request
+//  6. Handles any errors that occur during request construction
+//
+// For requests with a body:
+//   - Sets the Content-Length header automatically
+//   - Uses bytes.NewReader to create the request body
+//   - Merges builder headers into the request
+//
+// For requests without a body:
+//   - Creates a request with nil body
+//   - Merges builder headers into the request
+//
+// Parameters:
+//   - builder: A pointer to an http/builder.Builder containing request configuration
+//
+// Returns:
+//   - A Requester (ReaderIOResult[*http.Request]) that, when executed with a context,
+//     produces either an error or a configured *http.Request
+//
+// Example with body:
+//
+//	import (
+//	    B "github.com/IBM/fp-go/v2/http/builder"
+//	    RB "github.com/IBM/fp-go/v2/context/readerioresult/http/builder"
+//	)
+//
+//	builder := F.Pipe3(
+//	    B.Default,
+//	    B.WithURL("https://api.example.com/users"),
+//	    B.WithMethod("POST"),
+//	    B.WithJSONBody(map[string]string{"name": "John"}),
+//	)
+//	requester := RB.Requester(builder)
+//	result := requester(context.Background())()
+//
+// Example without body:
+//
+//	builder := F.Pipe2(
+//	    B.Default,
+//	    B.WithURL("https://api.example.com/users"),
+//	    B.WithMethod("GET"),
+//	)
+//	requester := RB.Requester(builder)
+//	result := requester(context.Background())()
+func Requester(builder *R.Builder) RIOEH.Requester {
+
+	withBody := F.Curry3(func(data []byte, url string, method string) RIOE.ReaderIOResult[*http.Request] {
+		return RIOE.TryCatch(func(ctx context.Context) func() (*http.Request, error) {
+			return func() (*http.Request, error) {
+				req, err := http.NewRequestWithContext(ctx, method, url, bytes.NewReader(data))
+				if err == nil {
+					req.Header.Set(H.ContentLength, strconv.Itoa(len(data)))
+					H.Monoid.Concat(req.Header, builder.GetHeaders())
+				}
+				return req, err
+			}
+		})
+	})
+
+	withoutBody := F.Curry2(func(url string, method string) RIOE.ReaderIOResult[*http.Request] {
+		return RIOE.TryCatch(func(ctx context.Context) func() (*http.Request, error) {
+			return func() (*http.Request, error) {
+				req, err := http.NewRequestWithContext(ctx, method, url, nil)
+				if err == nil {
+					H.Monoid.Concat(req.Header, builder.GetHeaders())
+				}
+				return req, err
+			}
+		})
+	})
+
+	return F.Pipe5(
+		builder.GetBody(),
+		O.Fold(LZ.Of(result.Of(withoutBody)), result.Map(withBody)),
+		result.Ap[RIOE.Kleisli[string, *http.Request]](builder.GetTargetURL()),
+		result.Flap[RIOE.ReaderIOResult[*http.Request]](builder.GetMethod()),
+		result.GetOrElse(RIOE.Left[*http.Request]),
+		RIOE.Map(func(req *http.Request) *http.Request {
+			req.Header = H.Monoid.Concat(req.Header, builder.GetHeaders())
+			return req
+		}),
+	)
+}

v2/context/readerioresult/http/builder/builder_test.go

@@ -0,0 +1,287 @@
+// Copyright (c) 2023 - 2025 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package builder
+
+import (
+	"context"
+	"net/http"
+	"net/url"
+	"testing"
+
+	RIOE "github.com/IBM/fp-go/v2/context/readerioresult"
+	E "github.com/IBM/fp-go/v2/either"
+	F "github.com/IBM/fp-go/v2/function"
+	R "github.com/IBM/fp-go/v2/http/builder"
+	IO "github.com/IBM/fp-go/v2/io"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestBuilderWithQuery(t *testing.T) {
+	// add some query
+	withLimit := R.WithQueryArg("limit")("10")
+	withURL := R.WithURL("http://www.example.org?a=b")
+
+	b := F.Pipe2(
+		R.Default,
+		withLimit,
+		withURL,
+	)
+
+	req := F.Pipe3(
+		b,
+		Requester,
+		RIOE.Map(func(r *http.Request) *url.URL {
+			return r.URL
+		}),
+		RIOE.ChainFirstIOK(func(u *url.URL) IO.IO[any] {
+			return IO.FromImpure(func() {
+				q := u.Query()
+				assert.Equal(t, "10", q.Get("limit"))
+				assert.Equal(t, "b", q.Get("a"))
+			})
+		}),
+	)
+
+	assert.True(t, E.IsRight(req(context.Background())()))
+}
+
+// TestBuilderWithoutBody tests creating a request without a body
+func TestBuilderWithoutBody(t *testing.T) {
+	builder := F.Pipe2(
+		R.Default,
+		R.WithURL("https://api.example.com/users"),
+		R.WithMethod("GET"),
+	)
+
+	requester := Requester(builder)
+	result := requester(context.Background())()
+
+	assert.True(t, E.IsRight(result), "Expected Right result")
+
+	req := E.GetOrElse(func(error) *http.Request { return nil })(result)
+	assert.NotNil(t, req, "Expected non-nil request")
+	assert.Equal(t, "GET", req.Method)
+	assert.Equal(t, "https://api.example.com/users", req.URL.String())
+	assert.Nil(t, req.Body, "Expected nil body for GET request")
+}
+
+// TestBuilderWithBody tests creating a request with a body
+func TestBuilderWithBody(t *testing.T) {
+	bodyData := []byte(`{"name":"John","age":30}`)
+
+	builder := F.Pipe3(
+		R.Default,
+		R.WithURL("https://api.example.com/users"),
+		R.WithMethod("POST"),
+		R.WithBytes(bodyData),
+	)
+
+	requester := Requester(builder)
+	result := requester(context.Background())()
+
+	assert.True(t, E.IsRight(result), "Expected Right result")
+
+	req := E.GetOrElse(func(error) *http.Request { return nil })(result)
+	assert.NotNil(t, req, "Expected non-nil request")
+	assert.Equal(t, "POST", req.Method)
+	assert.Equal(t, "https://api.example.com/users", req.URL.String())
+	assert.NotNil(t, req.Body, "Expected non-nil body for POST request")
+	assert.Equal(t, "24", req.Header.Get("Content-Length"))
+}
+
+// TestBuilderWithHeaders tests that headers are properly set
+func TestBuilderWithHeaders(t *testing.T) {
+	builder := F.Pipe3(
+		R.Default,
+		R.WithURL("https://api.example.com/data"),
+		R.WithHeader("Authorization")("Bearer token123"),
+		R.WithHeader("Accept")("application/json"),
+	)
+
+	requester := Requester(builder)
+	result := requester(context.Background())()
+
+	assert.True(t, E.IsRight(result), "Expected Right result")
+
+	req := E.GetOrElse(func(error) *http.Request { return nil })(result)
+	assert.NotNil(t, req, "Expected non-nil request")
+	assert.Equal(t, "Bearer token123", req.Header.Get("Authorization"))
+	assert.Equal(t, "application/json", req.Header.Get("Accept"))
+}
+
+// TestBuilderWithInvalidURL tests error handling for invalid URLs
+func TestBuilderWithInvalidURL(t *testing.T) {
+	builder := F.Pipe1(
+		R.Default,
+		R.WithURL("://invalid-url"),
+	)
+
+	requester := Requester(builder)
+	result := requester(context.Background())()
+
+	assert.True(t, E.IsLeft(result), "Expected Left result for invalid URL")
+}
+
+// TestBuilderWithEmptyMethod tests creating a request with empty method
+func TestBuilderWithEmptyMethod(t *testing.T) {
+	builder := F.Pipe2(
+		R.Default,
+		R.WithURL("https://api.example.com/users"),
+		R.WithMethod(""),
+	)
+
+	requester := Requester(builder)
+	result := requester(context.Background())()
+
+	// Empty method should still work (defaults to GET in http.NewRequest)
+	assert.True(t, E.IsRight(result), "Expected Right result")
+}
+
+// TestBuilderWithMultipleHeaders tests setting multiple headers
+func TestBuilderWithMultipleHeaders(t *testing.T) {
+	builder := F.Pipe4(
+		R.Default,
+		R.WithURL("https://api.example.com/data"),
+		R.WithHeader("X-Custom-Header-1")("value1"),
+		R.WithHeader("X-Custom-Header-2")("value2"),
+		R.WithHeader("X-Custom-Header-3")("value3"),
+	)
+
+	requester := Requester(builder)
+	result := requester(context.Background())()
+
+	assert.True(t, E.IsRight(result), "Expected Right result")
+
+	req := E.GetOrElse(func(error) *http.Request { return nil })(result)
+	assert.NotNil(t, req, "Expected non-nil request")
+	assert.Equal(t, "value1", req.Header.Get("X-Custom-Header-1"))
+	assert.Equal(t, "value2", req.Header.Get("X-Custom-Header-2"))
+	assert.Equal(t, "value3", req.Header.Get("X-Custom-Header-3"))
+}
+
+// TestBuilderWithBodyAndHeaders tests combining body and headers
+func TestBuilderWithBodyAndHeaders(t *testing.T) {
+	bodyData := []byte(`{"test":"data"}`)
+
+	builder := F.Pipe4(
+		R.Default,
+		R.WithURL("https://api.example.com/submit"),
+		R.WithMethod("PUT"),
+		R.WithBytes(bodyData),
+		R.WithHeader("X-Request-ID")("12345"),
+	)
+
+	requester := Requester(builder)
+	result := requester(context.Background())()
+
+	assert.True(t, E.IsRight(result), "Expected Right result")
+
+	req := E.GetOrElse(func(error) *http.Request { return nil })(result)
+	assert.NotNil(t, req, "Expected non-nil request")
+	assert.Equal(t, "PUT", req.Method)
+	assert.NotNil(t, req.Body, "Expected non-nil body")
+	assert.Equal(t, "12345", req.Header.Get("X-Request-ID"))
+	assert.Equal(t, "15", req.Header.Get("Content-Length"))
+}
+
+// TestBuilderContextCancellation tests that context cancellation is respected
+func TestBuilderContextCancellation(t *testing.T) {
+	builder := F.Pipe1(
+		R.Default,
+		R.WithURL("https://api.example.com/users"),
+	)
+
+	requester := Requester(builder)
+
+	// Create a cancelled context
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel() // Cancel immediately
+
+	result := requester(ctx)()
+
+	// The request should still be created (cancellation affects execution, not creation)
+	// But we verify the context is properly passed
+	req := E.GetOrElse(func(error) *http.Request { return nil })(result)
+	if req != nil {
+		assert.Equal(t, ctx, req.Context(), "Expected context to be set in request")
+	}
+}
+
+// TestBuilderWithDifferentMethods tests various HTTP methods
+func TestBuilderWithDifferentMethods(t *testing.T) {
+	methods := []string{"GET", "POST", "PUT", "DELETE", "PATCH", "HEAD", "OPTIONS"}
+
+	for _, method := range methods {
+		t.Run(method, func(t *testing.T) {
+			builder := F.Pipe2(
+				R.Default,
+				R.WithURL("https://api.example.com/resource"),
+				R.WithMethod(method),
+			)
+
+			requester := Requester(builder)
+			result := requester(context.Background())()
+
+			assert.True(t, E.IsRight(result), "Expected Right result for method %s", method)
+
+			req := E.GetOrElse(func(error) *http.Request { return nil })(result)
+			assert.NotNil(t, req, "Expected non-nil request for method %s", method)
+			assert.Equal(t, method, req.Method)
+		})
+	}
+}
+
+// TestBuilderWithJSON tests creating a request with JSON body
+func TestBuilderWithJSON(t *testing.T) {
+	data := map[string]string{"username": "testuser", "email": "test@example.com"}
+
+	builder := F.Pipe3(
+		R.Default,
+		R.WithURL("https://api.example.com/v1/users"),
+		R.WithMethod("POST"),
+		R.WithJSON(data),
+	)
+
+	requester := Requester(builder)
+	result := requester(context.Background())()
+
+	assert.True(t, E.IsRight(result), "Expected Right result")
+
+	req := E.GetOrElse(func(error) *http.Request { return nil })(result)
+	assert.NotNil(t, req, "Expected non-nil request")
+	assert.Equal(t, "POST", req.Method)
+	assert.Equal(t, "https://api.example.com/v1/users", req.URL.String())
+	assert.Equal(t, "application/json", req.Header.Get("Content-Type"))
+	assert.NotNil(t, req.Body)
+}
+
+// TestBuilderWithBearer tests adding Bearer token
+func TestBuilderWithBearer(t *testing.T) {
+	builder := F.Pipe2(
+		R.Default,
+		R.WithURL("https://api.example.com/protected"),
+		R.WithBearer("my-secret-token"),
+	)
+
+	requester := Requester(builder)
+	result := requester(context.Background())()
+
+	assert.True(t, E.IsRight(result), "Expected Right result")
+
+	req := E.GetOrElse(func(error) *http.Request { return nil })(result)
+	assert.NotNil(t, req, "Expected non-nil request")
+	assert.Equal(t, "Bearer my-secret-token", req.Header.Get("Authorization"))
+}

v2/context/readerioresult/http/builder/coverage.out

@@ -0,0 +1,15 @@
+mode: set
+github.com/IBM/fp-go/v2/context/readerioresult/http/builder/builder.go:117.52,119.103 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/builder/builder.go:119.103,120.80 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/builder/builder.go:120.80,121.41 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/builder/builder.go:121.41,123.19 2 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/builder/builder.go:123.19,126.6 2 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/builder/builder.go:127.5,127.20 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/builder/builder.go:132.2,132.93 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/builder/builder.go:132.93,133.80 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/builder/builder.go:133.80,134.41 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/builder/builder.go:134.41,136.19 2 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/builder/builder.go:136.19,138.6 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/builder/builder.go:139.5,139.20 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/builder/builder.go:144.2,150.50 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/builder/builder.go:150.50,153.4 2 1

v2/context/readerioresult/http/coverage.out

@@ -0,0 +1,11 @@
+mode: set
+github.com/IBM/fp-go/v2/context/readerioresult/http/request.go:111.76,116.2 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/request.go:134.49,136.2 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/request.go:161.90,162.65 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/request.go:162.65,166.76 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/request.go:166.76,176.5 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/request.go:198.73,203.2 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/request.go:222.74,227.2 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/request.go:234.76,236.2 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/request.go:245.74,254.2 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/http/request.go:281.76,286.2 1 1

v2/context/readerioresult/http/request.go

@@ -0,0 +1,286 @@
+// Copyright (c) 2023 - 2025 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package http provides functional HTTP client utilities built on top of ReaderIOResult monad.
+// It offers a composable way to make HTTP requests with context support, error handling,
+// and response parsing capabilities. The package follows functional programming principles
+// to ensure type-safe, testable, and maintainable HTTP operations.
+//
+// The main abstractions include:
+//   - Requester: A reader that constructs HTTP requests with context
+//   - Client: An interface for executing HTTP requests
+//   - Response readers: Functions to parse responses as bytes, text, or JSON
+//
+// Example usage:
+//
+//	client := MakeClient(http.DefaultClient)
+//	request := MakeGetRequest("https://api.example.com/data")
+//	result := ReadJSON[MyType](client)(request)
+//	response := result(context.Background())()
+package http
+
+import (
+	"io"
+	"net/http"
+
+	B "github.com/IBM/fp-go/v2/bytes"
+	RIOE "github.com/IBM/fp-go/v2/context/readerioresult"
+	F "github.com/IBM/fp-go/v2/function"
+	H "github.com/IBM/fp-go/v2/http"
+	IOE "github.com/IBM/fp-go/v2/ioeither"
+	IOEF "github.com/IBM/fp-go/v2/ioeither/file"
+	J "github.com/IBM/fp-go/v2/json"
+	P "github.com/IBM/fp-go/v2/pair"
+)
+
+type (
+	// Requester is a reader that constructs an HTTP request with context support.
+	// It represents a computation that, given a context, produces either an error
+	// or an HTTP request. This allows for composable request building with proper
+	// error handling and context propagation.
+	Requester = RIOE.ReaderIOResult[*http.Request]
+
+	// Client is an interface for executing HTTP requests in a functional way.
+	// It wraps the standard http.Client and provides a Do method that works
+	// with the ReaderIOResult monad for composable, type-safe HTTP operations.
+	Client interface {
+		// Do executes an HTTP request and returns the response wrapped in a ReaderIOResult.
+		// It takes a Requester (which builds the request) and returns a computation that,
+		// when executed with a context, performs the HTTP request and returns either
+		// an error or the HTTP response.
+		//
+		// Parameters:
+		//   - req: A Requester that builds the HTTP request
+		//
+		// Returns:
+		//   - A ReaderIOResult that produces either an error or an *http.Response
+		Do(Requester) RIOE.ReaderIOResult[*http.Response]
+	}
+
+	// client is the internal implementation of the Client interface.
+	// It wraps a standard http.Client and provides functional HTTP operations.
+	client struct {
+		delegate *http.Client
+		doIOE    func(*http.Request) IOE.IOEither[error, *http.Response]
+	}
+)
+
+var (
+	// MakeRequest is an eitherized version of http.NewRequestWithContext.
+	// It creates a Requester that builds an HTTP request with the given method, URL, and body.
+	// This function properly handles errors and wraps them in the Either monad.
+	//
+	// Parameters:
+	//   - method: HTTP method (GET, POST, PUT, DELETE, etc.)
+	//   - url: The target URL for the request
+	//   - body: Optional request body (can be nil)
+	//
+	// Returns:
+	//   - A Requester that produces either an error or an *http.Request
+	MakeRequest = RIOE.Eitherize3(http.NewRequestWithContext)
+
+	// makeRequest is a partially applied version of MakeRequest with the context parameter bound.
+	makeRequest = F.Bind13of3(MakeRequest)
+
+	// MakeGetRequest creates a GET request for the specified URL.
+	// It's a convenience function that specializes MakeRequest for GET requests with no body.
+	//
+	// Parameters:
+	//   - url: The target URL for the GET request
+	//
+	// Returns:
+	//   - A Requester that produces either an error or an *http.Request
+	//
+	// Example:
+	//   req := MakeGetRequest("https://api.example.com/users")
+	MakeGetRequest = makeRequest("GET", nil)
+)
+
+func (client client) Do(req Requester) RIOE.ReaderIOResult[*http.Response] {
+	return F.Pipe1(
+		req,
+		RIOE.ChainIOEitherK(client.doIOE),
+	)
+}
+
+// MakeClient creates a functional HTTP client wrapper around a standard http.Client.
+// The returned Client provides methods for executing HTTP requests in a functional,
+// composable way using the ReaderIOResult monad.
+//
+// Parameters:
+//   - httpClient: A standard *http.Client to wrap (e.g., http.DefaultClient)
+//
+// Returns:
+//   - A Client that can execute HTTP requests functionally
+//
+// Example:
+//
+//	client := MakeClient(http.DefaultClient)
+//	// or with custom client
+//	customClient := &http.Client{Timeout: 10 * time.Second}
+//	client := MakeClient(customClient)
+func MakeClient(httpClient *http.Client) Client {
+	return client{delegate: httpClient, doIOE: IOE.Eitherize1(httpClient.Do)}
+}
+
+// ReadFullResponse sends an HTTP request, reads the complete response body as a byte array,
+// and returns both the response and body as a tuple (FullResponse).
+// It validates the HTTP status code and handles errors appropriately.
+//
+// The function performs the following steps:
+//  1. Executes the HTTP request using the provided client
+//  2. Validates the response status code (checks for HTTP errors)
+//  3. Reads the entire response body into a byte array
+//  4. Returns a tuple containing the response and body
+//
+// Parameters:
+//   - client: The HTTP client to use for executing the request
+//
+// Returns:
+//   - A function that takes a Requester and returns a ReaderIOResult[FullResponse]
+//     where FullResponse is a tuple of (*http.Response, []byte)
+//
+// Example:
+//
+//	client := MakeClient(http.DefaultClient)
+//	request := MakeGetRequest("https://api.example.com/data")
+//	fullResp := ReadFullResponse(client)(request)
+//	result := fullResp(context.Background())()
+func ReadFullResponse(client Client) func(Requester) RIOE.ReaderIOResult[H.FullResponse] {
+	return func(req Requester) RIOE.ReaderIOResult[H.FullResponse] {
+		return F.Flow3(
+			client.Do(req),
+			IOE.ChainEitherK(H.ValidateResponse),
+			IOE.Chain(func(resp *http.Response) IOE.IOEither[error, H.FullResponse] {
+				return F.Pipe1(
+					F.Pipe3(
+						resp,
+						H.GetBody,
+						IOE.Of[error, io.ReadCloser],
+						IOEF.ReadAll[io.ReadCloser],
+					),
+					IOE.Map[error](F.Bind1st(P.MakePair[*http.Response, []byte], resp)),
+				)
+			}),
+		)
+	}
+}
+
+// ReadAll sends an HTTP request and reads the complete response body as a byte array.
+// It validates the HTTP status code and returns the raw response body bytes.
+// This is useful when you need to process the response body in a custom way.
+//
+// Parameters:
+//   - client: The HTTP client to use for executing the request
+//
+// Returns:
+//   - A function that takes a Requester and returns a ReaderIOResult[[]byte]
+//     containing the response body as bytes
+//
+// Example:
+//
+//	client := MakeClient(http.DefaultClient)
+//	request := MakeGetRequest("https://api.example.com/data")
+//	readBytes := ReadAll(client)
+//	result := readBytes(request)(context.Background())()
+func ReadAll(client Client) func(Requester) RIOE.ReaderIOResult[[]byte] {
+	return F.Flow2(
+		ReadFullResponse(client),
+		RIOE.Map(H.Body),
+	)
+}
+
+// ReadText sends an HTTP request, reads the response body, and converts it to a string.
+// It validates the HTTP status code and returns the response body as a UTF-8 string.
+// This is convenient for APIs that return plain text responses.
+//
+// Parameters:
+//   - client: The HTTP client to use for executing the request
+//
+// Returns:
+//   - A function that takes a Requester and returns a ReaderIOResult[string]
+//     containing the response body as a string
+//
+// Example:
+//
+//	client := MakeClient(http.DefaultClient)
+//	request := MakeGetRequest("https://api.example.com/text")
+//	readText := ReadText(client)
+//	result := readText(request)(context.Background())()
+func ReadText(client Client) func(Requester) RIOE.ReaderIOResult[string] {
+	return F.Flow2(
+		ReadAll(client),
+		RIOE.Map(B.ToString),
+	)
+}
+
+// ReadJson sends an HTTP request, reads the response, and parses it as JSON.
+//
+// Deprecated: Use [ReadJSON] instead. This function is kept for backward compatibility
+// but will be removed in a future version. The capitalized version follows Go naming
+// conventions for acronyms.
+func ReadJson[A any](client Client) func(Requester) RIOE.ReaderIOResult[A] {
+	return ReadJSON[A](client)
+}
+
+// readJSON is an internal helper that reads the response body and validates JSON content type.
+// It performs the following validations:
+//  1. Validates HTTP status code
+//  2. Validates that the response Content-Type is application/json
+//  3. Reads the response body as bytes
+//
+// This function is used internally by ReadJSON to ensure proper JSON response handling.
+func readJSON(client Client) func(Requester) RIOE.ReaderIOResult[[]byte] {
+	return F.Flow3(
+		ReadFullResponse(client),
+		RIOE.ChainFirstEitherK(F.Flow2(
+			H.Response,
+			H.ValidateJSONResponse,
+		)),
+		RIOE.Map(H.Body),
+	)
+}
+
+// ReadJSON sends an HTTP request, reads the response, and parses it as JSON into type A.
+// It validates both the HTTP status code and the Content-Type header to ensure the
+// response is valid JSON before attempting to unmarshal.
+//
+// Type Parameters:
+//   - A: The target type to unmarshal the JSON response into
+//
+// Parameters:
+//   - client: The HTTP client to use for executing the request
+//
+// Returns:
+//   - A function that takes a Requester and returns a ReaderIOResult[A]
+//     containing the parsed JSON data
+//
+// Example:
+//
+//	type User struct {
+//	    ID   int    `json:"id"`
+//	    Name string `json:"name"`
+//	}
+//
+//	client := MakeClient(http.DefaultClient)
+//	request := MakeGetRequest("https://api.example.com/user/1")
+//	readUser := ReadJSON[User](client)
+//	result := readUser(request)(context.Background())()
+func ReadJSON[A any](client Client) func(Requester) RIOE.ReaderIOResult[A] {
+	return F.Flow2(
+		readJSON(client),
+		RIOE.ChainEitherK(J.Unmarshal[A]),
+	)
+}

v2/context/readerioresult/http/request_test.go

@@ -0,0 +1,315 @@
+// Copyright (c) 2023 - 2025 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package http
+
+import (
+	"context"
+	"fmt"
+	"testing"
+
+	H "net/http"
+
+	R "github.com/IBM/fp-go/v2/context/readerioresult"
+	E "github.com/IBM/fp-go/v2/either"
+	"github.com/IBM/fp-go/v2/errors"
+	F "github.com/IBM/fp-go/v2/function"
+	IOE "github.com/IBM/fp-go/v2/ioeither"
+	"github.com/stretchr/testify/assert"
+)
+
+type PostItem struct {
+	UserID uint   `json:"userId"`
+	Id     uint   `json:"id"`
+	Title  string `json:"title"`
+	Body   string `json:"body"`
+}
+
+func getTitle(item PostItem) string {
+	return item.Title
+}
+
+type simpleRequestBuilder struct {
+	method  string
+	url     string
+	headers H.Header
+}
+
+func requestBuilder() simpleRequestBuilder {
+	return simpleRequestBuilder{method: "GET"}
+}
+
+func (b simpleRequestBuilder) WithURL(url string) simpleRequestBuilder {
+	b.url = url
+	return b
+}
+
+func (b simpleRequestBuilder) WithHeader(key, value string) simpleRequestBuilder {
+	if b.headers == nil {
+		b.headers = make(H.Header)
+	} else {
+		b.headers = b.headers.Clone()
+	}
+	b.headers.Set(key, value)
+	return b
+}
+
+func (b simpleRequestBuilder) Build() R.ReaderIOResult[*H.Request] {
+	return func(ctx context.Context) IOE.IOEither[error, *H.Request] {
+		return IOE.TryCatchError(func() (*H.Request, error) {
+			req, err := H.NewRequestWithContext(ctx, b.method, b.url, nil)
+			if err == nil {
+				req.Header = b.headers
+			}
+			return req, err
+		})
+	}
+}
+
+func TestSendSingleRequest(t *testing.T) {
+
+	client := MakeClient(H.DefaultClient)
+
+	req1 := MakeGetRequest("https://jsonplaceholder.typicode.com/posts/1")
+
+	readItem := ReadJSON[PostItem](client)
+
+	resp1 := readItem(req1)
+
+	resE := resp1(t.Context())()
+
+	fmt.Println(resE)
+}
+
+// setHeaderUnsafe updates a header value in a request object by mutating the request object
+func setHeaderUnsafe(key, value string) func(*H.Request) *H.Request {
+	return func(req *H.Request) *H.Request {
+		req.Header.Set(key, value)
+		return req
+	}
+}
+
+func TestSendSingleRequestWithHeaderUnsafe(t *testing.T) {
+
+	client := MakeClient(H.DefaultClient)
+
+	// this is not safe from a puristic perspective, because the map call mutates the request object
+	req1 := F.Pipe2(
+		"https://jsonplaceholder.typicode.com/posts/1",
+		MakeGetRequest,
+		R.Map(setHeaderUnsafe("Content-Type", "text/html")),
+	)
+
+	readItem := ReadJSON[PostItem](client)
+
+	resp1 := F.Pipe2(
+		req1,
+		readItem,
+		R.Map(getTitle),
+	)
+
+	res := F.Pipe1(
+		resp1(t.Context())(),
+		E.GetOrElse(errors.ToString),
+	)
+
+	assert.Equal(t, "sunt aut facere repellat provident occaecati excepturi optio reprehenderit", res)
+}
+
+func TestSendSingleRequestWithHeaderSafe(t *testing.T) {
+
+	client := MakeClient(H.DefaultClient)
+
+	// the request builder assembles config values to construct
+	// the final http request. Each `With` step creates a copy of the settings
+	// so the flow is pure
+	request := requestBuilder().
+		WithURL("https://jsonplaceholder.typicode.com/posts/1").
+		WithHeader("Content-Type", "text/html").
+		Build()
+
+	readItem := ReadJSON[PostItem](client)
+
+	response := F.Pipe2(
+		request,
+		readItem,
+		R.Map(getTitle),
+	)
+
+	res := F.Pipe1(
+		response(t.Context())(),
+		E.GetOrElse(errors.ToString),
+	)
+
+	assert.Equal(t, "sunt aut facere repellat provident occaecati excepturi optio reprehenderit", res)
+}
+
+// TestReadAll tests the ReadAll function which reads response as bytes
+func TestReadAll(t *testing.T) {
+	client := MakeClient(H.DefaultClient)
+
+	request := MakeGetRequest("https://jsonplaceholder.typicode.com/posts/1")
+	readBytes := ReadAll(client)
+
+	result := readBytes(request)(t.Context())()
+
+	assert.True(t, E.IsRight(result), "Expected Right result")
+
+	bytes := E.GetOrElse(func(error) []byte { return nil })(result)
+	assert.NotNil(t, bytes, "Expected non-nil bytes")
+	assert.Greater(t, len(bytes), 0, "Expected non-empty byte array")
+
+	// Verify it contains expected JSON content
+	content := string(bytes)
+	assert.Contains(t, content, "userId")
+	assert.Contains(t, content, "title")
+}
+
+// TestReadText tests the ReadText function which reads response as string
+func TestReadText(t *testing.T) {
+	client := MakeClient(H.DefaultClient)
+
+	request := MakeGetRequest("https://jsonplaceholder.typicode.com/posts/1")
+	readText := ReadText(client)
+
+	result := readText(request)(t.Context())()
+
+	assert.True(t, E.IsRight(result), "Expected Right result")
+
+	text := E.GetOrElse(func(error) string { return "" })(result)
+	assert.NotEmpty(t, text, "Expected non-empty text")
+
+	// Verify it contains expected JSON content as text
+	assert.Contains(t, text, "userId")
+	assert.Contains(t, text, "title")
+	assert.Contains(t, text, "sunt aut facere")
+}
+
+// TestReadJson tests the deprecated ReadJson function
+func TestReadJson(t *testing.T) {
+	client := MakeClient(H.DefaultClient)
+
+	request := MakeGetRequest("https://jsonplaceholder.typicode.com/posts/1")
+	readItem := ReadJson[PostItem](client)
+
+	result := readItem(request)(t.Context())()
+
+	assert.True(t, E.IsRight(result), "Expected Right result")
+
+	item := E.GetOrElse(func(error) PostItem { return PostItem{} })(result)
+	assert.Equal(t, uint(1), item.UserID, "Expected UserID to be 1")
+	assert.Equal(t, uint(1), item.Id, "Expected Id to be 1")
+	assert.NotEmpty(t, item.Title, "Expected non-empty title")
+	assert.NotEmpty(t, item.Body, "Expected non-empty body")
+}
+
+// TestReadAllWithInvalidURL tests ReadAll with an invalid URL
+func TestReadAllWithInvalidURL(t *testing.T) {
+	client := MakeClient(H.DefaultClient)
+
+	request := MakeGetRequest("http://invalid-domain-that-does-not-exist-12345.com")
+	readBytes := ReadAll(client)
+
+	result := readBytes(request)(t.Context())()
+
+	assert.True(t, E.IsLeft(result), "Expected Left result for invalid URL")
+}
+
+// TestReadTextWithInvalidURL tests ReadText with an invalid URL
+func TestReadTextWithInvalidURL(t *testing.T) {
+	client := MakeClient(H.DefaultClient)
+
+	request := MakeGetRequest("http://invalid-domain-that-does-not-exist-12345.com")
+	readText := ReadText(client)
+
+	result := readText(request)(t.Context())()
+
+	assert.True(t, E.IsLeft(result), "Expected Left result for invalid URL")
+}
+
+// TestReadJSONWithInvalidURL tests ReadJSON with an invalid URL
+func TestReadJSONWithInvalidURL(t *testing.T) {
+	client := MakeClient(H.DefaultClient)
+
+	request := MakeGetRequest("http://invalid-domain-that-does-not-exist-12345.com")
+	readItem := ReadJSON[PostItem](client)
+
+	result := readItem(request)(t.Context())()
+
+	assert.True(t, E.IsLeft(result), "Expected Left result for invalid URL")
+}
+
+// TestReadJSONWithInvalidJSON tests ReadJSON with non-JSON response
+func TestReadJSONWithInvalidJSON(t *testing.T) {
+	client := MakeClient(H.DefaultClient)
+
+	// This URL returns HTML, not JSON
+	request := MakeGetRequest("https://www.google.com")
+	readItem := ReadJSON[PostItem](client)
+
+	result := readItem(request)(t.Context())()
+
+	// Should fail because content-type is not application/json
+	assert.True(t, E.IsLeft(result), "Expected Left result for non-JSON response")
+}
+
+// TestMakeClientWithCustomClient tests MakeClient with a custom http.Client
+func TestMakeClientWithCustomClient(t *testing.T) {
+	customClient := H.DefaultClient
+
+	client := MakeClient(customClient)
+	assert.NotNil(t, client, "Expected non-nil client")
+
+	// Verify it works
+	request := MakeGetRequest("https://jsonplaceholder.typicode.com/posts/1")
+	readItem := ReadJSON[PostItem](client)
+	result := readItem(request)(t.Context())()
+
+	assert.True(t, E.IsRight(result), "Expected Right result")
+}
+
+// TestReadAllComposition tests composing ReadAll with other operations
+func TestReadAllComposition(t *testing.T) {
+	client := MakeClient(H.DefaultClient)
+
+	request := MakeGetRequest("https://jsonplaceholder.typicode.com/posts/1")
+
+	// Compose ReadAll with a map operation to get byte length
+	readBytes := ReadAll(client)(request)
+	readLength := R.Map(func(bytes []byte) int { return len(bytes) })(readBytes)
+
+	result := readLength(t.Context())()
+
+	assert.True(t, E.IsRight(result), "Expected Right result")
+	length := E.GetOrElse(func(error) int { return 0 })(result)
+	assert.Greater(t, length, 0, "Expected positive byte length")
+}
+
+// TestReadTextComposition tests composing ReadText with other operations
+func TestReadTextComposition(t *testing.T) {
+	client := MakeClient(H.DefaultClient)
+
+	request := MakeGetRequest("https://jsonplaceholder.typicode.com/posts/1")
+
+	// Compose ReadText with a map operation to get string length
+	readText := ReadText(client)(request)
+	readLength := R.Map(func(text string) int { return len(text) })(readText)
+
+	result := readLength(t.Context())()
+
+	assert.True(t, E.IsRight(result), "Expected Right result")
+	length := E.GetOrElse(func(error) int { return 0 })(result)
+	assert.Greater(t, length, 0, "Expected positive string length")
+}

v2/context/readerioresult/monoid.go

@@ -13,96 +13,75 @@
 //   See the License for the specific language governing permissions and
 //   limitations under the License.
 
-package readerioeither
+package readerioresult
 
 import (
+	"context"
+
 	"github.com/IBM/fp-go/v2/monoid"
+	RIOR "github.com/IBM/fp-go/v2/readerioresult"
 )
 
 type (
-	Monoid[A any] = monoid.Monoid[ReaderIOEither[A]]
+	Monoid[A any] = monoid.Monoid[ReaderIOResult[A]]
 )
 
-// ApplicativeMonoid returns a [Monoid] that concatenates [ReaderIOEither] instances via their applicative.
+// ApplicativeMonoid returns a [Monoid] that concatenates [ReaderIOResult] instances via their applicative.
 // This uses the default applicative behavior (parallel or sequential based on useParallel flag).
 //
-// The monoid combines two ReaderIOEither values by applying the underlying monoid's combine operation
+// The monoid combines two ReaderIOResult values by applying the underlying monoid's combine operation
 // to their success values using applicative application.
 //
 // Parameters:
 //   - m: The underlying monoid for type A
 //
-// Returns a Monoid for ReaderIOEither[A].
+// Returns a Monoid for ReaderIOResult[A].
 func ApplicativeMonoid[A any](m monoid.Monoid[A]) Monoid[A] {
-	return monoid.ApplicativeMonoid(
-		Of[A],
-		MonadMap[A, func(A) A],
-		MonadAp[A, A],
-		m,
-	)
+	return RIOR.ApplicativeMonoid[context.Context](m)
 }
 
-// ApplicativeMonoidSeq returns a [Monoid] that concatenates [ReaderIOEither] instances via their applicative.
+// ApplicativeMonoidSeq returns a [Monoid] that concatenates [ReaderIOResult] instances via their applicative.
 // This explicitly uses sequential execution for combining values.
 //
 // Parameters:
 //   - m: The underlying monoid for type A
 //
-// Returns a Monoid for ReaderIOEither[A] with sequential execution.
+// Returns a Monoid for ReaderIOResult[A] with sequential execution.
 func ApplicativeMonoidSeq[A any](m monoid.Monoid[A]) Monoid[A] {
-	return monoid.ApplicativeMonoid(
-		Of[A],
-		MonadMap[A, func(A) A],
-		MonadApSeq[A, A],
-		m,
-	)
+	return RIOR.ApplicativeMonoidSeq[context.Context](m)
 }
 
-// ApplicativeMonoidPar returns a [Monoid] that concatenates [ReaderIOEither] instances via their applicative.
+// ApplicativeMonoidPar returns a [Monoid] that concatenates [ReaderIOResult] instances via their applicative.
 // This explicitly uses parallel execution for combining values.
 //
 // Parameters:
 //   - m: The underlying monoid for type A
 //
-// Returns a Monoid for ReaderIOEither[A] with parallel execution.
+// Returns a Monoid for ReaderIOResult[A] with parallel execution.
 func ApplicativeMonoidPar[A any](m monoid.Monoid[A]) Monoid[A] {
-	return monoid.ApplicativeMonoid(
-		Of[A],
-		MonadMap[A, func(A) A],
-		MonadApPar[A, A],
-		m,
-	)
+	return RIOR.ApplicativeMonoidPar[context.Context](m)
 }
 
-// AlternativeMonoid is the alternative [Monoid] for [ReaderIOEither].
-// This combines ReaderIOEither values using the alternative semantics,
+// AlternativeMonoid is the alternative [Monoid] for [ReaderIOResult].
+// This combines ReaderIOResult values using the alternative semantics,
 // where the second value is only evaluated if the first fails.
 //
 // Parameters:
 //   - m: The underlying monoid for type A
 //
-// Returns a Monoid for ReaderIOEither[A] with alternative semantics.
+// Returns a Monoid for ReaderIOResult[A] with alternative semantics.
 func AlternativeMonoid[A any](m monoid.Monoid[A]) Monoid[A] {
-	return monoid.AlternativeMonoid(
-		Of[A],
-		MonadMap[A, func(A) A],
-		MonadAp[A, A],
-		MonadAlt[A],
-		m,
-	)
+	return RIOR.AlternativeMonoid[context.Context](m)
 }
 
-// AltMonoid is the alternative [Monoid] for a [ReaderIOEither].
+// AltMonoid is the alternative [Monoid] for a [ReaderIOResult].
 // This creates a monoid where the empty value is provided lazily,
 // and combination uses the Alt operation (try first, fallback to second on failure).
 //
 // Parameters:
 //   - zero: Lazy computation that provides the empty/identity value
 //
-// Returns a Monoid for ReaderIOEither[A] with Alt-based combination.
-func AltMonoid[A any](zero Lazy[ReaderIOEither[A]]) Monoid[A] {
-	return monoid.AltMonoid(
-		zero,
-		MonadAlt[A],
-	)
+// Returns a Monoid for ReaderIOResult[A] with Alt-based combination.
+func AltMonoid[A any](zero Lazy[ReaderIOResult[A]]) Monoid[A] {
+	return RIOR.AltMonoid(zero)
 }

v2/context/readerioresult/reader.go

@@ -0,0 +1,960 @@
+// Copyright (c) 2023 - 2025 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package readerioresult
+
+import (
+	"context"
+	"time"
+
+	"github.com/IBM/fp-go/v2/context/readerresult"
+	"github.com/IBM/fp-go/v2/either"
+	"github.com/IBM/fp-go/v2/errors"
+	"github.com/IBM/fp-go/v2/function"
+	"github.com/IBM/fp-go/v2/io"
+	"github.com/IBM/fp-go/v2/ioeither"
+	"github.com/IBM/fp-go/v2/ioresult"
+	"github.com/IBM/fp-go/v2/reader"
+	"github.com/IBM/fp-go/v2/readerio"
+	RIOR "github.com/IBM/fp-go/v2/readerioresult"
+	"github.com/IBM/fp-go/v2/readeroption"
+)
+
+const (
+	// useParallel is the feature flag to control if we use the parallel or the sequential implementation of ap
+	useParallel = true
+)
+
+// FromEither converts an [Either] into a [ReaderIOResult].
+// The resulting computation ignores the context and immediately returns the Either value.
+//
+// Parameters:
+//   - e: The Either value to lift into ReaderIOResult
+//
+// Returns a ReaderIOResult that produces the given Either value.
+//
+//go:inline
+func FromEither[A any](e Either[A]) ReaderIOResult[A] {
+	return RIOR.FromEither[context.Context](e)
+}
+
+// FromEither converts an [Either] into a [ReaderIOResult].
+// The resulting computation ignores the context and immediately returns the Either value.
+//
+// Parameters:
+//   - e: The Either value to lift into ReaderIOResult
+//
+// Returns a ReaderIOResult that produces the given Either value.
+//
+//go:inline
+func FromResult[A any](e Result[A]) ReaderIOResult[A] {
+	return RIOR.FromEither[context.Context](e)
+}
+
+// Left creates a [ReaderIOResult] that represents a failed computation with the given error.
+//
+// Parameters:
+//   - l: The error value
+//
+// Returns a ReaderIOResult that always fails with the given error.
+func Left[A any](l error) ReaderIOResult[A] {
+	return RIOR.Left[context.Context, A](l)
+}
+
+// Right creates a [ReaderIOResult] that represents a successful computation with the given value.
+//
+// Parameters:
+//   - r: The success value
+//
+// Returns a ReaderIOResult that always succeeds with the given value.
+//
+//go:inline
+func Right[A any](r A) ReaderIOResult[A] {
+	return RIOR.Right[context.Context](r)
+}
+
+// MonadMap transforms the success value of a [ReaderIOResult] using the provided function.
+// If the computation fails, the error is propagated unchanged.
+//
+// Parameters:
+//   - fa: The ReaderIOResult to transform
+//   - f: The transformation function
+//
+// Returns a new ReaderIOResult with the transformed value.
+//
+//go:inline
+func MonadMap[A, B any](fa ReaderIOResult[A], f func(A) B) ReaderIOResult[B] {
+	return RIOR.MonadMap(fa, f)
+}
+
+// Map transforms the success value of a [ReaderIOResult] using the provided function.
+// This is the curried version of [MonadMap], useful for composition.
+//
+// Parameters:
+//   - f: The transformation function
+//
+// Returns a function that transforms a ReaderIOResult.
+//
+//go:inline
+func Map[A, B any](f func(A) B) Operator[A, B] {
+	return RIOR.Map[context.Context](f)
+}
+
+// MonadMapTo replaces the success value of a [ReaderIOResult] with a constant value.
+// If the computation fails, the error is propagated unchanged.
+//
+// Parameters:
+//   - fa: The ReaderIOResult to transform
+//   - b: The constant value to use
+//
+// Returns a new ReaderIOResult with the constant value.
+//
+//go:inline
+func MonadMapTo[A, B any](fa ReaderIOResult[A], b B) ReaderIOResult[B] {
+	return RIOR.MonadMapTo(fa, b)
+}
+
+// MapTo replaces the success value of a [ReaderIOResult] with a constant value.
+// This is the curried version of [MonadMapTo].
+//
+// Parameters:
+//   - b: The constant value to use
+//
+// Returns a function that transforms a ReaderIOResult.
+//
+//go:inline
+func MapTo[A, B any](b B) Operator[A, B] {
+	return RIOR.MapTo[context.Context, A](b)
+}
+
+// MonadChain sequences two [ReaderIOResult] computations, where the second depends on the result of the first.
+// If the first computation fails, the second is not executed.
+//
+// Parameters:
+//   - ma: The first ReaderIOResult
+//   - f: Function that produces the second ReaderIOResult based on the first's result
+//
+// Returns a new ReaderIOResult representing the sequenced computation.
+//
+//go:inline
+func MonadChain[A, B any](ma ReaderIOResult[A], f Kleisli[A, B]) ReaderIOResult[B] {
+	return RIOR.MonadChain(ma, f)
+}
+
+// Chain sequences two [ReaderIOResult] computations, where the second depends on the result of the first.
+// This is the curried version of [MonadChain], useful for composition.
+//
+// Parameters:
+//   - f: Function that produces the second ReaderIOResult based on the first's result
+//
+// Returns a function that sequences ReaderIOResult computations.
+//
+//go:inline
+func Chain[A, B any](f Kleisli[A, B]) Operator[A, B] {
+	return RIOR.Chain(f)
+}
+
+// MonadChainFirst sequences two [ReaderIOResult] computations but returns the result of the first.
+// The second computation is executed for its side effects only.
+//
+// Parameters:
+//   - ma: The first ReaderIOResult
+//   - f: Function that produces the second ReaderIOResult
+//
+// Returns a ReaderIOResult with the result of the first computation.
+//
+//go:inline
+func MonadChainFirst[A, B any](ma ReaderIOResult[A], f Kleisli[A, B]) ReaderIOResult[A] {
+	return RIOR.MonadChainFirst(ma, f)
+}
+
+//go:inline
+func MonadTap[A, B any](ma ReaderIOResult[A], f Kleisli[A, B]) ReaderIOResult[A] {
+	return RIOR.MonadTap(ma, f)
+}
+
+// ChainFirst sequences two [ReaderIOResult] computations but returns the result of the first.
+// This is the curried version of [MonadChainFirst].
+//
+// Parameters:
+//   - f: Function that produces the second ReaderIOResult
+//
+// Returns a function that sequences ReaderIOResult computations.
+//
+//go:inline
+func ChainFirst[A, B any](f Kleisli[A, B]) Operator[A, A] {
+	return RIOR.ChainFirst(f)
+}
+
+//go:inline
+func Tap[A, B any](f Kleisli[A, B]) Operator[A, A] {
+	return RIOR.Tap(f)
+}
+
+// Of creates a [ReaderIOResult] that always succeeds with the given value.
+// This is the same as [Right] and represents the monadic return operation.
+//
+// Parameters:
+//   - a: The value to wrap
+//
+// Returns a ReaderIOResult that always succeeds with the given value.
+//
+//go:inline
+func Of[A any](a A) ReaderIOResult[A] {
+	return RIOR.Of[context.Context](a)
+}
+
+func withCancelCauseFunc[A any](cancel context.CancelCauseFunc, ma IOResult[A]) IOResult[A] {
+	return function.Pipe3(
+		ma,
+		ioresult.Swap[A],
+		ioeither.ChainFirstIOK[A](func(err error) func() any {
+			return io.FromImpure(func() { cancel(err) })
+		}),
+		ioeither.Swap[A],
+	)
+}
+
+// MonadApPar implements parallel applicative application for [ReaderIOResult].
+// It executes both computations in parallel and creates a sub-context that will be canceled
+// if either operation fails. This provides automatic cancellation propagation.
+//
+// Parameters:
+//   - fab: ReaderIOResult containing a function
+//   - fa: ReaderIOResult containing a value
+//
+// Returns a ReaderIOResult with the function applied to the value.
+func MonadApPar[B, A any](fab ReaderIOResult[func(A) B], fa ReaderIOResult[A]) ReaderIOResult[B] {
+	// context sensitive input
+	cfab := WithContext(fab)
+	cfa := WithContext(fa)
+
+	return func(ctx context.Context) IOResult[B] {
+		// quick check for cancellation
+		if err := context.Cause(ctx); err != nil {
+			return ioeither.Left[B](err)
+		}
+
+		return func() Result[B] {
+			// quick check for cancellation
+			if err := context.Cause(ctx); err != nil {
+				return either.Left[B](err)
+			}
+
+			// create sub-contexts for fa and fab, so they can cancel one other
+			ctxSub, cancelSub := context.WithCancelCause(ctx)
+			defer cancelSub(nil) // cancel has to be called in all paths
+
+			fabIOE := withCancelCauseFunc(cancelSub, cfab(ctxSub))
+			faIOE := withCancelCauseFunc(cancelSub, cfa(ctxSub))
+
+			return ioresult.MonadApPar(fabIOE, faIOE)()
+		}
+	}
+}
+
+// MonadAp implements applicative application for [ReaderIOResult].
+// By default, it uses parallel execution ([MonadApPar]) but can be configured to use
+// sequential execution ([MonadApSeq]) via the useParallel constant.
+//
+// Parameters:
+//   - fab: ReaderIOResult containing a function
+//   - fa: ReaderIOResult containing a value
+//
+// Returns a ReaderIOResult with the function applied to the value.
+func MonadAp[B, A any](fab ReaderIOResult[func(A) B], fa ReaderIOResult[A]) ReaderIOResult[B] {
+	// dispatch to the configured version
+	if useParallel {
+		return MonadApPar(fab, fa)
+	}
+	return MonadApSeq(fab, fa)
+}
+
+// MonadApSeq implements sequential applicative application for [ReaderIOResult].
+// It executes the function computation first, then the value computation.
+//
+// Parameters:
+//   - fab: ReaderIOResult containing a function
+//   - fa: ReaderIOResult containing a value
+//
+// Returns a ReaderIOResult with the function applied to the value.
+//
+//go:inline
+func MonadApSeq[B, A any](fab ReaderIOResult[func(A) B], fa ReaderIOResult[A]) ReaderIOResult[B] {
+	return RIOR.MonadApSeq(fab, fa)
+}
+
+// Ap applies a function wrapped in a [ReaderIOResult] to a value wrapped in a ReaderIOResult.
+// This is the curried version of [MonadAp], using the default execution mode.
+//
+// Parameters:
+//   - fa: ReaderIOResult containing a value
+//
+// Returns a function that applies a ReaderIOResult function to the value.
+//
+//go:inline
+func Ap[B, A any](fa ReaderIOResult[A]) Operator[func(A) B, B] {
+	return function.Bind2nd(MonadAp[B, A], fa)
+}
+
+// ApSeq applies a function wrapped in a [ReaderIOResult] to a value sequentially.
+// This is the curried version of [MonadApSeq].
+//
+// Parameters:
+//   - fa: ReaderIOResult containing a value
+//
+// Returns a function that applies a ReaderIOResult function to the value sequentially.
+//
+//go:inline
+func ApSeq[B, A any](fa ReaderIOResult[A]) Operator[func(A) B, B] {
+	return function.Bind2nd(MonadApSeq[B, A], fa)
+}
+
+// ApPar applies a function wrapped in a [ReaderIOResult] to a value in parallel.
+// This is the curried version of [MonadApPar].
+//
+// Parameters:
+//   - fa: ReaderIOResult containing a value
+//
+// Returns a function that applies a ReaderIOResult function to the value in parallel.
+//
+//go:inline
+func ApPar[B, A any](fa ReaderIOResult[A]) Operator[func(A) B, B] {
+	return function.Bind2nd(MonadApPar[B, A], fa)
+}
+
+// FromPredicate creates a [ReaderIOResult] from a predicate function.
+// If the predicate returns true, the value is wrapped in Right; otherwise, Left with the error from onFalse.
+//
+// Parameters:
+//   - pred: Predicate function to test the value
+//   - onFalse: Function to generate an error when predicate fails
+//
+// Returns a function that converts a value to ReaderIOResult based on the predicate.
+//
+//go:inline
+func FromPredicate[A any](pred func(A) bool, onFalse func(A) error) Kleisli[A, A] {
+	return RIOR.FromPredicate[context.Context](pred, onFalse)
+}
+
+// OrElse provides an alternative [ReaderIOResult] computation if the first one fails.
+// The alternative is only executed if the first computation results in a Left (error).
+//
+// Parameters:
+//   - onLeft: Function that produces an alternative ReaderIOResult from the error
+//
+// Returns a function that provides fallback behavior for failed computations.
+//
+//go:inline
+func OrElse[A any](onLeft Kleisli[error, A]) Operator[A, A] {
+	return RIOR.OrElse(onLeft)
+}
+
+// Ask returns a [ReaderIOResult] that provides access to the context.
+// This is useful for accessing the [context.Context] within a computation.
+//
+// Returns a ReaderIOResult that produces the context.
+//
+//go:inline
+func Ask() ReaderIOResult[context.Context] {
+	return RIOR.Ask[context.Context]()
+}
+
+// MonadChainEitherK chains a function that returns an [Either] into a [ReaderIOResult] computation.
+// This is useful for integrating pure Either-returning functions into ReaderIOResult workflows.
+//
+// Parameters:
+//   - ma: The ReaderIOResult to chain from
+//   - f: Function that produces an Either
+//
+// Returns a new ReaderIOResult with the chained computation.
+//
+//go:inline
+func MonadChainEitherK[A, B any](ma ReaderIOResult[A], f func(A) Either[B]) ReaderIOResult[B] {
+	return RIOR.MonadChainEitherK(ma, f)
+}
+
+// ChainEitherK chains a function that returns an [Either] into a [ReaderIOResult] computation.
+// This is the curried version of [MonadChainEitherK].
+//
+// Parameters:
+//   - f: Function that produces an Either
+//
+// Returns a function that chains the Either-returning function.
+//
+//go:inline
+func ChainEitherK[A, B any](f func(A) Either[B]) Operator[A, B] {
+	return RIOR.ChainEitherK[context.Context](f)
+}
+
+// MonadChainFirstEitherK chains a function that returns an [Either] but keeps the original value.
+// The Either-returning function is executed for its validation/side effects only.
+//
+// Parameters:
+//   - ma: The ReaderIOResult to chain from
+//   - f: Function that produces an Either
+//
+// Returns a ReaderIOResult with the original value if both computations succeed.
+//
+//go:inline
+func MonadChainFirstEitherK[A, B any](ma ReaderIOResult[A], f func(A) Either[B]) ReaderIOResult[A] {
+	return RIOR.MonadChainFirstEitherK(ma, f)
+}
+
+//go:inline
+func MonadTapEitherK[A, B any](ma ReaderIOResult[A], f func(A) Either[B]) ReaderIOResult[A] {
+	return RIOR.MonadTapEitherK(ma, f)
+}
+
+// ChainFirstEitherK chains a function that returns an [Either] but keeps the original value.
+// This is the curried version of [MonadChainFirstEitherK].
+//
+// Parameters:
+//   - f: Function that produces an Either
+//
+// Returns a function that chains the Either-returning function.
+//
+//go:inline
+func ChainFirstEitherK[A, B any](f func(A) Either[B]) Operator[A, A] {
+	return RIOR.ChainFirstEitherK[context.Context](f)
+}
+
+//go:inline
+func TapEitherK[A, B any](f func(A) Either[B]) Operator[A, A] {
+	return RIOR.TapEitherK[context.Context](f)
+}
+
+// ChainOptionK chains a function that returns an [Option] into a [ReaderIOResult] computation.
+// If the Option is None, the provided error function is called.
+//
+// Parameters:
+//   - onNone: Function to generate an error when Option is None
+//
+// Returns a function that chains Option-returning functions into ReaderIOResult.
+//
+//go:inline
+func ChainOptionK[A, B any](onNone func() error) func(func(A) Option[B]) Operator[A, B] {
+	return RIOR.ChainOptionK[context.Context, A, B](onNone)
+}
+
+// FromIOEither converts an [IOResult] into a [ReaderIOResult].
+// The resulting computation ignores the context.
+//
+// Parameters:
+//   - t: The IOResult to convert
+//
+// Returns a ReaderIOResult that executes the IOResult.
+//
+//go:inline
+func FromIOEither[A any](t IOResult[A]) ReaderIOResult[A] {
+	return RIOR.FromIOEither[context.Context](t)
+}
+
+//go:inline
+func FromIOResult[A any](t IOResult[A]) ReaderIOResult[A] {
+	return RIOR.FromIOResult[context.Context](t)
+}
+
+// FromIO converts an [IO] into a [ReaderIOResult].
+// The IO computation always succeeds, so it's wrapped in Right.
+//
+// Parameters:
+//   - t: The IO to convert
+//
+// Returns a ReaderIOResult that executes the IO and wraps the result in Right.
+//
+//go:inline
+func FromIO[A any](t IO[A]) ReaderIOResult[A] {
+	return RIOR.FromIO[context.Context](t)
+}
+
+//go:inline
+func FromReader[A any](t Reader[context.Context, A]) ReaderIOResult[A] {
+	return RIOR.FromReader(t)
+}
+
+//go:inline
+func FromReaderIO[A any](t ReaderIO[A]) ReaderIOResult[A] {
+	return RIOR.FromReaderIO(t)
+}
+
+// FromLazy converts a [Lazy] computation into a [ReaderIOResult].
+// The Lazy computation always succeeds, so it's wrapped in Right.
+// This is an alias for [FromIO] since Lazy and IO have the same structure.
+//
+// Parameters:
+//   - t: The Lazy computation to convert
+//
+// Returns a ReaderIOResult that executes the Lazy computation and wraps the result in Right.
+//
+//go:inline
+func FromLazy[A any](t Lazy[A]) ReaderIOResult[A] {
+	return RIOR.FromIO[context.Context](t)
+}
+
+// Never returns a [ReaderIOResult] that blocks indefinitely until the context is canceled.
+// This is useful for creating computations that wait for external cancellation signals.
+//
+// Returns a ReaderIOResult that waits for context cancellation and returns the cancellation error.
+func Never[A any]() ReaderIOResult[A] {
+	return func(ctx context.Context) IOResult[A] {
+		return func() Either[A] {
+			<-ctx.Done()
+			return either.Left[A](context.Cause(ctx))
+		}
+	}
+}
+
+// MonadChainIOK chains a function that returns an [IO] into a [ReaderIOResult] computation.
+// The IO computation always succeeds, so it's wrapped in Right.
+//
+// Parameters:
+//   - ma: The ReaderIOResult to chain from
+//   - f: Function that produces an IO
+//
+// Returns a new ReaderIOResult with the chained IO computation.
+//
+//go:inline
+func MonadChainIOK[A, B any](ma ReaderIOResult[A], f func(A) IO[B]) ReaderIOResult[B] {
+	return RIOR.MonadChainIOK(ma, f)
+}
+
+// ChainIOK chains a function that returns an [IO] into a [ReaderIOResult] computation.
+// This is the curried version of [MonadChainIOK].
+//
+// Parameters:
+//   - f: Function that produces an IO
+//
+// Returns a function that chains the IO-returning function.
+//
+//go:inline
+func ChainIOK[A, B any](f func(A) IO[B]) Operator[A, B] {
+	return RIOR.ChainIOK[context.Context](f)
+}
+
+// MonadChainFirstIOK chains a function that returns an [IO] but keeps the original value.
+// The IO computation is executed for its side effects only.
+//
+// Parameters:
+//   - ma: The ReaderIOResult to chain from
+//   - f: Function that produces an IO
+//
+// Returns a ReaderIOResult with the original value after executing the IO.
+//
+//go:inline
+func MonadChainFirstIOK[A, B any](ma ReaderIOResult[A], f func(A) IO[B]) ReaderIOResult[A] {
+	return RIOR.MonadChainFirstIOK(ma, f)
+}
+
+//go:inline
+func MonadTapIOK[A, B any](ma ReaderIOResult[A], f func(A) IO[B]) ReaderIOResult[A] {
+	return RIOR.MonadTapIOK(ma, f)
+}
+
+// ChainFirstIOK chains a function that returns an [IO] but keeps the original value.
+// This is the curried version of [MonadChainFirstIOK].
+//
+// Parameters:
+//   - f: Function that produces an IO
+//
+// Returns a function that chains the IO-returning function.
+//
+//go:inline
+func ChainFirstIOK[A, B any](f func(A) IO[B]) Operator[A, A] {
+	return RIOR.ChainFirstIOK[context.Context](f)
+}
+
+//go:inline
+func TapIOK[A, B any](f func(A) IO[B]) Operator[A, A] {
+	return RIOR.TapIOK[context.Context](f)
+}
+
+// ChainIOEitherK chains a function that returns an [IOResult] into a [ReaderIOResult] computation.
+// This is useful for integrating IOResult-returning functions into ReaderIOResult workflows.
+//
+// Parameters:
+//   - f: Function that produces an IOResult
+//
+// Returns a function that chains the IOResult-returning function.
+//
+//go:inline
+func ChainIOEitherK[A, B any](f func(A) IOResult[B]) Operator[A, B] {
+	return RIOR.ChainIOEitherK[context.Context](f)
+}
+
+// Delay creates an operation that delays execution by the specified duration.
+// The computation waits for either the delay to expire or the context to be canceled.
+//
+// Parameters:
+//   - delay: The duration to wait before executing the computation
+//
+// Returns a function that delays a ReaderIOResult computation.
+func Delay[A any](delay time.Duration) Operator[A, A] {
+	return func(ma ReaderIOResult[A]) ReaderIOResult[A] {
+		return func(ctx context.Context) IOResult[A] {
+			return func() Either[A] {
+				// manage the timeout
+				timeoutCtx, cancelTimeout := context.WithTimeout(ctx, delay)
+				defer cancelTimeout()
+				// whatever comes first
+				select {
+				case <-timeoutCtx.Done():
+					return ma(ctx)()
+				case <-ctx.Done():
+					return either.Left[A](context.Cause(ctx))
+				}
+			}
+		}
+	}
+}
+
+// Timer returns the current time after waiting for the specified delay.
+// This is useful for creating time-based computations.
+//
+// Parameters:
+//   - delay: The duration to wait before returning the time
+//
+// Returns a ReaderIOResult that produces the current time after the delay.
+func Timer(delay time.Duration) ReaderIOResult[time.Time] {
+	return function.Pipe2(
+		io.Now,
+		FromIO[time.Time],
+		Delay[time.Time](delay),
+	)
+}
+
+// Defer creates a [ReaderIOResult] by lazily generating a new computation each time it's executed.
+// This is useful for creating computations that should be re-evaluated on each execution.
+//
+// Parameters:
+//   - gen: Lazy generator function that produces a ReaderIOResult
+//
+// Returns a ReaderIOResult that generates a fresh computation on each execution.
+//
+//go:inline
+func Defer[A any](gen Lazy[ReaderIOResult[A]]) ReaderIOResult[A] {
+	return RIOR.Defer(gen)
+}
+
+// TryCatch wraps a function that returns a tuple (value) into a [ReaderIOResult].
+// This is the standard way to convert Go error-returning functions into ReaderIOResult.
+//
+// Parameters:
+//   - f: Function that takes a context and returns a function producing (value)
+//
+// Returns a ReaderIOResult that wraps the error-returning function.
+//
+//go:inline
+func TryCatch[A any](f func(context.Context) func() (A, error)) ReaderIOResult[A] {
+	return RIOR.TryCatch(f, errors.Identity)
+}
+
+// MonadAlt provides an alternative [ReaderIOResult] if the first one fails.
+// The alternative is lazily evaluated only if needed.
+//
+// Parameters:
+//   - first: The primary ReaderIOResult to try
+//   - second: Lazy alternative ReaderIOResult to use if first fails
+//
+// Returns a ReaderIOResult that tries the first, then the second if first fails.
+//
+//go:inline
+func MonadAlt[A any](first ReaderIOResult[A], second Lazy[ReaderIOResult[A]]) ReaderIOResult[A] {
+	return RIOR.MonadAlt(first, second)
+}
+
+// Alt provides an alternative [ReaderIOResult] if the first one fails.
+// This is the curried version of [MonadAlt].
+//
+// Parameters:
+//   - second: Lazy alternative ReaderIOResult to use if first fails
+//
+// Returns a function that provides fallback behavior.
+//
+//go:inline
+func Alt[A any](second Lazy[ReaderIOResult[A]]) Operator[A, A] {
+	return RIOR.Alt(second)
+}
+
+// Memoize computes the value of the provided [ReaderIOResult] monad lazily but exactly once.
+// The context used to compute the value is the context of the first call, so do not use this
+// method if the value has a functional dependency on the content of the context.
+//
+// Parameters:
+//   - rdr: The ReaderIOResult to memoize
+//
+// Returns a ReaderIOResult that caches its result after the first execution.
+//
+//go:inline
+func Memoize[A any](rdr ReaderIOResult[A]) ReaderIOResult[A] {
+	return RIOR.Memoize(rdr)
+}
+
+// Flatten converts a nested [ReaderIOResult] into a flat [ReaderIOResult].
+// This is equivalent to [MonadChain] with the identity function.
+//
+// Parameters:
+//   - rdr: The nested ReaderIOResult to flatten
+//
+// Returns a flattened ReaderIOResult.
+//
+//go:inline
+func Flatten[A any](rdr ReaderIOResult[ReaderIOResult[A]]) ReaderIOResult[A] {
+	return RIOR.Flatten(rdr)
+}
+
+// MonadFlap applies a value to a function wrapped in a [ReaderIOResult].
+// This is the reverse of [MonadAp], useful in certain composition scenarios.
+//
+// Parameters:
+//   - fab: ReaderIOResult containing a function
+//   - a: The value to apply to the function
+//
+// Returns a ReaderIOResult with the function applied to the value.
+//
+//go:inline
+func MonadFlap[B, A any](fab ReaderIOResult[func(A) B], a A) ReaderIOResult[B] {
+	return RIOR.MonadFlap(fab, a)
+}
+
+// Flap applies a value to a function wrapped in a [ReaderIOResult].
+// This is the curried version of [MonadFlap].
+//
+// Parameters:
+//   - a: The value to apply to the function
+//
+// Returns a function that applies the value to a ReaderIOResult function.
+//
+//go:inline
+func Flap[B, A any](a A) Operator[func(A) B, B] {
+	return RIOR.Flap[context.Context, B](a)
+}
+
+// Fold handles both success and error cases of a [ReaderIOResult] by providing handlers for each.
+// Both handlers return ReaderIOResult, allowing for further composition.
+//
+// Parameters:
+//   - onLeft: Handler for error case
+//   - onRight: Handler for success case
+//
+// Returns a function that folds a ReaderIOResult into a new ReaderIOResult.
+//
+//go:inline
+func Fold[A, B any](onLeft Kleisli[error, B], onRight Kleisli[A, B]) Operator[A, B] {
+	return RIOR.Fold(onLeft, onRight)
+}
+
+// GetOrElse extracts the value from a [ReaderIOResult], providing a default via a function if it fails.
+// The result is a [ReaderIO] that always succeeds.
+//
+// Parameters:
+//   - onLeft: Function to provide a default value from the error
+//
+// Returns a function that converts a ReaderIOResult to a ReaderIO.
+//
+//go:inline
+func GetOrElse[A any](onLeft func(error) ReaderIO[A]) func(ReaderIOResult[A]) ReaderIO[A] {
+	return RIOR.GetOrElse(onLeft)
+}
+
+// OrLeft transforms the error of a [ReaderIOResult] using the provided function.
+// The success value is left unchanged.
+//
+// Parameters:
+//   - onLeft: Function to transform the error
+//
+// Returns a function that transforms the error of a ReaderIOResult.
+//
+//go:inline
+func OrLeft[A any](onLeft func(error) ReaderIO[error]) Operator[A, A] {
+	return RIOR.OrLeft[A](onLeft)
+}
+
+//go:inline
+func FromReaderEither[A any](ma ReaderEither[context.Context, error, A]) ReaderIOResult[A] {
+	return RIOR.FromReaderEither(ma)
+}
+
+//go:inline
+func FromReaderResult[A any](ma ReaderResult[A]) ReaderIOResult[A] {
+	return RIOR.FromReaderEither(ma)
+}
+
+//go:inline
+func FromReaderOption[A any](onNone func() error) Kleisli[ReaderOption[context.Context, A], A] {
+	return RIOR.FromReaderOption[context.Context, A](onNone)
+}
+
+//go:inline
+func MonadChainReaderK[A, B any](ma ReaderIOResult[A], f reader.Kleisli[context.Context, A, B]) ReaderIOResult[B] {
+	return RIOR.MonadChainReaderK(ma, f)
+}
+
+//go:inline
+func ChainReaderK[A, B any](f reader.Kleisli[context.Context, A, B]) Operator[A, B] {
+	return RIOR.ChainReaderK(f)
+}
+
+//go:inline
+func MonadChainFirstReaderK[A, B any](ma ReaderIOResult[A], f reader.Kleisli[context.Context, A, B]) ReaderIOResult[A] {
+	return RIOR.MonadChainFirstReaderK(ma, f)
+}
+
+//go:inline
+func MonadTapReaderK[A, B any](ma ReaderIOResult[A], f reader.Kleisli[context.Context, A, B]) ReaderIOResult[A] {
+	return RIOR.MonadTapReaderK(ma, f)
+}
+
+//go:inline
+func ChainFirstReaderK[A, B any](f reader.Kleisli[context.Context, A, B]) Operator[A, A] {
+	return RIOR.ChainFirstReaderK(f)
+}
+
+//go:inline
+func TapReaderK[A, B any](f reader.Kleisli[context.Context, A, B]) Operator[A, A] {
+	return RIOR.TapReaderK(f)
+}
+
+//go:inline
+func MonadChainReaderResultK[A, B any](ma ReaderIOResult[A], f readerresult.Kleisli[A, B]) ReaderIOResult[B] {
+	return RIOR.MonadChainReaderResultK(ma, f)
+}
+
+//go:inline
+func ChainReaderResultK[A, B any](f readerresult.Kleisli[A, B]) Operator[A, B] {
+	return RIOR.ChainReaderResultK(f)
+}
+
+//go:inline
+func MonadChainFirstReaderResultK[A, B any](ma ReaderIOResult[A], f readerresult.Kleisli[A, B]) ReaderIOResult[A] {
+	return RIOR.MonadChainFirstReaderResultK(ma, f)
+}
+
+//go:inline
+func MonadTapReaderResultK[A, B any](ma ReaderIOResult[A], f readerresult.Kleisli[A, B]) ReaderIOResult[A] {
+	return RIOR.MonadTapReaderResultK(ma, f)
+}
+
+//go:inline
+func ChainFirstReaderResultK[A, B any](f readerresult.Kleisli[A, B]) Operator[A, A] {
+	return RIOR.ChainFirstReaderResultK(f)
+}
+
+//go:inline
+func TapReaderResultK[A, B any](f readerresult.Kleisli[A, B]) Operator[A, A] {
+	return RIOR.TapReaderResultK(f)
+}
+
+//go:inline
+func MonadChainReaderIOK[A, B any](ma ReaderIOResult[A], f readerio.Kleisli[context.Context, A, B]) ReaderIOResult[B] {
+	return RIOR.MonadChainReaderIOK(ma, f)
+}
+
+//go:inline
+func ChainReaderIOK[A, B any](f readerio.Kleisli[context.Context, A, B]) Operator[A, B] {
+	return RIOR.ChainReaderIOK(f)
+}
+
+//go:inline
+func MonadChainFirstReaderIOK[A, B any](ma ReaderIOResult[A], f readerio.Kleisli[context.Context, A, B]) ReaderIOResult[A] {
+	return RIOR.MonadChainFirstReaderIOK(ma, f)
+}
+
+//go:inline
+func MonadTapReaderIOK[A, B any](ma ReaderIOResult[A], f readerio.Kleisli[context.Context, A, B]) ReaderIOResult[A] {
+	return RIOR.MonadTapReaderIOK(ma, f)
+}
+
+//go:inline
+func ChainFirstReaderIOK[A, B any](f readerio.Kleisli[context.Context, A, B]) Operator[A, A] {
+	return RIOR.ChainFirstReaderIOK(f)
+}
+
+//go:inline
+func TapReaderIOK[A, B any](f readerio.Kleisli[context.Context, A, B]) Operator[A, A] {
+	return RIOR.TapReaderIOK(f)
+}
+
+//go:inline
+func ChainReaderOptionK[A, B any](onNone func() error) func(readeroption.Kleisli[context.Context, A, B]) Operator[A, B] {
+	return RIOR.ChainReaderOptionK[context.Context, A, B](onNone)
+}
+
+//go:inline
+func ChainFirstReaderOptionK[A, B any](onNone func() error) func(readeroption.Kleisli[context.Context, A, B]) Operator[A, A] {
+	return RIOR.ChainFirstReaderOptionK[context.Context, A, B](onNone)
+}
+
+//go:inline
+func TapReaderOptionK[A, B any](onNone func() error) func(readeroption.Kleisli[context.Context, A, B]) Operator[A, A] {
+	return RIOR.TapReaderOptionK[context.Context, A, B](onNone)
+}
+
+//go:inline
+func Read[A any](r context.Context) func(ReaderIOResult[A]) IOResult[A] {
+	return RIOR.Read[A](r)
+}
+
+// MonadChainLeft chains a computation on the left (error) side of a [ReaderIOResult].
+// If the input is a Left value, it applies the function f to transform the error and potentially
+// change the error type. If the input is a Right value, it passes through unchanged.
+//
+//go:inline
+func MonadChainLeft[A any](fa ReaderIOResult[A], f Kleisli[error, A]) ReaderIOResult[A] {
+	return RIOR.MonadChainLeft(fa, f)
+}
+
+// ChainLeft is the curried version of [MonadChainLeft].
+// It returns a function that chains a computation on the left (error) side of a [ReaderIOResult].
+//
+//go:inline
+func ChainLeft[A any](f Kleisli[error, A]) func(ReaderIOResult[A]) ReaderIOResult[A] {
+	return RIOR.ChainLeft(f)
+}
+
+// MonadChainFirstLeft chains a computation on the left (error) side but always returns the original error.
+// If the input is a Left value, it applies the function f to the error and executes the resulting computation,
+// but always returns the original Left error regardless of what f returns (Left or Right).
+// If the input is a Right value, it passes through unchanged without calling f.
+//
+// This is useful for side effects on errors (like logging or metrics) where you want to perform an action
+// when an error occurs but always propagate the original error, ensuring the error path is preserved.
+//
+//go:inline
+func MonadChainFirstLeft[A, B any](ma ReaderIOResult[A], f Kleisli[error, B]) ReaderIOResult[A] {
+	return RIOR.MonadChainFirstLeft(ma, f)
+}
+
+//go:inline
+func MonadTapLeft[A, B any](ma ReaderIOResult[A], f Kleisli[error, B]) ReaderIOResult[A] {
+	return RIOR.MonadTapLeft(ma, f)
+}
+
+// ChainFirstLeft is the curried version of [MonadChainFirstLeft].
+// It returns a function that chains a computation on the left (error) side while always preserving the original error.
+//
+// This is particularly useful for adding error handling side effects (like logging, metrics, or notifications)
+// in a functional pipeline. The original error is always returned regardless of what f returns (Left or Right),
+// ensuring the error path is preserved.
+//
+//go:inline
+func ChainFirstLeft[A, B any](f Kleisli[error, B]) Operator[A, A] {
+	return RIOR.ChainFirstLeft[A](f)
+}
+
+//go:inline
+func TapLeft[A, B any](f Kleisli[error, B]) Operator[A, A] {
+	return RIOR.TapLeft[A](f)
+}

v2/context/readerioresult/reader_bench_test.go

@@ -0,0 +1,886 @@
+// Copyright (c) 2023 - 2025 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package readerioresult
+
+import (
+	"context"
+	"errors"
+	"testing"
+	"time"
+
+	E "github.com/IBM/fp-go/v2/either"
+	F "github.com/IBM/fp-go/v2/function"
+	IOE "github.com/IBM/fp-go/v2/ioeither"
+	N "github.com/IBM/fp-go/v2/number"
+)
+
+var (
+	benchErr    = errors.New("benchmark error")
+	benchCtx    = context.Background()
+	benchResult Either[int]
+	benchRIOE   ReaderIOResult[int]
+	benchInt    int
+)
+
+// Benchmark core constructors
+func BenchmarkLeft(b *testing.B) {
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = Left[int](benchErr)
+	}
+}
+
+func BenchmarkRight(b *testing.B) {
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = Right(42)
+	}
+}
+
+func BenchmarkOf(b *testing.B) {
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = Of(42)
+	}
+}
+
+func BenchmarkFromEither_Right(b *testing.B) {
+	either := E.Right[error](42)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = FromEither(either)
+	}
+}
+
+func BenchmarkFromEither_Left(b *testing.B) {
+	either := E.Left[int](benchErr)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = FromEither(either)
+	}
+}
+
+func BenchmarkFromIO(b *testing.B) {
+	io := func() int { return 42 }
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = FromIO(io)
+	}
+}
+
+func BenchmarkFromIOEither_Right(b *testing.B) {
+	ioe := IOE.Of[error](42)
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = FromIOEither(ioe)
+	}
+}
+
+func BenchmarkFromIOEither_Left(b *testing.B) {
+	ioe := IOE.Left[int](benchErr)
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = FromIOEither(ioe)
+	}
+}
+
+// Benchmark execution
+func BenchmarkExecute_Right(b *testing.B) {
+	rioe := Right(42)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchResult = rioe(benchCtx)()
+	}
+}
+
+func BenchmarkExecute_Left(b *testing.B) {
+	rioe := Left[int](benchErr)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchResult = rioe(benchCtx)()
+	}
+}
+
+func BenchmarkExecute_WithContext(b *testing.B) {
+	rioe := Right(42)
+	ctx, cancel := context.WithCancel(benchCtx)
+	defer cancel()
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchResult = rioe(ctx)()
+	}
+}
+
+// Benchmark functor operations
+func BenchmarkMonadMap_Right(b *testing.B) {
+	rioe := Right(42)
+	mapper := N.Mul(2)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = MonadMap(rioe, mapper)
+	}
+}
+
+func BenchmarkMonadMap_Left(b *testing.B) {
+	rioe := Left[int](benchErr)
+	mapper := N.Mul(2)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = MonadMap(rioe, mapper)
+	}
+}
+
+func BenchmarkMap_Right(b *testing.B) {
+	rioe := Right(42)
+	mapper := Map(N.Mul(2))
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = mapper(rioe)
+	}
+}
+
+func BenchmarkMap_Left(b *testing.B) {
+	rioe := Left[int](benchErr)
+	mapper := Map(N.Mul(2))
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = mapper(rioe)
+	}
+}
+
+func BenchmarkMapTo_Right(b *testing.B) {
+	rioe := Right(42)
+	mapper := MapTo[int](99)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = mapper(rioe)
+	}
+}
+
+// Benchmark monad operations
+func BenchmarkMonadChain_Right(b *testing.B) {
+	rioe := Right(42)
+	chainer := func(a int) ReaderIOResult[int] { return Right(a * 2) }
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = MonadChain(rioe, chainer)
+	}
+}
+
+func BenchmarkMonadChain_Left(b *testing.B) {
+	rioe := Left[int](benchErr)
+	chainer := func(a int) ReaderIOResult[int] { return Right(a * 2) }
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = MonadChain(rioe, chainer)
+	}
+}
+
+func BenchmarkChain_Right(b *testing.B) {
+	rioe := Right(42)
+	chainer := Chain(func(a int) ReaderIOResult[int] { return Right(a * 2) })
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = chainer(rioe)
+	}
+}
+
+func BenchmarkChain_Left(b *testing.B) {
+	rioe := Left[int](benchErr)
+	chainer := Chain(func(a int) ReaderIOResult[int] { return Right(a * 2) })
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = chainer(rioe)
+	}
+}
+
+func BenchmarkChainFirst_Right(b *testing.B) {
+	rioe := Right(42)
+	chainer := ChainFirst(func(a int) ReaderIOResult[string] { return Right("logged") })
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = chainer(rioe)
+	}
+}
+
+func BenchmarkChainFirst_Left(b *testing.B) {
+	rioe := Left[int](benchErr)
+	chainer := ChainFirst(func(a int) ReaderIOResult[string] { return Right("logged") })
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = chainer(rioe)
+	}
+}
+
+func BenchmarkFlatten_Right(b *testing.B) {
+	nested := Right(Right(42))
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = Flatten(nested)
+	}
+}
+
+func BenchmarkFlatten_Left(b *testing.B) {
+	nested := Left[ReaderIOResult[int]](benchErr)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = Flatten(nested)
+	}
+}
+
+// Benchmark applicative operations
+func BenchmarkMonadApSeq_RightRight(b *testing.B) {
+	fab := Right(N.Mul(2))
+	fa := Right(42)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = MonadApSeq(fab, fa)
+	}
+}
+
+func BenchmarkMonadApSeq_RightLeft(b *testing.B) {
+	fab := Right(N.Mul(2))
+	fa := Left[int](benchErr)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = MonadApSeq(fab, fa)
+	}
+}
+
+func BenchmarkMonadApSeq_LeftRight(b *testing.B) {
+	fab := Left[func(int) int](benchErr)
+	fa := Right(42)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = MonadApSeq(fab, fa)
+	}
+}
+
+func BenchmarkMonadApPar_RightRight(b *testing.B) {
+	fab := Right(N.Mul(2))
+	fa := Right(42)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = MonadApPar(fab, fa)
+	}
+}
+
+func BenchmarkMonadApPar_RightLeft(b *testing.B) {
+	fab := Right(N.Mul(2))
+	fa := Left[int](benchErr)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = MonadApPar(fab, fa)
+	}
+}
+
+func BenchmarkMonadApPar_LeftRight(b *testing.B) {
+	fab := Left[func(int) int](benchErr)
+	fa := Right(42)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = MonadApPar(fab, fa)
+	}
+}
+
+// Benchmark execution of applicative operations
+func BenchmarkExecuteApSeq_RightRight(b *testing.B) {
+	fab := Right(N.Mul(2))
+	fa := Right(42)
+	rioe := MonadApSeq(fab, fa)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchResult = rioe(benchCtx)()
+	}
+}
+
+func BenchmarkExecuteApPar_RightRight(b *testing.B) {
+	fab := Right(N.Mul(2))
+	fa := Right(42)
+	rioe := MonadApPar(fab, fa)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchResult = rioe(benchCtx)()
+	}
+}
+
+// Benchmark alternative operations
+func BenchmarkAlt_RightRight(b *testing.B) {
+	rioe := Right(42)
+	alternative := Alt(func() ReaderIOResult[int] { return Right(99) })
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = alternative(rioe)
+	}
+}
+
+func BenchmarkAlt_LeftRight(b *testing.B) {
+	rioe := Left[int](benchErr)
+	alternative := Alt(func() ReaderIOResult[int] { return Right(99) })
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = alternative(rioe)
+	}
+}
+
+func BenchmarkOrElse_Right(b *testing.B) {
+	rioe := Right(42)
+	recover := OrElse(func(e error) ReaderIOResult[int] { return Right(0) })
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = recover(rioe)
+	}
+}
+
+func BenchmarkOrElse_Left(b *testing.B) {
+	rioe := Left[int](benchErr)
+	recover := OrElse(func(e error) ReaderIOResult[int] { return Right(0) })
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = recover(rioe)
+	}
+}
+
+// Benchmark chain operations with different types
+func BenchmarkChainEitherK_Right(b *testing.B) {
+	rioe := Right(42)
+	chainer := ChainEitherK(func(a int) Either[int] { return E.Right[error](a * 2) })
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = chainer(rioe)
+	}
+}
+
+func BenchmarkChainEitherK_Left(b *testing.B) {
+	rioe := Left[int](benchErr)
+	chainer := ChainEitherK(func(a int) Either[int] { return E.Right[error](a * 2) })
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = chainer(rioe)
+	}
+}
+
+func BenchmarkChainIOK_Right(b *testing.B) {
+	rioe := Right(42)
+	chainer := ChainIOK(func(a int) func() int { return func() int { return a * 2 } })
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = chainer(rioe)
+	}
+}
+
+func BenchmarkChainIOK_Left(b *testing.B) {
+	rioe := Left[int](benchErr)
+	chainer := ChainIOK(func(a int) func() int { return func() int { return a * 2 } })
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = chainer(rioe)
+	}
+}
+
+func BenchmarkChainIOEitherK_Right(b *testing.B) {
+	rioe := Right(42)
+	chainer := ChainIOEitherK(func(a int) IOEither[int] { return IOE.Of[error](a * 2) })
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = chainer(rioe)
+	}
+}
+
+func BenchmarkChainIOEitherK_Left(b *testing.B) {
+	rioe := Left[int](benchErr)
+	chainer := ChainIOEitherK(func(a int) IOEither[int] { return IOE.Of[error](a * 2) })
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = chainer(rioe)
+	}
+}
+
+// Benchmark context operations
+func BenchmarkAsk(b *testing.B) {
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = Ask()
+	}
+}
+
+func BenchmarkDefer(b *testing.B) {
+	gen := func() ReaderIOResult[int] { return Right(42) }
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = Defer(gen)
+	}
+}
+
+func BenchmarkMemoize(b *testing.B) {
+	rioe := Right(42)
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = Memoize(rioe)
+	}
+}
+
+// Benchmark delay operations
+func BenchmarkDelay_Construction(b *testing.B) {
+	rioe := Right(42)
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = Delay[int](time.Millisecond)(rioe)
+	}
+}
+
+func BenchmarkTimer_Construction(b *testing.B) {
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = Timer(time.Millisecond)
+	}
+}
+
+// Benchmark TryCatch
+func BenchmarkTryCatch_Success(b *testing.B) {
+	f := func(ctx context.Context) func() (int, error) {
+		return func() (int, error) { return 42, nil }
+	}
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = TryCatch(f)
+	}
+}
+
+func BenchmarkTryCatch_Error(b *testing.B) {
+	f := func(ctx context.Context) func() (int, error) {
+		return func() (int, error) { return 0, benchErr }
+	}
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = TryCatch(f)
+	}
+}
+
+func BenchmarkExecuteTryCatch_Success(b *testing.B) {
+	f := func(ctx context.Context) func() (int, error) {
+		return func() (int, error) { return 42, nil }
+	}
+	rioe := TryCatch(f)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchResult = rioe(benchCtx)()
+	}
+}
+
+func BenchmarkExecuteTryCatch_Error(b *testing.B) {
+	f := func(ctx context.Context) func() (int, error) {
+		return func() (int, error) { return 0, benchErr }
+	}
+	rioe := TryCatch(f)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchResult = rioe(benchCtx)()
+	}
+}
+
+// Benchmark pipeline operations
+func BenchmarkPipeline_Map_Right(b *testing.B) {
+	rioe := Right(21)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = F.Pipe1(
+			rioe,
+			Map(N.Mul(2)),
+		)
+	}
+}
+
+func BenchmarkPipeline_Map_Left(b *testing.B) {
+	rioe := Left[int](benchErr)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = F.Pipe1(
+			rioe,
+			Map(N.Mul(2)),
+		)
+	}
+}
+
+func BenchmarkPipeline_Chain_Right(b *testing.B) {
+	rioe := Right(21)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = F.Pipe1(
+			rioe,
+			Chain(func(x int) ReaderIOResult[int] { return Right(x * 2) }),
+		)
+	}
+}
+
+func BenchmarkPipeline_Chain_Left(b *testing.B) {
+	rioe := Left[int](benchErr)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = F.Pipe1(
+			rioe,
+			Chain(func(x int) ReaderIOResult[int] { return Right(x * 2) }),
+		)
+	}
+}
+
+func BenchmarkPipeline_Complex_Right(b *testing.B) {
+	rioe := Right(10)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = F.Pipe3(
+			rioe,
+			Map(N.Mul(2)),
+			Chain(func(x int) ReaderIOResult[int] { return Right(x + 1) }),
+			Map(N.Mul(2)),
+		)
+	}
+}
+
+func BenchmarkPipeline_Complex_Left(b *testing.B) {
+	rioe := Left[int](benchErr)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchRIOE = F.Pipe3(
+			rioe,
+			Map(N.Mul(2)),
+			Chain(func(x int) ReaderIOResult[int] { return Right(x + 1) }),
+			Map(N.Mul(2)),
+		)
+	}
+}
+
+func BenchmarkExecutePipeline_Complex_Right(b *testing.B) {
+	rioe := F.Pipe3(
+		Right(10),
+		Map(N.Mul(2)),
+		Chain(func(x int) ReaderIOResult[int] { return Right(x + 1) }),
+		Map(N.Mul(2)),
+	)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchResult = rioe(benchCtx)()
+	}
+}
+
+// Benchmark do-notation operations
+func BenchmarkDo(b *testing.B) {
+	type State struct{ value int }
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = Do(State{})
+	}
+}
+
+func BenchmarkBind_Right(b *testing.B) {
+	type State struct{ value int }
+	initial := Do(State{})
+	binder := Bind(
+		func(v int) func(State) State {
+			return func(s State) State { return State{value: v} }
+		},
+		func(s State) ReaderIOResult[int] {
+			return Right(42)
+		},
+	)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = binder(initial)
+	}
+}
+
+func BenchmarkLet_Right(b *testing.B) {
+	type State struct{ value int }
+	initial := Right(State{value: 10})
+	letter := Let(
+		func(v int) func(State) State {
+			return func(s State) State { return State{value: s.value + v} }
+		},
+		func(s State) int { return 32 },
+	)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = letter(initial)
+	}
+}
+
+func BenchmarkApS_Right(b *testing.B) {
+	type State struct{ value int }
+	initial := Right(State{value: 10})
+	aps := ApS(
+		func(v int) func(State) State {
+			return func(s State) State { return State{value: v} }
+		},
+		Right(42),
+	)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = aps(initial)
+	}
+}
+
+// Benchmark traverse operations
+func BenchmarkTraverseArray_Empty(b *testing.B) {
+	arr := []int{}
+	traverser := TraverseArray(func(x int) ReaderIOResult[int] {
+		return Right(x * 2)
+	})
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = traverser(arr)
+	}
+}
+
+func BenchmarkTraverseArray_Small(b *testing.B) {
+	arr := []int{1, 2, 3}
+	traverser := TraverseArray(func(x int) ReaderIOResult[int] {
+		return Right(x * 2)
+	})
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = traverser(arr)
+	}
+}
+
+func BenchmarkTraverseArray_Medium(b *testing.B) {
+	arr := make([]int, 10)
+	for i := range arr {
+		arr[i] = i
+	}
+	traverser := TraverseArray(func(x int) ReaderIOResult[int] {
+		return Right(x * 2)
+	})
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = traverser(arr)
+	}
+}
+
+func BenchmarkTraverseArraySeq_Small(b *testing.B) {
+	arr := []int{1, 2, 3}
+	traverser := TraverseArraySeq(func(x int) ReaderIOResult[int] {
+		return Right(x * 2)
+	})
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = traverser(arr)
+	}
+}
+
+func BenchmarkTraverseArrayPar_Small(b *testing.B) {
+	arr := []int{1, 2, 3}
+	traverser := TraverseArrayPar(func(x int) ReaderIOResult[int] {
+		return Right(x * 2)
+	})
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = traverser(arr)
+	}
+}
+
+func BenchmarkSequenceArray_Small(b *testing.B) {
+	arr := []ReaderIOResult[int]{
+		Right(1),
+		Right(2),
+		Right(3),
+	}
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = SequenceArray(arr)
+	}
+}
+
+func BenchmarkExecuteTraverseArray_Small(b *testing.B) {
+	arr := []int{1, 2, 3}
+	rioe := TraverseArray(func(x int) ReaderIOResult[int] {
+		return Right(x * 2)
+	})(arr)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = rioe(benchCtx)()
+	}
+}
+
+func BenchmarkExecuteTraverseArraySeq_Small(b *testing.B) {
+	arr := []int{1, 2, 3}
+	rioe := TraverseArraySeq(func(x int) ReaderIOResult[int] {
+		return Right(x * 2)
+	})(arr)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = rioe(benchCtx)()
+	}
+}
+
+func BenchmarkExecuteTraverseArrayPar_Small(b *testing.B) {
+	arr := []int{1, 2, 3}
+	rioe := TraverseArrayPar(func(x int) ReaderIOResult[int] {
+		return Right(x * 2)
+	})(arr)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = rioe(benchCtx)()
+	}
+}
+
+// Benchmark record operations
+func BenchmarkTraverseRecord_Small(b *testing.B) {
+	rec := map[string]int{"a": 1, "b": 2, "c": 3}
+	traverser := TraverseRecord[string](func(x int) ReaderIOResult[int] {
+		return Right(x * 2)
+	})
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = traverser(rec)
+	}
+}
+
+func BenchmarkSequenceRecord_Small(b *testing.B) {
+	rec := map[string]ReaderIOResult[int]{
+		"a": Right(1),
+		"b": Right(2),
+		"c": Right(3),
+	}
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = SequenceRecord(rec)
+	}
+}
+
+// Benchmark resource management
+func BenchmarkWithResource_Success(b *testing.B) {
+	acquire := Right(42)
+	release := func(int) ReaderIOResult[int] { return Right(0) }
+	body := func(x int) ReaderIOResult[int] { return Right(x * 2) }
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = WithResource[int](acquire, release)(body)
+	}
+}
+
+func BenchmarkExecuteWithResource_Success(b *testing.B) {
+	acquire := Right(42)
+	release := func(int) ReaderIOResult[int] { return Right(0) }
+	body := func(x int) ReaderIOResult[int] { return Right(x * 2) }
+	rioe := WithResource[int](acquire, release)(body)
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchResult = rioe(benchCtx)()
+	}
+}
+
+func BenchmarkExecuteWithResource_ErrorInBody(b *testing.B) {
+	acquire := Right(42)
+	release := func(int) ReaderIOResult[int] { return Right(0) }
+	body := func(x int) ReaderIOResult[int] { return Left[int](benchErr) }
+	rioe := WithResource[int](acquire, release)(body)
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchResult = rioe(benchCtx)()
+	}
+}
+
+// Benchmark context cancellation
+func BenchmarkExecute_CanceledContext(b *testing.B) {
+	rioe := Right(42)
+	ctx, cancel := context.WithCancel(benchCtx)
+	cancel() // Cancel immediately
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchResult = rioe(ctx)()
+	}
+}
+
+func BenchmarkExecuteApPar_CanceledContext(b *testing.B) {
+	fab := Right(N.Mul(2))
+	fa := Right(42)
+	rioe := MonadApPar(fab, fa)
+	ctx, cancel := context.WithCancel(benchCtx)
+	cancel() // Cancel immediately
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for b.Loop() {
+		benchResult = rioe(ctx)()
+	}
+}

v2/context/readerioresult/reader_extended_test.go

@@ -0,0 +1,878 @@
+// Copyright (c) 2023 - 2025 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package readerioresult
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"testing"
+	"time"
+
+	E "github.com/IBM/fp-go/v2/either"
+	IOG "github.com/IBM/fp-go/v2/io"
+	IOE "github.com/IBM/fp-go/v2/ioeither"
+	M "github.com/IBM/fp-go/v2/monoid"
+	N "github.com/IBM/fp-go/v2/number"
+	O "github.com/IBM/fp-go/v2/option"
+	R "github.com/IBM/fp-go/v2/reader"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFromEither(t *testing.T) {
+	t.Run("Right value", func(t *testing.T) {
+		either := E.Right[error]("success")
+		result := FromEither(either)
+		assert.Equal(t, E.Right[error]("success"), result(context.Background())())
+	})
+
+	t.Run("Left value", func(t *testing.T) {
+		err := errors.New("test error")
+		either := E.Left[string](err)
+		result := FromEither(either)
+		assert.Equal(t, E.Left[string](err), result(context.Background())())
+	})
+}
+
+func TestFromResult(t *testing.T) {
+	t.Run("Success", func(t *testing.T) {
+		result := FromResult(E.Right[error](42))
+		assert.Equal(t, E.Right[error](42), result(context.Background())())
+	})
+
+	t.Run("Error", func(t *testing.T) {
+		err := errors.New("test error")
+		result := FromResult(E.Left[int](err))
+		assert.Equal(t, E.Left[int](err), result(context.Background())())
+	})
+}
+
+func TestLeft(t *testing.T) {
+	err := errors.New("test error")
+	result := Left[string](err)
+	assert.Equal(t, E.Left[string](err), result(context.Background())())
+}
+
+func TestRight(t *testing.T) {
+	result := Right("success")
+	assert.Equal(t, E.Right[error]("success"), result(context.Background())())
+}
+
+func TestOf(t *testing.T) {
+	result := Of(42)
+	assert.Equal(t, E.Right[error](42), result(context.Background())())
+}
+
+func TestMonadMap(t *testing.T) {
+	t.Run("Map over Right", func(t *testing.T) {
+		result := MonadMap(Of(5), N.Mul(2))
+		assert.Equal(t, E.Right[error](10), result(context.Background())())
+	})
+
+	t.Run("Map over Left", func(t *testing.T) {
+		err := errors.New("test error")
+		result := MonadMap(Left[int](err), N.Mul(2))
+		assert.Equal(t, E.Left[int](err), result(context.Background())())
+	})
+}
+
+func TestMap(t *testing.T) {
+	t.Run("Map with success", func(t *testing.T) {
+		mapper := Map(N.Mul(2))
+		result := mapper(Of(5))
+		assert.Equal(t, E.Right[error](10), result(context.Background())())
+	})
+
+	t.Run("Map with error", func(t *testing.T) {
+		err := errors.New("test error")
+		mapper := Map(N.Mul(2))
+		result := mapper(Left[int](err))
+		assert.Equal(t, E.Left[int](err), result(context.Background())())
+	})
+}
+
+func TestMonadMapTo(t *testing.T) {
+	t.Run("MapTo with success", func(t *testing.T) {
+		result := MonadMapTo(Of("original"), 42)
+		assert.Equal(t, E.Right[error](42), result(context.Background())())
+	})
+
+	t.Run("MapTo with error", func(t *testing.T) {
+		err := errors.New("test error")
+		result := MonadMapTo(Left[string](err), 42)
+		assert.Equal(t, E.Left[int](err), result(context.Background())())
+	})
+}
+
+func TestMapTo(t *testing.T) {
+	mapper := MapTo[string](42)
+	result := mapper(Of("original"))
+	assert.Equal(t, E.Right[error](42), result(context.Background())())
+}
+
+func TestMonadChain(t *testing.T) {
+	t.Run("Chain with success", func(t *testing.T) {
+		result := MonadChain(Of(5), func(x int) ReaderIOResult[int] {
+			return Of(x * 2)
+		})
+		assert.Equal(t, E.Right[error](10), result(context.Background())())
+	})
+
+	t.Run("Chain with error in first", func(t *testing.T) {
+		err := errors.New("test error")
+		result := MonadChain(Left[int](err), func(x int) ReaderIOResult[int] {
+			return Of(x * 2)
+		})
+		assert.Equal(t, E.Left[int](err), result(context.Background())())
+	})
+
+	t.Run("Chain with error in second", func(t *testing.T) {
+		err := errors.New("test error")
+		result := MonadChain(Of(5), func(x int) ReaderIOResult[int] {
+			return Left[int](err)
+		})
+		assert.Equal(t, E.Left[int](err), result(context.Background())())
+	})
+}
+
+func TestChain(t *testing.T) {
+	chainer := Chain(func(x int) ReaderIOResult[int] {
+		return Of(x * 2)
+	})
+	result := chainer(Of(5))
+	assert.Equal(t, E.Right[error](10), result(context.Background())())
+}
+
+func TestMonadChainFirst(t *testing.T) {
+	t.Run("ChainFirst keeps first value", func(t *testing.T) {
+		result := MonadChainFirst(Of(5), func(x int) ReaderIOResult[string] {
+			return Of("ignored")
+		})
+		assert.Equal(t, E.Right[error](5), result(context.Background())())
+	})
+
+	t.Run("ChainFirst propagates error from second", func(t *testing.T) {
+		err := errors.New("test error")
+		result := MonadChainFirst(Of(5), func(x int) ReaderIOResult[string] {
+			return Left[string](err)
+		})
+		assert.Equal(t, E.Left[int](err), result(context.Background())())
+	})
+}
+
+func TestChainFirst(t *testing.T) {
+	chainer := ChainFirst(func(x int) ReaderIOResult[string] {
+		return Of("ignored")
+	})
+	result := chainer(Of(5))
+	assert.Equal(t, E.Right[error](5), result(context.Background())())
+}
+
+func TestMonadApSeq(t *testing.T) {
+	t.Run("ApSeq with success", func(t *testing.T) {
+		fab := Of(N.Mul(2))
+		fa := Of(5)
+		result := MonadApSeq(fab, fa)
+		assert.Equal(t, E.Right[error](10), result(context.Background())())
+	})
+
+	t.Run("ApSeq with error in function", func(t *testing.T) {
+		err := errors.New("test error")
+		fab := Left[func(int) int](err)
+		fa := Of(5)
+		result := MonadApSeq(fab, fa)
+		assert.Equal(t, E.Left[int](err), result(context.Background())())
+	})
+
+	t.Run("ApSeq with error in value", func(t *testing.T) {
+		err := errors.New("test error")
+		fab := Of(N.Mul(2))
+		fa := Left[int](err)
+		result := MonadApSeq(fab, fa)
+		assert.Equal(t, E.Left[int](err), result(context.Background())())
+	})
+}
+
+func TestApSeq(t *testing.T) {
+	fa := Of(5)
+	fab := Of(N.Mul(2))
+	result := MonadApSeq(fab, fa)
+	assert.Equal(t, E.Right[error](10), result(context.Background())())
+}
+
+func TestApPar(t *testing.T) {
+	t.Run("ApPar with success", func(t *testing.T) {
+		fa := Of(5)
+		fab := Of(N.Mul(2))
+		result := MonadApPar(fab, fa)
+		assert.Equal(t, E.Right[error](10), result(context.Background())())
+	})
+
+	t.Run("ApPar with cancelled context", func(t *testing.T) {
+		ctx, cancel := context.WithCancel(context.Background())
+		cancel()
+		fa := Of(5)
+		fab := Of(N.Mul(2))
+		result := MonadApPar(fab, fa)
+		res := result(ctx)()
+		assert.True(t, E.IsLeft(res))
+	})
+}
+
+func TestFromPredicate(t *testing.T) {
+	t.Run("Predicate true", func(t *testing.T) {
+		pred := FromPredicate(
+			func(x int) bool { return x > 0 },
+			func(x int) error { return fmt.Errorf("value %d is not positive", x) },
+		)
+		result := pred(5)
+		assert.Equal(t, E.Right[error](5), result(context.Background())())
+	})
+
+	t.Run("Predicate false", func(t *testing.T) {
+		pred := FromPredicate(
+			func(x int) bool { return x > 0 },
+			func(x int) error { return fmt.Errorf("value %d is not positive", x) },
+		)
+		result := pred(-5)
+		res := result(context.Background())()
+		assert.True(t, E.IsLeft(res))
+	})
+}
+
+func TestOrElse(t *testing.T) {
+	t.Run("OrElse with success", func(t *testing.T) {
+		fallback := OrElse(func(err error) ReaderIOResult[int] {
+			return Of(42)
+		})
+		result := fallback(Of(10))
+		assert.Equal(t, E.Right[error](10), result(context.Background())())
+	})
+
+	t.Run("OrElse with error", func(t *testing.T) {
+		err := errors.New("test error")
+		fallback := OrElse(func(err error) ReaderIOResult[int] {
+			return Of(42)
+		})
+		result := fallback(Left[int](err))
+		assert.Equal(t, E.Right[error](42), result(context.Background())())
+	})
+}
+
+func TestAsk(t *testing.T) {
+	result := Ask()
+	ctx := context.Background()
+	res := result(ctx)()
+	assert.True(t, E.IsRight(res))
+	ctxResult := E.ToOption(res)
+	assert.True(t, O.IsSome(ctxResult))
+}
+
+func TestMonadChainEitherK(t *testing.T) {
+	t.Run("ChainEitherK with success", func(t *testing.T) {
+		result := MonadChainEitherK(Of(5), func(x int) Either[int] {
+			return E.Right[error](x * 2)
+		})
+		assert.Equal(t, E.Right[error](10), result(context.Background())())
+	})
+
+	t.Run("ChainEitherK with error", func(t *testing.T) {
+		err := errors.New("test error")
+		result := MonadChainEitherK(Of(5), func(x int) Either[int] {
+			return E.Left[int](err)
+		})
+		assert.Equal(t, E.Left[int](err), result(context.Background())())
+	})
+}
+
+func TestChainEitherK(t *testing.T) {
+	chainer := ChainEitherK(func(x int) Either[int] {
+		return E.Right[error](x * 2)
+	})
+	result := chainer(Of(5))
+	assert.Equal(t, E.Right[error](10), result(context.Background())())
+}
+
+func TestMonadChainFirstEitherK(t *testing.T) {
+	t.Run("ChainFirstEitherK keeps first value", func(t *testing.T) {
+		result := MonadChainFirstEitherK(Of(5), func(x int) Either[string] {
+			return E.Right[error]("ignored")
+		})
+		assert.Equal(t, E.Right[error](5), result(context.Background())())
+	})
+
+	t.Run("ChainFirstEitherK propagates error", func(t *testing.T) {
+		err := errors.New("test error")
+		result := MonadChainFirstEitherK(Of(5), func(x int) Either[string] {
+			return E.Left[string](err)
+		})
+		assert.Equal(t, E.Left[int](err), result(context.Background())())
+	})
+}
+
+func TestChainFirstEitherK(t *testing.T) {
+	chainer := ChainFirstEitherK(func(x int) Either[string] {
+		return E.Right[error]("ignored")
+	})
+	result := chainer(Of(5))
+	assert.Equal(t, E.Right[error](5), result(context.Background())())
+}
+
+func TestChainOptionK(t *testing.T) {
+	t.Run("ChainOptionK with Some", func(t *testing.T) {
+		chainer := ChainOptionK[int, int](func() error {
+			return errors.New("none error")
+		})(func(x int) Option[int] {
+			return O.Some(x * 2)
+		})
+		result := chainer(Of(5))
+		assert.Equal(t, E.Right[error](10), result(context.Background())())
+	})
+
+	t.Run("ChainOptionK with None", func(t *testing.T) {
+		chainer := ChainOptionK[int, int](func() error {
+			return errors.New("none error")
+		})(func(x int) Option[int] {
+			return O.None[int]()
+		})
+		result := chainer(Of(5))
+		res := result(context.Background())()
+		assert.True(t, E.IsLeft(res))
+	})
+}
+
+func TestFromIOEither(t *testing.T) {
+	t.Run("FromIOEither with success", func(t *testing.T) {
+		ioe := IOE.Of[error](42)
+		result := FromIOEither(ioe)
+		assert.Equal(t, E.Right[error](42), result(context.Background())())
+	})
+
+	t.Run("FromIOEither with error", func(t *testing.T) {
+		err := errors.New("test error")
+		ioe := IOE.Left[int](err)
+		result := FromIOEither(ioe)
+		assert.Equal(t, E.Left[int](err), result(context.Background())())
+	})
+}
+
+func TestFromIOResult(t *testing.T) {
+	ioe := IOE.Of[error](42)
+	result := FromIOResult(ioe)
+	assert.Equal(t, E.Right[error](42), result(context.Background())())
+}
+
+func TestFromIO(t *testing.T) {
+	io := IOG.Of(42)
+	result := FromIO(io)
+	assert.Equal(t, E.Right[error](42), result(context.Background())())
+}
+
+func TestFromReader(t *testing.T) {
+	reader := R.Of[context.Context](42)
+	result := FromReader(reader)
+	assert.Equal(t, E.Right[error](42), result(context.Background())())
+}
+
+func TestFromLazy(t *testing.T) {
+	lazy := func() int { return 42 }
+	result := FromLazy(lazy)
+	assert.Equal(t, E.Right[error](42), result(context.Background())())
+}
+
+func TestNever(t *testing.T) {
+	t.Run("Never with cancelled context", func(t *testing.T) {
+		ctx, cancel := context.WithCancel(context.Background())
+		result := Never[int]()
+
+		// Cancel immediately
+		cancel()
+
+		res := result(ctx)()
+		assert.True(t, E.IsLeft(res))
+	})
+
+	t.Run("Never with timeout", func(t *testing.T) {
+		ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
+		defer cancel()
+
+		result := Never[int]()
+		res := result(ctx)()
+		assert.True(t, E.IsLeft(res))
+	})
+}
+
+func TestMonadChainIOK(t *testing.T) {
+	result := MonadChainIOK(Of(5), func(x int) IOG.IO[int] {
+		return IOG.Of(x * 2)
+	})
+	assert.Equal(t, E.Right[error](10), result(context.Background())())
+}
+
+func TestChainIOK(t *testing.T) {
+	chainer := ChainIOK(func(x int) IOG.IO[int] {
+		return IOG.Of(x * 2)
+	})
+	result := chainer(Of(5))
+	assert.Equal(t, E.Right[error](10), result(context.Background())())
+}
+
+func TestMonadChainFirstIOK(t *testing.T) {
+	result := MonadChainFirstIOK(Of(5), func(x int) IOG.IO[string] {
+		return IOG.Of("ignored")
+	})
+	assert.Equal(t, E.Right[error](5), result(context.Background())())
+}
+
+func TestChainFirstIOK(t *testing.T) {
+	chainer := ChainFirstIOK(func(x int) IOG.IO[string] {
+		return IOG.Of("ignored")
+	})
+	result := chainer(Of(5))
+	assert.Equal(t, E.Right[error](5), result(context.Background())())
+}
+
+func TestChainIOEitherK(t *testing.T) {
+	t.Run("ChainIOEitherK with success", func(t *testing.T) {
+		chainer := ChainIOEitherK(func(x int) IOResult[int] {
+			return IOE.Of[error](x * 2)
+		})
+		result := chainer(Of(5))
+		assert.Equal(t, E.Right[error](10), result(context.Background())())
+	})
+
+	t.Run("ChainIOEitherK with error", func(t *testing.T) {
+		err := errors.New("test error")
+		chainer := ChainIOEitherK(func(x int) IOResult[int] {
+			return IOE.Left[int](err)
+		})
+		result := chainer(Of(5))
+		assert.Equal(t, E.Left[int](err), result(context.Background())())
+	})
+}
+
+func TestDelay(t *testing.T) {
+	t.Run("Delay with success", func(t *testing.T) {
+		start := time.Now()
+		delayed := Delay[int](100 * time.Millisecond)
+		result := delayed(Of(42))
+		res := result(context.Background())()
+		elapsed := time.Since(start)
+
+		assert.True(t, E.IsRight(res))
+		assert.GreaterOrEqual(t, elapsed, 100*time.Millisecond)
+	})
+
+	t.Run("Delay with cancelled context", func(t *testing.T) {
+		ctx, cancel := context.WithCancel(context.Background())
+
+		delayed := Delay[int](100 * time.Millisecond)
+		result := delayed(Of(42))
+
+		// Cancel after starting but before delay completes
+		cancel()
+		res := result(ctx)()
+
+		// The result might be either Left (if cancelled) or Right (if completed before cancel)
+		// This is a race condition, so we just verify it completes
+		assert.True(t, E.IsLeft(res) || E.IsRight(res))
+	})
+}
+
+func TestDefer(t *testing.T) {
+	counter := 0
+	deferred := Defer(func() ReaderIOResult[int] {
+		counter++
+		return Of(counter)
+	})
+
+	// First execution
+	res1 := deferred(context.Background())()
+	assert.True(t, E.IsRight(res1))
+
+	// Second execution should generate a new computation
+	res2 := deferred(context.Background())()
+	assert.True(t, E.IsRight(res2))
+
+	// Counter should be incremented for each execution
+	assert.Equal(t, 2, counter)
+}
+
+func TestTryCatch(t *testing.T) {
+	t.Run("TryCatch with success", func(t *testing.T) {
+		result := TryCatch(func(ctx context.Context) func() (int, error) {
+			return func() (int, error) {
+				return 42, nil
+			}
+		})
+		assert.Equal(t, E.Right[error](42), result(context.Background())())
+	})
+
+	t.Run("TryCatch with error", func(t *testing.T) {
+		err := errors.New("test error")
+		result := TryCatch(func(ctx context.Context) func() (int, error) {
+			return func() (int, error) {
+				return 0, err
+			}
+		})
+		assert.Equal(t, E.Left[int](err), result(context.Background())())
+	})
+}
+
+func TestMonadAlt(t *testing.T) {
+	t.Run("Alt with first success", func(t *testing.T) {
+		first := Of(42)
+		second := func() ReaderIOResult[int] { return Of(100) }
+		result := MonadAlt(first, second)
+		assert.Equal(t, E.Right[error](42), result(context.Background())())
+	})
+
+	t.Run("Alt with first error", func(t *testing.T) {
+		err := errors.New("test error")
+		first := Left[int](err)
+		second := func() ReaderIOResult[int] { return Of(100) }
+		result := MonadAlt(first, second)
+		assert.Equal(t, E.Right[error](100), result(context.Background())())
+	})
+}
+
+func TestAlt(t *testing.T) {
+	err := errors.New("test error")
+	alternative := Alt(func() ReaderIOResult[int] { return Of(100) })
+	result := alternative(Left[int](err))
+	assert.Equal(t, E.Right[error](100), result(context.Background())())
+}
+
+func TestMemoize(t *testing.T) {
+	counter := 0
+	computation := Memoize(FromLazy(func() int {
+		counter++
+		return counter
+	}))
+
+	// First execution
+	res1 := computation(context.Background())()
+	assert.True(t, E.IsRight(res1))
+	val1 := E.ToOption(res1)
+	v1, _ := O.Unwrap(val1)
+	assert.Equal(t, 1, v1)
+
+	// Second execution should return cached value
+	res2 := computation(context.Background())()
+	assert.True(t, E.IsRight(res2))
+	val2 := E.ToOption(res2)
+	v2, _ := O.Unwrap(val2)
+	assert.Equal(t, 1, v2)
+
+	// Counter should only be incremented once
+	assert.Equal(t, 1, counter)
+}
+
+func TestFlatten(t *testing.T) {
+	nested := Of(Of(42))
+	result := Flatten(nested)
+	assert.Equal(t, E.Right[error](42), result(context.Background())())
+}
+
+func TestMonadFlap(t *testing.T) {
+	fab := Of(N.Mul(2))
+	result := MonadFlap(fab, 5)
+	assert.Equal(t, E.Right[error](10), result(context.Background())())
+}
+
+func TestFlap(t *testing.T) {
+	flapper := Flap[int](5)
+	result := flapper(Of(N.Mul(2)))
+	assert.Equal(t, E.Right[error](10), result(context.Background())())
+}
+
+func TestFold(t *testing.T) {
+	t.Run("Fold with success", func(t *testing.T) {
+		folder := Fold(
+			func(err error) ReaderIOResult[string] {
+				return Of("error: " + err.Error())
+			},
+			func(x int) ReaderIOResult[string] {
+				return Of(fmt.Sprintf("success: %d", x))
+			},
+		)
+		result := folder(Of(42))
+		assert.Equal(t, E.Right[error]("success: 42"), result(context.Background())())
+	})
+
+	t.Run("Fold with error", func(t *testing.T) {
+		err := errors.New("test error")
+		folder := Fold(
+			func(err error) ReaderIOResult[string] {
+				return Of("error: " + err.Error())
+			},
+			func(x int) ReaderIOResult[string] {
+				return Of(fmt.Sprintf("success: %d", x))
+			},
+		)
+		result := folder(Left[int](err))
+		assert.Equal(t, E.Right[error]("error: test error"), result(context.Background())())
+	})
+}
+
+func TestGetOrElse(t *testing.T) {
+	t.Run("GetOrElse with success", func(t *testing.T) {
+		getter := GetOrElse(func(err error) ReaderIO[int] {
+			return func(ctx context.Context) IOG.IO[int] {
+				return IOG.Of(0)
+			}
+		})
+		result := getter(Of(42))
+		assert.Equal(t, 42, result(context.Background())())
+	})
+
+	t.Run("GetOrElse with error", func(t *testing.T) {
+		err := errors.New("test error")
+		getter := GetOrElse(func(err error) ReaderIO[int] {
+			return func(ctx context.Context) IOG.IO[int] {
+				return IOG.Of(0)
+			}
+		})
+		result := getter(Left[int](err))
+		assert.Equal(t, 0, result(context.Background())())
+	})
+}
+
+func TestWithContext(t *testing.T) {
+	t.Run("WithContext with valid context", func(t *testing.T) {
+		computation := WithContext(Of(42))
+		result := computation(context.Background())()
+		assert.Equal(t, E.Right[error](42), result)
+	})
+
+	t.Run("WithContext with cancelled context", func(t *testing.T) {
+		ctx, cancel := context.WithCancel(context.Background())
+		cancel()
+
+		computation := WithContext(Of(42))
+		result := computation(ctx)()
+		assert.True(t, E.IsLeft(result))
+	})
+}
+
+func TestEitherize0(t *testing.T) {
+	f := func(ctx context.Context) (int, error) {
+		return 42, nil
+	}
+	eitherized := Eitherize0(f)
+	result := eitherized()
+	assert.Equal(t, E.Right[error](42), result(context.Background())())
+}
+
+func TestUneitherize0(t *testing.T) {
+	f := func() ReaderIOResult[int] {
+		return Of(42)
+	}
+	uneitherized := Uneitherize0(f)
+	result, err := uneitherized(context.Background())
+	assert.NoError(t, err)
+	assert.Equal(t, 42, result)
+}
+
+func TestEitherize1(t *testing.T) {
+	f := func(ctx context.Context, x int) (int, error) {
+		return x * 2, nil
+	}
+	eitherized := Eitherize1(f)
+	result := eitherized(5)
+	assert.Equal(t, E.Right[error](10), result(context.Background())())
+}
+
+func TestUneitherize1(t *testing.T) {
+	f := func(x int) ReaderIOResult[int] {
+		return Of(x * 2)
+	}
+	uneitherized := Uneitherize1(f)
+	result, err := uneitherized(context.Background(), 5)
+	assert.NoError(t, err)
+	assert.Equal(t, 10, result)
+}
+
+func TestSequenceT2(t *testing.T) {
+	result := SequenceT2(Of(1), Of(2))
+	res := result(context.Background())()
+	assert.True(t, E.IsRight(res))
+	tuple := E.ToOption(res)
+	assert.True(t, O.IsSome(tuple))
+	t1, _ := O.Unwrap(tuple)
+	assert.Equal(t, 1, t1.F1)
+	assert.Equal(t, 2, t1.F2)
+}
+
+func TestSequenceSeqT2(t *testing.T) {
+	result := SequenceSeqT2(Of(1), Of(2))
+	res := result(context.Background())()
+	assert.True(t, E.IsRight(res))
+}
+
+func TestSequenceParT2(t *testing.T) {
+	result := SequenceParT2(Of(1), Of(2))
+	res := result(context.Background())()
+	assert.True(t, E.IsRight(res))
+}
+
+func TestTraverseArray(t *testing.T) {
+	t.Run("TraverseArray with success", func(t *testing.T) {
+		arr := []int{1, 2, 3}
+		traverser := TraverseArray(func(x int) ReaderIOResult[int] {
+			return Of(x * 2)
+		})
+		result := traverser(arr)
+		res := result(context.Background())()
+		assert.True(t, E.IsRight(res))
+		arrOpt := E.ToOption(res)
+		assert.True(t, O.IsSome(arrOpt))
+		resultArr, _ := O.Unwrap(arrOpt)
+		assert.Equal(t, []int{2, 4, 6}, resultArr)
+	})
+
+	t.Run("TraverseArray with error", func(t *testing.T) {
+		arr := []int{1, 2, 3}
+		err := errors.New("test error")
+		traverser := TraverseArray(func(x int) ReaderIOResult[int] {
+			if x == 2 {
+				return Left[int](err)
+			}
+			return Of(x * 2)
+		})
+		result := traverser(arr)
+		res := result(context.Background())()
+		assert.True(t, E.IsLeft(res))
+	})
+}
+
+func TestSequenceArray(t *testing.T) {
+	arr := []ReaderIOResult[int]{Of(1), Of(2), Of(3)}
+	result := SequenceArray(arr)
+	res := result(context.Background())()
+	assert.True(t, E.IsRight(res))
+	arrOpt := E.ToOption(res)
+	assert.True(t, O.IsSome(arrOpt))
+	resultArr, _ := O.Unwrap(arrOpt)
+	assert.Equal(t, []int{1, 2, 3}, resultArr)
+}
+
+func TestTraverseRecord(t *testing.T) {
+	rec := map[string]int{"a": 1, "b": 2}
+	result := TraverseRecord[string](func(x int) ReaderIOResult[int] {
+		return Of(x * 2)
+	})(rec)
+	res := result(context.Background())()
+	assert.True(t, E.IsRight(res))
+	recOpt := E.ToOption(res)
+	assert.True(t, O.IsSome(recOpt))
+	resultRec, _ := O.Unwrap(recOpt)
+	assert.Equal(t, 2, resultRec["a"])
+	assert.Equal(t, 4, resultRec["b"])
+}
+
+func TestSequenceRecord(t *testing.T) {
+	rec := map[string]ReaderIOResult[int]{
+		"a": Of(1),
+		"b": Of(2),
+	}
+	result := SequenceRecord(rec)
+	res := result(context.Background())()
+	assert.True(t, E.IsRight(res))
+	recOpt := E.ToOption(res)
+	assert.True(t, O.IsSome(recOpt))
+	resultRec, _ := O.Unwrap(recOpt)
+	assert.Equal(t, 1, resultRec["a"])
+	assert.Equal(t, 2, resultRec["b"])
+}
+
+func TestAltSemigroup(t *testing.T) {
+	sg := AltSemigroup[int]()
+	err := errors.New("test error")
+
+	result := sg.Concat(Left[int](err), Of(42))
+	res := result(context.Background())()
+	assert.Equal(t, E.Right[error](42), res)
+}
+
+func TestApplicativeMonoid(t *testing.T) {
+	// Test with int addition monoid
+	intAddMonoid := ApplicativeMonoid(M.MakeMonoid(
+		func(a, b int) int { return a + b },
+		0,
+	))
+
+	result := intAddMonoid.Concat(Of(5), Of(10))
+	res := result(context.Background())()
+	assert.Equal(t, E.Right[error](15), res)
+}
+
+func TestBracket(t *testing.T) {
+	t.Run("Bracket with success", func(t *testing.T) {
+		var acquired, released bool
+
+		acquire := FromLazy(func() int {
+			acquired = true
+			return 42
+		})
+
+		use := func(x int) ReaderIOResult[int] {
+			return Of(x * 2)
+		}
+
+		release := func(x int, result Either[int]) ReaderIOResult[any] {
+			return FromLazy(func() any {
+				released = true
+				return nil
+			})
+		}
+
+		result := Bracket(acquire, use, release)
+		res := result(context.Background())()
+
+		assert.True(t, acquired)
+		assert.True(t, released)
+		assert.Equal(t, E.Right[error](84), res)
+	})
+
+	t.Run("Bracket with error in use", func(t *testing.T) {
+		var acquired, released bool
+		err := errors.New("use error")
+
+		acquire := FromLazy(func() int {
+			acquired = true
+			return 42
+		})
+
+		use := func(x int) ReaderIOResult[int] {
+			return Left[int](err)
+		}
+
+		release := func(x int, result Either[int]) ReaderIOResult[any] {
+			return FromLazy(func() any {
+				released = true
+				return nil
+			})
+		}
+
+		result := Bracket(acquire, use, release)
+		res := result(context.Background())()
+
+		assert.True(t, acquired)
+		assert.True(t, released)
+		assert.Equal(t, E.Left[int](err), res)
+	})
+}

v2/context/readerioresult/reader_test.go

@@ -13,7 +13,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package readerioeither
+package readerioresult
 
 import (
 	"context"
@@ -143,7 +143,7 @@ func TestCanceledApply(t *testing.T) {
 
 	applied := F.Pipe1(
 		fct,
-		Ap[string, string](errValue),
+		Ap[string](errValue),
 	)
 
 	res := applied(context.Background())()
@@ -156,7 +156,7 @@ func TestRegularApply(t *testing.T) {
 
 	applied := F.Pipe1(
 		fct,
-		Ap[string, string](value),
+		Ap[string](value),
 	)
 
 	res := applied(context.Background())()
@@ -171,14 +171,14 @@ func TestWithResourceNoErrors(t *testing.T) {
 		return countAcquire
 	})
 
-	release := func(int) ReaderIOEither[int] {
+	release := func(int) ReaderIOResult[int] {
 		return FromLazy(func() int {
 			countRelease++
 			return countRelease
 		})
 	}
 
-	body := func(int) ReaderIOEither[int] {
+	body := func(int) ReaderIOResult[int] {
 		return FromLazy(func() int {
 			countBody++
 			return countBody
@@ -203,7 +203,7 @@ func TestWithResourceErrorInBody(t *testing.T) {
 		return countAcquire
 	})
 
-	release := func(int) ReaderIOEither[int] {
+	release := func(int) ReaderIOResult[int] {
 		return FromLazy(func() int {
 			countRelease++
 			return countRelease
@@ -211,7 +211,7 @@ func TestWithResourceErrorInBody(t *testing.T) {
 	}
 
 	err := fmt.Errorf("error in body")
-	body := func(int) ReaderIOEither[int] {
+	body := func(int) ReaderIOResult[int] {
 		return Left[int](err)
 	}
 
@@ -231,14 +231,14 @@ func TestWithResourceErrorInAcquire(t *testing.T) {
 	err := fmt.Errorf("error in acquire")
 	acquire := Left[int](err)
 
-	release := func(int) ReaderIOEither[int] {
+	release := func(int) ReaderIOResult[int] {
 		return FromLazy(func() int {
 			countRelease++
 			return countRelease
 		})
 	}
 
-	body := func(int) ReaderIOEither[int] {
+	body := func(int) ReaderIOResult[int] {
 		return FromLazy(func() int {
 			countBody++
 			return countBody
@@ -264,11 +264,11 @@ func TestWithResourceErrorInRelease(t *testing.T) {
 	})
 
 	err := fmt.Errorf("error in release")
-	release := func(int) ReaderIOEither[int] {
+	release := func(int) ReaderIOResult[int] {
 		return Left[int](err)
 	}
 
-	body := func(int) ReaderIOEither[int] {
+	body := func(int) ReaderIOResult[int] {
 		return FromLazy(func() int {
 			countBody++
 			return countBody
@@ -284,3 +284,160 @@ func TestWithResourceErrorInRelease(t *testing.T) {
 	assert.Equal(t, 0, countRelease)
 	assert.Equal(t, E.Left[int](err), res)
 }
+
+func TestMonadChainFirstLeft(t *testing.T) {
+	ctx := context.Background()
+
+	// Test with Left value - function returns Left, always preserves original error
+	t.Run("Left value with function returning Left preserves original error", func(t *testing.T) {
+		sideEffectCalled := false
+		originalErr := fmt.Errorf("original error")
+		result := MonadChainFirstLeft(
+			Left[int](originalErr),
+			func(e error) ReaderIOResult[int] {
+				sideEffectCalled = true
+				return Left[int](fmt.Errorf("new error")) // This error is ignored
+			},
+		)
+		actualResult := result(ctx)()
+		assert.True(t, sideEffectCalled)
+		assert.Equal(t, E.Left[int](originalErr), actualResult)
+	})
+
+	// Test with Left value - function returns Right, still returns original Left
+	t.Run("Left value with function returning Right still returns original Left", func(t *testing.T) {
+		var capturedError error
+		originalErr := fmt.Errorf("validation failed")
+		result := MonadChainFirstLeft(
+			Left[int](originalErr),
+			func(e error) ReaderIOResult[int] {
+				capturedError = e
+				return Right(999) // This Right value is ignored
+			},
+		)
+		actualResult := result(ctx)()
+		assert.Equal(t, originalErr, capturedError)
+		assert.Equal(t, E.Left[int](originalErr), actualResult)
+	})
+
+	// Test with Right value - should pass through without calling function
+	t.Run("Right value passes through", func(t *testing.T) {
+		sideEffectCalled := false
+		result := MonadChainFirstLeft(
+			Right(42),
+			func(e error) ReaderIOResult[int] {
+				sideEffectCalled = true
+				return Left[int](fmt.Errorf("should not be called"))
+			},
+		)
+		assert.False(t, sideEffectCalled)
+		assert.Equal(t, E.Right[error](42), result(ctx)())
+	})
+
+	// Test that side effects are executed but original error is always preserved
+	t.Run("Side effects executed but original error preserved", func(t *testing.T) {
+		effectCount := 0
+		originalErr := fmt.Errorf("original error")
+		result := MonadChainFirstLeft(
+			Left[int](originalErr),
+			func(e error) ReaderIOResult[int] {
+				effectCount++
+				// Try to return Right, but original Left should still be returned
+				return Right(999)
+			},
+		)
+		actualResult := result(ctx)()
+		assert.Equal(t, 1, effectCount)
+		assert.Equal(t, E.Left[int](originalErr), actualResult)
+	})
+}
+
+func TestChainFirstLeft(t *testing.T) {
+	ctx := context.Background()
+
+	// Test with Left value - function returns Left, always preserves original error
+	t.Run("Left value with function returning Left preserves error", func(t *testing.T) {
+		var captured error
+		originalErr := fmt.Errorf("test error")
+		chainFn := ChainFirstLeft[int](func(e error) ReaderIOResult[int] {
+			captured = e
+			return Left[int](fmt.Errorf("ignored error"))
+		})
+		result := F.Pipe1(
+			Left[int](originalErr),
+			chainFn,
+		)
+		actualResult := result(ctx)()
+		assert.Equal(t, originalErr, captured)
+		assert.Equal(t, E.Left[int](originalErr), actualResult)
+	})
+
+	// Test with Left value - function returns Right, still returns original Left
+	t.Run("Left value with function returning Right still returns original Left", func(t *testing.T) {
+		var captured error
+		originalErr := fmt.Errorf("test error")
+		chainFn := ChainFirstLeft[int](func(e error) ReaderIOResult[int] {
+			captured = e
+			return Right(42) // This Right is ignored
+		})
+		result := F.Pipe1(
+			Left[int](originalErr),
+			chainFn,
+		)
+		actualResult := result(ctx)()
+		assert.Equal(t, originalErr, captured)
+		assert.Equal(t, E.Left[int](originalErr), actualResult)
+	})
+
+	// Test with Right value - should pass through without calling function
+	t.Run("Right value passes through", func(t *testing.T) {
+		called := false
+		chainFn := ChainFirstLeft[int](func(e error) ReaderIOResult[int] {
+			called = true
+			return Right(0)
+		})
+		result := F.Pipe1(
+			Right(100),
+			chainFn,
+		)
+		assert.False(t, called)
+		assert.Equal(t, E.Right[error](100), result(ctx)())
+	})
+
+	// Test that original error is always preserved regardless of what f returns
+	t.Run("Original error always preserved", func(t *testing.T) {
+		originalErr := fmt.Errorf("original")
+		chainFn := ChainFirstLeft[int](func(e error) ReaderIOResult[int] {
+			// Try to return Right, but original Left should still be returned
+			return Right(999)
+		})
+
+		result := F.Pipe1(
+			Left[int](originalErr),
+			chainFn,
+		)
+		assert.Equal(t, E.Left[int](originalErr), result(ctx)())
+	})
+
+	// Test logging with Left preservation
+	t.Run("Logging with Left preservation", func(t *testing.T) {
+		errorLog := []string{}
+		originalErr := fmt.Errorf("step1")
+		logError := ChainFirstLeft[string](func(e error) ReaderIOResult[string] {
+			errorLog = append(errorLog, "Logged: "+e.Error())
+			return Left[string](fmt.Errorf("log entry")) // This is ignored
+		})
+
+		result := F.Pipe2(
+			Left[string](originalErr),
+			logError,
+			ChainLeft(func(e error) ReaderIOResult[string] {
+				return Left[string](fmt.Errorf("step2"))
+			}),
+		)
+
+		actualResult := result(ctx)()
+		assert.Equal(t, []string{"Logged: step1"}, errorLog)
+		assert.Equal(t, E.Left[string](fmt.Errorf("step2")), actualResult)
+	})
+}

v2/context/readerioresult/resource.go

@@ -13,13 +13,10 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package readerioeither
+package readerioresult
 
 import (
-	"context"
-
-	"github.com/IBM/fp-go/v2/function"
-	RIE "github.com/IBM/fp-go/v2/readerioeither"
+	RIOR "github.com/IBM/fp-go/v2/readerioresult"
 )
 
 // WithResource constructs a function that creates a resource, then operates on it and then releases the resource.
@@ -32,22 +29,22 @@ import (
 //   - onRelease: Releases the resource (always called, even on error)
 //
 // Parameters:
-//   - onCreate: ReaderIOEither that creates the resource
+//   - onCreate: ReaderIOResult that creates the resource
 //   - onRelease: Function to release the resource
 //
-// Returns a function that takes a resource-using function and returns a ReaderIOEither.
+// Returns a function that takes a resource-using function and returns a ReaderIOResult.
 //
 // Example:
 //
 //	file := WithResource(
 //	    openFile("data.txt"),
-//	    func(f *os.File) ReaderIOEither[any] {
+//	    func(f *os.File) ReaderIOResult[any] {
 //	        return TryCatch(func(ctx context.Context) func() (any, error) {
 //	            return func() (any, error) { return nil, f.Close() }
 //	        })
 //	    },
 //	)
-//	result := file(func(f *os.File) ReaderIOEither[string] {
+//	result := file(func(f *os.File) ReaderIOResult[string] {
 //	    return TryCatch(func(ctx context.Context) func() (string, error) {
 //	        return func() (string, error) {
 //	            data, err := io.ReadAll(f)
@@ -55,9 +52,6 @@ import (
 //	        }
 //	    })
 //	})
-func WithResource[A, R, ANY any](onCreate ReaderIOEither[R], onRelease func(R) ReaderIOEither[ANY]) func(func(R) ReaderIOEither[A]) ReaderIOEither[A] {
-	return function.Flow2(
-		function.Bind2nd(function.Flow2[func(R) ReaderIOEither[A], Operator[A, A], R, ReaderIOEither[A], ReaderIOEither[A]], WithContext[A]),
-		RIE.WithResource[A, context.Context, error, R](WithContext(onCreate), onRelease),
-	)
+func WithResource[A, R, ANY any](onCreate ReaderIOResult[R], onRelease Kleisli[R, ANY]) Kleisli[Kleisli[R, A], A] {
+	return RIOR.WithResource[A](onCreate, onRelease)
 }

v2/context/readerioresult/resource_test.go

@@ -13,7 +13,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package readerioeither
+package readerioresult
 
 import (
 	"context"
@@ -37,7 +37,7 @@ var (
 	)
 )
 
-func closeFile(f *os.File) ReaderIOEither[string] {
+func closeFile(f *os.File) ReaderIOResult[string] {
 	return F.Pipe1(
 		TryCatch(func(_ context.Context) func() (string, error) {
 			return func() (string, error) {
@@ -52,7 +52,7 @@ func ExampleWithResource() {
 
 	stringReader := WithResource[string](openFile("data/file.txt"), closeFile)
 
-	rdr := stringReader(func(f *os.File) ReaderIOEither[string] {
+	rdr := stringReader(func(f *os.File) ReaderIOResult[string] {
 		return F.Pipe2(
 			TryCatch(func(_ context.Context) func() ([]byte, error) {
 				return func() ([]byte, error) {

v2/context/readerioresult/semigroup.go

@@ -13,21 +13,21 @@
 //   See the License for the specific language governing permissions and
 //   limitations under the License.
 
-package readerioeither
+package readerioresult
 
 import (
 	"github.com/IBM/fp-go/v2/semigroup"
 )
 
 type (
-	Semigroup[A any] = semigroup.Semigroup[ReaderIOEither[A]]
+	Semigroup[A any] = semigroup.Semigroup[ReaderIOResult[A]]
 )
 
 // AltSemigroup is a [Semigroup] that tries the first item and then the second one using an alternative.
-// This creates a semigroup where combining two ReaderIOEither values means trying the first one,
+// This creates a semigroup where combining two ReaderIOResult values means trying the first one,
 // and if it fails, trying the second one. This is useful for implementing fallback behavior.
 //
-// Returns a Semigroup for ReaderIOEither[A] with Alt-based combination.
+// Returns a Semigroup for ReaderIOResult[A] with Alt-based combination.
 //
 // Example:
 //

v2/context/readerioresult/sync.go

@@ -13,7 +13,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package readerioeither
+package readerioresult
 
 import (
 	"context"
@@ -29,9 +29,9 @@ import (
 // The lock parameter should return a CancelFunc that releases the lock when called.
 //
 // Parameters:
-//   - lock: ReaderIOEither that acquires a lock and returns a CancelFunc to release it
+//   - lock: ReaderIOResult that acquires a lock and returns a CancelFunc to release it
 //
-// Returns a function that wraps a ReaderIOEither with lock protection.
+// Returns a function that wraps a ReaderIOResult with lock protection.
 //
 // Example:
 //
@@ -43,9 +43,9 @@ import (
 //	    }
 //	})
 //	protectedOp := WithLock(lock)(myOperation)
-func WithLock[A any](lock ReaderIOEither[context.CancelFunc]) Operator[A, A] {
+func WithLock[A any](lock ReaderIOResult[context.CancelFunc]) Operator[A, A] {
 	return function.Flow2(
-		function.Constant1[context.CancelFunc, ReaderIOEither[A]],
+		function.Constant1[context.CancelFunc, ReaderIOResult[A]],
 		WithResource[A](lock, function.Flow2(
 			io.FromImpure[context.CancelFunc],
 			FromIO[any],

v2/context/readerioresult/traverse.go

@@ -0,0 +1,302 @@
+// Copyright (c) 2023 - 2025 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package readerioresult
+
+import (
+	"github.com/IBM/fp-go/v2/array"
+	"github.com/IBM/fp-go/v2/function"
+	"github.com/IBM/fp-go/v2/internal/record"
+)
+
+// TraverseArray transforms an array [[]A] into [[]ReaderIOResult[B]] and then resolves that into a [ReaderIOResult[[]B]].
+// This uses the default applicative behavior (parallel or sequential based on useParallel flag).
+//
+// Parameters:
+//   - f: Function that transforms each element into a ReaderIOResult
+//
+// Returns a function that transforms an array into a ReaderIOResult of an array.
+func TraverseArray[A, B any](f Kleisli[A, B]) Kleisli[[]A, []B] {
+	return array.Traverse(
+		Of[[]B],
+		Map[[]B, func(B) []B],
+		Ap[[]B, B],
+
+		f,
+	)
+}
+
+// TraverseArrayWithIndex transforms an array [[]A] into [[]ReaderIOResult[B]] and then resolves that into a [ReaderIOResult[[]B]].
+// The transformation function receives both the index and the element.
+//
+// Parameters:
+//   - f: Function that transforms each element with its index into a ReaderIOResult
+//
+// Returns a function that transforms an array into a ReaderIOResult of an array.
+func TraverseArrayWithIndex[A, B any](f func(int, A) ReaderIOResult[B]) Kleisli[[]A, []B] {
+	return array.TraverseWithIndex(
+		Of[[]B],
+		Map[[]B, func(B) []B],
+		Ap[[]B, B],
+
+		f,
+	)
+}
+
+// SequenceArray converts a homogeneous sequence of ReaderIOResult into a ReaderIOResult of sequence.
+// This is equivalent to TraverseArray with the identity function.
+//
+// Parameters:
+//   - ma: Array of ReaderIOResult values
+//
+// Returns a ReaderIOResult containing an array of values.
+func SequenceArray[A any](ma []ReaderIOResult[A]) ReaderIOResult[[]A] {
+	return TraverseArray(function.Identity[ReaderIOResult[A]])(ma)
+}
+
+// TraverseRecord transforms a record [map[K]A] into [map[K]ReaderIOResult[B]] and then resolves that into a [ReaderIOResult[map[K]B]].
+//
+// Parameters:
+//   - f: Function that transforms each value into a ReaderIOResult
+//
+// Returns a function that transforms a map into a ReaderIOResult of a map.
+func TraverseRecord[K comparable, A, B any](f Kleisli[A, B]) Kleisli[map[K]A, map[K]B] {
+	return record.Traverse[map[K]A](
+		Of[map[K]B],
+		Map[map[K]B, func(B) map[K]B],
+		Ap[map[K]B, B],
+
+		f,
+	)
+}
+
+// TraverseRecordWithIndex transforms a record [map[K]A] into [map[K]ReaderIOResult[B]] and then resolves that into a [ReaderIOResult[map[K]B]].
+// The transformation function receives both the key and the value.
+//
+// Parameters:
+//   - f: Function that transforms each key-value pair into a ReaderIOResult
+//
+// Returns a function that transforms a map into a ReaderIOResult of a map.
+func TraverseRecordWithIndex[K comparable, A, B any](f func(K, A) ReaderIOResult[B]) Kleisli[map[K]A, map[K]B] {
+	return record.TraverseWithIndex[map[K]A](
+		Of[map[K]B],
+		Map[map[K]B, func(B) map[K]B],
+		Ap[map[K]B, B],
+
+		f,
+	)
+}
+
+// SequenceRecord converts a homogeneous map of ReaderIOResult into a ReaderIOResult of map.
+//
+// Parameters:
+//   - ma: Map of ReaderIOResult values
+//
+// Returns a ReaderIOResult containing a map of values.
+func SequenceRecord[K comparable, A any](ma map[K]ReaderIOResult[A]) ReaderIOResult[map[K]A] {
+	return TraverseRecord[K](function.Identity[ReaderIOResult[A]])(ma)
+}
+
+// MonadTraverseArraySeq transforms an array [[]A] into [[]ReaderIOResult[B]] and then resolves that into a [ReaderIOResult[[]B]].
+// This explicitly uses sequential execution.
+//
+// Parameters:
+//   - as: The array to traverse
+//   - f: Function that transforms each element into a ReaderIOResult
+//
+// Returns a ReaderIOResult containing an array of transformed values.
+func MonadTraverseArraySeq[A, B any](as []A, f Kleisli[A, B]) ReaderIOResult[[]B] {
+	return array.MonadTraverse(
+		Of[[]B],
+		Map[[]B, func(B) []B],
+		ApSeq[[]B, B],
+		as,
+		f,
+	)
+}
+
+// TraverseArraySeq transforms an array [[]A] into [[]ReaderIOResult[B]] and then resolves that into a [ReaderIOResult[[]B]].
+// This is the curried version of [MonadTraverseArraySeq] with sequential execution.
+//
+// Parameters:
+//   - f: Function that transforms each element into a ReaderIOResult
+//
+// Returns a function that transforms an array into a ReaderIOResult of an array.
+func TraverseArraySeq[A, B any](f Kleisli[A, B]) Kleisli[[]A, []B] {
+	return array.Traverse(
+		Of[[]B],
+		Map[[]B, func(B) []B],
+		ApSeq[[]B, B],
+		f,
+	)
+}
+
+// TraverseArrayWithIndexSeq uses transforms an array [[]A] into [[]ReaderIOResult[B]] and then resolves that into a [ReaderIOResult[[]B]]
+func TraverseArrayWithIndexSeq[A, B any](f func(int, A) ReaderIOResult[B]) Kleisli[[]A, []B] {
+	return array.TraverseWithIndex(
+		Of[[]B],
+		Map[[]B, func(B) []B],
+		ApSeq[[]B, B],
+		f,
+	)
+}
+
+// SequenceArraySeq converts a homogeneous sequence of ReaderIOResult into a ReaderIOResult of sequence.
+// This explicitly uses sequential execution.
+//
+// Parameters:
+//   - ma: Array of ReaderIOResult values
+//
+// Returns a ReaderIOResult containing an array of values.
+func SequenceArraySeq[A any](ma []ReaderIOResult[A]) ReaderIOResult[[]A] {
+	return MonadTraverseArraySeq(ma, function.Identity[ReaderIOResult[A]])
+}
+
+// MonadTraverseRecordSeq uses transforms a record [map[K]A] into [map[K]ReaderIOResult[B]] and then resolves that into a [ReaderIOResult[map[K]B]]
+func MonadTraverseRecordSeq[K comparable, A, B any](as map[K]A, f Kleisli[A, B]) ReaderIOResult[map[K]B] {
+	return record.MonadTraverse(
+		Of[map[K]B],
+		Map[map[K]B, func(B) map[K]B],
+		ApSeq[map[K]B, B],
+		as,
+		f,
+	)
+}
+
+// TraverseRecordSeq uses transforms a record [map[K]A] into [map[K]ReaderIOResult[B]] and then resolves that into a [ReaderIOResult[map[K]B]]
+func TraverseRecordSeq[K comparable, A, B any](f Kleisli[A, B]) Kleisli[map[K]A, map[K]B] {
+	return record.Traverse[map[K]A](
+		Of[map[K]B],
+		Map[map[K]B, func(B) map[K]B],
+		ApSeq[map[K]B, B],
+
+		f,
+	)
+}
+
+// TraverseRecordWithIndexSeq uses transforms a record [map[K]A] into [map[K]ReaderIOResult[B]] and then resolves that into a [ReaderIOResult[map[K]B]]
+func TraverseRecordWithIndexSeq[K comparable, A, B any](f func(K, A) ReaderIOResult[B]) Kleisli[map[K]A, map[K]B] {
+	return record.TraverseWithIndex[map[K]A](
+		Of[map[K]B],
+		Map[map[K]B, func(B) map[K]B],
+		ApSeq[map[K]B, B],
+
+		f,
+	)
+}
+
+// SequenceRecordSeq converts a homogeneous sequence of either into an either of sequence
+func SequenceRecordSeq[K comparable, A any](ma map[K]ReaderIOResult[A]) ReaderIOResult[map[K]A] {
+	return MonadTraverseRecordSeq(ma, function.Identity[ReaderIOResult[A]])
+}
+
+// MonadTraverseArrayPar transforms an array [[]A] into [[]ReaderIOResult[B]] and then resolves that into a [ReaderIOResult[[]B]].
+// This explicitly uses parallel execution.
+//
+// Parameters:
+//   - as: The array to traverse
+//   - f: Function that transforms each element into a ReaderIOResult
+//
+// Returns a ReaderIOResult containing an array of transformed values.
+func MonadTraverseArrayPar[A, B any](as []A, f Kleisli[A, B]) ReaderIOResult[[]B] {
+	return array.MonadTraverse(
+		Of[[]B],
+		Map[[]B, func(B) []B],
+		ApPar[[]B, B],
+		as,
+		f,
+	)
+}
+
+// TraverseArrayPar transforms an array [[]A] into [[]ReaderIOResult[B]] and then resolves that into a [ReaderIOResult[[]B]].
+// This is the curried version of [MonadTraverseArrayPar] with parallel execution.
+//
+// Parameters:
+//   - f: Function that transforms each element into a ReaderIOResult
+//
+// Returns a function that transforms an array into a ReaderIOResult of an array.
+func TraverseArrayPar[A, B any](f Kleisli[A, B]) Kleisli[[]A, []B] {
+	return array.Traverse(
+		Of[[]B],
+		Map[[]B, func(B) []B],
+		ApPar[[]B, B],
+		f,
+	)
+}
+
+// TraverseArrayWithIndexPar uses transforms an array [[]A] into [[]ReaderIOResult[B]] and then resolves that into a [ReaderIOResult[[]B]]
+func TraverseArrayWithIndexPar[A, B any](f func(int, A) ReaderIOResult[B]) Kleisli[[]A, []B] {
+	return array.TraverseWithIndex(
+		Of[[]B],
+		Map[[]B, func(B) []B],
+		ApPar[[]B, B],
+		f,
+	)
+}
+
+// SequenceArrayPar converts a homogeneous sequence of ReaderIOResult into a ReaderIOResult of sequence.
+// This explicitly uses parallel execution.
+//
+// Parameters:
+//   - ma: Array of ReaderIOResult values
+//
+// Returns a ReaderIOResult containing an array of values.
+func SequenceArrayPar[A any](ma []ReaderIOResult[A]) ReaderIOResult[[]A] {
+	return MonadTraverseArrayPar(ma, function.Identity[ReaderIOResult[A]])
+}
+
+// TraverseRecordPar uses transforms a record [map[K]A] into [map[K]ReaderIOResult[B]] and then resolves that into a [ReaderIOResult[map[K]B]]
+func TraverseRecordPar[K comparable, A, B any](f Kleisli[A, B]) Kleisli[map[K]A, map[K]B] {
+	return record.Traverse[map[K]A](
+		Of[map[K]B],
+		Map[map[K]B, func(B) map[K]B],
+		ApPar[map[K]B, B],
+
+		f,
+	)
+}
+
+// TraverseRecordWithIndexPar uses transforms a record [map[K]A] into [map[K]ReaderIOResult[B]] and then resolves that into a [ReaderIOResult[map[K]B]]
+func TraverseRecordWithIndexPar[K comparable, A, B any](f func(K, A) ReaderIOResult[B]) Kleisli[map[K]A, map[K]B] {
+	return record.TraverseWithIndex[map[K]A](
+		Of[map[K]B],
+		Map[map[K]B, func(B) map[K]B],
+		ApPar[map[K]B, B],
+
+		f,
+	)
+}
+
+// MonadTraverseRecordPar uses transforms a record [map[K]A] into [map[K]ReaderIOResult[B]] and then resolves that into a [ReaderIOResult[map[K]B]]
+func MonadTraverseRecordPar[K comparable, A, B any](as map[K]A, f Kleisli[A, B]) ReaderIOResult[map[K]B] {
+	return record.MonadTraverse(
+		Of[map[K]B],
+		Map[map[K]B, func(B) map[K]B],
+		ApPar[map[K]B, B],
+		as,
+		f,
+	)
+}
+
+// SequenceRecordPar converts a homogeneous map of ReaderIOResult into a ReaderIOResult of map.
+// This explicitly uses parallel execution.
+//
+// Parameters:
+//   - ma: Map of ReaderIOResult values
+//
+// Returns a ReaderIOResult containing a map of values.
+func SequenceRecordPar[K comparable, A any](ma map[K]ReaderIOResult[A]) ReaderIOResult[map[K]A] {
+	return MonadTraverseRecordPar(ma, function.Identity[ReaderIOResult[A]])
+}

v2/context/readerioresult/type.go

@@ -13,19 +13,24 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package readerioeither
+package readerioresult
 
 import (
 	"context"
 
+	"github.com/IBM/fp-go/v2/context/ioresult"
+	"github.com/IBM/fp-go/v2/context/readerresult"
 	"github.com/IBM/fp-go/v2/either"
 	"github.com/IBM/fp-go/v2/io"
 	"github.com/IBM/fp-go/v2/ioeither"
 	"github.com/IBM/fp-go/v2/lazy"
 	"github.com/IBM/fp-go/v2/option"
 	"github.com/IBM/fp-go/v2/reader"
+	"github.com/IBM/fp-go/v2/readereither"
 	"github.com/IBM/fp-go/v2/readerio"
-	"github.com/IBM/fp-go/v2/readerioeither"
+	RIOR "github.com/IBM/fp-go/v2/readerioresult"
+	"github.com/IBM/fp-go/v2/readeroption"
+	"github.com/IBM/fp-go/v2/result"
 )
 
 type (
@@ -40,6 +45,8 @@ type (
 	// Either[A] is equivalent to Either[error, A] from the either package.
 	Either[A any] = either.Either[error, A]
 
+	Result[A any] = result.Result[A]
+
 	// Lazy represents a deferred computation that produces a value of type A when executed.
 	// The computation is not executed until explicitly invoked.
 	Lazy[A any] = lazy.Lazy[A]
@@ -56,6 +63,8 @@ type (
 	// IOEither[A] is equivalent to func() Either[error, A]
 	IOEither[A any] = ioeither.IOEither[error, A]
 
+	IOResult[A any] = ioresult.IOResult[A]
+
 	// Reader represents a computation that depends on a context of type R.
 	// This is used for dependency injection and accessing shared context.
 	//
@@ -68,21 +77,21 @@ type (
 	// ReaderIO[A] is equivalent to func(context.Context) func() A
 	ReaderIO[A any] = readerio.ReaderIO[context.Context, A]
 
-	// ReaderIOEither is the main type of this package. It represents a computation that:
+	// ReaderIOResult is the main type of this package. It represents a computation that:
 	//   - Depends on a [context.Context] (Reader aspect)
 	//   - Performs side effects (IO aspect)
 	//   - Can fail with an [error] (Either aspect)
 	//   - Produces a value of type A on success
 	//
-	// This is a specialization of [readerioeither.ReaderIOEither] with:
+	// This is a specialization of [readerioeither.ReaderIOResult] with:
 	//   - Context type fixed to [context.Context]
 	//   - Error type fixed to [error]
 	//
 	// The type is defined as:
-	//   ReaderIOEither[A] = func(context.Context) func() Either[error, A]
+	//   ReaderIOResult[A] = func(context.Context) func() Either[error, A]
 	//
 	// Example usage:
-	//   func fetchUser(id string) ReaderIOEither[User] {
+	//   func fetchUser(id string) ReaderIOResult[User] {
 	//       return func(ctx context.Context) func() Either[error, User] {
 	//           return func() Either[error, User] {
 	//               user, err := userService.Get(ctx, id)
@@ -97,12 +106,14 @@ type (
 	// The computation is executed by providing a context and then invoking the result:
 	//   ctx := context.Background()
 	//   result := fetchUser("123")(ctx)()
-	ReaderIOEither[A any] = readerioeither.ReaderIOEither[context.Context, error, A]
+	ReaderIOResult[A any] = RIOR.ReaderIOResult[context.Context, A]
 
-	// Operator represents a transformation from one ReaderIOEither to another.
+	Kleisli[A, B any] = reader.Reader[A, ReaderIOResult[B]]
+
+	// Operator represents a transformation from one ReaderIOResult to another.
 	// This is useful for point-free style composition and building reusable transformations.
 	//
-	// Operator[A, B] is equivalent to func(ReaderIOEither[A]) ReaderIOEither[B]
+	// Operator[A, B] is equivalent to Kleisli[ReaderIOResult[A], B]
 	//
 	// Example usage:
 	//   // Define a reusable transformation
@@ -110,5 +121,9 @@ type (
 	//
 	//   // Apply the transformation
 	//   result := toUpper(computation)
-	Operator[A, B any] = Reader[ReaderIOEither[A], ReaderIOEither[B]]
+	Operator[A, B any] = Kleisli[ReaderIOResult[A], B]
+
+	ReaderResult[A any]       = readerresult.ReaderResult[A]
+	ReaderEither[R, E, A any] = readereither.ReaderEither[R, E, A]
+	ReaderOption[R, A any]    = readeroption.ReaderOption[R, A]
 )

v2/context/readerresult/array.go

@@ -13,21 +13,21 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package readereither
+package readerresult
 
 import "github.com/IBM/fp-go/v2/readereither"
 
 // TraverseArray transforms an array
-func TraverseArray[A, B any](f func(A) ReaderEither[B]) func([]A) ReaderEither[[]B] {
+func TraverseArray[A, B any](f Kleisli[A, B]) Kleisli[[]A, []B] {
 	return readereither.TraverseArray(f)
 }
 
 // TraverseArrayWithIndex transforms an array
-func TraverseArrayWithIndex[A, B any](f func(int, A) ReaderEither[B]) func([]A) ReaderEither[[]B] {
+func TraverseArrayWithIndex[A, B any](f func(int, A) ReaderResult[B]) Kleisli[[]A, []B] {
 	return readereither.TraverseArrayWithIndex(f)
 }
 
 // SequenceArray converts a homogeneous sequence of either into an either of sequence
-func SequenceArray[A any](ma []ReaderEither[A]) ReaderEither[[]A] {
+func SequenceArray[A any](ma []ReaderResult[A]) ReaderResult[[]A] {
 	return readereither.SequenceArray(ma)
 }

v2/context/readerresult/bind.go

@@ -0,0 +1,304 @@
+// Copyright (c) 2023 - 2025 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package readerresult
+
+import (
+	F "github.com/IBM/fp-go/v2/function"
+	L "github.com/IBM/fp-go/v2/optics/lens"
+	G "github.com/IBM/fp-go/v2/readereither/generic"
+)
+
+// Do creates an empty context of type [S] to be used with the [Bind] operation.
+// This is the starting point for do-notation style composition.
+//
+// Example:
+//
+//	type State struct {
+//	    UserID   string
+//	    TenantID string
+//	}
+//	result := readereither.Do(State{})
+func Do[S any](
+	empty S,
+) ReaderResult[S] {
+	return G.Do[ReaderResult[S]](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2].
+// This enables sequential composition where each step can depend on the results of previous steps
+// and access the context.Context from the environment.
+//
+// The setter function takes the result of the computation and returns a function that
+// updates the context from S1 to S2.
+//
+// Example:
+//
+//	type State struct {
+//	    UserID   string
+//	    TenantID string
+//	}
+//
+//	result := F.Pipe2(
+//	    readereither.Do(State{}),
+//	    readereither.Bind(
+//	        func(uid string) func(State) State {
+//	            return func(s State) State { s.UserID = uid; return s }
+//	        },
+//	        func(s State) readereither.ReaderResult[string] {
+//	            return func(ctx context.Context) either.Either[error, string] {
+//	                if uid, ok := ctx.Value("userID").(string); ok {
+//	                    return either.Right[error](uid)
+//	                }
+//	                return either.Left[string](errors.New("no userID"))
+//	            }
+//	        },
+//	    ),
+//	    readereither.Bind(
+//	        func(tid string) func(State) State {
+//	            return func(s State) State { s.TenantID = tid; return s }
+//	        },
+//	        func(s State) readereither.ReaderResult[string] {
+//	            // This can access s.UserID from the previous step
+//	            return func(ctx context.Context) either.Either[error, string] {
+//	                return either.Right[error]("tenant-" + s.UserID)
+//	            }
+//	        },
+//	    ),
+//	)
+func Bind[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f Kleisli[S1, T],
+) Kleisli[ReaderResult[S1], S2] {
+	return G.Bind[ReaderResult[S1], ReaderResult[S2]](setter, f)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) T,
+) Kleisli[ReaderResult[S1], S2] {
+	return G.Let[ReaderResult[S1], ReaderResult[S2]](setter, f)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	b T,
+) Kleisli[ReaderResult[S1], S2] {
+	return G.LetTo[ReaderResult[S1], ReaderResult[S2]](setter, b)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[S1, T any](
+	setter func(T) S1,
+) Kleisli[ReaderResult[T], S1] {
+	return G.BindTo[ReaderResult[S1], ReaderResult[T]](setter)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering
+// the context and the value concurrently (using Applicative rather than Monad).
+// This allows independent computations to be combined without one depending on the result of the other.
+//
+// Unlike Bind, which sequences operations, ApS can be used when operations are independent
+// and can conceptually run in parallel.
+//
+// Example:
+//
+//	type State struct {
+//	    UserID   string
+//	    TenantID string
+//	}
+//
+//	// These operations are independent and can be combined with ApS
+//	getUserID := func(ctx context.Context) either.Either[error, string] {
+//	    return either.Right[error](ctx.Value("userID").(string))
+//	}
+//	getTenantID := func(ctx context.Context) either.Either[error, string] {
+//	    return either.Right[error](ctx.Value("tenantID").(string))
+//	}
+//
+//	result := F.Pipe2(
+//	    readereither.Do(State{}),
+//	    readereither.ApS(
+//	        func(uid string) func(State) State {
+//	            return func(s State) State { s.UserID = uid; return s }
+//	        },
+//	        getUserID,
+//	    ),
+//	    readereither.ApS(
+//	        func(tid string) func(State) State {
+//	            return func(s State) State { s.TenantID = tid; return s }
+//	        },
+//	        getTenantID,
+//	    ),
+//	)
+func ApS[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa ReaderResult[T],
+) Kleisli[ReaderResult[S1], S2] {
+	return G.ApS[ReaderResult[S1], ReaderResult[S2]](setter, fa)
+}
+
+// ApSL is a variant of ApS that uses a lens to focus on a specific field in the state.
+// Instead of providing a setter function, you provide a lens that knows how to get and set
+// the field. This is more convenient when working with nested structures.
+//
+// Parameters:
+//   - lens: A lens that focuses on a field of type T within state S
+//   - fa: A ReaderResult computation that produces a value of type T
+//
+// Returns:
+//   - A function that transforms ReaderResult[S] to ReaderResult[S] by setting the focused field
+//
+// Example:
+//
+//	type Person struct {
+//	    Name string
+//	    Age  int
+//	}
+//
+//	ageLens := lens.MakeLens(
+//	    func(p Person) int { return p.Age },
+//	    func(p Person, a int) Person { p.Age = a; return p },
+//	)
+//
+//	getAge := func(ctx context.Context) either.Either[error, int] {
+//	    return either.Right[error](30)
+//	}
+//
+//	result := F.Pipe1(
+//	    readereither.Do(Person{Name: "Alice", Age: 25}),
+//	    readereither.ApSL(ageLens, getAge),
+//	)
+func ApSL[S, T any](
+	lens L.Lens[S, T],
+	fa ReaderResult[T],
+) Kleisli[ReaderResult[S], S] {
+	return ApS(lens.Set, fa)
+}
+
+// BindL is a variant of Bind that uses a lens to focus on a specific field in the state.
+// It combines the lens-based field access with monadic composition, allowing you to:
+// 1. Extract a field value using the lens
+// 2. Use that value in a computation that may fail
+// 3. Update the field with the result
+//
+// Parameters:
+//   - lens: A lens that focuses on a field of type T within state S
+//   - f: A function that takes the current field value and returns a ReaderResult computation
+//
+// Returns:
+//   - A function that transforms ReaderResult[S] to ReaderResult[S]
+//
+// Example:
+//
+//	type Counter struct {
+//	    Value int
+//	}
+//
+//	valueLens := lens.MakeLens(
+//	    func(c Counter) int { return c.Value },
+//	    func(c Counter, v int) Counter { c.Value = v; return c },
+//	)
+//
+//	increment := func(v int) readereither.ReaderResult[int] {
+//	    return func(ctx context.Context) either.Either[error, int] {
+//	        if v >= 100 {
+//	            return either.Left[int](errors.New("value too large"))
+//	        }
+//	        return either.Right[error](v + 1)
+//	    }
+//	}
+//
+//	result := F.Pipe1(
+//	    readereither.Of[error](Counter{Value: 42}),
+//	    readereither.BindL(valueLens, increment),
+//	)
+func BindL[S, T any](
+	lens L.Lens[S, T],
+	f Kleisli[T, T],
+) Kleisli[ReaderResult[S], S] {
+	return Bind(lens.Set, F.Flow2(lens.Get, f))
+}
+
+// LetL is a variant of Let that uses a lens to focus on a specific field in the state.
+// It applies a pure transformation to the focused field without any effects.
+//
+// Parameters:
+//   - lens: A lens that focuses on a field of type T within state S
+//   - f: A pure function that transforms the field value
+//
+// Returns:
+//   - A function that transforms ReaderResult[S] to ReaderResult[S]
+//
+// Example:
+//
+//	type Counter struct {
+//	    Value int
+//	}
+//
+//	valueLens := lens.MakeLens(
+//	    func(c Counter) int { return c.Value },
+//	    func(c Counter, v int) Counter { c.Value = v; return c },
+//	)
+//
+//	double := func(v int) int { return v * 2 }
+//
+//	result := F.Pipe1(
+//	    readereither.Of[error](Counter{Value: 21}),
+//	    readereither.LetL(valueLens, double),
+//	)
+//	// result when executed will be Right(Counter{Value: 42})
+func LetL[S, T any](
+	lens L.Lens[S, T],
+	f func(T) T,
+) Kleisli[ReaderResult[S], S] {
+	return Let(lens.Set, F.Flow2(lens.Get, f))
+}
+
+// LetToL is a variant of LetTo that uses a lens to focus on a specific field in the state.
+// It sets the focused field to a constant value.
+//
+// Parameters:
+//   - lens: A lens that focuses on a field of type T within state S
+//   - b: The constant value to set
+//
+// Returns:
+//   - A function that transforms ReaderResult[S] to ReaderResult[S]
+//
+// Example:
+//
+//	type Config struct {
+//	    Debug   bool
+//	    Timeout int
+//	}
+//
+//	debugLens := lens.MakeLens(
+//	    func(c Config) bool { return c.Debug },
+//	    func(c Config, d bool) Config { c.Debug = d; return c },
+//	)
+//
+//	result := F.Pipe1(
+//	    readereither.Of[error](Config{Debug: true, Timeout: 30}),
+//	    readereither.LetToL(debugLens, false),
+//	)
+//	// result when executed will be Right(Config{Debug: false, Timeout: 30})
+func LetToL[S, T any](
+	lens L.Lens[S, T],
+	b T,
+) Kleisli[ReaderResult[S], S] {
+	return LetTo(lens.Set, b)
+}

v2/context/readerresult/bind_test.go

@@ -13,7 +13,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package readereither
+package readerresult
 
 import (
 	"context"
@@ -25,11 +25,11 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func getLastName(s utils.Initial) ReaderEither[string] {
+func getLastName(s utils.Initial) ReaderResult[string] {
 	return Of("Doe")
 }
 
-func getGivenName(s utils.WithLastName) ReaderEither[string] {
+func getGivenName(s utils.WithLastName) ReaderResult[string] {
 	return Of("John")
 }