fix: examples

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

.github/workflows/build.yml

@@ -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:
@@ -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'

.gitignore

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

README.md

@@ -1,207 +1,312 @@
-# Functional programming library for golang
+# fp-go: Functional Programming Library for Go
 
-**🚧 Work in progress! 🚧** Despite major version 1 because of <https://github.com/semantic-release/semantic-release/issues/1507>. Trying to not make breaking changes, but devil is in the details.
+[![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.
 
 ![logo](resources/images/logo.png)
 
-This library is strongly influenced by the awesome [fp-ts](https://github.com/gcanti/fp-ts).
+A comprehensive functional programming library for Go, strongly influenced by the excellent [fp-ts](https://github.com/gcanti/fp-ts) library for TypeScript.
 
-## Getting started
+## 📚 Table of Contents
+
+- [Getting Started](#-getting-started)
+- [Design Goals](#-design-goals)
+- [Core Concepts](#-core-concepts)
+- [Comparison to Idiomatic Go](#comparison-to-idiomatic-go)
+- [Implementation Notes](#implementation-notes)
+- [Common Operations](#common-operations)
+- [Resources](#-resources)
+
+## 🚀 Getting Started
+
+### Installation
 
 ```bash
 go get github.com/IBM/fp-go
 ```
 
-Refer to the [samples](./samples/).
+### Quick Example
 
-Find API documentation [here](https://pkg.go.dev/github.com/IBM/fp-go)
+```go
+import (
+    "errors"
+    "github.com/IBM/fp-go/either"
+    "github.com/IBM/fp-go/function"
+)
 
-## Design Goal
+// Pure function that can fail
+func divide(a, b int) either.Either[error, int] {
+    if b == 0 {
+        return either.Left[int](errors.New("division by zero"))
+    }
+    return either.Right[error](a / b)
+}
 
-This library aims to provide a set of data types and functions that make it easy and fun to write maintainable and testable code in golang. It encourages the following patterns:
+// Compose operations safely
+result := function.Pipe2(
+    divide(10, 2),
+    either.Map(func(x int) int { return x * 2 }),
+    either.GetOrElse(func() int { return 0 }),
+)
+// result = 10
+```
 
-- write many small, testable and pure functions, i.e. functions that produce output only depending on their input and that do not execute side effects
-- offer helpers to isolate side effects into lazily executed functions (IO)
-- expose a consistent set of composition to create new functions from existing ones
-  - for each data type there exists a small set of composition functions
-  - these functions are called the same across all data types, so you only have to learn a small number of function names
-  - the semantic of functions of the same name is consistent across all data types
+### Resources
 
-### How does this play with the [🧘🏽 Zen Of Go](https://the-zen-of-go.netlify.app/)?
+- 📖 [API Documentation](https://pkg.go.dev/github.com/IBM/fp-go)
+- 💡 [Code Samples](./samples/)
+- 🆕 [V2 Documentation](./v2/README.md) (requires Go 1.24+)
 
-#### 🧘🏽 Each package fulfills a single purpose
+## 🎯 Design Goals
 
-✔️ Each of the top level packages (e.g. Option, Either, ReaderIOEither, ...) fulfills the purpose of defining the respective data type and implementing the set of common operations for this data type.
+This library aims to provide a set of data types and functions that make it easy and fun to write maintainable and testable code in Go. It encourages the following patterns:
 
-#### 🧘🏽 Handle errors explicitly
+### Core Principles
 
-✔️ The library makes a clear distinction between that operations that cannot fail by design and operations that can fail. Failure is represented via the `Either` type and errors are handled explicitly by using `Either`'s monadic set of operations.
+- **Pure Functions**: Write many small, testable, and pure functions that produce output only depending on their input and execute no side effects
+- **Side Effect Isolation**: Isolate side effects into lazily executed functions using the `IO` monad
+- **Consistent Composition**: Expose a consistent set of composition functions across all data types
+  - Each data type has a small set of composition functions
+  - Functions are named consistently across all data types
+  - Semantics of same-named functions are consistent across data types
 
-#### 🧘🏽 Return early rather than nesting deeply
+### 🧘🏽 Alignment with the Zen of Go
 
-✔️ We recommend to implement simple, small functions that implement one feature and that would typically not invoke other functions. Interaction with other functions is done by function composition and the composition makes sure to run one function after the other. In the error case the `Either` monad makes sure to skip the error path.
+This library respects and aligns with [The Zen of Go](https://the-zen-of-go.netlify.app/):
 
-#### 🧘🏽 Leave concurrency to the caller
+| Principle | Alignment | Explanation |
+|-----------|-----------|-------------|
+| 🧘🏽 Each package fulfills a single purpose | ✔️ | Each top-level package (Option, Either, ReaderIOEither, etc.) defines one data type and its operations |
+| 🧘🏽 Handle errors explicitly | ✔️ | Clear distinction between operations that can/cannot fail; failures represented via `Either` type |
+| 🧘🏽 Return early rather than nesting deeply | ✔️ | Small, focused functions composed together; `Either` monad handles error paths automatically |
+| 🧘🏽 Leave concurrency to the caller | ✔️ | Pure functions are synchronous; I/O operations are asynchronous by default |
+| 🧘🏽 Before you launch a goroutine, know when it will stop | 🤷🏽 | Library doesn't start goroutines; Task monad supports cancellation via context |
+| 🧘🏽 Avoid package level state | ✔️ | No package-level state anywhere |
+| 🧘🏽 Simplicity matters | ✔️ | Small, consistent interface across data types; focus on business logic |
+| 🧘🏽 Write tests to lock in behaviour | 🟡 | Programming pattern encourages testing; library has growing test coverage |
+| 🧘🏽 If you think it's slow, first prove it with a benchmark | ✔️ | Performance claims should be backed by benchmarks |
+| 🧘🏽 Moderation is a virtue | ✔️ | No custom goroutines or expensive synchronization; atomic counters for coordination |
+| 🧘🏽 Maintainability counts | ✔️ | Small, concise operations; pure functions with clear type signatures |
 
-✔️ All pure are synchronous by default. The I/O operations are asynchronous per default.
+## 💡 Core Concepts
 
-#### 🧘🏽 Before you launch a goroutine, know when it will stop
+### Data Types
 
-🤷🏽 This is left to the user of the library since the library itself will not start goroutines on its own. The Task monad offers support for cancellation via the golang context, though.
+The library provides several key functional data types:
 
-#### 🧘🏽 Avoid package level state
+- **`Option[A]`**: Represents an optional value (Some or None)
+- **`Either[E, A]`**: Represents a value that can be one of two types (Left for errors, Right for success)
+- **`IO[A]`**: Represents a lazy computation that produces a value
+- **`IOEither[E, A]`**: Represents a lazy computation that can fail
+- **`Reader[R, A]`**: Represents a computation that depends on an environment
+- **`ReaderIOEither[R, E, A]`**: Combines Reader, IO, and Either for effectful computations with dependencies
+- **`Task[A]`**: Represents an asynchronous computation
+- **`State[S, A]`**: Represents a stateful computation
 
-✔️ No package level state anywhere, this would be a significant anti-pattern
+### Monadic Operations
 
-#### 🧘🏽 Simplicity matters
+All data types support common monadic operations:
 
-✔️ The library is simple in the sense that it offers a small, consistent interface to a variety of data types. Users can concentrate on implementing business logic rather than dealing with low level data structures.
-
-#### 🧘🏽 Write tests to lock in the behaviour of your package’s API
-
-🟡 The programming pattern suggested by this library encourages writing test cases. The library itself also has a growing number of tests, but not enough, yet. TBD
-
-#### 🧘🏽 If you think it’s slow, first prove it with a benchmark
-
-✔️ Absolutely. If you think the function composition offered by this library is too slow, please provide a benchmark.
-
-#### 🧘🏽 Moderation is a virtue
-
-✔️ The library does not implement its own goroutines and also does not require any expensive synchronization primitives. Coordination of IO operations is implemented via atomic counters without additional primitives.
-
-#### 🧘🏽 Maintainability counts
-
-✔️ Code that consumes this library is easy to maintain because of the small and concise set of operations exposed. Also the suggested programming paradigm to decompose an application into small functions increases maintainability, because these functions are easy to understand and if they are pure, it's often sufficient to look at the type signature to understand the purpose.
-
-The library itself also comprises many small functions, but it's admittedly harder to maintain than code that uses it. However this asymmetry is intended because it offloads complexity from users into a central component.
+- **`Map`**: Transform the value inside a context
+- **`Chain`** (FlatMap): Transform and flatten nested contexts
+- **`Ap`**: Apply a function in a context to a value in a context
+- **`Of`**: Wrap a value in a context
+- **`Fold`**: Extract a value from a context
 
 ## Comparison to Idiomatic Go
 
-In this section we discuss how the functional APIs differ from idiomatic go function signatures and how to convert back and forth.
+This section explains how functional APIs differ from idiomatic Go and how to convert between them.
 
-### Pure functions
+### Pure Functions
 
-Pure functions are functions that take input parameters and that compute an output without changing any global state and without mutating the input parameters. They will always return the same output for the same input.
+Pure functions take input parameters and compute output without changing global state or mutating inputs. They always return the same output for the same input.
 
 #### Without Errors
 
-If your pure function does not return an error, the idiomatic signature is just fine and no changes are required.
+If your pure function doesn't return an error, the idiomatic signature works as-is:
+
+```go
+func add(a, b int) int {
+    return a + b
+}
+```
 
 #### With Errors
 
-If your pure function can return an error, then it will have a `(T, error)` return value in idiomatic go. In functional style the return value is [Either[error, T]](https://pkg.go.dev/github.com/IBM/fp-go/either) because function composition is easier with such a return type. Use the `EitherizeXXX` methods in ["github.com/IBM/fp-go/either"](https://pkg.go.dev/github.com/IBM/fp-go/either) to convert from idiomatic to functional style and `UneitherizeXXX` to convert from functional to idiomatic style.
+**Idiomatic Go:**
+```go
+func divide(a, b int) (int, error) {
+    if b == 0 {
+        return 0, errors.New("division by zero")
+    }
+    return a / b, nil
+}
+```
 
-### Effectful functions
+**Functional Style:**
+```go
+func divide(a, b int) either.Either[error, int] {
+    if b == 0 {
+        return either.Left[int](errors.New("division by zero"))
+    }
+    return either.Right[error](a / b)
+}
+```
 
-An effectful function (or function with a side effect) is one that changes data outside the scope of the function or that does not always produce the same output for the same input (because it depends on some external, mutable state). There is no special way in idiomatic go to identify such a function other than documentation. In functional style we represent them as functions that do not take an input but that produce an output. The base type for these functions is [IO[T]](https://pkg.go.dev/github.com/IBM/fp-go/io) because in many cases such functions represent `I/O` operations.
+**Conversion:**
+- Use `either.EitherizeXXX` to convert from idiomatic to functional style
+- Use `either.UneitherizeXXX` to convert from functional to idiomatic style
+
+### Effectful Functions
+
+An effectful function changes data outside its scope or doesn't always produce the same output for the same input.
 
 #### Without Errors
 
-If your effectful function does not return an error, the functional signature is [IO[T]](https://pkg.go.dev/github.com/IBM/fp-go/io)
+**Functional signature:** `IO[T]`
+
+```go
+func getCurrentTime() io.IO[time.Time] {
+    return func() time.Time {
+        return time.Now()
+    }
+}
+```
 
 #### With Errors
 
-If your effectful function can return an error, the functional signature is [IOEither[error, T]](https://pkg.go.dev/github.com/IBM/fp-go/ioeither). Use `EitherizeXXX` from ["github.com/IBM/fp-go/ioeither"](https://pkg.go.dev/github.com/IBM/fp-go/ioeither) to convert an idiomatic go function to functional style.
+**Functional signature:** `IOEither[error, T]`
+
+```go
+func readFile(path string) ioeither.IOEither[error, []byte] {
+    return func() either.Either[error, []byte] {
+        data, err := os.ReadFile(path)
+        if err != nil {
+            return either.Left[[]byte](err)
+        }
+        return either.Right[error](data)
+    }
+}
+```
+
+**Conversion:**
+- Use `ioeither.EitherizeXXX` to convert idiomatic Go functions to functional style
 
 ### Go Context
 
-Functions that take a [context](https://pkg.go.dev/context) are per definition effectful because they depend on the context parameter that is designed to be mutable (it can e.g. be used to cancel a running operation). Furthermore in idiomatic go the parameter is typically passed as the first parameter to a function.
+Functions that take a `context.Context` are effectful because they depend on mutable context.
 
-In functional style we isolate the [context](https://pkg.go.dev/context) and represent the nature of the effectful function as an [IOEither[error, T]](https://pkg.go.dev/github.com/IBM/fp-go/ioeither). The resulting type is [ReaderIOEither[T]](https://pkg.go.dev/github.com/IBM/fp-go/context/readerioeither), a function taking a [context](https://pkg.go.dev/context) that returns a function without parameters returning an [Either[error, T]](https://pkg.go.dev/github.com/IBM/fp-go/either). Use the `EitherizeXXX` methods from ["github.com/IBM/fp-go/context/readerioeither"](https://pkg.go.dev/github.com/IBM/fp-go/context/readerioeither) to convert an idiomatic go function with a [context](https://pkg.go.dev/context) to functional style.
+**Idiomatic Go:**
+```go
+func fetchData(ctx context.Context, url string) ([]byte, error) {
+    // implementation
+}
+```
+
+**Functional Style:**
+```go
+func fetchData(url string) readerioeither.ReaderIOEither[context.Context, error, []byte] {
+    return func(ctx context.Context) ioeither.IOEither[error, []byte] {
+        return func() either.Either[error, []byte] {
+            // implementation
+        }
+    }
+}
+```
+
+**Conversion:**
+- Use `readerioeither.EitherizeXXX` to convert idiomatic Go functions with context to functional style
 
 ## Implementation Notes
 
 ### Generics
 
-All monadic operations are implemented via generics, i.e. they offer a type safe way to compose operations. This allows for convenient IDE support and also gives confidence about the correctness of the composition at compile time.
+All monadic operations use Go generics for type safety:
 
-Downside is that this will result in different versions of each operation per type, these versions are generated by the golang compiler at build time (unlike type erasure in languages such as Java of TypeScript). This might lead to large binaries for codebases with many different types. If this is a concern, you can always implement type erasure on top, i.e. use the monadic operations with the `any` type as if generics were not supported. You loose type safety, but this might result in smaller binaries.
+- ✅ **Pros**: Type-safe composition, IDE support, compile-time correctness
+- ⚠️ **Cons**: May result in larger binaries (different versions per type)
+- 💡 **Tip**: For binary size concerns, use type erasure with `any` type
 
 ### Ordering of Generic Type Parameters
 
-In go we need to specify all type parameters of a function on the global function definition, even if the function returns a higher order function and some of the type parameters are only applicable to the higher order function. So the following is not possible:
+Go requires all type parameters on the global function definition. Parameters that cannot be auto-detected come first:
 
 ```go
-func Map[A, B any](f func(A) B) [R, E any]func(fa ReaderIOEither[R, E, A]) ReaderIOEither[R, E, B]
+// Map: B cannot be auto-detected, so it comes first
+func Map[R, E, A, B any](f func(A) B) func(ReaderIOEither[R, E, A]) ReaderIOEither[R, E, B]
+
+// Ap: B cannot be auto-detected from the argument
+func Ap[B, R, E, A any](fa ReaderIOEither[R, E, A]) func(ReaderIOEither[R, E, func(A) B]) ReaderIOEither[R, E, B]
 ```
 
-Note that the parameters `R` and `E` are not needed by the first level of `Map` but only by the resulting higher order function. Instead we need to specify the following:
+This ordering maximizes type inference where possible.
 
-```go
-func Map[R, E, A, B any](f func(A) B) func(fa ReaderIOEither[R, E, A]) ReaderIOEither[R, E, B]
-```
+### Use of the ~ Operator
 
-which overspecifies `Map` on the global scope. As a result the go compiler will not be able to auto-detect these parameters, it can only auto detect `A` and `B` since they appear in the argument of `Map`. We need to explicitly pass values for these type parameters when `Map` is being used.
-
-Because of this limitation the order of parameters on a function matters. We want to make sure that we define those parameters that cannot be auto-detected, first, and the parameters that can be auto-detected, last. This can lead to inconsistencies in parameter ordering, but we believe that the gain in convenience is worth it. The parameter order of `Ap` is e.g. different from that of `Map`:
-
-```go
-func Ap[B, R, E, A any](fa ReaderIOEither[R, E, A]) func(fab ReaderIOEither[R, E, func(A) B]) ReaderIOEither[R, E, B]
-```
-
-because `R`, `E` and `A` can be determined from the argument to `Ap` but `B` cannot.
-
-### Use of the [~ Operator](https://go.googlesource.com/proposal/+/master/design/47781-parameterized-go-ast.md)
-
-The FP library attempts to be easy to consume and one aspect of this is the definition of higher level type definitions instead of having to use their low level equivalent. It is e.g. more convenient and readable to use
-
-```go
-ReaderIOEither[R, E, A]
-```
-
-than
-
-```go
-func(R) func() Either.Either[E, A]
-```
-
-although both are logically equivalent. At the time of this writing the go type system does not support generic type aliases, only generic type definition, i.e. it is not possible to write:
-
-```go
-type ReaderIOEither[R, E, A any] = RD.Reader[R, IOE.IOEither[E, A]]
-```
-
-only
+Go doesn't support generic type aliases (until Go 1.24), only type definitions. The `~` operator allows generic implementations to work with compatible types:
 
 ```go
 type ReaderIOEither[R, E, A any] RD.Reader[R, IOE.IOEither[E, A]]
 ```
 
-This makes a big difference, because in the second case the type `ReaderIOEither[R, E, A any]` is considered a completely new type, not compatible to its right hand side, so it's not just a shortcut but a fully new type.
+**Generic Subpackages:**
+- Each higher-level type has a `generic` subpackage with fully generic implementations
+- These are for library extensions, not end-users
+- Main packages specialize generic implementations for convenience
 
-From the implementation perspective however there is no reason to restrict the implementation to the new type, it can be generic for all compatible types. The way to express this in go is the [~](https://go.googlesource.com/proposal/+/master/design/47781-parameterized-go-ast.md) operator. This comes with some quite complicated type declarations in some cases, which undermines the goal of the library to be easy to use.
+### Higher Kinded Types (HKT)
 
-For that reason there exist sub-packages called `Generic` for all higher level types. These packages contain the fully generic implementation of the operations, preferring abstraction over usability. These packages are not meant to be used by end-users but are meant to be used by library extensions. The implementation for the convenient higher level types specializes the generic implementation for the particular higher level type, i.e. this layer does not contain any business logic but only *type magic*.
+Go doesn't support HKT natively. This library addresses this by:
 
-### Higher Kinded Types
+- Introducing HKTs as individual types (e.g., `HKTA` for `HKT[A]`)
+- Implementing generic algorithms in the `internal` package
+- Keeping complexity hidden from end-users
 
-Go does not support higher kinded types (HKT). Such types occur if a generic type itself is parametrized by another generic type. Example:
+## Common Operations
 
-The `Map` operation for `ReaderIOEither` is defined as:
+### Map/Chain/Ap/Flap
+
+| Operator | Parameter        | Monad           | Result   | Use Case |
+| -------- | ---------------- | --------------- | -------- | -------- |
+| Map      | `func(A) B`      | `HKT[A]`        | `HKT[B]` | Transform value in context |
+| Chain    | `func(A) HKT[B]` | `HKT[A]`        | `HKT[B]` | Transform and flatten |
+| Ap       | `HKT[A]`         | `HKT[func(A)B]` | `HKT[B]` | Apply function in context |
+| Flap     | `A`              | `HKT[func(A)B]` | `HKT[B]` | Apply value to function in context |
+
+### Example: Chaining Operations
 
 ```go
-func Map[R, E, A, B any](f func(A) B) func(fa ReaderIOEither[R, E, A]) ReaderIOEither[R, E, B]
+import (
+    "github.com/IBM/fp-go/either"
+    "github.com/IBM/fp-go/function"
+)
+
+result := function.Pipe3(
+    either.Right[error](10),
+    either.Map(func(x int) int { return x * 2 }),
+    either.Chain(func(x int) either.Either[error, int] {
+        if x > 15 {
+            return either.Right[error](x)
+        }
+        return either.Left[int](errors.New("too small"))
+    }),
+    either.GetOrElse(func() int { return 0 }),
+)
 ```
 
-and in fact the equivalent operations for all other monads follow the same pattern, we could try to introduce a new type for `ReaderIOEither` (without a parameter) as a HKT, e.g. like so (made-up syntax, does not work in go):
+## 📚 Resources
 
-```go
-func Map[HKT, R, E, A, B any](f func(A) B) func(HKT[R, E, A]) HKT[R, E, B]
-```
+- [API Documentation](https://pkg.go.dev/github.com/IBM/fp-go)
+- [Code Samples](./samples/)
+- [V2 Documentation](./v2/README.md) - New features in Go 1.24+
+- [fp-ts](https://github.com/gcanti/fp-ts) - Original TypeScript inspiration
 
-this would be the completely generic method signature for all possible monads. In particular in many cases it is possible to compose functions independent of the concrete knowledge of the actual `HKT`. From the perspective of a library this is the ideal situation because then a particular algorithm only has to be implemented and tested once.
+## 🤝 Contributing
 
-This FP library addresses this by introducing the HKTs as individual types, e.g. `HKT[A]` would be represented as a new generic type `HKTA`. This loses the correlation to the type `A` but allows to implement generic algorithms, at the price of readability.
+Contributions are welcome! Please feel free to submit issues or pull requests.
 
-For that reason these implementations are kept in the `internal` package. These are meant to be used by the library itself or by extensions, not by end users.
+## 📄 License
 
-## Map/Ap/Flap
-
-The following table lists the relationship between some selected operators
-
-| Operator | Parameter        | Monad           | Result   |
-| -------- | ---------------- | --------------- | -------- |
-| Map      | `func(A) B`      | `HKT[A]`        | `HKT[B]` |
-| Chain    | `func(A) HKT[B]` | `HKT[A]`        | `HKT[B]` |
-| Ap       | `HKT[A]`         | `HKT[func(A)B]` | `HKT[B]` |
-| Flap     | `A`              | `HKT[func(A)B]` | `HKT[B]` |
+This project is licensed under the Apache License 2.0 - see the LICENSE file for details.

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
@@ -31,7 +31,7 @@ type (
 
 // String prints some debug info for the object
 //
-// go:noinline
+//go:noinline
 func eitherString(s *either) string {
 	if s.isLeft {
 		return fmt.Sprintf("Left[%T](%v)", s.value, s.value)
@@ -41,7 +41,7 @@ func eitherString(s *either) string {
 
 // Format prints some debug info for the object
 //
-// go:noinline
+//go:noinline
 func eitherFormat(e *either, f fmt.State, c rune) {
 	switch c {
 	case 's':
@@ -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
 }

internal/array/array.go

@@ -17,6 +17,37 @@ package array
 
 func Slice[GA ~[]A, A any](low, high int) func(as GA) GA {
 	return func(as GA) GA {
+		length := len(as)
+
+		// Handle negative indices - count backward from the end
+		if low < 0 {
+			low = length + low
+			if low < 0 {
+				low = 0
+			}
+		}
+		if high < 0 {
+			high = length + high
+			if high < 0 {
+				high = 0
+			}
+		}
+
+		// Start index > array length: return empty array
+		if low > length {
+			return Empty[GA, A]()
+		}
+
+		// End index > array length: slice to the end
+		if high > length {
+			high = length
+		}
+
+		// Start >= end: return empty array
+		if low >= high {
+			return Empty[GA, A]()
+		}
+
 		return as[low:high]
 	}
 }

option/core.go

@@ -35,7 +35,7 @@ type Option[A any] struct {
 
 // optString prints some debug info for the object
 //
-// go:noinline
+//go:noinline
 func optString(isSome bool, value any) string {
 	if isSome {
 		return fmt.Sprintf("Some[%T](%v)", value, value)
@@ -45,7 +45,7 @@ func optString(isSome bool, value any) string {
 
 // optFormat prints some debug info for the object
 //
-// go:noinline
+//go:noinline
 func optFormat(isSome bool, value any, f fmt.State, c rune) {
 	switch c {
 	case 's':
@@ -78,7 +78,7 @@ func (s Option[A]) MarshalJSON() ([]byte, error) {
 
 // optUnmarshalJSON unmarshals the [Option] from a JSON string
 //
-// go:noinline
+//go:noinline
 func optUnmarshalJSON(isSome *bool, value any, data []byte) error {
 	// decode the value
 	if bytes.Equal(data, jsonNull) {

pair/pair.go

@@ -34,14 +34,14 @@ type (
 
 // String prints some debug info for the object
 //
-// go:noinline
+//go:noinline
 func pairString(s *pair) string {
 	return fmt.Sprintf("Pair[%T, %T](%v, %v)", s.h, s.t, s.h, s.t)
 }
 
 // Format prints some debug info for the object
 //
-// go:noinline
+//go:noinline
 func pairFormat(e *pair, f fmt.State, c rune) {
 	switch c {
 	case 's':

renovate.json

@@ -1,11 +1,20 @@
 {
     "$schema": "https://docs.renovatebot.com/renovate-schema.json",
     "extends": [
-        "config:base",
+        "config:recommended",
         ":dependencyDashboard"
     ],
     "rangeStrategy": "bump",
     "packageRules": [
+        {
+            "matchDatasources": [
+                "golang-version"
+            ],
+            "matchPackageNames": [
+                "go"
+            ],
+            "enabled": false
+        },
         {
             "matchManagers": [
                 "gomod"
@@ -25,15 +34,6 @@
             ],
             "automerge": true,
             "groupName": "go dependencies"
-        },
-        {
-            "matchPackageNames": [
-                "conventional-changelog-conventionalcommits"
-            ],
-            "matchUpdateTypes": [
-                "major"
-            ],
-            "enabled": false
         }
     ]
 }

v2/README.md

@@ -1,43 +1,497 @@
-# Functional programming library for golang V2
+# fp-go V2: Enhanced Functional Programming for Go 1.24+
 
-Go 1.24 introduces [generic type aliases](https://github.com/golang/go/issues/46477) which are leveraged by V2.
+[![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)
 
-## ⚠️ Breaking Changes
+**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.
 
-- use of [generic type aliases](https://github.com/golang/go/issues/46477) which requires [go1.24](https://tip.golang.org/doc/go1.24)
-- order of generic type arguments adjusted such that types that _cannot_ be inferred by the method argument come first, e.g. in the `Ap` methods
-- monadic operations for `Pair` operate on the second argument, to be compatible with the [Haskell](https://hackage.haskell.org/package/TypeCompose-0.9.14/docs/Data-Pair.html) definition
+## 📚 Table of Contents
 
-## Simplifications
+- [Overview](#-overview)
+- [Features](#-features)
+- [Requirements](#-requirements)
+- [Installation](#-installation)
+- [Quick Start](#-quick-start)
+- [Breaking Changes](#️-breaking-changes)
+- [Key Improvements](#-key-improvements)
+- [Migration Guide](#-migration-guide)
+- [What's New](#-whats-new)
+- [Documentation](#-documentation)
+- [Contributing](#-contributing)
+- [License](#-license)
 
-- use type aliases to get rid of namespace imports for type declarations, e.g. instead of
+## 🎯 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)
+
+## 📦 Installation
+
+```bash
+go get github.com/IBM/fp-go/v2
+```
+
+## 🚀 Quick Start
+
+### Working with Option
 
 ```go
+package main
+
 import (
-    ET "github.com/IBM/fp-go/v2/either"
+    "fmt"
+    "github.com/IBM/fp-go/v2/option"
 )
 
-func doSth() ET.Either[error, string] {
-    ...
+func main() {
+    // Create an Option
+    some := option.Some(42)
+    none := option.None[int]()
+    
+    // Map over values
+    doubled := option.Map(func(x int) int { return x * 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
 }
 ```
 
-you can declare your type once 
+### 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.
+
+**V1:**
+```go
+type ReaderIOEither[R, E, A any] RD.Reader[R, IOE.IOEither[E, A]]
+```
+
+**V2:**
+```go
+type ReaderIOEither[R, E, A any] = RD.Reader[R, IOE.IOEither[E, A]]
+```
+
+#### 2. Generic Type Parameter Ordering
+
+Type parameters that **cannot** be inferred from function arguments now come first, improving type inference.
+
+**V1:**
+```go
+// Ap in V1 - less intuitive ordering
+func Ap[R, E, A, B any](fa ReaderIOEither[R, E, A]) func(ReaderIOEither[R, E, func(A) B]) ReaderIOEither[R, E, B]
+```
+
+**V2:**
+```go
+// Ap in V2 - B comes first as it cannot be inferred
+func Ap[B, R, E, A any](fa ReaderIOEither[R, E, A]) func(ReaderIOEither[R, E, func(A) B]) ReaderIOEither[R, E, B]
+```
+
+This change allows the Go compiler to infer more types automatically, reducing the need for explicit type parameters.
+
+#### 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).
+
+**V1:**
+```go
+// Operations on first element
+pair := MakePair(1, "hello")
+result := Map(func(x int) int { return x * 2 })(pair) // Pair(2, "hello")
+```
+
+**V2:**
+```go
+// Operations on second element (Haskell-compatible)
+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 := func(x int) int { return x * 2 }
+increment := func(x int) int { return x + 1 }
+composed := Compose(double, increment)
+result := composed(5) // (5 * 2) + 1 = 11
+```
+
+**V2:**
+```go
+// Compose executes RIGHT-TO-LEFT (mathematical composition)
+double := func(x int) int { return x * 2 }
+increment := func(x int) int { return x + 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
+
+Generic type aliases eliminate the need for namespace imports in type declarations.
+
+**V1 Approach:**
+```go
+import (
+    ET "github.com/IBM/fp-go/either"
+    OPT "github.com/IBM/fp-go/option"
+)
+
+func processData(input string) ET.Either[error, OPT.Option[int]] {
+    // implementation
+}
+```
+
+**V2 Approach:**
+```go
+import (
+    "github.com/IBM/fp-go/v2/result"
+    "github.com/IBM/fp-go/v2/option"
+)
+
+// Define type aliases once
+type Result[A any] = result.Result[A]
+type Option[A any] = option.Option[A]
+
+// Use them throughout your codebase
+func processData(input string) Result[Option[int]] {
+    // implementation
+}
+```
+
+### 2. No More `generic` Subpackages
+
+The library implementation no longer requires separate `generic` subpackages, making the codebase simpler and easier to understand.
+
+**V1 Structure:**
+```
+either/
+  either.go
+  generic/
+    either.go  // Generic implementation
+```
+
+**V2 Structure:**
+```
+either/
+  either.go  // Single, clean implementation
+```
+
+### 3. Better Type Inference
+
+The reordered type parameters allow the Go compiler to infer more types automatically:
+
+**V1:**
+```go
+// Often need explicit type parameters
+result := Map[Context, error, int, string](transform)(value)
+```
+
+**V2:**
+```go
+// Compiler can infer more types
+result := Map(transform)(value)  // Cleaner!
+```
+
+## 🚀 Migration Guide
+
+### Step 1: Update Go Version
+
+Ensure you're using Go 1.24 or later:
+
+```bash
+go version  # Should show go1.24 or higher
+```
+
+### Step 2: Update Import Paths
+
+Change all import paths from `github.com/IBM/fp-go` to `github.com/IBM/fp-go/v2`:
+
+**Before:**
+```go
+import (
+    "github.com/IBM/fp-go/either"
+    "github.com/IBM/fp-go/option"
+)
+```
+
+**After:**
+```go
+import (
+    "github.com/IBM/fp-go/v2/either"
+    "github.com/IBM/fp-go/v2/option"
+)
+```
+
+### Step 3: Remove `generic` Subpackage Imports
+
+If you were using generic subpackages, remove them:
+
+**Before:**
+```go
+import (
+    E "github.com/IBM/fp-go/either/generic"
+)
+```
+
+**After:**
 ```go
 import (
     "github.com/IBM/fp-go/v2/either"
 )
-
-type Either[A any] = either.Either[error, A]
 ```
 
-and then use it across your codebase
+### Step 4: Update Type Parameter Order
+
+Review functions like `Ap` where type parameter order has changed. The compiler will help identify these:
+
+**Before:**
+```go
+result := Ap[Context, error, int, string](value)(funcInContext)
+```
+
+**After:**
+```go
+result := Ap[string, Context, error, int](value)(funcInContext)
+// Or better yet, let the compiler infer:
+result := Ap(value)(funcInContext)
+```
+
+### Step 5: Update Pair Operations
+
+If you're using `Pair`, update operations to work on the second element:
+
+**Before (V1):**
+```go
+pair := MakePair(42, "data")
+// Map operates on first element
+result := Map(func(x int) int { return x * 2 })(pair)
+```
+
+**After (V2):**
+```go
+pair := MakePair(42, "data")
+// Map operates on second element
+result := Map(func(s string) string { return s + "!" })(pair)
+```
+
+### Step 6: Simplify Type Aliases
+
+Create project-wide type aliases for common patterns:
 
 ```go
-func doSth() Either[string] {
-    ...
+// types.go - Define once, use everywhere
+package myapp
+
+import (
+    "github.com/IBM/fp-go/v2/result"
+    "github.com/IBM/fp-go/v2/option"
+    "github.com/IBM/fp-go/v2/ioresult"
+)
+
+type Result[A any] = result.Result[A]
+type Option[A any] = option.Option[A]
+type IOResult[A any] = ioresult.IOResult[A]
+```
+
+## 🆕 What's New
+
+### Cleaner API Surface
+
+The elimination of `generic` subpackages means:
+- Fewer imports to manage
+- Simpler package structure
+- Easier to navigate documentation
+- More intuitive API
+
+### Example: Before and After
+
+**V1 Complex Example:**
+```go
+import (
+    ET "github.com/IBM/fp-go/either"
+    EG "github.com/IBM/fp-go/either/generic"
+    IOET "github.com/IBM/fp-go/ioeither"
+    IOEG "github.com/IBM/fp-go/ioeither/generic"
+)
+
+func process() IOET.IOEither[error, string] {
+    return IOEG.Map[error, int, string](
+        strconv.Itoa,
+    )(fetchData())
 }
 ```
 
-- library implementation does no longer need to use the `generic` subpackage, this simplifies reading and understanding of the code
+**V2 Simplified Example:**
+```go
+import (
+    "strconv"
+    "github.com/IBM/fp-go/v2/ioresult"
+)
+
+type IOResult[A any] = ioresult.IOResult[A]
+
+func process() IOResult[string] {
+    return ioresult.Map(
+        strconv.Itoa,
+    )(fetchData())
+}
+```
+
+## 📚 Documentation
+
+- **[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?
+
+**Migrate to V2 if:**
+- ✅ You can use Go 1.24+
+- ✅ You want cleaner, more maintainable code
+- ✅ You want better type inference
+- ✅ You're starting a new project
+
+**Stay on V1 if:**
+- ⚠️ You're locked to Go < 1.24
+- ⚠️ 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](https://github.com/IBM/fp-go/blob/main/LICENSE) file for details.
+
+---
+
+**Made with ❤️ by IBM**

v2/array/any.go

@@ -29,6 +29,8 @@ import (
 //	    return i%2 == 0 && x%2 == 0
 //	})
 //	result := hasEvenAtEvenIndex([]int{1, 3, 4, 5}) // true (4 is at index 2)
+//
+//go:inline
 func AnyWithIndex[A any](pred func(int, A) bool) func([]A) bool {
 	return G.AnyWithIndex[[]A](pred)
 }
@@ -41,6 +43,8 @@ func AnyWithIndex[A any](pred func(int, A) bool) func([]A) bool {
 //
 //	hasEven := array.Any(func(x int) bool { return x%2 == 0 })
 //	result := hasEven([]int{1, 3, 4, 5}) // true
+//
+//go:inline
 func Any[A any](pred func(A) bool) func([]A) bool {
 	return G.Any[[]A](pred)
 }

v2/array/array.go

@@ -26,22 +26,30 @@ import (
 )
 
 // From constructs an array from a set of variadic arguments
+//
+//go:inline
 func From[A any](data ...A) []A {
 	return G.From[[]A](data...)
 }
 
 // MakeBy returns a `Array` of length `n` with element `i` initialized with `f(i)`.
+//
+//go:inline
 func MakeBy[F ~func(int) A, A any](n int, f F) []A {
 	return G.MakeBy[[]A](n, f)
 }
 
 // Replicate creates a `Array` containing a value repeated the specified number of times.
+//
+//go:inline
 func Replicate[A any](n int, a A) []A {
 	return G.Replicate[[]A](n, a)
 }
 
 // MonadMap applies a function to each element of an array, returning a new array with the results.
 // 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 {
 	return G.MonadMap[[]A, []B](as, f)
 }
@@ -58,6 +66,8 @@ 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 {
 	return G.MapWithIndex[[]A, []B](f)
 }
@@ -69,8 +79,10 @@ func MapWithIndex[A, B any](f func(int, A) B) func([]A) []B {
 //
 //	double := array.Map(func(x int) int { return x * 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)
+	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.
@@ -104,11 +116,15 @@ 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] {
 	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] {
 	return G.FilterWithIndex[[]A](pred)
 }
@@ -120,27 +136,37 @@ func FilterRef[A any](pred func(*A) bool) EM.Endomorphism[[]A] {
 
 // MonadFilterMap maps an array with a function that returns an Option and keeps only the Some values.
 // 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 {
 	return G.MonadFilterMap[[]A, []B](fa, f)
 }
 
 // MonadFilterMapWithIndex maps an array with a function that takes an index and returns an Option,
 // 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 {
 	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.
+//
+//go:inline
 func FilterMap[A, B any](f func(A) O.Option[B]) func([]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.
+//
+//go:inline
 func FilterMapWithIndex[A, B any](f func(int, A) O.Option[B]) func([]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.
+//
+//go:inline
 func FilterChain[A, B any](f func(A) O.Option[[]B]) func([]A) []B {
 	return G.FilterChain[[]A](f)
 }
@@ -161,6 +187,7 @@ func reduceRef[A, B any](fa []A, f func(B, *A) B, initial B) B {
 	return current
 }
 
+//go:inline
 func MonadReduce[A, B any](fa []A, f func(B, A) B, initial B) B {
 	return G.MonadReduce(fa, f, initial)
 }
@@ -171,23 +198,31 @@ func MonadReduce[A, B any](fa []A, f func(B, A) B, initial B) B {
 //
 //	sum := array.Reduce(func(acc, x int) int { return acc + x }, 0)
 //	result := sum([]int{1, 2, 3, 4, 5}) // 15
+//
+//go:inline
 func Reduce[A, B any](f func(B, A) B, initial B) func([]A) B {
 	return G.Reduce[[]A](f, initial)
 }
 
 // ReduceWithIndex folds an array from left to right with access to the index,
 // applying a function to accumulate a result.
+//
+//go:inline
 func ReduceWithIndex[A, B any](f func(int, B, A) B, initial B) func([]A) B {
 	return G.ReduceWithIndex[[]A](f, initial)
 }
 
 // ReduceRight folds an array from right to left, applying a function to accumulate a result.
+//
+//go:inline
 func ReduceRight[A, B any](f func(A, B) B, initial B) func([]A) B {
 	return G.ReduceRight[[]A](f, initial)
 }
 
 // ReduceRightWithIndex folds an array from right to left with access to the index,
 // applying a function to accumulate a result.
+//
+//go:inline
 func ReduceRightWithIndex[A, B any](f func(int, A, B) B, initial B) func([]A) B {
 	return G.ReduceRightWithIndex[[]A](f, initial)
 }
@@ -201,11 +236,15 @@ func ReduceRef[A, B any](f func(B, *A) B, initial B) func([]A) B {
 }
 
 // Append adds an element to the end of an array, returning a new array.
+//
+//go:inline
 func Append[A any](as []A, a A) []A {
 	return G.Append(as, a)
 }
 
 // IsEmpty checks if an array has no elements.
+//
+//go:inline
 func IsEmpty[A any](as []A) bool {
 	return G.IsEmpty(as)
 }
@@ -216,6 +255,8 @@ func IsNonEmpty[A any](as []A) bool {
 }
 
 // Empty returns an empty array of type A.
+//
+//go:inline
 func Empty[A any]() []A {
 	return G.Empty[[]A]()
 }
@@ -226,14 +267,18 @@ func Zero[A any]() []A {
 }
 
 // Of constructs a single element array
+//
+//go:inline
 func Of[A any](a A) []A {
 	return G.Of[[]A](a)
 }
 
 // MonadChain applies a function that returns an array to each element and flattens the results.
 // 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)
+	return G.MonadChain(fa, f)
 }
 
 // Chain applies a function that returns an array to each element and flattens the results.
@@ -243,52 +288,70 @@ func MonadChain[A, B any](fa []A, f func(a A) []B) []B {
 //
 //	duplicate := array.Chain(func(x int) []int { return []int{x, x} })
 //	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)
+	return G.Chain[[]A](f)
 }
 
 // MonadAp applies an array of functions to an array of values, producing all combinations.
 // This is the monadic version that takes both arrays as parameters.
+//
+//go:inline
 func MonadAp[B, A any](fab []func(A) B, fa []A) []B {
 	return G.MonadAp[[]B](fab, fa)
 }
 
 // Ap applies an array of functions to an array of values, producing all combinations.
 // This is the curried version.
+//
+//go:inline
 func Ap[B, A any](fa []A) func([]func(A) B) []B {
 	return G.Ap[[]B, []func(A) B](fa)
 }
 
 // Match performs pattern matching on an array, calling onEmpty if empty or onNonEmpty if not.
+//
+//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] {
 	return G.Tail(as)
 }
 
 // Head returns the first element of an array, wrapped in an Option.
 // Returns None if the array is empty.
+//
+//go:inline
 func Head[A any](as []A) O.Option[A] {
 	return G.Head(as)
 }
 
 // First returns the first element of an array, wrapped in an Option (alias for Head).
 // Returns None if the array is empty.
+//
+//go:inline
 func First[A any](as []A) O.Option[A] {
 	return G.First(as)
 }
 
 // Last returns the last element of an array, wrapped in an Option.
 // Returns None if the array is empty.
+//
+//go:inline
 func Last[A any](as []A) O.Option[A] {
 	return G.Last(as)
 }
@@ -327,7 +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)))
 	}
 }
 
@@ -336,6 +399,8 @@ func Intercalate[A any](m M.Monoid[A]) func(A) func([]A) A {
 // Example:
 //
 //	result := array.Flatten([][]int{{1, 2}, {3, 4}, {5}}) // [1, 2, 3, 4, 5]
+//
+//go:inline
 func Flatten[A any](mma [][]A) []A {
 	return G.Flatten(mma)
 }
@@ -347,17 +412,23 @@ func Slice[A any](low, high int) func(as []A) []A {
 
 // Lookup returns the element at the specified index, wrapped in an Option.
 // Returns None if the index is out of bounds.
+//
+//go:inline
 func Lookup[A any](idx int) func([]A) O.Option[A] {
 	return G.Lookup[[]A](idx)
 }
 
 // UpsertAt returns a function that inserts or updates an element at a specific index.
 // If the index is out of bounds, the element is appended.
+//
+//go:inline
 func UpsertAt[A any](a A) EM.Endomorphism[[]A] {
 	return G.UpsertAt[[]A](a)
 }
 
 // Size returns the number of elements in an array.
+//
+//go:inline
 func Size[A any](as []A) int {
 	return G.Size(as)
 }
@@ -365,12 +436,16 @@ func Size[A any](as []A) int {
 // MonadPartition splits an array into two arrays based on a predicate.
 // The first array contains elements for which the predicate returns false,
 // the second contains elements for which it returns true.
+//
+//go:inline
 func MonadPartition[A any](as []A, pred func(A) bool) tuple.Tuple2[[]A, []A] {
 	return G.MonadPartition(as, pred)
 }
 
 // Partition creates two new arrays out of one, the left result contains the elements
 // for which the predicate returns false, the right one those for which the predicate returns true
+//
+//go:inline
 func Partition[A any](pred func(A) bool) func([]A) tuple.Tuple2[[]A, []A] {
 	return G.Partition[[]A](pred)
 }
@@ -391,53 +466,73 @@ 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] {
 	return G.SliceRight[[]A](start)
 }
 
 // Copy creates a shallow copy of the array
+//
+//go:inline
 func Copy[A any](b []A) []A {
 	return G.Copy(b)
 }
 
 // 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 {
 	return G.Clone[[]A](f)
 }
 
 // FoldMap maps and folds an array. Map the Array passing each value to the iterating function. Then fold the results using the provided Monoid.
+//
+//go:inline
 func FoldMap[A, B any](m M.Monoid[B]) func(func(A) B) func([]A) B {
 	return G.FoldMap[[]A](m)
 }
 
 // FoldMapWithIndex maps and folds an array. Map the Array passing each value to the iterating function. Then fold the results using the provided Monoid.
+//
+//go:inline
 func FoldMapWithIndex[A, B any](m M.Monoid[B]) func(func(int, A) B) func([]A) B {
 	return G.FoldMapWithIndex[[]A](m)
 }
 
 // Fold folds the array using the provided Monoid.
+//
+//go:inline
 func Fold[A any](m M.Monoid[A]) func([]A) A {
 	return G.Fold[[]A](m)
 }
 
 // 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)
 }
 
 // MonadFlap applies a value to an array of functions, producing an array of results.
 // This is the monadic version that takes both parameters.
+//
+//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)
+	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)
 }

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

@@ -29,10 +29,12 @@ import (
 //	    Y int
 //	}
 //	result := array.Do(State{})
+//
+//go:inline
 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.
@@ -50,11 +52,13 @@ func Do[S any](
 //	        func(s struct{}) []int { return []int{1, 2} },
 //	    ),
 //	)
+//
+//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)
+	return G.Bind[[]S1, []S2](setter, f)
 }
 
 // Let attaches the result of a pure computation to a context S1 to produce a context S2.
@@ -70,11 +74,13 @@ func Bind[S1, S2, T any](
 //	    },
 //	    func(s struct{ X int }) int { return s.X * 2 },
 //	)
+//
+//go:inline
 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)
+	return G.Let[[]S1, []S2](setter, f)
 }
 
 // LetTo attaches a constant value to a context S1 to produce a context S2.
@@ -90,11 +96,13 @@ func Let[S1, S2, T any](
 //	    },
 //	    "constant",
 //	)
+//
+//go:inline
 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)
+	return G.LetTo[[]S1, []S2](setter, b)
 }
 
 // BindTo initializes a new state S1 from a value T.
@@ -108,10 +116,12 @@ func LetTo[S1, S2, T any](
 //	        return struct{ X int }{x}
 //	    }),
 //	)
+//
+//go:inline
 func BindTo[S1, T any](
 	setter func(T) S1,
 ) func([]T) []S1 {
-	return G.BindTo[[]S1, []T, S1, T](setter)
+	return G.BindTo[[]S1, []T](setter)
 }
 
 // ApS attaches a value to a context S1 to produce a context S2 by considering
@@ -128,9 +138,11 @@ func BindTo[S1, T any](
 //	    },
 //	    []int{10, 20},
 //	)
+//
+//go:inline
 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)
+	return G.ApS[[]S1, []S2](setter, fa)
 }

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

@@ -28,6 +28,8 @@ import (
 //	findGreaterThan3 := array.FindFirst(func(x int) bool { return x > 3 })
 //	result := findGreaterThan3([]int{1, 2, 4, 5}) // Some(4)
 //	result2 := findGreaterThan3([]int{1, 2, 3}) // None
+//
+//go:inline
 func FindFirst[A any](pred func(A) bool) func([]A) O.Option[A] {
 	return G.FindFirst[[]A](pred)
 }
@@ -41,6 +43,8 @@ func FindFirst[A any](pred func(A) bool) func([]A) O.Option[A] {
 //	    return i%2 == 0 && x%2 == 0
 //	})
 //	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] {
 	return G.FindFirstWithIndex[[]A](pred)
 }
@@ -59,12 +63,16 @@ func FindFirstWithIndex[A any](pred func(int, A) bool) func([]A) O.Option[A] {
 //	    return option.None[int]()
 //	})
 //	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] {
 	return G.FindFirstMap[[]A](sel)
 }
 
 // FindFirstMapWithIndex finds the first element for which the selector function returns Some.
 // 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] {
 	return G.FindFirstMapWithIndex[[]A](sel)
 }
@@ -76,24 +84,32 @@ func FindFirstMapWithIndex[A, B any](sel func(int, A) O.Option[B]) func([]A) O.O
 //
 //	findGreaterThan3 := array.FindLast(func(x int) bool { return x > 3 })
 //	result := findGreaterThan3([]int{1, 4, 2, 5}) // Some(5)
+//
+//go:inline
 func FindLast[A any](pred func(A) bool) func([]A) O.Option[A] {
 	return G.FindLast[[]A](pred)
 }
 
 // FindLastWithIndex finds the last element which satisfies a predicate function that also receives the index.
 // 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] {
 	return G.FindLastWithIndex[[]A](pred)
 }
 
 // FindLastMap finds the last element for which the selector function returns Some.
 // 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] {
 	return G.FindLastMap[[]A](sel)
 }
 
 // FindLastMapWithIndex finds the last element for which the selector function returns Some.
 // 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] {
 	return G.FindLastMapWithIndex[[]A](sel)
 }

v2/array/generic/array.go

@@ -31,25 +31,25 @@ func Of[GA ~[]A, A any](value A) GA {
 
 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)
 	}
 }
 
@@ -296,16 +296,14 @@ func MatchLeft[AS ~[]A, A, B any](onEmpty func() B, onNonEmpty func(A, AS) B) fu
 	}
 }
 
+//go:inline
 func Slice[AS ~[]A, A any](start int, end int) func(AS) AS {
-	return func(a AS) AS {
-		return a[start:end]
-	}
+	return array.Slice[AS](start, end)
 }
 
+//go:inline
 func SliceRight[AS ~[]A, A any](start int) func(AS) AS {
-	return func(a AS) AS {
-		return a[start:]
-	}
+	return array.SliceRight[AS](start)
 }
 
 func Copy[AS ~[]A, A any](b AS) AS {

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/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/magma.go

@@ -33,6 +33,8 @@ import (
 //	// Concatenate all strings
 //	concatStrings := array.ConcatAll(monoid.MonoidString())
 //	result2 := concatStrings([]string{"Hello", " ", "World"}) // "Hello World"
+//
+//go:inline
 func ConcatAll[A any](m M.Monoid[A]) func([]A) A {
 	return Reduce(m.Concat, m.Empty())
 }

v2/array/monad.go

@@ -34,6 +34,8 @@ import (
 //	    return []string{fmt.Sprintf("%d", x), fmt.Sprintf("%d!", x)}
 //	})
 //	// Result: ["1", "1!", "2", "2!", "3", "3!"]
+//
+//go:inline
 func Monad[A, B any]() monad.Monad[A, B, []A, []B, []func(A) B] {
 	return G.Monad[A, B, []A, []B, []func(A) B]()
 }

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/slice_test.go

@@ -0,0 +1,405 @@
+// 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 array
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// TestSliceBasicCases tests normal slicing operations
+func TestSliceBasicCases(t *testing.T) {
+	data := []int{0, 1, 2, 3, 4, 5}
+
+	t.Run("normal slice from middle", func(t *testing.T) {
+		assert.Equal(t, []int{1, 2, 3}, Slice[int](1, 4)(data))
+	})
+
+	t.Run("slice from start", func(t *testing.T) {
+		assert.Equal(t, []int{0, 1, 2}, Slice[int](0, 3)(data))
+	})
+
+	t.Run("slice to end", func(t *testing.T) {
+		assert.Equal(t, []int{3, 4, 5}, Slice[int](3, 6)(data))
+	})
+
+	t.Run("slice single element", func(t *testing.T) {
+		assert.Equal(t, []int{2}, Slice[int](2, 3)(data))
+	})
+
+	t.Run("slice entire array", func(t *testing.T) {
+		assert.Equal(t, []int{0, 1, 2, 3, 4, 5}, Slice[int](0, 6)(data))
+	})
+}
+
+// TestSliceNegativeIndices tests negative index handling (counting from end)
+func TestSliceNegativeIndices(t *testing.T) {
+	data := []int{0, 1, 2, 3, 4, 5}
+
+	t.Run("negative start index", func(t *testing.T) {
+		// -2 means length + (-2) = 6 - 2 = 4
+		assert.Equal(t, []int{4, 5}, Slice[int](-2, 6)(data))
+	})
+
+	t.Run("negative end index", func(t *testing.T) {
+		// -2 means length + (-2) = 6 - 2 = 4
+		assert.Equal(t, []int{0, 1, 2, 3}, Slice[int](0, -2)(data))
+	})
+
+	t.Run("both negative indices", func(t *testing.T) {
+		// -4 = 2, -2 = 4
+		assert.Equal(t, []int{2, 3}, Slice[int](-4, -2)(data))
+	})
+
+	t.Run("negative index beyond array start", func(t *testing.T) {
+		// -10 would be -4, clamped to 0
+		assert.Equal(t, []int{0, 1, 2}, Slice[int](-10, 3)(data))
+	})
+
+	t.Run("negative end index beyond array start", func(t *testing.T) {
+		// -10 would be -4, clamped to 0
+		assert.Equal(t, []int{}, Slice[int](0, -10)(data))
+	})
+}
+
+// TestSliceEmptyArray tests slicing on empty arrays (totality proof)
+func TestSliceEmptyArray(t *testing.T) {
+	empty := []int{}
+
+	t.Run("slice empty array with zero indices", func(t *testing.T) {
+		assert.Equal(t, []int{}, Slice[int](0, 0)(empty))
+	})
+
+	t.Run("slice empty array with positive indices", func(t *testing.T) {
+		assert.Equal(t, []int{}, Slice[int](0, 5)(empty))
+	})
+
+	t.Run("slice empty array with negative indices", func(t *testing.T) {
+		assert.Equal(t, []int{}, Slice[int](-1, -1)(empty))
+	})
+
+	t.Run("slice empty array with mixed indices", func(t *testing.T) {
+		assert.Equal(t, []int{}, Slice[int](-5, 5)(empty))
+	})
+}
+
+// TestSliceOutOfBounds tests out-of-bounds scenarios (totality proof)
+func TestSliceOutOfBounds(t *testing.T) {
+	data := []int{0, 1, 2, 3, 4}
+
+	t.Run("start index beyond array length", func(t *testing.T) {
+		assert.Equal(t, []int{}, Slice[int](10, 15)(data))
+	})
+
+	t.Run("end index beyond array length", func(t *testing.T) {
+		assert.Equal(t, []int{2, 3, 4}, Slice[int](2, 100)(data))
+	})
+
+	t.Run("both indices beyond array length", func(t *testing.T) {
+		assert.Equal(t, []int{}, Slice[int](10, 20)(data))
+	})
+
+	t.Run("start equals array length", func(t *testing.T) {
+		assert.Equal(t, []int{}, Slice[int](5, 10)(data))
+	})
+
+	t.Run("end equals array length", func(t *testing.T) {
+		assert.Equal(t, []int{3, 4}, Slice[int](3, 5)(data))
+	})
+}
+
+// TestSliceInvalidRanges tests invalid range scenarios (totality proof)
+func TestSliceInvalidRanges(t *testing.T) {
+	data := []int{0, 1, 2, 3, 4}
+
+	t.Run("start equals end", func(t *testing.T) {
+		assert.Equal(t, []int{}, Slice[int](2, 2)(data))
+	})
+
+	t.Run("start greater than end", func(t *testing.T) {
+		assert.Equal(t, []int{}, Slice[int](4, 2)(data))
+	})
+
+	t.Run("start greater than end with negative indices", func(t *testing.T) {
+		// -1 = 4, -3 = 2
+		assert.Equal(t, []int{}, Slice[int](-1, -3)(data))
+	})
+
+	t.Run("zero range at start", func(t *testing.T) {
+		assert.Equal(t, []int{}, Slice[int](0, 0)(data))
+	})
+
+	t.Run("zero range at end", func(t *testing.T) {
+		assert.Equal(t, []int{}, Slice[int](5, 5)(data))
+	})
+}
+
+// TestSliceEdgeCases tests additional edge cases (totality proof)
+func TestSliceEdgeCases(t *testing.T) {
+	t.Run("single element array - slice all", func(t *testing.T) {
+		data := []int{42}
+		assert.Equal(t, []int{42}, Slice[int](0, 1)(data))
+	})
+
+	t.Run("single element array - slice none", func(t *testing.T) {
+		data := []int{42}
+		assert.Equal(t, []int{}, Slice[int](1, 1)(data))
+	})
+
+	t.Run("single element array - negative indices", func(t *testing.T) {
+		data := []int{42}
+		assert.Equal(t, []int{42}, Slice[int](-1, 1)(data))
+	})
+
+	t.Run("large array slice", func(t *testing.T) {
+		data := MakeBy(1000, func(i int) int { return i })
+		result := Slice[int](100, 200)(data)
+		assert.Equal(t, 100, len(result))
+		assert.Equal(t, 100, result[0])
+		assert.Equal(t, 199, result[99])
+	})
+}
+
+// TestSliceWithDifferentTypes tests that Slice works with different types (totality proof)
+func TestSliceWithDifferentTypes(t *testing.T) {
+	t.Run("string slice", func(t *testing.T) {
+		data := []string{"a", "b", "c", "d", "e"}
+		assert.Equal(t, []string{"b", "c", "d"}, Slice[string](1, 4)(data))
+	})
+
+	t.Run("float slice", func(t *testing.T) {
+		data := []float64{1.1, 2.2, 3.3, 4.4, 5.5}
+		assert.Equal(t, []float64{2.2, 3.3}, Slice[float64](1, 3)(data))
+	})
+
+	t.Run("bool slice", func(t *testing.T) {
+		data := []bool{true, false, true, false}
+		assert.Equal(t, []bool{false, true}, Slice[bool](1, 3)(data))
+	})
+
+	t.Run("struct slice", func(t *testing.T) {
+		type Point struct{ X, Y int }
+		data := []Point{{1, 2}, {3, 4}, {5, 6}}
+		assert.Equal(t, []Point{{3, 4}}, Slice[Point](1, 2)(data))
+	})
+
+	t.Run("pointer slice", func(t *testing.T) {
+		a, b, c := 1, 2, 3
+		data := []*int{&a, &b, &c}
+		result := Slice[*int](1, 3)(data)
+		assert.Equal(t, 2, len(result))
+		assert.Equal(t, 2, *result[0])
+		assert.Equal(t, 3, *result[1])
+	})
+}
+
+// TestSliceNilArray tests behavior with nil arrays (totality proof)
+func TestSliceNilArray(t *testing.T) {
+	var nilArray []int
+
+	t.Run("slice nil array with zero indices", func(t *testing.T) {
+		assert.Equal(t, []int{}, Slice[int](0, 0)(nilArray))
+	})
+
+	t.Run("slice nil array with positive indices", func(t *testing.T) {
+		assert.Equal(t, []int{}, Slice[int](0, 5)(nilArray))
+	})
+
+	t.Run("slice nil array with negative indices", func(t *testing.T) {
+		assert.Equal(t, []int{}, Slice[int](-1, 1)(nilArray))
+	})
+
+	t.Run("slice nil array with out of bounds indices", func(t *testing.T) {
+		assert.Equal(t, []int{}, Slice[int](10, 20)(nilArray))
+	})
+}
+
+// TestSliceComposition tests that Slice can be composed with other functions
+func TestSliceComposition(t *testing.T) {
+	data := []int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
+
+	t.Run("compose multiple slices", func(t *testing.T) {
+		// First slice [2:8], then slice [1:4] of result
+		slice1 := Slice[int](2, 8)
+		slice2 := Slice[int](1, 4)
+		result := slice2(slice1(data))
+		// [2,3,4,5,6,7] -> [3,4,5]
+		assert.Equal(t, []int{3, 4, 5}, result)
+	})
+
+	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)
+		assert.Equal(t, []int{4, 6, 8}, mapped)
+	})
+
+	t.Run("slice then filter", func(t *testing.T) {
+		sliced := Slice[int](0, 6)(data)
+		filtered := Filter(func(x int) bool { return x%2 == 0 })(sliced)
+		assert.Equal(t, []int{0, 2, 4}, filtered)
+	})
+}
+
+// TestSliceImmutability tests that Slice doesn't modify the original array
+func TestSliceImmutability(t *testing.T) {
+	original := []int{0, 1, 2, 3, 4}
+	originalCopy := []int{0, 1, 2, 3, 4}
+
+	t.Run("slicing doesn't modify original", func(t *testing.T) {
+		result := Slice[int](1, 4)(original)
+		assert.Equal(t, []int{1, 2, 3}, result)
+		assert.Equal(t, originalCopy, original)
+	})
+
+	t.Run("slice shares underlying array with original", func(t *testing.T) {
+		// Note: Go's slice operation creates a view of the underlying array,
+		// not a deep copy. This is expected behavior and matches Go's built-in slice semantics.
+		result := Slice[int](1, 4)(original)
+		result[0] = 999
+		// The original array is affected because slices share the underlying array
+		assert.Equal(t, 999, original[1], "Slices share underlying array (expected Go behavior)")
+	})
+}
+
+// TestSliceTotality is a comprehensive test proving Slice is a total function
+// A total function is defined for all possible inputs and never panics
+func TestSliceTotality(t *testing.T) {
+	testCases := []struct {
+		name  string
+		data  []int
+		low   int
+		high  int
+		panic bool // Should always be false for a total function
+	}{
+		// Normal cases
+		{"normal range", []int{1, 2, 3, 4, 5}, 1, 3, false},
+		{"full range", []int{1, 2, 3}, 0, 3, false},
+		{"empty result", []int{1, 2, 3}, 1, 1, false},
+
+		// Edge cases with empty/nil arrays
+		{"empty array", []int{}, 0, 0, false},
+		{"empty array with indices", []int{}, 1, 5, false},
+		{"nil array", nil, 0, 5, false},
+
+		// Negative indices
+		{"negative low", []int{1, 2, 3, 4, 5}, -2, 5, false},
+		{"negative high", []int{1, 2, 3, 4, 5}, 0, -1, false},
+		{"both negative", []int{1, 2, 3, 4, 5}, -3, -1, false},
+		{"negative beyond bounds", []int{1, 2, 3}, -100, -50, false},
+
+		// Out of bounds
+		{"low beyond length", []int{1, 2, 3}, 10, 20, false},
+		{"high beyond length", []int{1, 2, 3}, 1, 100, false},
+		{"both beyond length", []int{1, 2, 3}, 10, 20, false},
+
+		// Invalid ranges
+		{"low equals high", []int{1, 2, 3}, 2, 2, false},
+		{"low greater than high", []int{1, 2, 3}, 3, 1, false},
+		{"negative invalid range", []int{1, 2, 3, 4, 5}, -1, -3, false},
+
+		// Extreme values
+		{"very large indices", []int{1, 2, 3}, 1000000, 2000000, false},
+		{"very negative indices", []int{1, 2, 3}, -1000000, -500000, false},
+		{"mixed extreme", []int{1, 2, 3}, -1000000, 1000000, false},
+
+		// Zero values
+		{"zero indices", []int{1, 2, 3}, 0, 0, false},
+		{"zero low", []int{1, 2, 3}, 0, 3, false},
+		{"zero high", []int{1, 2, 3}, 0, 0, false},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			// This test proves totality by ensuring no panic occurs
+			defer func() {
+				if r := recover(); r != nil {
+					if !tc.panic {
+						t.Errorf("Slice panicked unexpectedly: %v", r)
+					}
+				} else {
+					if tc.panic {
+						t.Errorf("Slice should have panicked but didn't")
+					}
+				}
+			}()
+
+			// Execute the function - if it's total, it will never panic
+			result := Slice[int](tc.low, tc.high)(tc.data)
+
+			// Additional verification: result should always be a valid slice
+			assert.NotNil(t, result, "Result should never be nil")
+			assert.True(t, len(result) >= 0, "Result length should be non-negative")
+		})
+	}
+}
+
+// TestSlicePropertyBased tests mathematical properties of Slice
+func TestSlicePropertyBased(t *testing.T) {
+	data := []int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
+
+	t.Run("identity: Slice(0, len) returns copy of array", func(t *testing.T) {
+		result := Slice[int](0, len(data))(data)
+		assert.Equal(t, data, result)
+	})
+
+	t.Run("empty: Slice(i, i) always returns empty", func(t *testing.T) {
+		for i := 0; i <= len(data); i++ {
+			result := Slice[int](i, i)(data)
+			assert.Equal(t, []int{}, result)
+		}
+	})
+
+	t.Run("length property: len(Slice(i, j)) = max(0, min(j, len) - max(i, 0))", func(t *testing.T) {
+		testCases := []struct{ low, high, expected int }{
+			{0, 5, 5},
+			{2, 7, 5},
+			{5, 5, 0},
+			{3, 2, 0},   // invalid range
+			{-2, 10, 2}, // -2 becomes 8, so slice [8:10] has length 2
+			{0, 100, 10},
+		}
+
+		for _, tc := range testCases {
+			result := Slice[int](tc.low, tc.high)(data)
+			assert.Equal(t, tc.expected, len(result),
+				"Slice(%d, %d) should have length %d", tc.low, tc.high, tc.expected)
+		}
+	})
+
+	t.Run("concatenation: Slice(0,i) + Slice(i,len) = original", func(t *testing.T) {
+		for i := 0; i <= len(data); i++ {
+			left := Slice[int](0, i)(data)
+			right := Slice[int](i, len(data))(data)
+			concatenated := append(left, right...)
+			assert.Equal(t, data, concatenated)
+		}
+	})
+
+	t.Run("subset property: all elements in slice are in original", func(t *testing.T) {
+		result := Slice[int](2, 7)(data)
+		for _, elem := range result {
+			found := false
+			for _, orig := range data {
+				if elem == orig {
+					found = true
+					break
+				}
+			}
+			assert.True(t, found, "Element %d should be in original array", elem)
+		}
+	})
+}

v2/array/sort.go

@@ -30,6 +30,8 @@ import (
 //	numbers := []int{3, 1, 4, 1, 5, 9, 2, 6}
 //	sorted := array.Sort(ord.FromStrictCompare[int]())(numbers)
 //	// Result: [1, 1, 2, 3, 4, 5, 6, 9]
+//
+//go:inline
 func Sort[T any](ord O.Ord[T]) func(ma []T) []T {
 	return G.Sort[[]T](ord)
 }
@@ -58,6 +60,8 @@ func Sort[T any](ord O.Ord[T]) func(ma []T) []T {
 //	)
 //	sorted := sortByAge(people)
 //	// 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 {
 	return G.SortByKey[[]T](ord, f)
 }
@@ -87,6 +91,8 @@ func SortByKey[K, T any](ord O.Ord[K], f func(T) K) func(ma []T) []T {
 //	})
 //	sorted := sortByName(people)
 //	// 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)
+	return G.SortBy[[]T](ord)
 }

v2/array/traverse.go

@@ -52,6 +52,8 @@ import (
 //
 //	result := parseAll([]string{"1", "2", "3"}) // Some([1, 2, 3])
 //	result2 := parseAll([]string{"1", "x", "3"}) // None
+//
+//go:inline
 func Traverse[A, B, HKTB, HKTAB, HKTRB any](
 	fof func([]B) HKTRB,
 	fmap func(func([]B) func(B) []B) func(HKTRB) HKTAB,
@@ -66,6 +68,8 @@ func Traverse[A, B, HKTB, HKTAB, HKTRB any](
 // into an effect of an array.
 //
 // This is useful when you want to apply the traverse operation directly without currying.
+//
+//go:inline
 func MonadTraverse[A, B, HKTB, HKTAB, HKTRB any](
 	fof func([]B) HKTRB,
 	fmap func(func([]B) func(B) []B) func(HKTRB) HKTAB,

v2/array/uniq.go

@@ -15,8 +15,10 @@ import (
 //
 //	strings := []string{"a", "b", "a", "c", "b"}
 //	unique2 := array.StrictUniq(strings) // ["a", "b", "c"]
+//
+//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
@@ -42,6 +44,8 @@ func StrictUniq[A comparable](as []A) []A {
 //	uniqueByName := array.Uniq(func(p Person) string { return p.Name })
 //	result := uniqueByName(people)
 //	// Result: [{"Alice", 30}, {"Bob", 25}, {"Charlie", 30}]
+//
+//go:inline
 func Uniq[A any, K comparable](f func(A) K) func(as []A) []A {
 	return G.Uniq[[]A](f)
 }

v2/array/zip.go

@@ -33,8 +33,10 @@ import (
 //	    return fmt.Sprintf("%s is %d years old", name, age)
 //	})
 //	// Result: ["Alice is 30 years old", "Bob is 25 years old", "Charlie is 35 years old"]
+//
+//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).
@@ -51,6 +53,8 @@ func ZipWith[FCT ~func(A, B) C, A, B, C any](fa []A, fb []B, f FCT) []C {
 //	// With different lengths
 //	pairs2 := array.Zip([]int{1, 2})([]string{"a", "b", "c"})
 //	// Result: [(a, 1), (b, 2)]
+//
+//go:inline
 func Zip[A, B any](fb []B) func([]A) []T.Tuple2[A, B] {
 	return G.Zip[[]A, []B, []T.Tuple2[A, B]](fb)
 }
@@ -72,6 +76,8 @@ func Zip[A, B any](fb []B) func([]A) []T.Tuple2[A, B] {
 //	// Result: (["Alice", "Bob", "Charlie"], [30, 25, 35])
 //	names := result.Head  // ["Alice", "Bob", "Charlie"]
 //	ages := result.Tail   // [30, 25, 35]
+//
+//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_test.go

@@ -19,8 +19,8 @@ import (
 	"fmt"
 	"testing"
 
-	E "github.com/IBM/fp-go/v2/either"
-	EQ "github.com/IBM/fp-go/v2/eq"
+	"github.com/IBM/fp-go/v2/eq"
+	"github.com/IBM/fp-go/v2/result"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -28,82 +28,82 @@ var (
 	errTest = fmt.Errorf("test failure")
 
 	// Eq is the equal predicate checking if objects are equal
-	Eq = EQ.FromEquals(assert.ObjectsAreEqual)
+	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] {
+func wrap1[T any](wrapped func(t assert.TestingT, expected, actual any, msgAndArgs ...any) bool, t *testing.T, expected T) result.Kleisli[T, T] {
+	return func(actual T) Result[T] {
 		ok := wrapped(t, expected, actual)
 		if ok {
-			return E.Of[error](actual)
+			return result.Of(actual)
 		}
-		return E.Left[T](errTest)
+		return result.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] {
+func NotEqual[T any](t *testing.T, expected T) result.Kleisli[T, 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] {
+func Equal[T any](t *testing.T, expected T) result.Kleisli[T, 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] {
+func Length[T any](t *testing.T, expected int) result.Kleisli[[]T, []T] {
+	return func(actual []T) Result[[]T] {
 		ok := assert.Len(t, actual, expected)
 		if ok {
-			return E.Of[error](actual)
+			return result.Of(actual)
 		}
-		return E.Left[[]T](errTest)
+		return result.Left[[]T](errTest)
 	}
 }
 
 // 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] {
+func NoError[T any](t *testing.T) result.Operator[T, T] {
+	return func(actual Result[T]) Result[T] {
+		return result.MonadFold(actual, func(e error) Result[T] {
 			assert.NoError(t, e)
-			return E.Left[T](e)
-		}, func(value T) E.Either[error, T] {
+			return result.Left[T](e)
+		}, func(value T) Result[T] {
 			assert.NoError(t, nil)
-			return E.Right[error](value)
+			return result.Of(value)
 		})
 	}
 }
 
 // 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] {
+func ArrayContains[T any](t *testing.T, expected T) result.Kleisli[[]T, []T] {
+	return func(actual []T) Result[[]T] {
 		ok := assert.Contains(t, actual, expected)
 		if ok {
-			return E.Of[error](actual)
+			return result.Of(actual)
 		}
-		return E.Left[[]T](errTest)
+		return result.Left[[]T](errTest)
 	}
 }
 
 // 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] {
+func ContainsKey[T any, K comparable](t *testing.T, expected K) result.Kleisli[map[K]T, map[K]T] {
+	return func(actual map[K]T) Result[map[K]T] {
 		ok := assert.Contains(t, actual, expected)
 		if ok {
-			return E.Of[error](actual)
+			return result.Of(actual)
 		}
-		return E.Left[map[K]T](errTest)
+		return result.Left[map[K]T](errTest)
 	}
 }
 
 // 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] {
+func NotContainsKey[T any, K comparable](t *testing.T, expected K) result.Kleisli[map[K]T, map[K]T] {
+	return func(actual map[K]T) Result[map[K]T] {
 		ok := assert.NotContains(t, actual, expected)
 		if ok {
-			return E.Of[error](actual)
+			return result.Of(actual)
 		}
-		return E.Left[map[K]T](errTest)
+		return result.Left[map[K]T](errTest)
 	}
 }

v2/assert/types.go

@@ -0,0 +1,7 @@
+package assert
+
+import "github.com/IBM/fp-go/v2/result"
+
+type (
+	Result[T any] = result.Result[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 i := 0; i < b.N; i++ {
+			_ = 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 i := 0; i < b.N; i++ {
+			_ = ToString(large)
+		}
+	})
+}
+
+func BenchmarkSize(b *testing.B) {
+	data := []byte("Hello, World!")
+
+	for i := 0; i < b.N; i++ {
+		_ = Size(data)
+	}
+}
+
+func BenchmarkMonoidConcat(b *testing.B) {
+	a := []byte("Hello")
+	c := []byte(" World")
+
+	b.Run("small slices", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			_ = Monoid.Concat(a, c)
+		}
+	})
+
+	b.Run("large slices", func(b *testing.B) {
+		large1 := make([]byte, 10000)
+		large2 := make([]byte, 10000)
+		b.ResetTimer()
+		for i := 0; i < b.N; i++ {
+			_ = 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 i := 0; i < b.N; i++ {
+			_ = 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 i := 0; i < b.N; i++ {
+			_ = ConcatAll(many...)
+		}
+	})
+}
+
+func BenchmarkOrdCompare(b *testing.B) {
+	a := []byte("abc")
+	c := []byte("abd")
+
+	b.Run("equal", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			_ = Ord.Compare(a, a)
+		}
+	})
+
+	b.Run("different", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			_ = 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 i := 0; i < b.N; i++ {
+			_ = 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 +1,657 @@
+// 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
+	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 struct {
+	// mandatory fields
+{{- range .Fields}}
+	{{.Name}} L.Lens[{{$.Name}}, {{.TypeName}}]
+{{- end}}
+	// optional fields
+{{- range .Fields}}
+	{{.Name}}O LO.LensO[{{$.Name}}, {{.TypeName}}]
+{{- end}}
+}
+
+// {{.Name}}RefLenses provides lenses for accessing fields of {{.Name}} via a reference to {{.Name}}
+type {{.Name}}RefLenses struct {
+	// mandatory fields
+{{- range .Fields}}
+	{{.Name}} L.Lens[*{{$.Name}}, {{.TypeName}}]
+{{- end}}
+	// optional fields
+{{- range .Fields}}
+	{{.Name}}O LO.LensO[*{{$.Name}}, {{.TypeName}}]
+{{- end}}
+}
+`
+
+const lensConstructorTemplate = `
+// Make{{.Name}}Lenses creates a new {{.Name}}Lenses with lenses for all fields
+func Make{{.Name}}Lenses() {{.Name}}Lenses {
+	// mandatory lenses
+{{- range .Fields}}
+	lens{{.Name}} := L.MakeLens(
+		func(s {{$.Name}}) {{.TypeName}} { return s.{{.Name}} },
+		func(s {{$.Name}}, v {{.TypeName}}) {{$.Name}} { s.{{.Name}} = v; return s },
+	)
+{{- end}}
+	// optional lenses
+{{- range .Fields}}
+	lens{{.Name}}O := LO.FromIso[{{$.Name}}](IO.FromZero[{{.TypeName}}]())(lens{{.Name}})
+{{- end}}
+	return {{.Name}}Lenses{
+		// mandatory lenses
+{{- range .Fields}}
+		{{.Name}}: lens{{.Name}},
+{{- end}}
+		// optional lenses
+{{- range .Fields}}
+		{{.Name}}O: lens{{.Name}}O,
+{{- end}}
+	}
+}
+
+// Make{{.Name}}RefLenses creates a new {{.Name}}RefLenses with lenses for all fields
+func Make{{.Name}}RefLenses() {{.Name}}RefLenses {
+	// mandatory lenses
+{{- range .Fields}}
+{{- if .IsComparable}}
+	lens{{.Name}} := L.MakeLensStrict(
+		func(s *{{$.Name}}) {{.TypeName}} { return s.{{.Name}} },
+		func(s *{{$.Name}}, v {{.TypeName}}) *{{$.Name}} { s.{{.Name}} = v; return s },
+	)
+{{- else}}
+	lens{{.Name}} := L.MakeLensRef(
+		func(s *{{$.Name}}) {{.TypeName}} { return s.{{.Name}} },
+		func(s *{{$.Name}}, v {{.TypeName}}) *{{$.Name}} { s.{{.Name}} = v; return s },
+	)
+{{- end}}
+{{- end}}
+	// optional lenses
+{{- range .Fields}}
+	lens{{.Name}}O := LO.FromIso[*{{$.Name}}](IO.FromZero[{{.TypeName}}]())(lens{{.Name}})
+{{- end}}
+	return {{.Name}}RefLenses{
+		// mandatory lenses
+{{- range .Fields}}
+		{{.Name}}: lens{{.Name}},
+{{- end}}
+		// optional lenses
+{{- range .Fields}}
+		{{.Name}}O: lens{{.Name}}O,
+{{- 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
+func isComparableType(expr ast.Expr) bool {
+	switch t := expr.(type) {
+	case *ast.Ident:
+		// 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)
+	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
+	}
+}
+
+// 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)
+
+		for _, field := range structType.Fields.List {
+			if len(field.Names) == 0 {
+				// Embedded field, skip for now
+				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)
+					// 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 {
+			structs = append(structs, structInfo{
+				Name:    typeSpec.Name.Name,
+				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/cli/lens_test.go

@@ -0,0 +1,757 @@
+// 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"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestHasLensAnnotation(t *testing.T) {
+	tests := []struct {
+		name     string
+		comment  string
+		expected bool
+	}{
+		{
+			name:     "has annotation",
+			comment:  "// fp-go:Lens",
+			expected: true,
+		},
+		{
+			name:     "has annotation with other text",
+			comment:  "// This is a struct with fp-go:Lens annotation",
+			expected: true,
+		},
+		{
+			name:     "no annotation",
+			comment:  "// This is just a regular comment",
+			expected: false,
+		},
+		{
+			name:     "nil comment",
+			comment:  "",
+			expected: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var doc *ast.CommentGroup
+			if tt.comment != "" {
+				doc = &ast.CommentGroup{
+					List: []*ast.Comment{
+						{Text: tt.comment},
+					},
+				}
+			}
+			result := hasLensAnnotation(doc)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}
+
+func TestGetTypeName(t *testing.T) {
+	tests := []struct {
+		name     string
+		code     string
+		expected string
+	}{
+		{
+			name:     "simple type",
+			code:     "type T struct { F string }",
+			expected: "string",
+		},
+		{
+			name:     "pointer type",
+			code:     "type T struct { F *string }",
+			expected: "*string",
+		},
+		{
+			name:     "slice type",
+			code:     "type T struct { F []int }",
+			expected: "[]int",
+		},
+		{
+			name:     "map type",
+			code:     "type T struct { F map[string]int }",
+			expected: "map[string]int",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			fset := token.NewFileSet()
+			file, err := parser.ParseFile(fset, "", "package test\n"+tt.code, 0)
+			require.NoError(t, err)
+
+			var fieldType ast.Expr
+			ast.Inspect(file, func(n ast.Node) bool {
+				if field, ok := n.(*ast.Field); ok && len(field.Names) > 0 {
+					fieldType = field.Type
+					return false
+				}
+				return true
+			})
+
+			require.NotNil(t, fieldType)
+			result := getTypeName(fieldType)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}
+
+func TestIsPointerType(t *testing.T) {
+	tests := []struct {
+		name     string
+		code     string
+		expected bool
+	}{
+		{
+			name:     "pointer type",
+			code:     "type T struct { F *string }",
+			expected: true,
+		},
+		{
+			name:     "non-pointer type",
+			code:     "type T struct { F string }",
+			expected: false,
+		},
+		{
+			name:     "slice type",
+			code:     "type T struct { F []string }",
+			expected: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			fset := token.NewFileSet()
+			file, err := parser.ParseFile(fset, "", "package test\n"+tt.code, 0)
+			require.NoError(t, err)
+
+			var fieldType ast.Expr
+			ast.Inspect(file, func(n ast.Node) bool {
+				if field, ok := n.(*ast.Field); ok && len(field.Names) > 0 {
+					fieldType = field.Type
+					return false
+				}
+				return true
+			})
+
+			require.NotNil(t, fieldType)
+			result := isPointerType(fieldType)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}
+
+func TestIsComparableType(t *testing.T) {
+	tests := []struct {
+		name     string
+		code     string
+		expected bool
+	}{
+		{
+			name:     "basic type - string",
+			code:     "type T struct { F string }",
+			expected: true,
+		},
+		{
+			name:     "basic type - int",
+			code:     "type T struct { F int }",
+			expected: true,
+		},
+		{
+			name:     "basic type - bool",
+			code:     "type T struct { F bool }",
+			expected: true,
+		},
+		{
+			name:     "pointer type",
+			code:     "type T struct { F *string }",
+			expected: true,
+		},
+		{
+			name:     "slice type - not comparable",
+			code:     "type T struct { F []string }",
+			expected: false,
+		},
+		{
+			name:     "map type - not comparable",
+			code:     "type T struct { F map[string]int }",
+			expected: false,
+		},
+		{
+			name:     "array type - comparable if element is",
+			code:     "type T struct { F [5]int }",
+			expected: true,
+		},
+		{
+			name:     "interface type",
+			code:     "type T struct { F interface{} }",
+			expected: true,
+		},
+		{
+			name:     "channel type",
+			code:     "type T struct { F chan int }",
+			expected: true,
+		},
+		{
+			name:     "function type - not comparable",
+			code:     "type T struct { F func() }",
+			expected: false,
+		},
+		{
+			name:     "struct literal - conservatively not comparable",
+			code:     "type T struct { F struct{ X int } }",
+			expected: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			fset := token.NewFileSet()
+			file, err := parser.ParseFile(fset, "", "package test\n"+tt.code, 0)
+			require.NoError(t, err)
+
+			var fieldType ast.Expr
+			ast.Inspect(file, func(n ast.Node) bool {
+				if field, ok := n.(*ast.Field); ok && len(field.Names) > 0 {
+					fieldType = field.Type
+					return false
+				}
+				return true
+			})
+
+			require.NotNil(t, fieldType)
+			result := isComparableType(fieldType)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}
+
+func TestHasOmitEmpty(t *testing.T) {
+	tests := []struct {
+		name     string
+		tag      string
+		expected bool
+	}{
+		{
+			name:     "has omitempty",
+			tag:      "`json:\"field,omitempty\"`",
+			expected: true,
+		},
+		{
+			name:     "has omitempty with other options",
+			tag:      "`json:\"field,omitempty,string\"`",
+			expected: true,
+		},
+		{
+			name:     "no omitempty",
+			tag:      "`json:\"field\"`",
+			expected: false,
+		},
+		{
+			name:     "no tag",
+			tag:      "",
+			expected: false,
+		},
+		{
+			name:     "different tag",
+			tag:      "`xml:\"field\"`",
+			expected: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var tag *ast.BasicLit
+			if tt.tag != "" {
+				tag = &ast.BasicLit{
+					Value: tt.tag,
+				}
+			}
+			result := hasOmitEmpty(tag)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}
+
+func TestParseFile(t *testing.T) {
+	// Create a temporary test file
+	tmpDir := t.TempDir()
+	testFile := filepath.Join(tmpDir, "test.go")
+
+	testCode := `package testpkg
+
+// fp-go:Lens
+type Person struct {
+	Name  string
+	Age   int
+	Phone *string
+}
+
+// fp-go:Lens
+type Address struct {
+	Street string
+	City   string
+}
+
+// Not annotated
+type Other struct {
+	Field string
+}
+`
+
+	err := os.WriteFile(testFile, []byte(testCode), 0644)
+	require.NoError(t, err)
+
+	// Parse the file
+	structs, pkg, err := parseFile(testFile)
+	require.NoError(t, err)
+
+	// Verify results
+	assert.Equal(t, "testpkg", pkg)
+	assert.Len(t, structs, 2)
+
+	// Check Person struct
+	person := structs[0]
+	assert.Equal(t, "Person", person.Name)
+	assert.Len(t, person.Fields, 3)
+
+	assert.Equal(t, "Name", person.Fields[0].Name)
+	assert.Equal(t, "string", person.Fields[0].TypeName)
+	assert.False(t, person.Fields[0].IsOptional)
+
+	assert.Equal(t, "Age", person.Fields[1].Name)
+	assert.Equal(t, "int", person.Fields[1].TypeName)
+	assert.False(t, person.Fields[1].IsOptional)
+
+	assert.Equal(t, "Phone", person.Fields[2].Name)
+	assert.Equal(t, "*string", person.Fields[2].TypeName)
+	assert.True(t, person.Fields[2].IsOptional)
+
+	// Check Address struct
+	address := structs[1]
+	assert.Equal(t, "Address", address.Name)
+	assert.Len(t, address.Fields, 2)
+
+	assert.Equal(t, "Street", address.Fields[0].Name)
+	assert.Equal(t, "City", address.Fields[1].Name)
+}
+
+func TestParseFileWithOmitEmpty(t *testing.T) {
+	// Create a temporary test file
+	tmpDir := t.TempDir()
+	testFile := filepath.Join(tmpDir, "test.go")
+
+	testCode := `package testpkg
+
+// fp-go:Lens
+type Config struct {
+	Name     string
+	Value    string  ` + "`json:\"value,omitempty\"`" + `
+	Count    int     ` + "`json:\",omitempty\"`" + `
+	Optional *string ` + "`json:\"optional,omitempty\"`" + `
+	Required int     ` + "`json:\"required\"`" + `
+}
+`
+
+	err := os.WriteFile(testFile, []byte(testCode), 0644)
+	require.NoError(t, err)
+
+	// Parse the file
+	structs, pkg, err := parseFile(testFile)
+	require.NoError(t, err)
+
+	// Verify results
+	assert.Equal(t, "testpkg", pkg)
+	assert.Len(t, structs, 1)
+
+	// Check Config struct
+	config := structs[0]
+	assert.Equal(t, "Config", config.Name)
+	assert.Len(t, config.Fields, 5)
+
+	// Name - no tag, not optional
+	assert.Equal(t, "Name", config.Fields[0].Name)
+	assert.Equal(t, "string", config.Fields[0].TypeName)
+	assert.False(t, config.Fields[0].IsOptional)
+
+	// Value - has omitempty, should be optional
+	assert.Equal(t, "Value", config.Fields[1].Name)
+	assert.Equal(t, "string", config.Fields[1].TypeName)
+	assert.True(t, config.Fields[1].IsOptional, "Value field with omitempty should be optional")
+
+	// Count - has omitempty (no field name in tag), should be optional
+	assert.Equal(t, "Count", config.Fields[2].Name)
+	assert.Equal(t, "int", config.Fields[2].TypeName)
+	assert.True(t, config.Fields[2].IsOptional, "Count field with omitempty should be optional")
+
+	// Optional - pointer with omitempty, should be optional
+	assert.Equal(t, "Optional", config.Fields[3].Name)
+	assert.Equal(t, "*string", config.Fields[3].TypeName)
+	assert.True(t, config.Fields[3].IsOptional)
+
+	// Required - has json tag but no omitempty, not optional
+	assert.Equal(t, "Required", config.Fields[4].Name)
+	assert.Equal(t, "int", config.Fields[4].TypeName)
+	assert.False(t, config.Fields[4].IsOptional, "Required field without omitempty should not be optional")
+}
+
+func TestParseFileWithComparableTypes(t *testing.T) {
+	// Create a temporary test file
+	tmpDir := t.TempDir()
+	testFile := filepath.Join(tmpDir, "test.go")
+
+	testCode := `package testpkg
+
+// fp-go:Lens
+type TypeTest struct {
+	Name      string
+	Age       int
+	Pointer   *string
+	Slice     []string
+	Map       map[string]int
+	Channel   chan int
+}
+`
+
+	err := os.WriteFile(testFile, []byte(testCode), 0644)
+	require.NoError(t, err)
+
+	// Parse the file
+	structs, pkg, err := parseFile(testFile)
+	require.NoError(t, err)
+
+	// Verify results
+	assert.Equal(t, "testpkg", pkg)
+	assert.Len(t, structs, 1)
+
+	// Check TypeTest struct
+	typeTest := structs[0]
+	assert.Equal(t, "TypeTest", typeTest.Name)
+	assert.Len(t, typeTest.Fields, 6)
+
+	// Name - string is comparable
+	assert.Equal(t, "Name", typeTest.Fields[0].Name)
+	assert.Equal(t, "string", typeTest.Fields[0].TypeName)
+	assert.False(t, typeTest.Fields[0].IsOptional)
+	assert.True(t, typeTest.Fields[0].IsComparable, "string should be comparable")
+
+	// Age - int is comparable
+	assert.Equal(t, "Age", typeTest.Fields[1].Name)
+	assert.Equal(t, "int", typeTest.Fields[1].TypeName)
+	assert.False(t, typeTest.Fields[1].IsOptional)
+	assert.True(t, typeTest.Fields[1].IsComparable, "int should be comparable")
+
+	// Pointer - pointer is optional, IsComparable not checked for optional fields
+	assert.Equal(t, "Pointer", typeTest.Fields[2].Name)
+	assert.Equal(t, "*string", typeTest.Fields[2].TypeName)
+	assert.True(t, typeTest.Fields[2].IsOptional)
+
+	// Slice - not comparable
+	assert.Equal(t, "Slice", typeTest.Fields[3].Name)
+	assert.Equal(t, "[]string", typeTest.Fields[3].TypeName)
+	assert.False(t, typeTest.Fields[3].IsOptional)
+	assert.False(t, typeTest.Fields[3].IsComparable, "slice should not be comparable")
+
+	// Map - not comparable
+	assert.Equal(t, "Map", typeTest.Fields[4].Name)
+	assert.Equal(t, "map[string]int", typeTest.Fields[4].TypeName)
+	assert.False(t, typeTest.Fields[4].IsOptional)
+	assert.False(t, typeTest.Fields[4].IsComparable, "map should not be comparable")
+
+	// Channel - comparable (note: getTypeName returns "any" for channel types, but isComparableType correctly identifies them)
+	assert.Equal(t, "Channel", typeTest.Fields[5].Name)
+	assert.Equal(t, "any", typeTest.Fields[5].TypeName) // getTypeName doesn't handle chan types specifically
+	assert.False(t, typeTest.Fields[5].IsOptional)
+	assert.True(t, typeTest.Fields[5].IsComparable, "channel should be comparable")
+}
+
+func TestLensRefTemplatesWithComparable(t *testing.T) {
+	s := structInfo{
+		Name: "TestStruct",
+		Fields: []fieldInfo{
+			{Name: "Name", TypeName: "string", IsOptional: false, IsComparable: true},
+			{Name: "Age", TypeName: "int", IsOptional: false, IsComparable: true},
+			{Name: "Data", TypeName: "[]byte", IsOptional: false, IsComparable: false},
+			{Name: "Pointer", TypeName: "*string", IsOptional: true, IsComparable: false},
+		},
+	}
+
+	// Test constructor template for RefLenses
+	var constructorBuf bytes.Buffer
+	err := constructorTmpl.Execute(&constructorBuf, s)
+	require.NoError(t, err)
+
+	constructorStr := constructorBuf.String()
+
+	// Check that MakeLensStrict is used for comparable types in RefLenses
+	assert.Contains(t, constructorStr, "func MakeTestStructRefLenses() TestStructRefLenses")
+
+	// Name field - comparable, should use MakeLensStrict
+	assert.Contains(t, constructorStr, "lensName := L.MakeLensStrict(",
+		"comparable field Name should use MakeLensStrict in RefLenses")
+
+	// Age field - comparable, should use MakeLensStrict
+	assert.Contains(t, constructorStr, "lensAge := L.MakeLensStrict(",
+		"comparable field Age should use MakeLensStrict in RefLenses")
+
+	// Data field - not comparable, should use MakeLensRef
+	assert.Contains(t, constructorStr, "lensData := L.MakeLensRef(",
+		"non-comparable field Data should use MakeLensRef in RefLenses")
+
+}
+
+func TestGenerateLensHelpersWithComparable(t *testing.T) {
+	// Create a temporary directory with test files
+	tmpDir := t.TempDir()
+
+	testCode := `package testpkg
+
+// fp-go:Lens
+type TestStruct struct {
+	Name  string
+	Count int
+	Data  []byte
+}
+`
+
+	testFile := filepath.Join(tmpDir, "test.go")
+	err := os.WriteFile(testFile, []byte(testCode), 0644)
+	require.NoError(t, err)
+
+	// Generate lens code
+	outputFile := "gen.go"
+	err = generateLensHelpers(tmpDir, outputFile, false)
+	require.NoError(t, err)
+
+	// Verify the generated file exists
+	genPath := filepath.Join(tmpDir, outputFile)
+	_, err = os.Stat(genPath)
+	require.NoError(t, err)
+
+	// Read and verify the generated content
+	content, err := os.ReadFile(genPath)
+	require.NoError(t, err)
+
+	contentStr := string(content)
+
+	// Check for expected content in RefLenses
+	assert.Contains(t, contentStr, "MakeTestStructRefLenses")
+
+	// Name and Count are comparable, should use MakeLensStrict
+	assert.Contains(t, contentStr, "L.MakeLensStrict",
+		"comparable fields should use MakeLensStrict in RefLenses")
+
+	// Data is not comparable (slice), should use MakeLensRef
+	assert.Contains(t, contentStr, "L.MakeLensRef",
+		"non-comparable fields should use MakeLensRef in RefLenses")
+
+	// Verify the pattern appears for Name field (comparable)
+	namePattern := "lensName := L.MakeLensStrict("
+	assert.Contains(t, contentStr, namePattern,
+		"Name field should use MakeLensStrict")
+
+	// Verify the pattern appears for Data field (not comparable)
+	dataPattern := "lensData := L.MakeLensRef("
+	assert.Contains(t, contentStr, dataPattern,
+		"Data field should use MakeLensRef")
+}
+
+func TestGenerateLensHelpers(t *testing.T) {
+	// Create a temporary directory with test files
+	tmpDir := t.TempDir()
+
+	testCode := `package testpkg
+
+// fp-go:Lens
+type TestStruct struct {
+	Name  string
+	Value *int
+}
+`
+
+	testFile := filepath.Join(tmpDir, "test.go")
+	err := os.WriteFile(testFile, []byte(testCode), 0644)
+	require.NoError(t, err)
+
+	// Generate lens code
+	outputFile := "gen.go"
+	err = generateLensHelpers(tmpDir, outputFile, false)
+	require.NoError(t, err)
+
+	// Verify the generated file exists
+	genPath := filepath.Join(tmpDir, outputFile)
+	_, err = os.Stat(genPath)
+	require.NoError(t, err)
+
+	// Read and verify the generated content
+	content, err := os.ReadFile(genPath)
+	require.NoError(t, err)
+
+	contentStr := string(content)
+
+	// Check for expected content
+	assert.Contains(t, contentStr, "package testpkg")
+	assert.Contains(t, contentStr, "Code generated by go generate")
+	assert.Contains(t, contentStr, "TestStructLenses")
+	assert.Contains(t, contentStr, "MakeTestStructLenses")
+	assert.Contains(t, contentStr, "L.Lens[TestStruct, string]")
+	assert.Contains(t, contentStr, "LO.LensO[TestStruct, *int]")
+	assert.Contains(t, contentStr, "IO.FromZero")
+}
+
+func TestGenerateLensHelpersNoAnnotations(t *testing.T) {
+	// Create a temporary directory with test files
+	tmpDir := t.TempDir()
+
+	testCode := `package testpkg
+
+// No annotation
+type TestStruct struct {
+	Name string
+}
+`
+
+	testFile := filepath.Join(tmpDir, "test.go")
+	err := os.WriteFile(testFile, []byte(testCode), 0644)
+	require.NoError(t, err)
+
+	// Generate lens code (should not create file)
+	outputFile := "gen.go"
+	err = generateLensHelpers(tmpDir, outputFile, false)
+	require.NoError(t, err)
+
+	// Verify the generated file does not exist
+	genPath := filepath.Join(tmpDir, outputFile)
+	_, err = os.Stat(genPath)
+	assert.True(t, os.IsNotExist(err))
+}
+
+func TestLensTemplates(t *testing.T) {
+	s := structInfo{
+		Name: "TestStruct",
+		Fields: []fieldInfo{
+			{Name: "Name", TypeName: "string", IsOptional: false},
+			{Name: "Value", TypeName: "*int", IsOptional: true},
+		},
+	}
+
+	// Test struct template
+	var structBuf bytes.Buffer
+	err := structTmpl.Execute(&structBuf, s)
+	require.NoError(t, err)
+
+	structStr := structBuf.String()
+	assert.Contains(t, structStr, "type TestStructLenses struct")
+	assert.Contains(t, structStr, "Name L.Lens[TestStruct, string]")
+	assert.Contains(t, structStr, "NameO LO.LensO[TestStruct, string]")
+	assert.Contains(t, structStr, "Value L.Lens[TestStruct, *int]")
+	assert.Contains(t, structStr, "ValueO LO.LensO[TestStruct, *int]")
+
+	// Test constructor template
+	var constructorBuf bytes.Buffer
+	err = constructorTmpl.Execute(&constructorBuf, s)
+	require.NoError(t, err)
+
+	constructorStr := constructorBuf.String()
+	assert.Contains(t, constructorStr, "func MakeTestStructLenses() TestStructLenses")
+	assert.Contains(t, constructorStr, "return TestStructLenses{")
+	assert.Contains(t, constructorStr, "Name: lensName,")
+	assert.Contains(t, constructorStr, "NameO: lensNameO,")
+	assert.Contains(t, constructorStr, "Value: lensValue,")
+	assert.Contains(t, constructorStr, "ValueO: lensValueO,")
+	assert.Contains(t, constructorStr, "IO.FromZero")
+}
+
+func TestLensTemplatesWithOmitEmpty(t *testing.T) {
+	s := structInfo{
+		Name: "ConfigStruct",
+		Fields: []fieldInfo{
+			{Name: "Name", TypeName: "string", IsOptional: false},
+			{Name: "Value", TypeName: "string", IsOptional: true},    // non-pointer with omitempty
+			{Name: "Count", TypeName: "int", IsOptional: true},       // non-pointer with omitempty
+			{Name: "Pointer", TypeName: "*string", IsOptional: true}, // pointer
+		},
+	}
+
+	// Test struct template
+	var structBuf bytes.Buffer
+	err := structTmpl.Execute(&structBuf, s)
+	require.NoError(t, err)
+
+	structStr := structBuf.String()
+	assert.Contains(t, structStr, "type ConfigStructLenses struct")
+	assert.Contains(t, structStr, "Name L.Lens[ConfigStruct, string]")
+	assert.Contains(t, structStr, "NameO LO.LensO[ConfigStruct, string]")
+	assert.Contains(t, structStr, "Value L.Lens[ConfigStruct, string]")
+	assert.Contains(t, structStr, "ValueO LO.LensO[ConfigStruct, string]", "non-pointer with omitempty should have optional lens")
+	assert.Contains(t, structStr, "Count L.Lens[ConfigStruct, int]")
+	assert.Contains(t, structStr, "CountO LO.LensO[ConfigStruct, int]", "non-pointer with omitempty should have optional lens")
+	assert.Contains(t, structStr, "Pointer L.Lens[ConfigStruct, *string]")
+	assert.Contains(t, structStr, "PointerO LO.LensO[ConfigStruct, *string]")
+
+	// Test constructor template
+	var constructorBuf bytes.Buffer
+	err = constructorTmpl.Execute(&constructorBuf, s)
+	require.NoError(t, err)
+
+	constructorStr := constructorBuf.String()
+	assert.Contains(t, constructorStr, "func MakeConfigStructLenses() ConfigStructLenses")
+	assert.Contains(t, constructorStr, "IO.FromZero[string]()")
+	assert.Contains(t, constructorStr, "IO.FromZero[int]()")
+	assert.Contains(t, constructorStr, "IO.FromZero[*string]()")
+}
+
+func TestLensCommandFlags(t *testing.T) {
+	cmd := LensCommand()
+
+	assert.Equal(t, "lens", cmd.Name)
+	assert.Equal(t, "generate lens code for annotated structs", cmd.Usage)
+	assert.Contains(t, strings.ToLower(cmd.Description), "fp-go:lens")
+	assert.Contains(t, strings.ToLower(cmd.Description), "lenso", "Description should mention LensO for optional lenses")
+
+	// Check flags
+	assert.Len(t, cmd.Flags, 3)
+
+	var hasDir, hasFilename, hasVerbose bool
+	for _, flag := range cmd.Flags {
+		switch flag.Names()[0] {
+		case "dir":
+			hasDir = true
+		case "filename":
+			hasFilename = true
+		case "verbose":
+			hasVerbose = true
+		}
+	}
+
+	assert.True(t, hasDir, "should have dir flag")
+	assert.True(t, hasFilename, "should have filename flag")
+	assert.True(t, hasVerbose, "should have verbose flag")
+}

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/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
-github.com/IBM/fp-go/v2/context/readerioeither/bind.go:27.21,29.2 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/bind.go:35.47,42.2 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/bind.go:48.47,54.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/bind.go:60.47,66.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/bind.go:71.46,76.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/bind.go:82.47,89.2 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/bracket.go:33.21,44.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/cancel.go:35.65,36.47 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/cancel.go:36.47,37.44 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/cancel.go:37.44,39.4 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/cancel.go:40.3,40.40 1 1
-github.com/IBM/fp-go/v2/context/readerioeither/eq.go:42.84,44.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:18.91,20.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:24.93,26.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:30.101,32.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:36.103,38.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:43.36,48.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:53.36,58.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:63.36,68.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:71.98,76.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:79.101,84.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:87.101,92.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:95.129,96.68 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:96.68,102.4 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:106.132,107.68 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:107.68,113.4 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:117.132,118.68 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:118.68,124.4 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:129.113,131.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:135.115,137.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:143.40,150.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:156.40,163.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:169.40,176.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:179.126,185.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:188.129,194.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:197.129,203.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:206.185,207.76 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:207.76,215.4 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:219.188,220.76 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:220.76,228.4 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:232.188,233.76 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:233.76,241.4 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:246.125,248.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:252.127,254.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:261.44,270.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:277.44,286.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:293.44,302.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:305.154,312.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:315.157,322.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:325.157,332.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:335.241,336.84 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:336.84,346.4 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:350.244,351.84 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:351.84,361.4 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:365.244,366.84 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:366.84,376.4 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/gen.go:381.137,383.2 1 0
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-github.com/IBM/fp-go/v2/context/readerioeither/monoid.go:68.64,75.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/monoid.go:85.61,93.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/monoid.go:103.63,108.2 1 0
-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:42.55,44.2 1 1
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-github.com/IBM/fp-go/v2/context/readerioeither/reader.go:165.39,167.2 1 1
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-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
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-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

@@ -0,0 +1,251 @@
+mode: set
+github.com/IBM/fp-go/v2/context/readerioresult/bind.go:27.21,29.2 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/bind.go:35.47,42.2 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/bind.go:48.47,54.2 1 0
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+github.com/IBM/fp-go/v2/context/readerioresult/bind.go:71.46,76.2 1 0
+github.com/IBM/fp-go/v2/context/readerioresult/bind.go:82.47,89.2 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/bracket.go:33.21,44.2 1 0
+github.com/IBM/fp-go/v2/context/readerioresult/cancel.go:35.65,36.47 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/cancel.go:36.47,37.44 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/cancel.go:37.44,39.4 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/cancel.go:40.3,40.40 1 1
+github.com/IBM/fp-go/v2/context/readerioresult/eq.go:42.84,44.2 1 0
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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"
+	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"
+)
+
+// 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(E.Of[error](withoutBody)), E.Map[error](withBody)),
+		E.Ap[func(string) RIOE.ReaderIOResult[*http.Request]](builder.GetTargetURL()),
+		E.Flap[error, RIOE.ReaderIOResult[*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/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 +1,843 @@
+// 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)
+}
+
+// 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)
+}
+
+// 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)
+}
+
+// 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)
+}
+
+// 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)
+}
+
+// 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)
+}
+
+// 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.IdentityError)
+}
+
+// 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 ChainFirstReaderK[A, B any](f reader.Kleisli[context.Context, A, B]) Operator[A, A] {
+	return RIOR.ChainFirstReaderK(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 ChainFirstReaderResultK[A, B any](f readerresult.Kleisli[A, B]) Operator[A, A] {
+	return RIOR.ChainFirstReaderResultK(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 ChainFirstReaderIOK[A, B any](f readerio.Kleisli[context.Context, A, B]) Operator[A, A] {
+	return RIOR.ChainFirstReaderIOK(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 Read[A any](r context.Context) func(ReaderIOResult[A]) IOResult[A] {
+	return RIOR.Read[A](r)
+}

v2/context/readerioresult/reader_bench_test.go

@@ -0,0 +1,885 @@
+// 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"
+)
+
+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 i := 0; i < b.N; i++ {
+		benchRIOE = Left[int](benchErr)
+	}
+}
+
+func BenchmarkRight(b *testing.B) {
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = Right(42)
+	}
+}
+
+func BenchmarkOf(b *testing.B) {
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = Of(42)
+	}
+}
+
+func BenchmarkFromEither_Right(b *testing.B) {
+	either := E.Right[error](42)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = FromEither(either)
+	}
+}
+
+func BenchmarkFromEither_Left(b *testing.B) {
+	either := E.Left[int](benchErr)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = FromEither(either)
+	}
+}
+
+func BenchmarkFromIO(b *testing.B) {
+	io := func() int { return 42 }
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = FromIO(io)
+	}
+}
+
+func BenchmarkFromIOEither_Right(b *testing.B) {
+	ioe := IOE.Of[error](42)
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = FromIOEither(ioe)
+	}
+}
+
+func BenchmarkFromIOEither_Left(b *testing.B) {
+	ioe := IOE.Left[int](benchErr)
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = FromIOEither(ioe)
+	}
+}
+
+// Benchmark execution
+func BenchmarkExecute_Right(b *testing.B) {
+	rioe := Right(42)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchResult = rioe(benchCtx)()
+	}
+}
+
+func BenchmarkExecute_Left(b *testing.B) {
+	rioe := Left[int](benchErr)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchResult = rioe(benchCtx)()
+	}
+}
+
+func BenchmarkExecute_WithContext(b *testing.B) {
+	rioe := Right(42)
+	ctx, cancel := context.WithCancel(benchCtx)
+	defer cancel()
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchResult = rioe(ctx)()
+	}
+}
+
+// Benchmark functor operations
+func BenchmarkMonadMap_Right(b *testing.B) {
+	rioe := Right(42)
+	mapper := func(a int) int { return a * 2 }
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = MonadMap(rioe, mapper)
+	}
+}
+
+func BenchmarkMonadMap_Left(b *testing.B) {
+	rioe := Left[int](benchErr)
+	mapper := func(a int) int { return a * 2 }
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = MonadMap(rioe, mapper)
+	}
+}
+
+func BenchmarkMap_Right(b *testing.B) {
+	rioe := Right(42)
+	mapper := Map(func(a int) int { return a * 2 })
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = mapper(rioe)
+	}
+}
+
+func BenchmarkMap_Left(b *testing.B) {
+	rioe := Left[int](benchErr)
+	mapper := Map(func(a int) int { return a * 2 })
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = mapper(rioe)
+	}
+}
+
+func BenchmarkMapTo_Right(b *testing.B) {
+	rioe := Right(42)
+	mapper := MapTo[int](99)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		benchRIOE = chainer(rioe)
+	}
+}
+
+func BenchmarkFlatten_Right(b *testing.B) {
+	nested := Right(Right(42))
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = Flatten(nested)
+	}
+}
+
+func BenchmarkFlatten_Left(b *testing.B) {
+	nested := Left[ReaderIOResult[int]](benchErr)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = Flatten(nested)
+	}
+}
+
+// Benchmark applicative operations
+func BenchmarkMonadApSeq_RightRight(b *testing.B) {
+	fab := Right(func(a int) int { return a * 2 })
+	fa := Right(42)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = MonadApSeq(fab, fa)
+	}
+}
+
+func BenchmarkMonadApSeq_RightLeft(b *testing.B) {
+	fab := Right(func(a int) int { return a * 2 })
+	fa := Left[int](benchErr)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = MonadApSeq(fab, fa)
+	}
+}
+
+func BenchmarkMonadApSeq_LeftRight(b *testing.B) {
+	fab := Left[func(int) int](benchErr)
+	fa := Right(42)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = MonadApSeq(fab, fa)
+	}
+}
+
+func BenchmarkMonadApPar_RightRight(b *testing.B) {
+	fab := Right(func(a int) int { return a * 2 })
+	fa := Right(42)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = MonadApPar(fab, fa)
+	}
+}
+
+func BenchmarkMonadApPar_RightLeft(b *testing.B) {
+	fab := Right(func(a int) int { return a * 2 })
+	fa := Left[int](benchErr)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = MonadApPar(fab, fa)
+	}
+}
+
+func BenchmarkMonadApPar_LeftRight(b *testing.B) {
+	fab := Left[func(int) int](benchErr)
+	fa := Right(42)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = MonadApPar(fab, fa)
+	}
+}
+
+// Benchmark execution of applicative operations
+func BenchmarkExecuteApSeq_RightRight(b *testing.B) {
+	fab := Right(func(a int) int { return a * 2 })
+	fa := Right(42)
+	rioe := MonadApSeq(fab, fa)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchResult = rioe(benchCtx)()
+	}
+}
+
+func BenchmarkExecuteApPar_RightRight(b *testing.B) {
+	fab := Right(func(a int) int { return a * 2 })
+	fa := Right(42)
+	rioe := MonadApPar(fab, fa)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		benchRIOE = chainer(rioe)
+	}
+}
+
+// Benchmark context operations
+func BenchmarkAsk(b *testing.B) {
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = Ask()
+	}
+}
+
+func BenchmarkDefer(b *testing.B) {
+	gen := func() ReaderIOResult[int] { return Right(42) }
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = Defer(gen)
+	}
+}
+
+func BenchmarkMemoize(b *testing.B) {
+	rioe := Right(42)
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = Memoize(rioe)
+	}
+}
+
+// Benchmark delay operations
+func BenchmarkDelay_Construction(b *testing.B) {
+	rioe := Right(42)
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = Delay[int](time.Millisecond)(rioe)
+	}
+}
+
+func BenchmarkTimer_Construction(b *testing.B) {
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = 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 i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		benchResult = rioe(benchCtx)()
+	}
+}
+
+// Benchmark pipeline operations
+func BenchmarkPipeline_Map_Right(b *testing.B) {
+	rioe := Right(21)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = F.Pipe1(
+			rioe,
+			Map(func(x int) int { return x * 2 }),
+		)
+	}
+}
+
+func BenchmarkPipeline_Map_Left(b *testing.B) {
+	rioe := Left[int](benchErr)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = F.Pipe1(
+			rioe,
+			Map(func(x int) int { return x * 2 }),
+		)
+	}
+}
+
+func BenchmarkPipeline_Chain_Right(b *testing.B) {
+	rioe := Right(21)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		benchRIOE = F.Pipe3(
+			rioe,
+			Map(func(x int) int { return x * 2 }),
+			Chain(func(x int) ReaderIOResult[int] { return Right(x + 1) }),
+			Map(func(x int) int { return x * 2 }),
+		)
+	}
+}
+
+func BenchmarkPipeline_Complex_Left(b *testing.B) {
+	rioe := Left[int](benchErr)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchRIOE = F.Pipe3(
+			rioe,
+			Map(func(x int) int { return x * 2 }),
+			Chain(func(x int) ReaderIOResult[int] { return Right(x + 1) }),
+			Map(func(x int) int { return x * 2 }),
+		)
+	}
+}
+
+func BenchmarkExecutePipeline_Complex_Right(b *testing.B) {
+	rioe := F.Pipe3(
+		Right(10),
+		Map(func(x int) int { return x * 2 }),
+		Chain(func(x int) ReaderIOResult[int] { return Right(x + 1) }),
+		Map(func(x int) int { return x * 2 }),
+	)
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchResult = rioe(benchCtx)()
+	}
+}
+
+// Benchmark do-notation operations
+func BenchmarkDo(b *testing.B) {
+	type State struct{ value int }
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = 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 i := 0; i < b.N; i++ {
+		_ = 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 i := 0; i < b.N; i++ {
+		_ = 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 i := 0; i < b.N; i++ {
+		_ = 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 i := 0; i < b.N; i++ {
+		_ = 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 i := 0; i < b.N; i++ {
+		_ = 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 i := 0; i < b.N; i++ {
+		_ = 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 i := 0; i < b.N; i++ {
+		_ = 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 i := 0; i < b.N; i++ {
+		_ = traverser(arr)
+	}
+}
+
+func BenchmarkSequenceArray_Small(b *testing.B) {
+	arr := []ReaderIOResult[int]{
+		Right(1),
+		Right(2),
+		Right(3),
+	}
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = 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 i := 0; i < b.N; i++ {
+		_ = 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 i := 0; i < b.N; i++ {
+		_ = 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 i := 0; i < b.N; i++ {
+		_ = 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 i := 0; i < b.N; i++ {
+		_ = 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 i := 0; i < b.N; i++ {
+		_ = 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 i := 0; i < b.N; i++ {
+		_ = 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 i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		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 i := 0; i < b.N; i++ {
+		benchResult = rioe(ctx)()
+	}
+}
+
+func BenchmarkExecuteApPar_CanceledContext(b *testing.B) {
+	fab := Right(func(a int) int { return a * 2 })
+	fa := Right(42)
+	rioe := MonadApPar(fab, fa)
+	ctx, cancel := context.WithCancel(benchCtx)
+	cancel() // Cancel immediately
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		benchResult = rioe(ctx)()
+	}
+}

v2/context/readerioresult/reader_extended_test.go

@@ -0,0 +1,877 @@
+// 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"
+	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), func(x int) int { return x * 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), func(x int) int { return x * 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(func(x int) int { return x * 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(func(x int) int { return x * 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(func(x int) int { return x * 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(func(x int) int { return x * 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(func(x int) int { return x * 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(func(x int) int { return x * 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(func(x int) int { return x * 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(func(x int) int { return x * 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(func(x int) int { return x * 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

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 +1,306 @@
+// 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/function"
+	"github.com/IBM/fp-go/v2/internal/array"
+	"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[[]A](
+		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[[]A](
+		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[[]A](
+		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[[]A](
+		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[[]A](
+		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[[]A](
+		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")
 }
 

v2/context/readerresult/cancel.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"
@@ -21,8 +21,8 @@ import (
 	E "github.com/IBM/fp-go/v2/either"
 )
 
-// withContext wraps an existing ReaderEither and performs a context check for cancellation before deletating
-func WithContext[A any](ma ReaderEither[A]) ReaderEither[A] {
+// withContext wraps an existing ReaderResult and performs a context check for cancellation before deletating
+func WithContext[A any](ma ReaderResult[A]) ReaderResult[A] {
 	return func(ctx context.Context) E.Either[error, A] {
 		if err := context.Cause(ctx); err != nil {
 			return E.Left[A](err)

v2/context/readerresult/curry.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"
@@ -24,30 +24,30 @@ import (
 // these functions curry a golang function with the context as the firsr parameter into a either reader with the context as the last parameter
 // this goes back to the advice in https://pkg.go.dev/context to put the context as a first parameter as a convention
 
-func Curry0[A any](f func(context.Context) (A, error)) ReaderEither[A] {
+func Curry0[A any](f func(context.Context) (A, error)) ReaderResult[A] {
 	return readereither.Curry0(f)
 }
 
-func Curry1[T1, A any](f func(context.Context, T1) (A, error)) func(T1) ReaderEither[A] {
+func Curry1[T1, A any](f func(context.Context, T1) (A, error)) Kleisli[T1, A] {
 	return readereither.Curry1(f)
 }
 
-func Curry2[T1, T2, A any](f func(context.Context, T1, T2) (A, error)) func(T1) func(T2) ReaderEither[A] {
+func Curry2[T1, T2, A any](f func(context.Context, T1, T2) (A, error)) func(T1) Kleisli[T2, A] {
 	return readereither.Curry2(f)
 }
 
-func Curry3[T1, T2, T3, A any](f func(context.Context, T1, T2, T3) (A, error)) func(T1) func(T2) func(T3) ReaderEither[A] {
+func Curry3[T1, T2, T3, A any](f func(context.Context, T1, T2, T3) (A, error)) func(T1) func(T2) Kleisli[T3, A] {
 	return readereither.Curry3(f)
 }
 
-func Uncurry1[T1, A any](f func(T1) ReaderEither[A]) func(context.Context, T1) (A, error) {
+func Uncurry1[T1, A any](f Kleisli[T1, A]) func(context.Context, T1) (A, error) {
 	return readereither.Uncurry1(f)
 }
 
-func Uncurry2[T1, T2, A any](f func(T1) func(T2) ReaderEither[A]) func(context.Context, T1, T2) (A, error) {
+func Uncurry2[T1, T2, A any](f func(T1) Kleisli[T2, A]) func(context.Context, T1, T2) (A, error) {
 	return readereither.Uncurry2(f)
 }
 
-func Uncurry3[T1, T2, T3, A any](f func(T1) func(T2) func(T3) ReaderEither[A]) func(context.Context, T1, T2, T3) (A, error) {
+func Uncurry3[T1, T2, T3, A any](f func(T1) func(T2) Kleisli[T3, A]) func(context.Context, T1, T2, T3) (A, error) {
 	return readereither.Uncurry3(f)
 }

v2/context/readerresult/exec/exec.go

@@ -18,11 +18,10 @@ package exec
 import (
 	"context"
 
-	"github.com/IBM/fp-go/v2/context/readereither"
-	"github.com/IBM/fp-go/v2/either"
 	"github.com/IBM/fp-go/v2/exec"
 	"github.com/IBM/fp-go/v2/function"
 	INTE "github.com/IBM/fp-go/v2/internal/exec"
+	"github.com/IBM/fp-go/v2/result"
 )
 
 var (
@@ -32,8 +31,8 @@ var (
 	Command = function.Curry3(command)
 )
 
-func command(name string, args []string, in []byte) readereither.ReaderEither[exec.CommandOutput] {
-	return func(ctx context.Context) either.Either[error, exec.CommandOutput] {
-		return either.TryCatchError(INTE.Exec(ctx, name, args, in))
+func command(name string, args []string, in []byte) ReaderResult[exec.CommandOutput] {
+	return func(ctx context.Context) Result[exec.CommandOutput] {
+		return result.TryCatchError(INTE.Exec(ctx, name, args, in))
 	}
 }

v2/context/readerresult/exec/type.go

@@ -0,0 +1,27 @@
+// 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 implements a specialization of the Reader monad assuming a golang context as the context of the monad and a standard golang error
+package exec
+
+import (
+	"github.com/IBM/fp-go/v2/context/readerresult"
+	"github.com/IBM/fp-go/v2/result"
+)
+
+type (
+	Result[T any]       = result.Result[T]
+	ReaderResult[T any] = readerresult.ReaderResult[T]
+)

v2/context/readerresult/from.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"
@@ -24,18 +24,18 @@ import (
 // these functions curry a golang function with the context as the firsr parameter into a either reader with the context as the last parameter
 // this goes back to the advice in https://pkg.go.dev/context to put the context as a first parameter as a convention
 
-func From0[A any](f func(context.Context) (A, error)) func() ReaderEither[A] {
+func From0[A any](f func(context.Context) (A, error)) func() ReaderResult[A] {
 	return readereither.From0(f)
 }
 
-func From1[T1, A any](f func(context.Context, T1) (A, error)) func(T1) ReaderEither[A] {
+func From1[T1, A any](f func(context.Context, T1) (A, error)) Kleisli[T1, A] {
 	return readereither.From1(f)
 }
 
-func From2[T1, T2, A any](f func(context.Context, T1, T2) (A, error)) func(T1, T2) ReaderEither[A] {
+func From2[T1, T2, A any](f func(context.Context, T1, T2) (A, error)) func(T1, T2) ReaderResult[A] {
 	return readereither.From2(f)
 }
 
-func From3[T1, T2, T3, A any](f func(context.Context, T1, T2, T3) (A, error)) func(T1, T2, T3) ReaderEither[A] {
+func From3[T1, T2, T3, A any](f func(context.Context, T1, T2, T3) (A, error)) func(T1, T2, T3) ReaderResult[A] {
 	return readereither.From3(f)
 }

v2/context/readerresult/reader.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"
@@ -21,19 +21,19 @@ import (
 	"github.com/IBM/fp-go/v2/readereither"
 )
 
-func FromEither[A any](e Either[A]) ReaderEither[A] {
+func FromEither[A any](e Either[A]) ReaderResult[A] {
 	return readereither.FromEither[context.Context](e)
 }
 
-func Left[A any](l error) ReaderEither[A] {
+func Left[A any](l error) ReaderResult[A] {
 	return readereither.Left[context.Context, A](l)
 }
 
-func Right[A any](r A) ReaderEither[A] {
+func Right[A any](r A) ReaderResult[A] {
 	return readereither.Right[context.Context, error](r)
 }
 
-func MonadMap[A, B any](fa ReaderEither[A], f func(A) B) ReaderEither[B] {
+func MonadMap[A, B any](fa ReaderResult[A], f func(A) B) ReaderResult[B] {
 	return readereither.MonadMap(fa, f)
 }
 
@@ -41,43 +41,43 @@ func Map[A, B any](f func(A) B) Operator[A, B] {
 	return readereither.Map[context.Context, error](f)
 }
 
-func MonadChain[A, B any](ma ReaderEither[A], f func(A) ReaderEither[B]) ReaderEither[B] {
+func MonadChain[A, B any](ma ReaderResult[A], f Kleisli[A, B]) ReaderResult[B] {
 	return readereither.MonadChain(ma, f)
 }
 
-func Chain[A, B any](f func(A) ReaderEither[B]) Operator[A, B] {
+func Chain[A, B any](f Kleisli[A, B]) Operator[A, B] {
 	return readereither.Chain(f)
 }
 
-func Of[A any](a A) ReaderEither[A] {
+func Of[A any](a A) ReaderResult[A] {
 	return readereither.Of[context.Context, error](a)
 }
 
-func MonadAp[A, B any](fab ReaderEither[func(A) B], fa ReaderEither[A]) ReaderEither[B] {
+func MonadAp[A, B any](fab ReaderResult[func(A) B], fa ReaderResult[A]) ReaderResult[B] {
 	return readereither.MonadAp(fab, fa)
 }
 
-func Ap[A, B any](fa ReaderEither[A]) func(ReaderEither[func(A) B]) ReaderEither[B] {
+func Ap[A, B any](fa ReaderResult[A]) func(ReaderResult[func(A) B]) ReaderResult[B] {
 	return readereither.Ap[B](fa)
 }
 
-func FromPredicate[A any](pred func(A) bool, onFalse func(A) error) func(A) ReaderEither[A] {
+func FromPredicate[A any](pred func(A) bool, onFalse func(A) error) Kleisli[A, A] {
 	return readereither.FromPredicate[context.Context](pred, onFalse)
 }
 
-func OrElse[A any](onLeft func(error) ReaderEither[A]) func(ReaderEither[A]) ReaderEither[A] {
+func OrElse[A any](onLeft Kleisli[error, A]) Kleisli[ReaderResult[A], A] {
 	return readereither.OrElse(onLeft)
 }
 
-func Ask() ReaderEither[context.Context] {
+func Ask() ReaderResult[context.Context] {
 	return readereither.Ask[context.Context, error]()
 }
 
-func MonadChainEitherK[A, B any](ma ReaderEither[A], f func(A) Either[B]) ReaderEither[B] {
+func MonadChainEitherK[A, B any](ma ReaderResult[A], f func(A) Either[B]) ReaderResult[B] {
 	return readereither.MonadChainEitherK(ma, f)
 }
 
-func ChainEitherK[A, B any](f func(A) Either[B]) func(ma ReaderEither[A]) ReaderEither[B] {
+func ChainEitherK[A, B any](f func(A) Either[B]) func(ma ReaderResult[A]) ReaderResult[B] {
 	return readereither.ChainEitherK[context.Context](f)
 }
 
@@ -85,10 +85,15 @@ func ChainOptionK[A, B any](onNone func() error) func(func(A) Option[B]) Operato
 	return readereither.ChainOptionK[context.Context, A, B](onNone)
 }
 
-func MonadFlap[B, A any](fab ReaderEither[func(A) B], a A) ReaderEither[B] {
+func MonadFlap[B, A any](fab ReaderResult[func(A) B], a A) ReaderResult[B] {
 	return readereither.MonadFlap(fab, a)
 }
 
 func Flap[B, A any](a A) Operator[func(A) B, B] {
 	return readereither.Flap[context.Context, error, B](a)
 }
+
+//go:inline
+func Read[A any](r context.Context) func(ReaderResult[A]) Result[A] {
+	return readereither.Read[error, A](r)
+}

v2/context/readerresult/sequence.go

@@ -13,7 +13,7 @@
 // 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"
@@ -22,18 +22,18 @@ import (
 
 // SequenceT converts n inputs of higher kinded types into a higher kinded types of n strongly typed values, represented as a tuple
 
-func SequenceT1[A any](a ReaderEither[A]) ReaderEither[tuple.Tuple1[A]] {
+func SequenceT1[A any](a ReaderResult[A]) ReaderResult[tuple.Tuple1[A]] {
 	return readereither.SequenceT1(a)
 }
 
-func SequenceT2[A, B any](a ReaderEither[A], b ReaderEither[B]) ReaderEither[tuple.Tuple2[A, B]] {
+func SequenceT2[A, B any](a ReaderResult[A], b ReaderResult[B]) ReaderResult[tuple.Tuple2[A, B]] {
 	return readereither.SequenceT2(a, b)
 }
 
-func SequenceT3[A, B, C any](a ReaderEither[A], b ReaderEither[B], c ReaderEither[C]) ReaderEither[tuple.Tuple3[A, B, C]] {
+func SequenceT3[A, B, C any](a ReaderResult[A], b ReaderResult[B], c ReaderResult[C]) ReaderResult[tuple.Tuple3[A, B, C]] {
 	return readereither.SequenceT3(a, b, c)
 }
 
-func SequenceT4[A, B, C, D any](a ReaderEither[A], b ReaderEither[B], c ReaderEither[C], d ReaderEither[D]) ReaderEither[tuple.Tuple4[A, B, C, D]] {
+func SequenceT4[A, B, C, D any](a ReaderResult[A], b ReaderResult[B], c ReaderResult[C], d ReaderResult[D]) ReaderResult[tuple.Tuple4[A, B, C, D]] {
 	return readereither.SequenceT4(a, b, c, d)
 }

v2/context/readerresult/type.go

@@ -13,8 +13,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// Package readereither implements a specialization of the Reader monad assuming a golang context as the context of the monad and a standard golang error
-package readereither
+// package readerresult implements a specialization of the Reader monad assuming a golang context as the context of the monad and a standard golang error
+package readerresult
 
 import (
 	"context"
@@ -23,13 +23,16 @@ import (
 	"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/result"
 )
 
 type (
 	Option[A any] = option.Option[A]
 	Either[A any] = either.Either[error, A]
-	// ReaderEither is a specialization of the Reader monad for the typical golang scenario
-	ReaderEither[A any] = readereither.ReaderEither[context.Context, error, A]
+	Result[A any] = result.Result[A]
+	// ReaderResult is a specialization of the Reader monad for the typical golang scenario
+	ReaderResult[A any] = readereither.ReaderEither[context.Context, error, A]
 
-	Operator[A, B any] = reader.Reader[ReaderEither[A], ReaderEither[B]]
+	Kleisli[A, B any]  = reader.Reader[A, ReaderResult[B]]
+	Operator[A, B any] = Kleisli[ReaderResult[A], B]
 )

v2/di/app.go

@@ -19,7 +19,7 @@ import (
 	DIE "github.com/IBM/fp-go/v2/di/erasure"
 	F "github.com/IBM/fp-go/v2/function"
 	IO "github.com/IBM/fp-go/v2/io"
-	IOE "github.com/IBM/fp-go/v2/ioeither"
+	IOR "github.com/IBM/fp-go/v2/ioresult"
 )
 
 var (
@@ -34,5 +34,5 @@ var (
 var RunMain = F.Flow3(
 	DIE.MakeInjector,
 	Main,
-	IOE.Fold(IO.Of[error], F.Constant1[any](IO.Of[error](nil))),
+	IOR.Fold(IO.Of[error], F.Constant1[any](IO.Of[error](nil))),
 )