fix: merge

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

.github/workflows/build.yml

@@ -4,9 +4,7 @@ on:
   push:
     branches:
       - main
-
   pull_request:
-
   workflow_dispatch:
     inputs:
       dryRun:
@@ -15,35 +13,60 @@ on:
         required: false
 
 env:
-  # Currently no way to detect automatically
   DEFAULT_BRANCH: main
-  GO_VERSION: 1.21.6 # renovate: datasource=golang-version depName=golang
+  LATEST_GO_VERSION: 1.21.6 # renovate: datasource=golang-version depName=golang
   NODE_VERSION: 22
   DRY_RUN: true
 
 jobs:
-  build:
+  build-v1:
+    name: Build v1 (Go ${{ matrix.go-version }})
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go-version: [ '1.20.x', '1.21.x', '1.22.x', '1.23.x']
+        go-version: ['1.20.x', '1.21.x', '1.22.x', '1.23.x']
+      fail-fast: false  # Continue with other versions if one fails
     steps:
       # full checkout for semantic-release
       - uses: actions/checkout@08eba0b27e820071cde6df949e0beb9ba4906955 # v4.3.0
         with:
           fetch-depth: 0
-      - name: Set up go ${{ matrix.go-version }}
+      - name: Set up Go ${{ matrix.go-version }}
         uses: actions/setup-go@v5
         with:
           go-version: ${{ matrix.go-version }}
-      -
+          cache: true  # Enable Go module caching
-        name: Tests
+      - name: Run tests
         run: |
           go mod tidy
           go test -v ./...
 
+  build-v2:
+    name: Build v2 (Go ${{ matrix.go-version }})
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        go-version: ['1.24.x']
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+        with:
+          fetch-depth: 0
+      - name: Set up Go ${{ matrix.go-version }}
+        uses: actions/setup-go@v5
+        with:
+          go-version: ${{ matrix.go-version }}
+          cache: true  # Enable Go module caching
+      - name: Run tests
+        run: |
+          cd v2
+          go mod tidy
+          go test -v ./...
+
   release:
-    needs: [build]
+    name: Release
+    needs: 
+      - build-v1
+      - build-v2
     if: github.repository == 'IBM/fp-go' && github.event_name != 'pull_request'
     runs-on: ubuntu-latest
     timeout-minutes: 15
@@ -51,7 +74,6 @@ jobs:
       contents: write
       issues: write
       pull-requests: write
-
     steps:
       # full checkout for semantic-release
       - name: Full checkout
@@ -63,26 +85,27 @@ jobs:
         uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4.4.0
         with:
           node-version: ${{ env.NODE_VERSION }}
+          cache: 'npm'  # Enable npm caching
 
-      - name: Set up go ${{env.GO_VERSION}}
+      - name: Set up Go
         uses: actions/setup-go@v5
         with:
-          go-version: ${{env.GO_VERSION}}
+          go-version: ${{ env.LATEST_GO_VERSION }}
+          cache: true  # Enable Go module caching
 
-      # The dry-run evaluation is only made for non PR events. Manual trigger w/dryRun true, main branch and any tagged branches will set DRY run to false
+      - name: Determine release mode
-      - name: Check dry run
+        id: release-mode
         run: |
-          if [[ "${{github.event_name}}" == "workflow_dispatch" && "${{ github.event.inputs.dryRun }}" != "true"  ]]; then
+          if [[ "${{ github.event_name }}" == "workflow_dispatch" && "${{ github.event.inputs.dryRun }}" != "true" ]]; then
-              echo "DRY_RUN=false" >> $GITHUB_ENV
-          elif [[ "${{github.ref}}" == "refs/heads/${{env.DEFAULT_BRANCH}}" ]]; then
             echo "DRY_RUN=false" >> $GITHUB_ENV
-          elif [[ "${{github.ref}}" =~ ^refs/heads/v[0-9]+(\.[0-9]+)?$ ]]; then
+          elif [[ "${{ github.ref }}" == "refs/heads/${{ env.DEFAULT_BRANCH }}" ]]; then
+            echo "DRY_RUN=false" >> $GITHUB_ENV
+          elif [[ "${{ github.ref }}" =~ ^refs/heads/v[0-9]+(\.[0-9]+)?$ ]]; then
             echo "DRY_RUN=false" >> $GITHUB_ENV
           fi
 
-      - name: Semantic Release
+      - name: Run semantic release
         run: |
-          npx -p conventional-changelog-conventionalcommits -p semantic-release semantic-release --dry-run ${{env.DRY_RUN}}
+          npx -p conventional-changelog-conventionalcommits -p semantic-release semantic-release --dry-run ${{ env.DRY_RUN }}
         env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-  

internal/bracket/bracket.go

@@ -13,7 +13,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package file
+package bracket
 
 import (
 	F "github.com/IBM/fp-go/function"

v2/README.md

@@ -0,0 +1,43 @@
+# Functional programming library for golang V2
+
+Go 1.24 introduces [generic type aliases](https://github.com/golang/go/issues/46477) which are leveraged by V2.
+
+## ⚠️ Breaking Changes
+
+- 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
+
+## Simplifications
+
+- use type aliases to get rid of namespace imports for type declarations, e.g. instead of
+
+```go
+import (
+    ET "github.com/IBM/fp-go/v2/either"
+)
+
+func doSth() ET.Either[error, string] {
+    ...
+}
+```
+
+you can declare your type once 
+
+```go
+import (
+    "github.com/IBM/fp-go/v2/either"
+)
+
+type Either[A any] = either.Either[error, A]
+```
+
+and then use it across your codebase
+
+```go
+func doSth() Either[string] {
+    ...
+}
+```
+
+- library implementation does no longer need to use the `generic` subpackage, this simplifies reading and understanding of the code

v2/array/any.go

@@ -0,0 +1,46 @@
+// 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 (
+	G "github.com/IBM/fp-go/v2/array/generic"
+)
+
+// AnyWithIndex tests if any of the elements in the array matches the predicate.
+// The predicate receives both the index and the element.
+// Returns true if at least one element satisfies the predicate, false otherwise.
+//
+// Example:
+//
+//	hasEvenAtEvenIndex := array.AnyWithIndex(func(i, x int) bool {
+//	    return i%2 == 0 && x%2 == 0
+//	})
+//	result := hasEvenAtEvenIndex([]int{1, 3, 4, 5}) // true (4 is at index 2)
+func AnyWithIndex[A any](pred func(int, A) bool) func([]A) bool {
+	return G.AnyWithIndex[[]A](pred)
+}
+
+// Any tests if any of the elements in the array matches the predicate.
+// Returns true if at least one element satisfies the predicate, false otherwise.
+// Returns false for an empty array.
+//
+// Example:
+//
+//	hasEven := array.Any(func(x int) bool { return x%2 == 0 })
+//	result := hasEven([]int{1, 3, 4, 5}) // true
+func Any[A any](pred func(A) bool) func([]A) bool {
+	return G.Any[[]A](pred)
+}

v2/array/any_test.go

@@ -0,0 +1,30 @@
+// 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"
+
+	F "github.com/IBM/fp-go/v2/function"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAny(t *testing.T) {
+	anyBool := Any(F.Identity[bool])
+
+	assert.True(t, anyBool(From(false, true, false)))
+	assert.False(t, anyBool(From(false, false, false)))
+}

v2/array/array.go

@@ -0,0 +1,439 @@
+// 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 (
+	G "github.com/IBM/fp-go/v2/array/generic"
+	EM "github.com/IBM/fp-go/v2/endomorphism"
+	F "github.com/IBM/fp-go/v2/function"
+	"github.com/IBM/fp-go/v2/internal/array"
+	M "github.com/IBM/fp-go/v2/monoid"
+	O "github.com/IBM/fp-go/v2/option"
+	"github.com/IBM/fp-go/v2/tuple"
+)
+
+// From constructs an array from a set of variadic arguments
+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)`.
+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.
+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.
+func MonadMap[A, B any](as []A, f func(a A) B) []B {
+	return G.MonadMap[[]A, []B](as, f)
+}
+
+// MonadMapRef applies a function to a pointer to each element of an array, returning a new array with the results.
+// This is useful when you need to access elements by reference without copying.
+func MonadMapRef[A, B any](as []A, f func(a *A) B) []B {
+	count := len(as)
+	bs := make([]B, count)
+	for i := count - 1; i >= 0; i-- {
+		bs[i] = f(&as[i])
+	}
+	return bs
+}
+
+// MapWithIndex applies a function to each element and its index in an array, returning a new array with the results.
+func MapWithIndex[A, B any](f func(int, A) B) func([]A) []B {
+	return G.MapWithIndex[[]A, []B](f)
+}
+
+// Map applies a function to each element of an array, returning a new array with the results.
+// This is the curried version that returns a function.
+//
+// Example:
+//
+//	double := array.Map(func(x int) int { return x * 2 })
+//	result := double([]int{1, 2, 3}) // [2, 4, 6]
+func Map[A, B any](f func(a A) B) func([]A) []B {
+	return G.Map[[]A, []B, A, B](f)
+}
+
+// MapRef applies a function to a pointer to each element of an array, returning a new array with the results.
+// This is the curried version that returns a function.
+func MapRef[A, B any](f func(a *A) B) func([]A) []B {
+	return F.Bind2nd(MonadMapRef[A, B], f)
+}
+
+func filterRef[A any](fa []A, pred func(a *A) bool) []A {
+	var result []A
+	count := len(fa)
+	for i := 0; i < count; i++ {
+		a := fa[i]
+		if pred(&a) {
+			result = append(result, a)
+		}
+	}
+	return result
+}
+
+func filterMapRef[A, B any](fa []A, pred func(a *A) bool, f func(a *A) B) []B {
+	var result []B
+	count := len(fa)
+	for i := 0; i < count; i++ {
+		a := fa[i]
+		if pred(&a) {
+			result = append(result, f(&a))
+		}
+	}
+	return result
+}
+
+// Filter returns a new array with all elements from the original array that match a predicate
+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
+func FilterWithIndex[A any](pred func(int, A) bool) EM.Endomorphism[[]A] {
+	return G.FilterWithIndex[[]A](pred)
+}
+
+// FilterRef returns a new array with all elements from the original array that match a predicate operating on pointers.
+func FilterRef[A any](pred func(*A) bool) EM.Endomorphism[[]A] {
+	return F.Bind2nd(filterRef[A], pred)
+}
+
+// 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.
+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.
+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.
+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.
+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.
+func FilterChain[A, B any](f func(A) O.Option[[]B]) func([]A) []B {
+	return G.FilterChain[[]A](f)
+}
+
+// FilterMapRef filters an array using a predicate on pointers and maps the matching elements using a function on pointers.
+func FilterMapRef[A, B any](pred func(a *A) bool, f func(a *A) B) func([]A) []B {
+	return func(fa []A) []B {
+		return filterMapRef(fa, pred, f)
+	}
+}
+
+func reduceRef[A, B any](fa []A, f func(B, *A) B, initial B) B {
+	current := initial
+	count := len(fa)
+	for i := 0; i < count; i++ {
+		current = f(current, &fa[i])
+	}
+	return current
+}
+
+// Reduce folds an array from left to right, applying a function to accumulate a result.
+//
+// Example:
+//
+//	sum := array.Reduce(func(acc, x int) int { return acc + x }, 0)
+//	result := sum([]int{1, 2, 3, 4, 5}) // 15
+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.
+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.
+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.
+func ReduceRightWithIndex[A, B any](f func(int, A, B) B, initial B) func([]A) B {
+	return G.ReduceRightWithIndex[[]A](f, initial)
+}
+
+// ReduceRef folds an array from left to right using pointers to elements,
+// applying a function to accumulate a result.
+func ReduceRef[A, B any](f func(B, *A) B, initial B) func([]A) B {
+	return func(as []A) B {
+		return reduceRef(as, f, initial)
+	}
+}
+
+// Append adds an element to the end of an array, returning a new array.
+func Append[A any](as []A, a A) []A {
+	return G.Append(as, a)
+}
+
+// IsEmpty checks if an array has no elements.
+func IsEmpty[A any](as []A) bool {
+	return G.IsEmpty(as)
+}
+
+// IsNonEmpty checks if an array has at least one element.
+func IsNonEmpty[A any](as []A) bool {
+	return len(as) > 0
+}
+
+// Empty returns an empty array of type A.
+func Empty[A any]() []A {
+	return G.Empty[[]A]()
+}
+
+// Zero returns an empty array of type A (alias for Empty).
+func Zero[A any]() []A {
+	return Empty[A]()
+}
+
+// Of constructs a single element array
+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).
+func MonadChain[A, B any](fa []A, f func(a A) []B) []B {
+	return G.MonadChain[[]A, []B](fa, f)
+}
+
+// Chain applies a function that returns an array to each element and flattens the results.
+// This is the curried version (also known as FlatMap).
+//
+// Example:
+//
+//	duplicate := array.Chain(func(x int) []int { return []int{x, x} })
+//	result := duplicate([]int{1, 2, 3}) // [1, 1, 2, 2, 3, 3]
+func Chain[A, B any](f func(A) []B) func([]A) []B {
+	return G.Chain[[]A, []B](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.
+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.
+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.
+func Match[A, B any](onEmpty func() B, onNonEmpty func([]A) B) func([]A) B {
+	return G.Match[[]A](onEmpty, onNonEmpty)
+}
+
+// MatchLeft performs pattern matching on an array, calling onEmpty if empty or onNonEmpty with head and tail if not.
+func MatchLeft[A, B any](onEmpty func() B, onNonEmpty func(A, []A) B) func([]A) B {
+	return G.MatchLeft[[]A](onEmpty, onNonEmpty)
+}
+
+// Tail returns all elements except the first, wrapped in an Option.
+// Returns None if the array is empty.
+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.
+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.
+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.
+func Last[A any](as []A) O.Option[A] {
+	return G.Last(as)
+}
+
+// PrependAll inserts a separator before each element of an array.
+func PrependAll[A any](middle A) EM.Endomorphism[[]A] {
+	return func(as []A) []A {
+		count := len(as)
+		dst := count * 2
+		result := make([]A, dst)
+		for i := count - 1; i >= 0; i-- {
+			dst--
+			result[dst] = as[i]
+			dst--
+			result[dst] = middle
+		}
+		return result
+	}
+}
+
+// Intersperse inserts a separator between each element of an array.
+//
+// Example:
+//
+//	result := array.Intersperse(0)([]int{1, 2, 3}) // [1, 0, 2, 0, 3]
+func Intersperse[A any](middle A) EM.Endomorphism[[]A] {
+	prepend := PrependAll(middle)
+	return func(as []A) []A {
+		if IsEmpty(as) {
+			return as
+		}
+		return prepend(as)[1:]
+	}
+}
+
+// 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)))
+	}
+}
+
+// Flatten converts a nested array into a flat array by concatenating all inner arrays.
+//
+// Example:
+//
+//	result := array.Flatten([][]int{{1, 2}, {3, 4}, {5}}) // [1, 2, 3, 4, 5]
+func Flatten[A any](mma [][]A) []A {
+	return G.Flatten(mma)
+}
+
+// Slice extracts a subarray from index low (inclusive) to high (exclusive).
+func Slice[A any](low, high int) func(as []A) []A {
+	return array.Slice[[]A](low, high)
+}
+
+// Lookup returns the element at the specified index, wrapped in an Option.
+// Returns None if the index is out of bounds.
+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.
+func UpsertAt[A any](a A) EM.Endomorphism[[]A] {
+	return G.UpsertAt[[]A](a)
+}
+
+// Size returns the number of elements in an array.
+func Size[A any](as []A) int {
+	return G.Size(as)
+}
+
+// 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.
+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
+func Partition[A any](pred func(A) bool) func([]A) tuple.Tuple2[[]A, []A] {
+	return G.Partition[[]A](pred)
+}
+
+// IsNil checks if the array is set to nil
+func IsNil[A any](as []A) bool {
+	return array.IsNil(as)
+}
+
+// IsNonNil checks if the array is set to nil
+func IsNonNil[A any](as []A) bool {
+	return array.IsNonNil(as)
+}
+
+// ConstNil returns a nil array
+func ConstNil[A any]() []A {
+	return array.ConstNil[[]A]()
+}
+
+// SliceRight extracts a subarray from the specified start index to the end.
+func SliceRight[A any](start int) EM.Endomorphism[[]A] {
+	return G.SliceRight[[]A](start)
+}
+
+// Copy creates a shallow copy of the array
+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
+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.
+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.
+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.
+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).
+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.
+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)
+}
+
+// Flap applies a value to an array of functions, producing an array of results.
+// This is the curried version.
+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)
+}
+
+// Prepend adds an element to the beginning of an array, returning a new array.
+func Prepend[A any](head A) EM.Endomorphism[[]A] {
+	return G.Prepend[EM.Endomorphism[[]A]](head)
+}

v2/array/array_extended_test.go

@@ -0,0 +1,323 @@
+// 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 (
+	"fmt"
+	"testing"
+
+	N "github.com/IBM/fp-go/v2/number"
+	O "github.com/IBM/fp-go/v2/option"
+	S "github.com/IBM/fp-go/v2/string"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestReplicate(t *testing.T) {
+	result := Replicate(3, "a")
+	assert.Equal(t, []string{"a", "a", "a"}, result)
+
+	empty := Replicate(0, 42)
+	assert.Equal(t, []int{}, empty)
+}
+
+func TestMonadMap(t *testing.T) {
+	src := []int{1, 2, 3}
+	result := MonadMap(src, func(x int) int { return x * 2 })
+	assert.Equal(t, []int{2, 4, 6}, result)
+}
+
+func TestMonadMapRef(t *testing.T) {
+	src := []int{1, 2, 3}
+	result := MonadMapRef(src, func(x *int) int { return *x * 2 })
+	assert.Equal(t, []int{2, 4, 6}, result)
+}
+
+func TestMapWithIndex(t *testing.T) {
+	src := []string{"a", "b", "c"}
+	mapper := MapWithIndex(func(i int, s string) string {
+		return fmt.Sprintf("%d:%s", i, s)
+	})
+	result := mapper(src)
+	assert.Equal(t, []string{"0:a", "1:b", "2:c"}, result)
+}
+
+func TestMapRef(t *testing.T) {
+	src := []int{1, 2, 3}
+	mapper := MapRef(func(x *int) int { return *x * 2 })
+	result := mapper(src)
+	assert.Equal(t, []int{2, 4, 6}, result)
+}
+
+func TestFilterWithIndex(t *testing.T) {
+	src := []int{1, 2, 3, 4, 5}
+	filter := FilterWithIndex(func(i, x int) bool {
+		return i%2 == 0 && x > 2
+	})
+	result := filter(src)
+	assert.Equal(t, []int{3, 5}, result)
+}
+
+func TestFilterRef(t *testing.T) {
+	src := []int{1, 2, 3, 4, 5}
+	filter := FilterRef(func(x *int) bool { return *x > 2 })
+	result := filter(src)
+	assert.Equal(t, []int{3, 4, 5}, result)
+}
+
+func TestMonadFilterMap(t *testing.T) {
+	src := []int{1, 2, 3, 4}
+	result := MonadFilterMap(src, func(x int) O.Option[string] {
+		if x%2 == 0 {
+			return O.Some(fmt.Sprintf("even:%d", x))
+		}
+		return O.None[string]()
+	})
+	assert.Equal(t, []string{"even:2", "even:4"}, result)
+}
+
+func TestMonadFilterMapWithIndex(t *testing.T) {
+	src := []int{1, 2, 3, 4}
+	result := MonadFilterMapWithIndex(src, func(i, x int) O.Option[string] {
+		if i%2 == 0 {
+			return O.Some(fmt.Sprintf("%d:%d", i, x))
+		}
+		return O.None[string]()
+	})
+	assert.Equal(t, []string{"0:1", "2:3"}, result)
+}
+
+func TestFilterMapWithIndex(t *testing.T) {
+	src := []int{1, 2, 3, 4}
+	filter := FilterMapWithIndex(func(i, x int) O.Option[string] {
+		if i%2 == 0 {
+			return O.Some(fmt.Sprintf("%d:%d", i, x))
+		}
+		return O.None[string]()
+	})
+	result := filter(src)
+	assert.Equal(t, []string{"0:1", "2:3"}, result)
+}
+
+func TestFilterMapRef(t *testing.T) {
+	src := []int{1, 2, 3, 4, 5}
+	filter := FilterMapRef(
+		func(x *int) bool { return *x > 2 },
+		func(x *int) string { return fmt.Sprintf("val:%d", *x) },
+	)
+	result := filter(src)
+	assert.Equal(t, []string{"val:3", "val:4", "val:5"}, result)
+}
+
+func TestReduceWithIndex(t *testing.T) {
+	src := []int{1, 2, 3}
+	reducer := ReduceWithIndex(func(i, acc, x int) int {
+		return acc + i + x
+	}, 0)
+	result := reducer(src)
+	assert.Equal(t, 9, result) // 0 + (0+1) + (1+2) + (2+3) = 9
+}
+
+func TestReduceRightWithIndex(t *testing.T) {
+	src := []string{"a", "b", "c"}
+	reducer := ReduceRightWithIndex(func(i int, x, acc string) string {
+		return fmt.Sprintf("%s%d:%s", acc, i, x)
+	}, "")
+	result := reducer(src)
+	assert.Equal(t, "2:c1:b0:a", result)
+}
+
+func TestReduceRef(t *testing.T) {
+	src := []int{1, 2, 3}
+	reducer := ReduceRef(func(acc int, x *int) int {
+		return acc + *x
+	}, 0)
+	result := reducer(src)
+	assert.Equal(t, 6, result)
+}
+
+func TestZero(t *testing.T) {
+	result := Zero[int]()
+	assert.Equal(t, []int{}, result)
+	assert.True(t, IsEmpty(result))
+}
+
+func TestMonadChain(t *testing.T) {
+	src := []int{1, 2, 3}
+	result := MonadChain(src, func(x int) []int {
+		return []int{x, x * 10}
+	})
+	assert.Equal(t, []int{1, 10, 2, 20, 3, 30}, result)
+}
+
+func TestChain(t *testing.T) {
+	src := []int{1, 2, 3}
+	chain := Chain(func(x int) []int {
+		return []int{x, x * 10}
+	})
+	result := chain(src)
+	assert.Equal(t, []int{1, 10, 2, 20, 3, 30}, result)
+}
+
+func TestMonadAp(t *testing.T) {
+	fns := []func(int) int{
+		func(x int) int { return x * 2 },
+		func(x int) int { return x + 10 },
+	}
+	values := []int{1, 2}
+	result := MonadAp(fns, values)
+	assert.Equal(t, []int{2, 4, 11, 12}, result)
+}
+
+func TestMatchLeft(t *testing.T) {
+	matcher := MatchLeft(
+		func() string { return "empty" },
+		func(head int, tail []int) string {
+			return fmt.Sprintf("head:%d,tail:%v", head, tail)
+		},
+	)
+
+	assert.Equal(t, "empty", matcher([]int{}))
+	assert.Equal(t, "head:1,tail:[2 3]", matcher([]int{1, 2, 3}))
+}
+
+func TestTail(t *testing.T) {
+	assert.Equal(t, O.None[[]int](), Tail([]int{}))
+	assert.Equal(t, O.Some([]int{2, 3}), Tail([]int{1, 2, 3}))
+	assert.Equal(t, O.Some([]int{}), Tail([]int{1}))
+}
+
+func TestFirst(t *testing.T) {
+	assert.Equal(t, O.None[int](), First([]int{}))
+	assert.Equal(t, O.Some(1), First([]int{1, 2, 3}))
+}
+
+func TestLast(t *testing.T) {
+	assert.Equal(t, O.None[int](), Last([]int{}))
+	assert.Equal(t, O.Some(3), Last([]int{1, 2, 3}))
+	assert.Equal(t, O.Some(1), Last([]int{1}))
+}
+
+func TestUpsertAt(t *testing.T) {
+	src := []int{1, 2, 3}
+	upsert := UpsertAt(99)
+
+	result1 := upsert(src)
+	assert.Equal(t, []int{1, 2, 3, 99}, result1)
+}
+
+func TestSize(t *testing.T) {
+	assert.Equal(t, 0, Size([]int{}))
+	assert.Equal(t, 3, Size([]int{1, 2, 3}))
+}
+
+func TestMonadPartition(t *testing.T) {
+	src := []int{1, 2, 3, 4, 5}
+	result := MonadPartition(src, func(x int) bool { return x > 2 })
+	assert.Equal(t, []int{1, 2}, result.F1)
+	assert.Equal(t, []int{3, 4, 5}, result.F2)
+}
+
+func TestIsNil(t *testing.T) {
+	var nilSlice []int
+	assert.True(t, IsNil(nilSlice))
+	assert.False(t, IsNil([]int{}))
+	assert.False(t, IsNil([]int{1}))
+}
+
+func TestIsNonNil(t *testing.T) {
+	var nilSlice []int
+	assert.False(t, IsNonNil(nilSlice))
+	assert.True(t, IsNonNil([]int{}))
+	assert.True(t, IsNonNil([]int{1}))
+}
+
+func TestConstNil(t *testing.T) {
+	result := ConstNil[int]()
+	assert.True(t, IsNil(result))
+}
+
+func TestSliceRight(t *testing.T) {
+	src := []int{1, 2, 3, 4, 5}
+	slicer := SliceRight[int](2)
+	result := slicer(src)
+	assert.Equal(t, []int{3, 4, 5}, result)
+}
+
+func TestCopy(t *testing.T) {
+	src := []int{1, 2, 3}
+	copied := Copy(src)
+	assert.Equal(t, src, copied)
+	// Verify it's a different slice
+	copied[0] = 99
+	assert.Equal(t, 1, src[0])
+	assert.Equal(t, 99, copied[0])
+}
+
+func TestClone(t *testing.T) {
+	src := []int{1, 2, 3}
+	cloner := Clone(func(x int) int { return x * 2 })
+	result := cloner(src)
+	assert.Equal(t, []int{2, 4, 6}, result)
+}
+
+func TestFoldMapWithIndex(t *testing.T) {
+	src := []string{"a", "b", "c"}
+	folder := FoldMapWithIndex[string](S.Monoid)(func(i int, s string) string {
+		return fmt.Sprintf("%d:%s", i, s)
+	})
+	result := folder(src)
+	assert.Equal(t, "0:a1:b2:c", result)
+}
+
+func TestFold(t *testing.T) {
+	src := []int{1, 2, 3, 4, 5}
+	folder := Fold(N.MonoidSum[int]())
+	result := folder(src)
+	assert.Equal(t, 15, result)
+}
+
+func TestPush(t *testing.T) {
+	src := []int{1, 2, 3}
+	pusher := Push(4)
+	result := pusher(src)
+	assert.Equal(t, []int{1, 2, 3, 4}, result)
+}
+
+func TestMonadFlap(t *testing.T) {
+	fns := []func(int) string{
+		func(x int) string { return fmt.Sprintf("a%d", x) },
+		func(x int) string { return fmt.Sprintf("b%d", x) },
+	}
+	result := MonadFlap(fns, 5)
+	assert.Equal(t, []string{"a5", "b5"}, result)
+}
+
+func TestFlap(t *testing.T) {
+	fns := []func(int) string{
+		func(x int) string { return fmt.Sprintf("a%d", x) },
+		func(x int) string { return fmt.Sprintf("b%d", x) },
+	}
+	flapper := Flap[string](5)
+	result := flapper(fns)
+	assert.Equal(t, []string{"a5", "b5"}, result)
+}
+
+func TestPrepend(t *testing.T) {
+	src := []int{2, 3, 4}
+	prepender := Prepend(1)
+	result := prepender(src)
+	assert.Equal(t, []int{1, 2, 3, 4}, result)
+}

v2/array/array_test.go

@@ -0,0 +1,216 @@
+// 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 (
+	"fmt"
+	"strings"
+	"testing"
+
+	F "github.com/IBM/fp-go/v2/function"
+	"github.com/IBM/fp-go/v2/internal/utils"
+	O "github.com/IBM/fp-go/v2/option"
+	S "github.com/IBM/fp-go/v2/string"
+	T "github.com/IBM/fp-go/v2/tuple"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMap1(t *testing.T) {
+
+	src := []string{"a", "b", "c"}
+
+	up := Map(strings.ToUpper)(src)
+
+	var up1 = []string{}
+	for _, s := range src {
+		up1 = append(up1, strings.ToUpper(s))
+	}
+
+	var up2 = []string{}
+	for i := range src {
+		up2 = append(up2, strings.ToUpper(src[i]))
+	}
+
+	assert.Equal(t, up, up1)
+	assert.Equal(t, up, up2)
+}
+
+func TestMap(t *testing.T) {
+
+	mapper := Map(utils.Upper)
+
+	src := []string{"a", "b", "c"}
+
+	dst := mapper(src)
+
+	assert.Equal(t, dst, []string{"A", "B", "C"})
+}
+
+func TestReduceRight(t *testing.T) {
+	values := From("a", "b", "c")
+	f := func(a, acc string) string {
+		return fmt.Sprintf("%s%s", acc, a)
+	}
+	b := ""
+
+	assert.Equal(t, "cba", ReduceRight(f, b)(values))
+	assert.Equal(t, "", ReduceRight(f, b)(Empty[string]()))
+}
+
+func TestReduce(t *testing.T) {
+
+	values := MakeBy(101, F.Identity[int])
+
+	sum := func(val int, current int) int {
+		return val + current
+	}
+	reducer := Reduce(sum, 0)
+
+	result := reducer(values)
+	assert.Equal(t, result, 5050)
+
+}
+
+func TestEmpty(t *testing.T) {
+	assert.True(t, IsNonEmpty(MakeBy(101, F.Identity[int])))
+	assert.True(t, IsEmpty([]int{}))
+}
+
+func TestAp(t *testing.T) {
+	assert.Equal(t,
+		[]int{2, 4, 6, 3, 6, 9},
+		F.Pipe1(
+			[]func(int) int{
+				utils.Double,
+				utils.Triple,
+			},
+			Ap[int, int]([]int{1, 2, 3}),
+		),
+	)
+}
+
+func TestIntercalate(t *testing.T) {
+	is := Intercalate(S.Monoid)("-")
+
+	assert.Equal(t, "", is(Empty[string]()))
+	assert.Equal(t, "a", is([]string{"a"}))
+	assert.Equal(t, "a-b-c", is([]string{"a", "b", "c"}))
+	assert.Equal(t, "a--c", is([]string{"a", "", "c"}))
+	assert.Equal(t, "a-b", is([]string{"a", "b"}))
+	assert.Equal(t, "a-b-c-d", is([]string{"a", "b", "c", "d"}))
+}
+
+func TestIntersperse(t *testing.T) {
+	// Test with empty array
+	assert.Equal(t, []int{}, Intersperse(0)([]int{}))
+
+	// Test with single element
+	assert.Equal(t, []int{1}, Intersperse(0)([]int{1}))
+
+	// Test with multiple elements
+	assert.Equal(t, []int{1, 0, 2, 0, 3}, Intersperse(0)([]int{1, 2, 3}))
+}
+
+func TestPrependAll(t *testing.T) {
+	empty := Empty[int]()
+	prep := PrependAll(0)
+	assert.Equal(t, empty, prep(empty))
+	assert.Equal(t, []int{0, 1, 0, 2, 0, 3}, prep([]int{1, 2, 3}))
+	assert.Equal(t, []int{0, 1}, prep([]int{1}))
+	assert.Equal(t, []int{0, 1, 0, 2, 0, 3, 0, 4}, prep([]int{1, 2, 3, 4}))
+}
+
+func TestFlatten(t *testing.T) {
+	assert.Equal(t, []int{1, 2, 3}, Flatten([][]int{{1}, {2}, {3}}))
+}
+
+func TestLookup(t *testing.T) {
+	data := []int{0, 1, 2}
+	none := O.None[int]()
+
+	assert.Equal(t, none, Lookup[int](-1)(data))
+	assert.Equal(t, none, Lookup[int](10)(data))
+	assert.Equal(t, O.Some(1), Lookup[int](1)(data))
+}
+
+func TestSlice(t *testing.T) {
+	data := []int{0, 1, 2, 3}
+
+	assert.Equal(t, []int{1, 2}, Slice[int](1, 3)(data))
+}
+
+func TestFrom(t *testing.T) {
+	assert.Equal(t, []int{1, 2, 3}, From(1, 2, 3))
+}
+
+func TestPartition(t *testing.T) {
+
+	pred := func(n int) bool {
+		return n > 2
+	}
+
+	assert.Equal(t, T.MakeTuple2(Empty[int](), Empty[int]()), Partition(pred)(Empty[int]()))
+	assert.Equal(t, T.MakeTuple2(From(1), From(3)), Partition(pred)(From(1, 3)))
+}
+
+func TestFilterChain(t *testing.T) {
+	src := From(1, 2, 3)
+
+	f := func(i int) O.Option[[]string] {
+		if i%2 != 0 {
+			return O.Of(From(fmt.Sprintf("a%d", i), fmt.Sprintf("b%d", i)))
+		}
+		return O.None[[]string]()
+	}
+
+	res := FilterChain(f)(src)
+
+	assert.Equal(t, From("a1", "b1", "a3", "b3"), res)
+}
+
+func TestFilterMap(t *testing.T) {
+	src := From(1, 2, 3)
+
+	f := func(i int) O.Option[string] {
+		if i%2 != 0 {
+			return O.Of(fmt.Sprintf("a%d", i))
+		}
+		return O.None[string]()
+	}
+
+	res := FilterMap(f)(src)
+
+	assert.Equal(t, From("a1", "a3"), res)
+}
+
+func TestFoldMap(t *testing.T) {
+	src := From("a", "b", "c")
+
+	fold := FoldMap[string](S.Monoid)(strings.ToUpper)
+
+	assert.Equal(t, "ABC", fold(src))
+}
+
+func ExampleFoldMap() {
+	src := From("a", "b", "c")
+
+	fold := FoldMap[string](S.Monoid)(strings.ToUpper)
+
+	fmt.Println(fold(src))
+
+	// Output: ABC
+
+}

v2/array/bind.go

@@ -0,0 +1,136 @@
+// 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 (
+	G "github.com/IBM/fp-go/v2/array/generic"
+)
+
+// Do creates an empty context of type S to be used with the Bind operation.
+// This is the starting point for monadic do-notation style computations.
+//
+// Example:
+//
+//	type State struct {
+//	    X int
+//	    Y int
+//	}
+//	result := array.Do(State{})
+func Do[S any](
+	empty S,
+) []S {
+	return G.Do[[]S, S](empty)
+}
+
+// Bind attaches the result of a computation to a context S1 to produce a context S2.
+// The setter function defines how to update the context with the computation result.
+// This enables monadic composition where each step can produce multiple results.
+//
+// Example:
+//
+//	result := F.Pipe2(
+//	    array.Do(struct{ X, Y int }{}),
+//	    array.Bind(
+//	        func(x int) func(s struct{}) struct{ X int } {
+//	            return func(s struct{}) struct{ X int } { return struct{ X int }{x} }
+//	        },
+//	        func(s struct{}) []int { return []int{1, 2} },
+//	    ),
+//	)
+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)
+}
+
+// Let attaches the result of a pure computation to a context S1 to produce a context S2.
+// Unlike Bind, the computation function returns a plain value T rather than []T.
+//
+// Example:
+//
+//	result := array.Let(
+//	    func(sum int) func(s struct{ X int }) struct{ X, Sum int } {
+//	        return func(s struct{ X int }) struct{ X, Sum int } {
+//	            return struct{ X, Sum int }{s.X, sum}
+//	        }
+//	    },
+//	    func(s struct{ X int }) int { return s.X * 2 },
+//	)
+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)
+}
+
+// LetTo attaches a constant value to a context S1 to produce a context S2.
+// This is useful for adding constant values to the context.
+//
+// Example:
+//
+//	result := array.LetTo(
+//	    func(name string) func(s struct{ X int }) struct{ X int; Name string } {
+//	        return func(s struct{ X int }) struct{ X int; Name string } {
+//	            return struct{ X int; Name string }{s.X, name}
+//	        }
+//	    },
+//	    "constant",
+//	)
+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)
+}
+
+// BindTo initializes a new state S1 from a value T.
+// This is typically the first operation after Do to start building the context.
+//
+// Example:
+//
+//	result := F.Pipe2(
+//	    []int{1, 2, 3},
+//	    array.BindTo(func(x int) struct{ X int } {
+//	        return struct{ X int }{x}
+//	    }),
+//	)
+func BindTo[S1, T any](
+	setter func(T) S1,
+) func([]T) []S1 {
+	return G.BindTo[[]S1, []T, S1, 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 semantics).
+// This produces all combinations of context values and array values.
+//
+// Example:
+//
+//	result := array.ApS(
+//	    func(y int) func(s struct{ X int }) struct{ X, Y int } {
+//	        return func(s struct{ X int }) struct{ X, Y int } {
+//	            return struct{ X, Y int }{s.X, y}
+//	        }
+//	    },
+//	    []int{10, 20},
+//	)
+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)
+}

v2/array/bind_extended_test.go

@@ -0,0 +1,78 @@
+// 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"
+
+	F "github.com/IBM/fp-go/v2/function"
+	"github.com/stretchr/testify/assert"
+)
+
+type TestState1 struct {
+	X int
+}
+
+type TestState2 struct {
+	X int
+	Y int
+}
+
+func TestLet(t *testing.T) {
+	result := F.Pipe2(
+		Do(TestState1{}),
+		Let(
+			func(y int) func(s TestState1) TestState2 {
+				return func(s TestState1) TestState2 {
+					return TestState2{X: s.X, Y: y}
+				}
+			},
+			func(s TestState1) int { return s.X * 2 },
+		),
+		Map(func(s TestState2) int { return s.X + s.Y }),
+	)
+
+	assert.Equal(t, []int{0}, result)
+}
+
+func TestLetTo(t *testing.T) {
+	result := F.Pipe2(
+		Do(TestState1{X: 5}),
+		LetTo(
+			func(y int) func(s TestState1) TestState2 {
+				return func(s TestState1) TestState2 {
+					return TestState2{X: s.X, Y: y}
+				}
+			},
+			42,
+		),
+		Map(func(s TestState2) int { return s.X + s.Y }),
+	)
+
+	assert.Equal(t, []int{47}, result)
+}
+
+func TestBindTo(t *testing.T) {
+	result := F.Pipe1(
+		[]int{1, 2, 3},
+		BindTo(func(x int) TestState1 {
+			return TestState1{X: x}
+		}),
+	)
+
+	expected := []TestState1{{X: 1}, {X: 2}, {X: 3}}
+	assert.Equal(t, expected, result)
+}

v2/array/bind_test.go

@@ -0,0 +1,56 @@
+// 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"
+
+	F "github.com/IBM/fp-go/v2/function"
+	"github.com/IBM/fp-go/v2/internal/utils"
+	"github.com/stretchr/testify/assert"
+)
+
+func getLastName(s utils.Initial) []string {
+	return Of("Doe")
+}
+
+func getGivenName(s utils.WithLastName) []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, Of("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, Of("John Doe"))
+}

v2/array/doc.go

@@ -0,0 +1,251 @@
+// 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 provides functional programming utilities for working with Go slices.
+//
+// This package treats Go slices as immutable arrays and provides a rich set of operations
+// for transforming, filtering, folding, and combining arrays in a functional style.
+// All operations return new arrays rather than modifying existing ones.
+//
+// # Core Concepts
+//
+// The array package implements several functional programming abstractions:
+//   - Functor: Transform array elements with Map
+//   - Applicative: Apply functions in arrays to values in arrays
+//   - Monad: Chain operations that produce arrays with Chain/FlatMap
+//   - Foldable: Reduce arrays to single values with Reduce/Fold
+//   - Traversable: Transform arrays while preserving structure
+//
+// # Basic Operations
+//
+//	// Creating arrays
+//	arr := array.From(1, 2, 3, 4, 5)
+//	repeated := array.Replicate(3, "hello")
+//	generated := array.MakeBy(5, func(i int) int { return i * 2 })
+//
+//	// Transforming arrays
+//	doubled := array.Map(func(x int) int { return x * 2 })(arr)
+//	filtered := array.Filter(func(x int) bool { return x > 2 })(arr)
+//
+//	// Combining arrays
+//	combined := array.Flatten([][]int{{1, 2}, {3, 4}})
+//	zipped := array.Zip([]string{"a", "b"})([]int{1, 2})
+//
+// # Mapping and Filtering
+//
+// Transform array elements with Map, or filter elements with Filter:
+//
+//	numbers := []int{1, 2, 3, 4, 5}
+//
+//	// Map transforms each element
+//	doubled := array.Map(func(x int) int { return x * 2 })(numbers)
+//	// Result: [2, 4, 6, 8, 10]
+//
+//	// Filter keeps elements matching a predicate
+//	evens := array.Filter(func(x int) bool { return x%2 == 0 })(numbers)
+//	// Result: [2, 4]
+//
+//	// FilterMap combines both operations
+//	import "github.com/IBM/fp-go/v2/option"
+//	result := array.FilterMap(func(x int) option.Option[int] {
+//	    if x%2 == 0 {
+//	        return option.Some(x * 2)
+//	    }
+//	    return option.None[int]()
+//	})(numbers)
+//	// Result: [4, 8]
+//
+// # Folding and Reducing
+//
+// Reduce arrays to single values:
+//
+//	numbers := []int{1, 2, 3, 4, 5}
+//
+//	// Sum all elements
+//	sum := array.Reduce(func(acc, x int) int { return acc + x }, 0)(numbers)
+//	// Result: 15
+//
+//	// Using a Monoid
+//	import "github.com/IBM/fp-go/v2/monoid"
+//	sum := array.Fold(monoid.MonoidSum[int]())(numbers)
+//	// Result: 15
+//
+// # Chaining Operations
+//
+// Chain operations that produce arrays (also known as FlatMap):
+//
+//	numbers := []int{1, 2, 3}
+//	result := array.Chain(func(x int) []int {
+//	    return []int{x, x * 10}
+//	})(numbers)
+//	// Result: [1, 10, 2, 20, 3, 30]
+//
+// # Finding Elements
+//
+// Search for elements matching predicates:
+//
+//	numbers := []int{1, 2, 3, 4, 5}
+//
+//	// Find first element > 3
+//	first := array.FindFirst(func(x int) bool { return x > 3 })(numbers)
+//	// Result: Some(4)
+//
+//	// Find last element > 3
+//	last := array.FindLast(func(x int) bool { return x > 3 })(numbers)
+//	// Result: Some(5)
+//
+//	// Get head and tail
+//	head := array.Head(numbers) // Some(1)
+//	tail := array.Tail(numbers) // Some([2, 3, 4, 5])
+//
+// # Sorting
+//
+// Sort arrays using Ord instances:
+//
+//	import "github.com/IBM/fp-go/v2/ord"
+//
+//	numbers := []int{3, 1, 4, 1, 5}
+//	sorted := array.Sort(ord.FromStrictCompare[int]())(numbers)
+//	// Result: [1, 1, 3, 4, 5]
+//
+//	// Sort by extracted key
+//	type Person struct { Name string; Age int }
+//	people := []Person{{"Alice", 30}, {"Bob", 25}}
+//	byAge := array.SortByKey(ord.FromStrictCompare[int](), func(p Person) int {
+//	    return p.Age
+//	})(people)
+//
+// # Uniqueness
+//
+// Remove duplicate elements:
+//
+//	numbers := []int{1, 2, 2, 3, 3, 3}
+//	unique := array.StrictUniq(numbers)
+//	// Result: [1, 2, 3]
+//
+//	// Unique by key
+//	type Person struct { Name string; Age int }
+//	people := []Person{{"Alice", 30}, {"Bob", 25}, {"Alice", 35}}
+//	uniqueByName := array.Uniq(func(p Person) string { return p.Name })(people)
+//	// Result: [{"Alice", 30}, {"Bob", 25}]
+//
+// # Zipping
+//
+// Combine multiple arrays:
+//
+//	names := []string{"Alice", "Bob", "Charlie"}
+//	ages := []int{30, 25, 35}
+//
+//	// Zip into tuples
+//	pairs := array.Zip(ages)(names)
+//	// Result: [(Alice, 30), (Bob, 25), (Charlie, 35)]
+//
+//	// Zip with custom function
+//	result := array.ZipWith(names, ages, func(name string, age int) string {
+//	    return fmt.Sprintf("%s is %d", name, age)
+//	})
+//
+// # Monadic Do Notation
+//
+// Build complex array computations using do-notation style:
+//
+//	result := array.Do(
+//	    struct{ X, Y int }{},
+//	)(
+//	    array.Bind(
+//	        func(x int) func(s struct{}) struct{ X int } {
+//	            return func(s struct{}) struct{ X int } { return struct{ X int }{x} }
+//	        },
+//	        func(s struct{}) []int { return []int{1, 2, 3} },
+//	    ),
+//	    array.Bind(
+//	        func(y int) func(s struct{ X int }) struct{ X, Y int } {
+//	            return func(s struct{ X int }) struct{ X, Y int } {
+//	                return struct{ X, Y int }{s.X, y}
+//	            }
+//	        },
+//	        func(s struct{ X int }) []int { return []int{4, 5} },
+//	    ),
+//	)
+//	// Produces all combinations: [{1,4}, {1,5}, {2,4}, {2,5}, {3,4}, {3,5}]
+//
+// # Sequence and Traverse
+//
+// Transform arrays of effects into effects of arrays:
+//
+//	import "github.com/IBM/fp-go/v2/option"
+//
+//	// Sequence: []Option[A] -> Option[[]A]
+//	opts := []option.Option[int]{
+//	    option.Some(1),
+//	    option.Some(2),
+//	    option.Some(3),
+//	}
+//	result := array.ArrayOption[int]()(opts)
+//	// Result: Some([1, 2, 3])
+//
+//	// If any is None, result is None
+//	opts2 := []option.Option[int]{
+//	    option.Some(1),
+//	    option.None[int](),
+//	    option.Some(3),
+//	}
+//	result2 := array.ArrayOption[int]()(opts2)
+//	// Result: None
+//
+// # Equality and Comparison
+//
+// Compare arrays for equality:
+//
+//	import "github.com/IBM/fp-go/v2/eq"
+//
+//	eq := array.Eq(eq.FromStrictEquals[int]())
+//	equal := eq.Equals([]int{1, 2, 3}, []int{1, 2, 3})
+//	// Result: true
+//
+// # Monoid Operations
+//
+// Combine arrays using monoid operations:
+//
+//	import "github.com/IBM/fp-go/v2/monoid"
+//
+//	// Concatenate arrays
+//	m := array.Monoid[int]()
+//	result := m.Concat([]int{1, 2}, []int{3, 4})
+//	// Result: [1, 2, 3, 4]
+//
+//	// Concatenate multiple arrays efficiently
+//	result := array.ArrayConcatAll(
+//	    []int{1, 2},
+//	    []int{3, 4},
+//	    []int{5, 6},
+//	)
+//	// Result: [1, 2, 3, 4, 5, 6]
+//
+// # Performance Considerations
+//
+// Most operations create new arrays rather than modifying existing ones. For performance-critical
+// code, consider:
+//   - Using Copy for shallow copies when needed
+//   - Using Clone with a custom cloning function for deep copies
+//   - Batching operations to minimize intermediate allocations
+//   - Using ArrayConcatAll for efficient concatenation of multiple arrays
+//
+// # Subpackages
+//
+//   - array/generic: Generic implementations for custom array-like types
+//   - array/nonempty: Operations for non-empty arrays with compile-time guarantees
+//   - array/testing: Testing utilities for array laws and properties
+package array

v2/array/eq.go

@@ -0,0 +1,51 @@
+// 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 (
+	E "github.com/IBM/fp-go/v2/eq"
+)
+
+func equals[T any](left []T, right []T, eq func(T, T) bool) bool {
+	if len(left) != len(right) {
+		return false
+	}
+	for i, v1 := range left {
+		v2 := right[i]
+		if !eq(v1, v2) {
+			return false
+		}
+	}
+	return true
+}
+
+// Eq creates an equality checker for arrays given an equality checker for elements.
+// Two arrays are considered equal if they have the same length and all corresponding
+// elements are equal according to the provided Eq instance.
+//
+// Example:
+//
+//	import "github.com/IBM/fp-go/v2/eq"
+//
+//	intArrayEq := array.Eq(eq.FromStrictEquals[int]())
+//	result := intArrayEq.Equals([]int{1, 2, 3}, []int{1, 2, 3}) // true
+//	result2 := intArrayEq.Equals([]int{1, 2, 3}, []int{1, 2, 4}) // false
+func Eq[T any](e E.Eq[T]) E.Eq[[]T] {
+	eq := e.Equals
+	return E.FromEquals(func(left, right []T) bool {
+		return equals(left, right, eq)
+	})
+}

v2/array/eq_test.go

@@ -0,0 +1,44 @@
+// 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"
+
+	E "github.com/IBM/fp-go/v2/eq"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestEq(t *testing.T) {
+	intEq := Eq(E.FromStrictEquals[int]())
+
+	// Test equal arrays
+	assert.True(t, intEq.Equals([]int{1, 2, 3}, []int{1, 2, 3}))
+
+	// Test different lengths
+	assert.False(t, intEq.Equals([]int{1, 2, 3}, []int{1, 2}))
+
+	// Test different values
+	assert.False(t, intEq.Equals([]int{1, 2, 3}, []int{1, 2, 4}))
+
+	// Test empty arrays
+	assert.True(t, intEq.Equals([]int{}, []int{}))
+
+	// Test string arrays
+	stringEq := Eq(E.FromStrictEquals[string]())
+	assert.True(t, stringEq.Equals([]string{"a", "b"}, []string{"a", "b"}))
+	assert.False(t, stringEq.Equals([]string{"a", "b"}, []string{"a", "c"}))
+}

v2/array/example_any_test.go

@@ -0,0 +1,77 @@
+// 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 (
+	"fmt"
+
+	F "github.com/IBM/fp-go/v2/function"
+	O "github.com/IBM/fp-go/v2/option"
+)
+
+func Example_any() {
+
+	pred := func(val int) bool {
+		return val&2 == 0
+	}
+
+	data1 := From(1, 2, 3)
+
+	fmt.Println(Any(pred)(data1))
+
+	// Output:
+	// true
+}
+
+func Example_any_filter() {
+
+	pred := func(val int) bool {
+		return val&2 == 0
+	}
+
+	data1 := From(1, 2, 3)
+
+	// Any tests if any of the entries in the array matches the condition
+	Any := F.Flow2(
+		Filter(pred),
+		IsNonEmpty[int],
+	)
+
+	fmt.Println(Any(data1))
+
+	// Output:
+	// true
+}
+
+func Example_any_find() {
+
+	pred := func(val int) bool {
+		return val&2 == 0
+	}
+
+	data1 := From(1, 2, 3)
+
+	// Any tests if any of the entries in the array matches the condition
+	Any := F.Flow2(
+		FindFirst(pred),
+		O.IsSome[int],
+	)
+
+	fmt.Println(Any(data1))
+
+	// Output:
+	// true
+}

v2/array/example_find_test.go

@@ -0,0 +1,55 @@
+// 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 (
+	"fmt"
+
+	F "github.com/IBM/fp-go/v2/function"
+)
+
+func Example_find() {
+
+	pred := func(val int) bool {
+		return val&2 == 0
+	}
+
+	data1 := From(1, 2, 3)
+
+	fmt.Println(FindFirst(pred)(data1))
+
+	// Output:
+	// Some[int](1)
+}
+
+func Example_find_filter() {
+
+	pred := func(val int) bool {
+		return val&2 == 0
+	}
+
+	data1 := From(1, 2, 3)
+
+	Find := F.Flow2(
+		Filter(pred),
+		Head[int],
+	)
+
+	fmt.Println(Find(data1))
+
+	// Output:
+	// Some[int](1)
+}

v2/array/examples_basic_test.go

@@ -0,0 +1,59 @@
+// 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 (
+	"fmt"
+
+	F "github.com/IBM/fp-go/v2/function"
+	O "github.com/IBM/fp-go/v2/option"
+)
+
+// Example_basic adapts examples from [https://github.com/inato/fp-ts-cheatsheet#basic-manipulation]
+func Example_basic() {
+
+	someArray := From(0, 1, 2, 3, 4, 5, 6, 7, 8, 9) // []int
+
+	isEven := func(num int) bool {
+		return num%2 == 0
+	}
+
+	square := func(num int) int {
+		return num * num
+	}
+
+	// filter and map
+	result := F.Pipe2(
+		someArray,
+		Filter(isEven),
+		Map(square),
+	) // [0 4 16 36 64]
+
+	// or in one go with filterMap
+	resultFilterMap := F.Pipe1(
+		someArray,
+		FilterMap(
+			F.Flow2(O.FromPredicate(isEven), O.Map(square)),
+		),
+	)
+
+	fmt.Println(result)
+	fmt.Println(resultFilterMap)
+
+	// Output:
+	// [0 4 16 36 64]
+	// [0 4 16 36 64]
+}

v2/array/examples_sort_test.go

@@ -0,0 +1,92 @@
+// 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 (
+	"fmt"
+
+	F "github.com/IBM/fp-go/v2/function"
+	I "github.com/IBM/fp-go/v2/number/integer"
+	O "github.com/IBM/fp-go/v2/option"
+	"github.com/IBM/fp-go/v2/ord"
+	S "github.com/IBM/fp-go/v2/string"
+)
+
+type user struct {
+	name string
+	age  O.Option[int]
+}
+
+func (user user) GetName() string {
+	return user.name
+}
+
+func (user user) GetAge() O.Option[int] {
+	return user.age
+}
+
+// Example_sort adapts examples from [https://github.com/inato/fp-ts-cheatsheet#sort-elements-with-ord]
+func Example_sort() {
+
+	strings := From("zyx", "abc", "klm")
+
+	sortedStrings := F.Pipe1(
+		strings,
+		Sort(S.Ord),
+	) // => ['abc', 'klm', 'zyx']
+
+	// reverse sort
+	reverseSortedStrings := F.Pipe1(
+		strings,
+		Sort(ord.Reverse(S.Ord)),
+	) // => ['zyx', 'klm', 'abc']
+
+	// sort Option
+	optionalNumbers := From(O.Some(1337), O.None[int](), O.Some(42))
+
+	sortedNums := F.Pipe1(
+		optionalNumbers,
+		Sort(O.Ord(I.Ord)),
+	)
+
+	// complex object with different rules
+	byName := F.Pipe1(
+		S.Ord,
+		ord.Contramap(user.GetName),
+	) // ord.Ord[user]
+
+	byAge := F.Pipe1(
+		O.Ord(I.Ord),
+		ord.Contramap(user.GetAge),
+	) // ord.Ord[user]
+
+	sortedUsers := F.Pipe1(
+		From(user{name: "a", age: O.Of(30)}, user{name: "d", age: O.Of(10)}, user{name: "c"}, user{name: "b", age: O.Of(10)}),
+		SortBy(From(byAge, byName)),
+	)
+
+	fmt.Println(sortedStrings)
+	fmt.Println(reverseSortedStrings)
+	fmt.Println(sortedNums)
+	fmt.Println(sortedUsers)
+
+	// Output:
+	// [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}}]
+
+}

v2/array/find.go

@@ -0,0 +1,99 @@
+// 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 (
+	G "github.com/IBM/fp-go/v2/array/generic"
+	O "github.com/IBM/fp-go/v2/option"
+)
+
+// FindFirst finds the first element which satisfies a predicate function.
+// Returns Some(element) if found, None if no element matches.
+//
+// Example:
+//
+//	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
+func FindFirst[A any](pred func(A) bool) func([]A) O.Option[A] {
+	return G.FindFirst[[]A](pred)
+}
+
+// FindFirstWithIndex finds the first element which satisfies a predicate function that also receives the index.
+// Returns Some(element) if found, None if no element matches.
+//
+// Example:
+//
+//	findEvenAtEvenIndex := array.FindFirstWithIndex(func(i, x int) bool {
+//	    return i%2 == 0 && x%2 == 0
+//	})
+//	result := findEvenAtEvenIndex([]int{1, 3, 4, 5}) // Some(4)
+func FindFirstWithIndex[A any](pred func(int, A) bool) func([]A) O.Option[A] {
+	return G.FindFirstWithIndex[[]A](pred)
+}
+
+// FindFirstMap finds the first element for which the selector function returns Some.
+// This combines finding and mapping in a single operation.
+//
+// Example:
+//
+//	import "strconv"
+//
+//	parseFirst := array.FindFirstMap(func(s string) option.Option[int] {
+//	    if n, err := strconv.Atoi(s); err == nil {
+//	        return option.Some(n)
+//	    }
+//	    return option.None[int]()
+//	})
+//	result := parseFirst([]string{"a", "42", "b"}) // Some(42)
+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.
+func FindFirstMapWithIndex[A, B any](sel func(int, A) O.Option[B]) func([]A) O.Option[B] {
+	return G.FindFirstMapWithIndex[[]A](sel)
+}
+
+// FindLast finds the last element which satisfies a predicate function.
+// Returns Some(element) if found, None if no element matches.
+//
+// Example:
+//
+//	findGreaterThan3 := array.FindLast(func(x int) bool { return x > 3 })
+//	result := findGreaterThan3([]int{1, 4, 2, 5}) // Some(5)
+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.
+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.
+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.
+func FindLastMapWithIndex[A, B any](sel func(int, A) O.Option[B]) func([]A) O.Option[B] {
+	return G.FindLastMapWithIndex[[]A](sel)
+}

v2/array/find_test.go

@@ -0,0 +1,105 @@
+// 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 (
+	"fmt"
+	"testing"
+
+	O "github.com/IBM/fp-go/v2/option"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFindFirstWithIndex(t *testing.T) {
+	src := []int{1, 2, 3, 4, 5}
+	finder := FindFirstWithIndex(func(i, x int) bool {
+		return i > 2 && x%2 == 0
+	})
+	result := finder(src)
+	assert.Equal(t, O.Some(4), result)
+
+	notFound := FindFirstWithIndex(func(i, x int) bool {
+		return i > 10
+	})
+	assert.Equal(t, O.None[int](), notFound(src))
+}
+
+func TestFindFirstMap(t *testing.T) {
+	src := []string{"a", "42", "b", "100"}
+	finder := FindFirstMap(func(s string) O.Option[int] {
+		if len(s) > 1 {
+			return O.Some(len(s))
+		}
+		return O.None[int]()
+	})
+	result := finder(src)
+	assert.Equal(t, O.Some(2), result)
+}
+
+func TestFindFirstMapWithIndex(t *testing.T) {
+	src := []string{"a", "b", "c", "d"}
+	finder := FindFirstMapWithIndex(func(i int, s string) O.Option[string] {
+		if i > 1 {
+			return O.Some(fmt.Sprintf("%d:%s", i, s))
+		}
+		return O.None[string]()
+	})
+	result := finder(src)
+	assert.Equal(t, O.Some("2:c"), result)
+}
+
+func TestFindLast(t *testing.T) {
+	src := []int{1, 2, 3, 4, 5}
+	finder := FindLast(func(x int) bool { return x%2 == 0 })
+	result := finder(src)
+	assert.Equal(t, O.Some(4), result)
+
+	notFound := FindLast(func(x int) bool { return x > 10 })
+	assert.Equal(t, O.None[int](), notFound(src))
+}
+
+func TestFindLastWithIndex(t *testing.T) {
+	src := []int{1, 2, 3, 4, 5}
+	finder := FindLastWithIndex(func(i, x int) bool {
+		return i < 3 && x%2 == 0
+	})
+	result := finder(src)
+	assert.Equal(t, O.Some(2), result)
+}
+
+func TestFindLastMap(t *testing.T) {
+	src := []string{"a", "42", "b", "100"}
+	finder := FindLastMap(func(s string) O.Option[int] {
+		if len(s) > 1 {
+			return O.Some(len(s))
+		}
+		return O.None[int]()
+	})
+	result := finder(src)
+	assert.Equal(t, O.Some(3), result)
+}
+
+func TestFindLastMapWithIndex(t *testing.T) {
+	src := []string{"a", "b", "c", "d"}
+	finder := FindLastMapWithIndex(func(i int, s string) O.Option[string] {
+		if i < 3 {
+			return O.Some(fmt.Sprintf("%d:%s", i, s))
+		}
+		return O.None[string]()
+	})
+	result := finder(src)
+	assert.Equal(t, O.Some("2:c"), result)
+}

v2/array/generic/any.go

@@ -0,0 +1,34 @@
+// 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 generic
+
+import (
+	F "github.com/IBM/fp-go/v2/function"
+	O "github.com/IBM/fp-go/v2/option"
+)
+
+// AnyWithIndex tests if any of the elements in the array matches the predicate
+func AnyWithIndex[AS ~[]A, PRED ~func(int, A) bool, A any](pred PRED) func(AS) bool {
+	return F.Flow2(
+		FindFirstWithIndex[AS](pred),
+		O.IsSome[A],
+	)
+}
+
+// Any tests if any of the elements in the array matches the predicate
+func Any[AS ~[]A, PRED ~func(A) bool, A any](pred PRED) func(AS) bool {
+	return AnyWithIndex[AS](F.Ignore1of2[int](pred))
+}

v2/array/generic/array.go

@@ -0,0 +1,368 @@
+// 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 generic
+
+import (
+	F "github.com/IBM/fp-go/v2/function"
+	"github.com/IBM/fp-go/v2/internal/array"
+	FC "github.com/IBM/fp-go/v2/internal/functor"
+	M "github.com/IBM/fp-go/v2/monoid"
+	O "github.com/IBM/fp-go/v2/option"
+	"github.com/IBM/fp-go/v2/tuple"
+)
+
+// Of constructs a single element array
+func Of[GA ~[]A, A any](value A) GA {
+	return GA{value}
+}
+
+func Reduce[GA ~[]A, A, B any](f func(B, A) B, initial B) func(GA) B {
+	return func(as GA) B {
+		return MonadReduce[GA](as, f, initial)
+	}
+}
+
+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)
+	}
+}
+
+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)
+	}
+}
+
+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)
+	}
+}
+
+func MonadReduce[GA ~[]A, A, B any](fa GA, f func(B, A) B, initial B) B {
+	return array.Reduce(fa, f, initial)
+}
+
+func MonadReduceWithIndex[GA ~[]A, A, B any](fa GA, f func(int, B, A) B, initial B) B {
+	return array.ReduceWithIndex(fa, f, initial)
+}
+
+func MonadReduceRight[GA ~[]A, A, B any](fa GA, f func(A, B) B, initial B) B {
+	return array.ReduceRight(fa, f, initial)
+}
+
+func MonadReduceRightWithIndex[GA ~[]A, A, B any](fa GA, f func(int, A, B) B, initial B) B {
+	return array.ReduceRightWithIndex(fa, f, initial)
+}
+
+// From constructs an array from a set of variadic arguments
+func From[GA ~[]A, A any](data ...A) GA {
+	return data
+}
+
+// MakeBy returns a `Array` of length `n` with element `i` initialized with `f(i)`.
+func MakeBy[AS ~[]A, F ~func(int) A, A any](n int, f F) AS {
+	// sanity check
+	if n <= 0 {
+		return Empty[AS]()
+	}
+	// run the generator function across the input
+	as := make(AS, n)
+	for i := n - 1; i >= 0; i-- {
+		as[i] = f(i)
+	}
+	return as
+}
+
+func Replicate[AS ~[]A, A any](n int, a A) AS {
+	return MakeBy[AS](n, F.Constant1[int](a))
+}
+
+func Lookup[GA ~[]A, A any](idx int) func(GA) O.Option[A] {
+	none := O.None[A]()
+	if idx < 0 {
+		return F.Constant1[GA](none)
+	}
+	return func(as GA) O.Option[A] {
+		if idx < len(as) {
+			return O.Some(as[idx])
+		}
+		return none
+	}
+}
+
+func Tail[GA ~[]A, A any](as GA) O.Option[GA] {
+	if array.IsEmpty(as) {
+		return O.None[GA]()
+	}
+	return O.Some(as[1:])
+}
+
+func Head[GA ~[]A, A any](as GA) O.Option[A] {
+	if array.IsEmpty(as) {
+		return O.None[A]()
+	}
+	return O.Some(as[0])
+}
+
+func First[GA ~[]A, A any](as GA) O.Option[A] {
+	return Head(as)
+}
+
+func Last[GA ~[]A, A any](as GA) O.Option[A] {
+	if array.IsEmpty(as) {
+		return O.None[A]()
+	}
+	return O.Some(as[len(as)-1])
+}
+
+func Append[GA ~[]A, A any](as GA, a A) GA {
+	return array.Append(as, a)
+}
+
+func Empty[GA ~[]A, A any]() GA {
+	return array.Empty[GA]()
+}
+
+func UpsertAt[GA ~[]A, A any](a A) func(GA) GA {
+	return array.UpsertAt[GA](a)
+}
+
+func MonadMap[GA ~[]A, GB ~[]B, A, B any](as GA, f func(a A) B) GB {
+	return array.MonadMap[GA, GB](as, f)
+}
+
+func Map[GA ~[]A, GB ~[]B, A, B any](f func(a A) B) func(GA) GB {
+	return array.Map[GA, GB](f)
+}
+
+func MonadMapWithIndex[GA ~[]A, GB ~[]B, A, B any](as GA, f func(int, A) B) GB {
+	return array.MonadMapWithIndex[GA, GB](as, f)
+}
+
+func MapWithIndex[GA ~[]A, GB ~[]B, A, B any](f func(int, A) B) func(GA) GB {
+	return F.Bind2nd(MonadMapWithIndex[GA, GB, A, B], f)
+}
+
+func Size[GA ~[]A, A any](as GA) int {
+	return len(as)
+}
+
+func filterMap[GA ~[]A, GB ~[]B, A, B any](fa GA, f func(A) O.Option[B]) GB {
+	result := make(GB, 0, len(fa))
+	for _, a := range fa {
+		O.Map(func(b B) B {
+			result = append(result, b)
+			return b
+		})(f(a))
+	}
+	return result
+}
+
+func filterMapWithIndex[GA ~[]A, GB ~[]B, A, B any](fa GA, f func(int, A) O.Option[B]) GB {
+	result := make(GB, 0, len(fa))
+	for i, a := range fa {
+		O.Map(func(b B) B {
+			result = append(result, b)
+			return b
+		})(f(i, a))
+	}
+	return result
+}
+
+func MonadFilterMap[GA ~[]A, GB ~[]B, A, B any](fa GA, f func(A) O.Option[B]) GB {
+	return filterMap[GA, GB](fa, f)
+}
+
+func MonadFilterMapWithIndex[GA ~[]A, GB ~[]B, A, B any](fa GA, f func(int, A) O.Option[B]) GB {
+	return filterMapWithIndex[GA, GB](fa, f)
+}
+
+func filterWithIndex[AS ~[]A, PRED ~func(int, A) bool, A any](fa AS, pred PRED) AS {
+	result := make(AS, 0, len(fa))
+	for i, a := range fa {
+		if pred(i, a) {
+			result = append(result, a)
+		}
+	}
+	return result
+}
+
+func FilterWithIndex[AS ~[]A, PRED ~func(int, A) bool, A any](pred PRED) func(AS) AS {
+	return F.Bind2nd(filterWithIndex[AS, PRED, A], pred)
+}
+
+func Filter[AS ~[]A, PRED ~func(A) bool, A any](pred PRED) func(AS) AS {
+	return FilterWithIndex[AS](F.Ignore1of2[int](pred))
+}
+
+func FilterChain[GA ~[]A, GB ~[]B, A, B any](f func(a A) O.Option[GB]) func(GA) GB {
+	return F.Flow2(
+		FilterMap[GA, []GB](f),
+		Flatten[[]GB],
+	)
+}
+
+func Flatten[GAA ~[]GA, GA ~[]A, A any](mma GAA) GA {
+	return MonadChain(mma, F.Identity[GA])
+}
+
+func FilterMap[GA ~[]A, GB ~[]B, A, B any](f func(A) O.Option[B]) func(GA) GB {
+	return F.Bind2nd(MonadFilterMap[GA, GB, A, B], f)
+}
+
+func FilterMapWithIndex[GA ~[]A, GB ~[]B, A, B any](f func(int, A) O.Option[B]) func(GA) GB {
+	return F.Bind2nd(MonadFilterMapWithIndex[GA, GB, A, B], f)
+}
+
+func MonadPartition[GA ~[]A, A any](as GA, pred func(A) bool) tuple.Tuple2[GA, GA] {
+	left := Empty[GA]()
+	right := Empty[GA]()
+	array.Reduce(as, func(c bool, a A) bool {
+		if pred(a) {
+			right = append(right, a)
+		} else {
+			left = append(left, a)
+		}
+		return c
+	}, true)
+	// returns the partition
+	return tuple.MakeTuple2(left, right)
+}
+
+func Partition[GA ~[]A, A any](pred func(A) bool) func(GA) tuple.Tuple2[GA, GA] {
+	return F.Bind2nd(MonadPartition[GA, A], pred)
+}
+
+func MonadChain[AS ~[]A, BS ~[]B, A, B any](fa AS, f func(a A) BS) BS {
+	return array.Reduce(fa, func(bs BS, a A) BS {
+		return append(bs, f(a)...)
+	}, Empty[BS]())
+}
+
+func Chain[AS ~[]A, BS ~[]B, A, B any](f func(A) BS) func(AS) BS {
+	return F.Bind2nd(MonadChain[AS, BS, A, B], f)
+}
+
+func MonadAp[BS ~[]B, ABS ~[]func(A) B, AS ~[]A, B, A any](fab ABS, fa AS) BS {
+	return MonadChain(fab, F.Bind1st(MonadMap[AS, BS, A, B], fa))
+}
+
+func Ap[BS ~[]B, ABS ~[]func(A) B, AS ~[]A, B, A any](fa AS) func(ABS) BS {
+	return F.Bind2nd(MonadAp[BS, ABS, AS], fa)
+}
+
+func IsEmpty[AS ~[]A, A any](as AS) bool {
+	return array.IsEmpty(as)
+}
+
+func IsNil[GA ~[]A, A any](as GA) bool {
+	return array.IsNil(as)
+}
+
+func IsNonNil[GA ~[]A, A any](as GA) bool {
+	return array.IsNonNil(as)
+}
+
+func Match[AS ~[]A, A, B any](onEmpty func() B, onNonEmpty func(AS) B) func(AS) B {
+	return func(as AS) B {
+		if IsEmpty(as) {
+			return onEmpty()
+		}
+		return onNonEmpty(as)
+	}
+}
+
+func MatchLeft[AS ~[]A, A, B any](onEmpty func() B, onNonEmpty func(A, AS) B) func(AS) B {
+	return func(as AS) B {
+		if IsEmpty(as) {
+			return onEmpty()
+		}
+		return onNonEmpty(as[0], as[1:])
+	}
+}
+
+func Slice[AS ~[]A, A any](start int, end int) func(AS) AS {
+	return func(a AS) AS {
+		return a[start:end]
+	}
+}
+
+func SliceRight[AS ~[]A, A any](start int) func(AS) AS {
+	return func(a AS) AS {
+		return a[start:]
+	}
+}
+
+func Copy[AS ~[]A, A any](b AS) AS {
+	buf := make(AS, len(b))
+	copy(buf, b)
+	return buf
+}
+
+func Clone[AS ~[]A, A any](f func(A) A) func(as AS) AS {
+	// implementation assumes that map does not optimize for the empty array
+	return Map[AS, AS](f)
+}
+
+func FoldMap[AS ~[]A, A, B any](m M.Monoid[B]) func(func(A) B) func(AS) B {
+	empty := m.Empty()
+	concat := m.Concat
+	return func(f func(A) B) func(AS) B {
+		return func(as AS) B {
+			return array.Reduce(as, func(cur B, a A) B {
+				return concat(cur, f(a))
+			}, empty)
+		}
+	}
+}
+
+func FoldMapWithIndex[AS ~[]A, A, B any](m M.Monoid[B]) func(func(int, A) B) func(AS) B {
+	empty := m.Empty()
+	concat := m.Concat
+	return func(f func(int, A) B) func(AS) B {
+		return func(as AS) B {
+			return array.ReduceWithIndex(as, func(idx int, cur B, a A) B {
+				return concat(cur, f(idx, a))
+			}, empty)
+		}
+	}
+}
+
+func Fold[AS ~[]A, A any](m M.Monoid[A]) func(AS) A {
+	empty := m.Empty()
+	concat := m.Concat
+	return func(as AS) A {
+		return array.Reduce(as, concat, empty)
+	}
+}
+
+func Push[ENDO ~func(GA) GA, GA ~[]A, A any](a A) ENDO {
+	return F.Bind2nd(array.Push[GA, A], a)
+}
+
+func MonadFlap[FAB ~func(A) B, GFAB ~[]FAB, GB ~[]B, A, B any](fab GFAB, a A) GB {
+	return FC.MonadFlap(MonadMap[GFAB, GB], fab, a)
+}
+
+func Flap[FAB ~func(A) B, GFAB ~[]FAB, GB ~[]B, A, B any](a A) func(GFAB) GB {
+	return FC.Flap(Map[GFAB, GB], a)
+}
+
+func Prepend[ENDO ~func(AS) AS, AS []A, A any](head A) ENDO {
+	return array.Prepend[ENDO](head)
+}

v2/array/generic/bind.go

@@ -0,0 +1,89 @@
+// 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 generic
+
+import (
+	A "github.com/IBM/fp-go/v2/internal/apply"
+	C "github.com/IBM/fp-go/v2/internal/chain"
+	F "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[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]
+func Bind[GS1 ~[]S1, GS2 ~[]S2, GT ~[]T, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) GT,
+) func(GS1) GS2 {
+	return C.Bind(
+		Chain[GS1, GS2, S1, S2],
+		Map[GT, GS2, T, S2],
+		setter,
+		f,
+	)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[GS1 ~[]S1, GS2 ~[]S2, S1, S2, T any](
+	key func(T) func(S1) S2,
+	f func(S1) T,
+) func(GS1) GS2 {
+	return F.Let(
+		Map[GS1, GS2, S1, S2],
+		key,
+		f,
+	)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[GS1 ~[]S1, GS2 ~[]S2, S1, S2, B any](
+	key func(B) func(S1) S2,
+	b B,
+) func(GS1) GS2 {
+	return F.LetTo(
+		Map[GS1, GS2, S1, S2],
+		key,
+		b,
+	)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[GS1 ~[]S1, GT ~[]T, S1, T any](
+	setter func(T) S1,
+) func(GT) GS1 {
+	return C.BindTo(
+		Map[GT, GS1, 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[GS1 ~[]S1, GS2 ~[]S2, GT ~[]T, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa GT,
+) func(GS1) GS2 {
+	return A.ApS(
+		Ap[GS2, []func(T) S2, GT, S2, T],
+		Map[GS1, []func(T) S2, S1, func(T) S2],
+		setter,
+		fa,
+	)
+}

v2/array/generic/find.go

@@ -0,0 +1,97 @@
+// 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 generic
+
+import (
+	F "github.com/IBM/fp-go/v2/function"
+	O "github.com/IBM/fp-go/v2/option"
+)
+
+// FindFirstWithIndex finds the first element which satisfies a predicate (or a refinement) function
+func FindFirstWithIndex[AS ~[]A, PRED ~func(int, A) bool, A any](pred PRED) func(AS) O.Option[A] {
+	none := O.None[A]()
+	return func(as AS) O.Option[A] {
+		for i, a := range as {
+			if pred(i, a) {
+				return O.Some(a)
+			}
+		}
+		return none
+	}
+}
+
+// FindFirst finds the first element which satisfies a predicate (or a refinement) function
+func FindFirst[AS ~[]A, PRED ~func(A) bool, A any](pred PRED) func(AS) O.Option[A] {
+	return FindFirstWithIndex[AS](F.Ignore1of2[int](pred))
+}
+
+// FindFirstMapWithIndex finds the first element returned by an [O.Option] based selector function
+func FindFirstMapWithIndex[AS ~[]A, PRED ~func(int, A) O.Option[B], A, B any](pred PRED) func(AS) O.Option[B] {
+	none := O.None[B]()
+	return func(as AS) O.Option[B] {
+		count := len(as)
+		for i := 0; i < count; i++ {
+			out := pred(i, as[i])
+			if O.IsSome(out) {
+				return out
+			}
+		}
+		return none
+	}
+}
+
+// FindFirstMap finds the first element returned by an [O.Option] based selector function
+func FindFirstMap[AS ~[]A, PRED ~func(A) O.Option[B], A, B any](pred PRED) func(AS) O.Option[B] {
+	return FindFirstMapWithIndex[AS](F.Ignore1of2[int](pred))
+}
+
+// FindLastWithIndex finds the first element which satisfies a predicate (or a refinement) function
+func FindLastWithIndex[AS ~[]A, PRED ~func(int, A) bool, A any](pred PRED) func(AS) O.Option[A] {
+	none := O.None[A]()
+	return func(as AS) O.Option[A] {
+		for i := len(as) - 1; i >= 0; i-- {
+			a := as[i]
+			if pred(i, a) {
+				return O.Some(a)
+			}
+		}
+		return none
+	}
+}
+
+// FindLast finds the first element which satisfies a predicate (or a refinement) function
+func FindLast[AS ~[]A, PRED ~func(A) bool, A any](pred PRED) func(AS) O.Option[A] {
+	return FindLastWithIndex[AS](F.Ignore1of2[int](pred))
+}
+
+// FindLastMapWithIndex finds the first element returned by an [O.Option] based selector function
+func FindLastMapWithIndex[AS ~[]A, PRED ~func(int, A) O.Option[B], A, B any](pred PRED) func(AS) O.Option[B] {
+	none := O.None[B]()
+	return func(as AS) O.Option[B] {
+		for i := len(as) - 1; i >= 0; i-- {
+			out := pred(i, as[i])
+			if O.IsSome(out) {
+				return out
+			}
+		}
+		return none
+	}
+}
+
+// FindLastMap finds the first element returned by an [O.Option] based selector function
+func FindLastMap[AS ~[]A, PRED ~func(A) O.Option[B], A, B any](pred PRED) func(AS) O.Option[B] {
+	return FindLastMapWithIndex[AS](F.Ignore1of2[int](pred))
+}

v2/array/generic/monad.go

@@ -0,0 +1,43 @@
+// Copyright (c) 2024 - 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 generic
+
+import (
+	"github.com/IBM/fp-go/v2/internal/monad"
+)
+
+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)
+}
+
+func (o *arrayMonad[A, B, GA, GB, GAB]) Map(f func(A) B) func(GA) GB {
+	return Map[GA, GB, A, B](f)
+}
+
+func (o *arrayMonad[A, B, GA, GB, GAB]) Chain(f func(A) GB) func(GA) GB {
+	return Chain[GA, GB, A, B](f)
+}
+
+func (o *arrayMonad[A, B, GA, GB, GAB]) Ap(fa GA) func(GAB) GB {
+	return Ap[GB, GAB, GA, B, A](fa)
+}
+
+// Monad implements the monadic operations for an array
+func Monad[A, B any, GA ~[]A, GB ~[]B, GAB ~[]func(A) B]() monad.Monad[A, B, GA, GB, GAB] {
+	return &arrayMonad[A, B, GA, GB, GAB]{}
+}

v2/array/generic/sort.go

@@ -0,0 +1,56 @@
+// 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 generic
+
+import (
+	"sort"
+
+	F "github.com/IBM/fp-go/v2/function"
+	O "github.com/IBM/fp-go/v2/ord"
+)
+
+// Sort implements a stable sort on the array given the provided ordering
+func Sort[GA ~[]T, T any](ord O.Ord[T]) func(ma GA) GA {
+	return SortByKey[GA](ord, F.Identity[T])
+}
+
+// SortByKey implements a stable sort on the array given the provided ordering on an extracted key
+func SortByKey[GA ~[]T, K, T any](ord O.Ord[K], f func(T) K) func(ma GA) GA {
+
+	return func(ma GA) GA {
+		// nothing to sort
+		l := len(ma)
+		if l < 2 {
+			return ma
+		}
+		// copy
+		cpy := make(GA, l)
+		copy(cpy, ma)
+		sort.Slice(cpy, func(i, j int) bool {
+			return ord.Compare(f(cpy[i]), f(cpy[j])) < 0
+		})
+		return cpy
+	}
+}
+
+// SortBy implements a stable sort on the array given the provided ordering
+func SortBy[GA ~[]T, GO ~[]O.Ord[T], T any](ord GO) func(ma GA) GA {
+	return F.Pipe2(
+		ord,
+		Fold[GO](O.Monoid[T]()),
+		Sort[GA, T],
+	)
+}

v2/array/generic/uniq.go

@@ -0,0 +1,32 @@
+package generic
+
+import F "github.com/IBM/fp-go/v2/function"
+
+// StrictUniq converts an array of arbitrary items into an array or unique items
+// where uniqueness is determined by the built-in uniqueness constraint
+func StrictUniq[AS ~[]A, A comparable](as AS) AS {
+	return Uniq[AS](F.Identity[A])(as)
+}
+
+// uniquePredUnsafe returns a predicate on a map for uniqueness
+func uniquePredUnsafe[PRED ~func(A) K, A any, K comparable](f PRED) func(int, A) bool {
+	lookup := make(map[K]bool)
+	return func(_ int, a A) bool {
+		k := f(a)
+		_, has := lookup[k]
+		if has {
+			return false
+		}
+		lookup[k] = true
+		return true
+	}
+}
+
+// Uniq converts an array of arbitrary items into an array or unique items
+// where uniqueness is determined based on a key extractor function
+func Uniq[AS ~[]A, PRED ~func(A) K, A any, K comparable](f PRED) func(as AS) AS {
+	return func(as AS) AS {
+		// we need to create a new predicate for each iteration
+		return filterWithIndex(as, uniquePredUnsafe(f))
+	}
+}

v2/array/generic/zip.go

@@ -0,0 +1,52 @@
+// 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 generic
+
+import (
+	F "github.com/IBM/fp-go/v2/function"
+	N "github.com/IBM/fp-go/v2/number"
+	T "github.com/IBM/fp-go/v2/tuple"
+)
+
+// ZipWith applies a function to pairs of elements at the same index in two arrays, collecting the results in a new array. If one
+// input array is short, excess elements of the longer array are discarded.
+func ZipWith[AS ~[]A, BS ~[]B, CS ~[]C, FCT ~func(A, B) C, A, B, C any](fa AS, fb BS, f FCT) CS {
+	l := N.Min(len(fa), len(fb))
+	res := make(CS, l)
+	for i := l - 1; i >= 0; i-- {
+		res[i] = f(fa[i], fb[i])
+	}
+	return res
+}
+
+// Zip takes two arrays and returns an array of corresponding pairs. If one input array is short, excess elements of the
+// longer array are discarded
+func Zip[AS ~[]A, BS ~[]B, CS ~[]T.Tuple2[A, B], A, B any](fb BS) func(AS) CS {
+	return F.Bind23of3(ZipWith[AS, BS, CS, func(A, B) T.Tuple2[A, B]])(fb, T.MakeTuple2[A, B])
+}
+
+// Unzip is the function is reverse of [Zip]. Takes an array of pairs and return two corresponding arrays
+func Unzip[AS ~[]A, BS ~[]B, CS ~[]T.Tuple2[A, B], A, B any](cs CS) T.Tuple2[AS, BS] {
+	l := len(cs)
+	as := make(AS, l)
+	bs := make(BS, l)
+	for i := l - 1; i >= 0; i-- {
+		t := cs[i]
+		as[i] = t.F1
+		bs[i] = t.F2
+	}
+	return T.MakeTuple2(as, bs)
+}

v2/array/magma.go

@@ -0,0 +1,38 @@
+// 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 (
+	M "github.com/IBM/fp-go/v2/monoid"
+)
+
+// ConcatAll concatenates all elements of an array using the provided Monoid.
+// This reduces the array to a single value by repeatedly applying the Monoid's concat operation.
+//
+// Example:
+//
+//	import "github.com/IBM/fp-go/v2/monoid"
+//
+//	// Sum all numbers
+//	sumAll := array.ConcatAll(monoid.MonoidSum[int]())
+//	result := sumAll([]int{1, 2, 3, 4, 5}) // 15
+//
+//	// Concatenate all strings
+//	concatStrings := array.ConcatAll(monoid.MonoidString())
+//	result2 := concatStrings([]string{"Hello", " ", "World"}) // "Hello World"
+func ConcatAll[A any](m M.Monoid[A]) func([]A) A {
+	return Reduce(m.Concat, m.Empty())
+}

v2/array/magma_test.go

@@ -0,0 +1,36 @@
+// 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"
+
+	M "github.com/IBM/fp-go/v2/monoid"
+)
+
+var subInt = M.MakeMonoid(func(first int, second int) int {
+	return first - second
+}, 0)
+
+func TestConcatAll(t *testing.T) {
+
+	var subAll = ConcatAll(subInt)
+
+	assert.Equal(t, subAll([]int{1, 2, 3}), -6)
+
+}

v2/array/misc_test.go

@@ -0,0 +1,161 @@
+// 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"
+
+	O "github.com/IBM/fp-go/v2/option"
+	OR "github.com/IBM/fp-go/v2/ord"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAnyWithIndex(t *testing.T) {
+	src := []int{1, 2, 3, 4, 5}
+	checker := AnyWithIndex(func(i, x int) bool {
+		return i == 2 && x == 3
+	})
+	assert.True(t, checker(src))
+
+	checker2 := AnyWithIndex(func(i, x int) bool {
+		return i == 10
+	})
+	assert.False(t, checker2(src))
+}
+
+func TestSemigroup(t *testing.T) {
+	sg := Semigroup[int]()
+	result := sg.Concat([]int{1, 2}, []int{3, 4})
+	assert.Equal(t, []int{1, 2, 3, 4}, result)
+}
+
+func TestArrayConcatAll(t *testing.T) {
+	result := ArrayConcatAll(
+		[]int{1, 2},
+		[]int{3, 4},
+		[]int{5, 6},
+	)
+	assert.Equal(t, []int{1, 2, 3, 4, 5, 6}, result)
+
+	// Test with empty arrays
+	result2 := ArrayConcatAll(
+		[]int{},
+		[]int{1},
+		[]int{},
+	)
+	assert.Equal(t, []int{1}, result2)
+}
+
+func TestMonad(t *testing.T) {
+	m := Monad[int, string]()
+
+	// Test Map
+	mapFn := m.Map(func(x int) string {
+		return string(rune('a' + x - 1))
+	})
+	mapped := mapFn([]int{1, 2, 3})
+	assert.Equal(t, []string{"a", "b", "c"}, mapped)
+
+	// Test Chain
+	chainFn := m.Chain(func(x int) []string {
+		return []string{string(rune('a' + x - 1))}
+	})
+	chained := chainFn([]int{1, 2})
+	assert.Equal(t, []string{"a", "b"}, chained)
+
+	// Test Of
+	ofResult := m.Of(42)
+	assert.Equal(t, []int{42}, ofResult)
+}
+
+func TestSortByKey(t *testing.T) {
+	type Person struct {
+		Name string
+		Age  int
+	}
+
+	people := []Person{
+		{"Alice", 30},
+		{"Bob", 25},
+		{"Charlie", 35},
+	}
+
+	sorter := SortByKey(OR.FromStrictCompare[int](), func(p Person) int {
+		return p.Age
+	})
+	result := sorter(people)
+
+	assert.Equal(t, "Bob", result[0].Name)
+	assert.Equal(t, "Alice", result[1].Name)
+	assert.Equal(t, "Charlie", result[2].Name)
+}
+
+func TestMonadTraverse(t *testing.T) {
+	result := MonadTraverse(
+		O.Of[[]int],
+		O.Map[[]int, func(int) []int],
+		O.Ap[[]int, int],
+		[]int{1, 3, 5},
+		func(n int) O.Option[int] {
+			if n%2 == 1 {
+				return O.Some(n * 2)
+			}
+			return O.None[int]()
+		},
+	)
+
+	assert.Equal(t, O.Some([]int{2, 6, 10}), result)
+
+	// Test with None case
+	result2 := MonadTraverse(
+		O.Of[[]int],
+		O.Map[[]int, func(int) []int],
+		O.Ap[[]int, int],
+		[]int{1, 2, 3},
+		func(n int) O.Option[int] {
+			if n%2 == 1 {
+				return O.Some(n * 2)
+			}
+			return O.None[int]()
+		},
+	)
+
+	assert.Equal(t, O.None[[]int](), result2)
+}
+
+func TestUniqByKey(t *testing.T) {
+	type Person struct {
+		Name string
+		Age  int
+	}
+
+	people := []Person{
+		{"Alice", 30},
+		{"Bob", 25},
+		{"Alice", 35},
+		{"Charlie", 30},
+	}
+
+	uniquer := Uniq(func(p Person) string {
+		return p.Name
+	})
+	result := uniquer(people)
+
+	assert.Equal(t, 3, len(result))
+	assert.Equal(t, "Alice", result[0].Name)
+	assert.Equal(t, "Bob", result[1].Name)
+	assert.Equal(t, "Charlie", result[2].Name)
+}

v2/array/monad.go

@@ -0,0 +1,39 @@
+// Copyright (c) 2024 - 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 (
+	G "github.com/IBM/fp-go/v2/array/generic"
+	"github.com/IBM/fp-go/v2/internal/monad"
+)
+
+// Monad returns the monadic operations for an array.
+// This provides a structured way to access all monad operations (Map, Chain, Ap, Of)
+// for arrays in a single interface.
+//
+// The Monad interface is useful when you need to pass monadic operations as parameters
+// or when working with generic code that operates on any monad.
+//
+// Example:
+//
+//	m := array.Monad[int, string]()
+//	result := m.Chain([]int{1, 2, 3}, func(x int) []string {
+//	    return []string{fmt.Sprintf("%d", x), fmt.Sprintf("%d!", x)}
+//	})
+//	// Result: ["1", "1!", "2", "2!", "3", "3!"]
+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/monoid.go

@@ -0,0 +1,89 @@
+// 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 (
+	"github.com/IBM/fp-go/v2/internal/array"
+	M "github.com/IBM/fp-go/v2/monoid"
+	S "github.com/IBM/fp-go/v2/semigroup"
+)
+
+func concat[T any](left, right []T) []T {
+	// some performance checks
+	ll := len(left)
+	if ll == 0 {
+		return right
+	}
+	lr := len(right)
+	if lr == 0 {
+		return left
+	}
+	// need to copy
+	buf := make([]T, ll+lr)
+	copy(buf[copy(buf, left):], right)
+	return buf
+}
+
+// Monoid returns a Monoid instance for arrays.
+// The Monoid combines arrays through concatenation, with an empty array as the identity element.
+//
+// Example:
+//
+//	m := array.Monoid[int]()
+//	result := m.Concat([]int{1, 2}, []int{3, 4}) // [1, 2, 3, 4]
+//	empty := m.Empty() // []
+func Monoid[T any]() M.Monoid[[]T] {
+	return M.MakeMonoid(concat[T], Empty[T]())
+}
+
+// Semigroup returns a Semigroup instance for arrays.
+// The Semigroup combines arrays through concatenation.
+//
+// Example:
+//
+//	s := array.Semigroup[int]()
+//	result := s.Concat([]int{1, 2}, []int{3, 4}) // [1, 2, 3, 4]
+func Semigroup[T any]() S.Semigroup[[]T] {
+	return S.MakeSemigroup(concat[T])
+}
+
+func addLen[A any](count int, data []A) int {
+	return count + len(data)
+}
+
+// ArrayConcatAll efficiently concatenates multiple arrays into a single array.
+// This function pre-allocates the exact amount of memory needed and performs
+// a single copy operation for each input array, making it more efficient than
+// repeated concatenations.
+//
+// Example:
+//
+//	result := array.ArrayConcatAll(
+//	    []int{1, 2},
+//	    []int{3, 4},
+//	    []int{5, 6},
+//	) // [1, 2, 3, 4, 5, 6]
+func ArrayConcatAll[A any](data ...[]A) []A {
+	// get the full size
+	count := array.Reduce(data, addLen[A], 0)
+	buf := make([]A, count)
+	// copy
+	array.Reduce(data, func(idx int, seg []A) int {
+		return idx + copy(buf[idx:], seg)
+	}, 0)
+	// returns the final array
+	return buf
+}

v2/array/monoid_test.go

@@ -0,0 +1,26 @@
+// 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"
+
+	M "github.com/IBM/fp-go/v2/monoid/testing"
+)
+
+func TestMonoid(t *testing.T) {
+	M.AssertLaws(t, Monoid[int]())([][]int{{}, {1}, {1, 2}})
+}

v2/array/nonempty/array.go

@@ -0,0 +1,136 @@
+// 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 nonempty
+
+import (
+	G "github.com/IBM/fp-go/v2/array/generic"
+	EM "github.com/IBM/fp-go/v2/endomorphism"
+	F "github.com/IBM/fp-go/v2/function"
+	"github.com/IBM/fp-go/v2/internal/array"
+	S "github.com/IBM/fp-go/v2/semigroup"
+)
+
+// NonEmptyArray represents an array with at least one element
+type NonEmptyArray[A any] []A
+
+// Of constructs a single element array
+func Of[A any](first A) NonEmptyArray[A] {
+	return G.Of[NonEmptyArray[A]](first)
+}
+
+// From constructs a [NonEmptyArray] from a set of variadic arguments
+func From[A any](first A, data ...A) NonEmptyArray[A] {
+	count := len(data)
+	if count == 0 {
+		return Of(first)
+	}
+	// allocate the requested buffer
+	buffer := make(NonEmptyArray[A], count+1)
+	buffer[0] = first
+	copy(buffer[1:], data)
+	return buffer
+}
+
+func IsEmpty[A any](_ NonEmptyArray[A]) bool {
+	return false
+}
+
+func IsNonEmpty[A any](_ NonEmptyArray[A]) bool {
+	return true
+}
+
+func MonadMap[A, B any](as NonEmptyArray[A], f func(a A) B) NonEmptyArray[B] {
+	return G.MonadMap[NonEmptyArray[A], NonEmptyArray[B]](as, f)
+}
+
+func Map[A, B any](f func(a A) B) func(NonEmptyArray[A]) NonEmptyArray[B] {
+	return F.Bind2nd(MonadMap[A, B], f)
+}
+
+func Reduce[A, B any](f func(B, A) B, initial B) func(NonEmptyArray[A]) B {
+	return func(as NonEmptyArray[A]) B {
+		return array.Reduce(as, f, initial)
+	}
+}
+
+func ReduceRight[A, B any](f func(A, B) B, initial B) func(NonEmptyArray[A]) B {
+	return func(as NonEmptyArray[A]) B {
+		return array.ReduceRight(as, f, initial)
+	}
+}
+
+func Tail[A any](as NonEmptyArray[A]) []A {
+	return as[1:]
+}
+
+func Head[A any](as NonEmptyArray[A]) A {
+	return as[0]
+}
+
+func First[A any](as NonEmptyArray[A]) A {
+	return as[0]
+}
+
+func Last[A any](as NonEmptyArray[A]) A {
+	return as[len(as)-1]
+}
+
+func Size[A any](as NonEmptyArray[A]) int {
+	return G.Size(as)
+}
+
+func Flatten[A any](mma NonEmptyArray[NonEmptyArray[A]]) NonEmptyArray[A] {
+	return G.Flatten(mma)
+}
+
+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)
+}
+
+func Chain[A, B any](f func(A) NonEmptyArray[B]) func(NonEmptyArray[A]) NonEmptyArray[B] {
+	return G.Chain[NonEmptyArray[A], NonEmptyArray[B]](f)
+}
+
+func MonadAp[B, A any](fab NonEmptyArray[func(A) B], fa NonEmptyArray[A]) NonEmptyArray[B] {
+	return G.MonadAp[NonEmptyArray[B]](fab, fa)
+}
+
+func Ap[B, A any](fa NonEmptyArray[A]) func(NonEmptyArray[func(A) B]) NonEmptyArray[B] {
+	return G.Ap[NonEmptyArray[B], NonEmptyArray[func(A) B]](fa)
+}
+
+// FoldMap maps and folds a [NonEmptyArray]. Map the [NonEmptyArray] passing each value to the iterating function. Then fold the results using the provided [Semigroup].
+func FoldMap[A, B any](s S.Semigroup[B]) func(func(A) B) func(NonEmptyArray[A]) B {
+	return func(f func(A) B) func(NonEmptyArray[A]) B {
+		return func(as NonEmptyArray[A]) B {
+			return array.Reduce(Tail(as), func(cur B, a A) B {
+				return s.Concat(cur, f(a))
+			}, f(Head(as)))
+		}
+	}
+}
+
+// Fold folds the [NonEmptyArray] using the provided [Semigroup].
+func Fold[A any](s S.Semigroup[A]) func(NonEmptyArray[A]) A {
+	return func(as NonEmptyArray[A]) A {
+		return array.Reduce(Tail(as), s.Concat, Head(as))
+	}
+}
+
+// Prepend prepends a single value to an array
+func Prepend[A any](head A) EM.Endomorphism[NonEmptyArray[A]] {
+	return array.Prepend[EM.Endomorphism[NonEmptyArray[A]]](head)
+}

v2/array/sequence.go

@@ -0,0 +1,95 @@
+// 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 (
+	F "github.com/IBM/fp-go/v2/function"
+	O "github.com/IBM/fp-go/v2/option"
+)
+
+// Sequence takes an array where elements are HKT<A> (higher kinded type) and,
+// using an applicative of that HKT, returns an HKT of []A.
+//
+// For example, it can turn:
+//   - []Either[error, string] into Either[error, []string]
+//   - []Option[int] into Option[[]int]
+//
+// Sequence requires an Applicative of the HKT you are targeting. To turn an
+// []Either[E, A] into an Either[E, []A], it needs an Applicative for Either.
+// To turn an []Option[A] into an Option[[]A], it needs an Applicative for Option.
+//
+// Note: We need to pass the members of the applicative explicitly because Go does not
+// support higher kinded types or template methods on structs or interfaces.
+//
+// Type parameters:
+//   - HKTA = HKT<A> (e.g., Option[A], Either[E, A])
+//   - HKTRA = HKT<[]A> (e.g., Option[[]A], Either[E, []A])
+//   - HKTFRA = HKT<func(A)[]A> (e.g., Option[func(A)[]A])
+//
+// Example:
+//
+//	import "github.com/IBM/fp-go/v2/option"
+//
+//	opts := []option.Option[int]{
+//	    option.Some(1),
+//	    option.Some(2),
+//	    option.Some(3),
+//	}
+//
+//	seq := array.Sequence(
+//	    option.Of[[]int],
+//	    option.MonadMap[[]int, func(int) []int],
+//	    option.MonadAp[[]int, int],
+//	)
+//	result := seq(opts) // Some([1, 2, 3])
+func Sequence[A, HKTA, HKTRA, HKTFRA any](
+	_of func([]A) HKTRA,
+	_map func(HKTRA, func([]A) func(A) []A) HKTFRA,
+	_ap func(HKTFRA, HKTA) HKTRA,
+) func([]HKTA) HKTRA {
+	ca := F.Curry2(Append[A])
+	empty := _of(Empty[A]())
+	return Reduce(func(fas HKTRA, fa HKTA) HKTRA {
+		return _ap(_map(fas, ca), fa)
+	}, empty)
+}
+
+// ArrayOption returns a function to convert a sequence of options into an option of a sequence.
+// If all options are Some, returns Some containing an array of all values.
+// If any option is None, returns None.
+//
+// Example:
+//
+//	opts := []option.Option[int]{
+//	    option.Some(1),
+//	    option.Some(2),
+//	    option.Some(3),
+//	}
+//	result := array.ArrayOption[int]()(opts) // Some([1, 2, 3])
+//
+//	opts2 := []option.Option[int]{
+//	    option.Some(1),
+//	    option.None[int](),
+//	    option.Some(3),
+//	}
+//	result2 := array.ArrayOption[int]()(opts2) // None
+func ArrayOption[A any]() func([]O.Option[A]) O.Option[[]A] {
+	return Sequence(
+		O.Of[[]A],
+		O.MonadMap[[]A, func(A) []A],
+		O.MonadAp[[]A, A],
+	)
+}

v2/array/sequence_test.go

@@ -0,0 +1,31 @@
+// 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"
+
+	O "github.com/IBM/fp-go/v2/option"
+)
+
+func TestSequenceOption(t *testing.T) {
+	seq := ArrayOption[int]()
+
+	assert.Equal(t, O.Of([]int{1, 3}), seq([]O.Option[int]{O.Of(1), O.Of(3)}))
+	assert.Equal(t, O.None[[]int](), seq([]O.Option[int]{O.Of(1), O.None[int]()}))
+}

v2/array/sort.go

@@ -0,0 +1,92 @@
+// 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 (
+	G "github.com/IBM/fp-go/v2/array/generic"
+	O "github.com/IBM/fp-go/v2/ord"
+)
+
+// Sort implements a stable sort on the array given the provided ordering.
+// The sort is stable, meaning that elements that compare equal retain their original order.
+//
+// Example:
+//
+//	import "github.com/IBM/fp-go/v2/ord"
+//
+//	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]
+func Sort[T any](ord O.Ord[T]) func(ma []T) []T {
+	return G.Sort[[]T](ord)
+}
+
+// SortByKey implements a stable sort on the array given the provided ordering on an extracted key.
+// This is useful when you want to sort complex types by a specific field.
+//
+// Example:
+//
+//	import "github.com/IBM/fp-go/v2/ord"
+//
+//	type Person struct {
+//	    Name string
+//	    Age  int
+//	}
+//
+//	people := []Person{
+//	    {"Alice", 30},
+//	    {"Bob", 25},
+//	    {"Charlie", 35},
+//	}
+//
+//	sortByAge := array.SortByKey(
+//	    ord.FromStrictCompare[int](),
+//	    func(p Person) int { return p.Age },
+//	)
+//	sorted := sortByAge(people)
+//	// Result: [{"Bob", 25}, {"Alice", 30}, {"Charlie", 35}]
+func SortByKey[K, T any](ord O.Ord[K], f func(T) K) func(ma []T) []T {
+	return G.SortByKey[[]T](ord, f)
+}
+
+// SortBy implements a stable sort on the array using multiple ordering criteria.
+// The orderings are applied in sequence: if two elements are equal according to the first
+// ordering, the second ordering is used, and so on.
+//
+// Example:
+//
+//	import "github.com/IBM/fp-go/v2/ord"
+//
+//	type Person struct {
+//	    LastName  string
+//	    FirstName string
+//	}
+//
+//	people := []Person{
+//	    {"Smith", "John"},
+//	    {"Smith", "Alice"},
+//	    {"Jones", "Bob"},
+//	}
+//
+//	sortByName := array.SortBy([]ord.Ord[Person]{
+//	    ord.Contramap(func(p Person) string { return p.LastName })(ord.FromStrictCompare[string]()),
+//	    ord.Contramap(func(p Person) string { return p.FirstName })(ord.FromStrictCompare[string]()),
+//	})
+//	sorted := sortByName(people)
+//	// Result: [{"Jones", "Bob"}, {"Smith", "Alice"}, {"Smith", "John"}]
+func SortBy[T any](ord []O.Ord[T]) func(ma []T) []T {
+	return G.SortBy[[]T, []O.Ord[T]](ord)
+}

v2/array/sort_test.go

@@ -0,0 +1,36 @@
+// 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"
+
+	O "github.com/IBM/fp-go/v2/ord"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSort(t *testing.T) {
+
+	ordInt := O.FromStrictCompare[int]()
+
+	input := []int{2, 1, 3}
+
+	res := Sort(ordInt)(input)
+
+	assert.Equal(t, []int{1, 2, 3}, res)
+	assert.Equal(t, []int{2, 1, 3}, input)
+
+}

v2/array/testing/laws.go

@@ -0,0 +1,74 @@
+// 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 testing
+
+import (
+	"testing"
+
+	RA "github.com/IBM/fp-go/v2/array"
+	EQ "github.com/IBM/fp-go/v2/eq"
+	L "github.com/IBM/fp-go/v2/internal/monad/testing"
+)
+
+// AssertLaws asserts the apply monad laws for the array monad
+func AssertLaws[A, B, C any](t *testing.T,
+	eqa EQ.Eq[A],
+	eqb EQ.Eq[B],
+	eqc EQ.Eq[C],
+
+	ab func(A) B,
+	bc func(B) C,
+) func(a A) bool {
+
+	return L.AssertLaws(t,
+		RA.Eq(eqa),
+		RA.Eq(eqb),
+		RA.Eq(eqc),
+
+		RA.Of[A],
+		RA.Of[B],
+		RA.Of[C],
+
+		RA.Of[func(A) A],
+		RA.Of[func(A) B],
+		RA.Of[func(B) C],
+		RA.Of[func(func(A) B) B],
+
+		RA.MonadMap[A, A],
+		RA.MonadMap[A, B],
+		RA.MonadMap[A, C],
+		RA.MonadMap[B, C],
+
+		RA.MonadMap[func(B) C, func(func(A) B) func(A) C],
+
+		RA.MonadChain[A, A],
+		RA.MonadChain[A, B],
+		RA.MonadChain[A, C],
+		RA.MonadChain[B, C],
+
+		RA.MonadAp[A, A],
+		RA.MonadAp[B, A],
+		RA.MonadAp[C, B],
+		RA.MonadAp[C, A],
+
+		RA.MonadAp[B, func(A) B],
+		RA.MonadAp[func(A) C, func(A) B],
+
+		ab,
+		bc,
+	)
+
+}

v2/array/testing/laws_test.go

@@ -0,0 +1,47 @@
+// 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 testing
+
+import (
+	"fmt"
+	"testing"
+
+	EQ "github.com/IBM/fp-go/v2/eq"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMonadLaws(t *testing.T) {
+	// some comparison
+	eqa := EQ.FromStrictEquals[bool]()
+	eqb := EQ.FromStrictEquals[int]()
+	eqc := EQ.FromStrictEquals[string]()
+
+	ab := func(a bool) int {
+		if a {
+			return 1
+		}
+		return 0
+	}
+
+	bc := func(b int) string {
+		return fmt.Sprintf("value %d", b)
+	}
+
+	laws := AssertLaws(t, eqa, eqb, eqc, ab, bc)
+
+	assert.True(t, laws(true))
+	assert.True(t, laws(false))
+}

v2/array/traverse.go

@@ -0,0 +1,78 @@
+// 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 (
+	"github.com/IBM/fp-go/v2/internal/array"
+)
+
+// Traverse maps each element of an array to an effect (HKT), then collects the results
+// into an effect of an array. This is like a combination of Map and Sequence.
+//
+// Unlike Sequence which works with []HKT<A> -> HKT<[]A>, Traverse works with
+// []A -> (A -> HKT<B>) -> HKT<[]B>, allowing you to transform elements while sequencing effects.
+//
+// Type parameters:
+//   - HKTB = HKT<B> (e.g., Option[B], Either[E, B])
+//   - HKTAB = HKT<func(B)[]B> (intermediate type for applicative)
+//   - HKTRB = HKT<[]B> (e.g., Option[[]B], Either[E, []B])
+//
+// Example:
+//
+//	import (
+//	    "github.com/IBM/fp-go/v2/option"
+//	    "strconv"
+//	)
+//
+//	// Parse strings to ints, returning None if any parse fails
+//	parseAll := array.Traverse(
+//	    option.Of[[]int],
+//	    option.Map[[]int, func(int) []int],
+//	    option.Ap[[]int, int],
+//	    func(s string) option.Option[int] {
+//	        if n, err := strconv.Atoi(s); err == nil {
+//	            return option.Some(n)
+//	        }
+//	        return option.None[int]()
+//	    },
+//	)
+//
+//	result := parseAll([]string{"1", "2", "3"}) // Some([1, 2, 3])
+//	result2 := parseAll([]string{"1", "x", "3"}) // None
+func Traverse[A, B, HKTB, HKTAB, HKTRB any](
+	fof func([]B) HKTRB,
+	fmap func(func([]B) func(B) []B) func(HKTRB) HKTAB,
+	fap func(HKTB) func(HKTAB) HKTRB,
+
+	f func(A) HKTB) func([]A) HKTRB {
+	return array.Traverse[[]A](fof, fmap, fap, f)
+}
+
+// MonadTraverse is the monadic version of Traverse that takes the array as a parameter.
+// It maps each element of an array to an effect (HKT), then collects the results
+// into an effect of an array.
+//
+// This is useful when you want to apply the traverse operation directly without currying.
+func MonadTraverse[A, B, HKTB, HKTAB, HKTRB any](
+	fof func([]B) HKTRB,
+	fmap func(func([]B) func(B) []B) func(HKTRB) HKTAB,
+	fap func(HKTB) func(HKTAB) HKTRB,
+
+	ta []A,
+	f func(A) HKTB) HKTRB {
+
+	return array.MonadTraverse(fof, fmap, fap, ta, f)
+}

v2/array/traverse_test.go

@@ -0,0 +1,43 @@
+// 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"
+
+	O "github.com/IBM/fp-go/v2/option"
+	"github.com/stretchr/testify/assert"
+)
+
+type ArrayType = []int
+
+func TestTraverse(t *testing.T) {
+
+	traverse := Traverse(
+		O.Of[ArrayType],
+		O.Map[ArrayType, func(int) ArrayType],
+		O.Ap[ArrayType, int],
+
+		func(n int) O.Option[int] {
+			if n%2 == 0 {
+				return O.None[int]()
+			}
+			return O.Of(n)
+		})
+
+	assert.Equal(t, O.None[[]int](), traverse(ArrayType{1, 2}))
+	assert.Equal(t, O.Of(ArrayType{1, 3}), traverse(ArrayType{1, 3}))
+}

v2/array/uniq.go

@@ -0,0 +1,47 @@
+package array
+
+import (
+	G "github.com/IBM/fp-go/v2/array/generic"
+)
+
+// StrictUniq converts an array of arbitrary items into an array of unique items
+// where uniqueness is determined by the built-in equality constraint (comparable).
+// The first occurrence of each unique value is kept, subsequent duplicates are removed.
+//
+// Example:
+//
+//	numbers := []int{1, 2, 2, 3, 3, 3, 4}
+//	unique := array.StrictUniq(numbers) // [1, 2, 3, 4]
+//
+//	strings := []string{"a", "b", "a", "c", "b"}
+//	unique2 := array.StrictUniq(strings) // ["a", "b", "c"]
+func StrictUniq[A comparable](as []A) []A {
+	return G.StrictUniq[[]A](as)
+}
+
+// Uniq converts an array of arbitrary items into an array of unique items
+// where uniqueness is determined based on a key extractor function.
+// The first occurrence of each unique key is kept, subsequent duplicates are removed.
+//
+// This is useful for removing duplicates from arrays of complex types based on a specific field.
+//
+// Example:
+//
+//	type Person struct {
+//	    Name string
+//	    Age  int
+//	}
+//
+//	people := []Person{
+//	    {"Alice", 30},
+//	    {"Bob", 25},
+//	    {"Alice", 35}, // duplicate name
+//	    {"Charlie", 30},
+//	}
+//
+//	uniqueByName := array.Uniq(func(p Person) string { return p.Name })
+//	result := uniqueByName(people)
+//	// Result: [{"Alice", 30}, {"Bob", 25}, {"Charlie", 30}]
+func Uniq[A any, K comparable](f func(A) K) func(as []A) []A {
+	return G.Uniq[[]A](f)
+}

v2/array/uniq_test.go

@@ -0,0 +1,14 @@
+package array
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestUniq(t *testing.T) {
+	data := From(1, 2, 3, 2, 4, 1)
+
+	uniq := StrictUniq(data)
+	assert.Equal(t, From(1, 2, 3, 4), uniq)
+}

v2/array/zip.go

@@ -0,0 +1,77 @@
+// 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 (
+	G "github.com/IBM/fp-go/v2/array/generic"
+	T "github.com/IBM/fp-go/v2/tuple"
+)
+
+// ZipWith applies a function to pairs of elements at the same index in two arrays,
+// collecting the results in a new array. If one input array is shorter, excess elements
+// of the longer array are discarded.
+//
+// Example:
+//
+//	names := []string{"Alice", "Bob", "Charlie"}
+//	ages := []int{30, 25, 35}
+//
+//	result := array.ZipWith(names, ages, func(name string, age int) string {
+//	    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"]
+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)
+}
+
+// Zip takes two arrays and returns an array of corresponding pairs (tuples).
+// If one input array is shorter, excess elements of the longer array are discarded.
+//
+// Example:
+//
+//	names := []string{"Alice", "Bob", "Charlie"}
+//	ages := []int{30, 25, 35}
+//
+//	pairs := array.Zip(ages)(names)
+//	// Result: [(Alice, 30), (Bob, 25), (Charlie, 35)]
+//
+//	// With different lengths
+//	pairs2 := array.Zip([]int{1, 2})([]string{"a", "b", "c"})
+//	// Result: [(a, 1), (b, 2)]
+func Zip[A, B any](fb []B) func([]A) []T.Tuple2[A, B] {
+	return G.Zip[[]A, []B, []T.Tuple2[A, B]](fb)
+}
+
+// Unzip is the reverse of Zip. It takes an array of pairs (tuples) and returns
+// two corresponding arrays, one containing all first elements and one containing all second elements.
+//
+// Example:
+//
+//	import "github.com/IBM/fp-go/v2/tuple"
+//
+//	pairs := []tuple.Tuple2[string, int]{
+//	    tuple.MakeTuple2("Alice", 30),
+//	    tuple.MakeTuple2("Bob", 25),
+//	    tuple.MakeTuple2("Charlie", 35),
+//	}
+//
+//	result := array.Unzip(pairs)
+//	// Result: (["Alice", "Bob", "Charlie"], [30, 25, 35])
+//	names := result.Head  // ["Alice", "Bob", "Charlie"]
+//	ages := result.Tail   // [30, 25, 35]
+func Unzip[A, B any](cs []T.Tuple2[A, B]) T.Tuple2[[]A, []B] {
+	return G.Unzip[[]A, []B, []T.Tuple2[A, B]](cs)
+}

v2/array/zip_test.go

@@ -0,0 +1,56 @@
+// 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 (
+	"fmt"
+	"testing"
+
+	T "github.com/IBM/fp-go/v2/tuple"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestZipWith(t *testing.T) {
+	left := From(1, 2, 3)
+	right := From("a", "b", "c", "d")
+
+	res := ZipWith(left, right, func(l int, r string) string {
+		return fmt.Sprintf("%s%d", r, l)
+	})
+
+	assert.Equal(t, From("a1", "b2", "c3"), res)
+}
+
+func TestZip(t *testing.T) {
+	left := From(1, 2, 3)
+	right := From("a", "b", "c", "d")
+
+	res := Zip[string](left)(right)
+
+	assert.Equal(t, From(T.MakeTuple2("a", 1), T.MakeTuple2("b", 2), T.MakeTuple2("c", 3)), res)
+}
+
+func TestUnzip(t *testing.T) {
+	left := From(1, 2, 3)
+	right := From("a", "b", "c")
+
+	zipped := Zip[string](left)(right)
+
+	unzipped := Unzip(zipped)
+
+	assert.Equal(t, right, unzipped.F1)
+	assert.Equal(t, left, unzipped.F2)
+}

v2/assert/assert_test.go

@@ -0,0 +1,109 @@
+// Copyright (c) 2023 - 2025 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package assert
+
+import (
+	"fmt"
+	"testing"
+
+	E "github.com/IBM/fp-go/v2/either"
+	EQ "github.com/IBM/fp-go/v2/eq"
+	"github.com/stretchr/testify/assert"
+)
+
+var (
+	errTest = fmt.Errorf("test failure")
+
+	// Eq is the equal predicate checking if objects are equal
+	Eq = EQ.FromEquals(assert.ObjectsAreEqual)
+)
+
+func wrap1[T any](wrapped func(t assert.TestingT, expected, actual any, msgAndArgs ...any) bool, t *testing.T, expected T) func(actual T) E.Either[error, T] {
+	return func(actual T) E.Either[error, T] {
+		ok := wrapped(t, expected, actual)
+		if ok {
+			return E.Of[error](actual)
+		}
+		return E.Left[T](errTest)
+	}
+}
+
+// NotEqual tests if the expected and the actual values are not equal
+func NotEqual[T any](t *testing.T, expected T) func(actual T) E.Either[error, T] {
+	return wrap1(assert.NotEqual, t, expected)
+}
+
+// Equal tests if the expected and the actual values are equal
+func Equal[T any](t *testing.T, expected T) func(actual T) E.Either[error, T] {
+	return wrap1(assert.Equal, t, expected)
+}
+
+// Length tests if an array has the expected length
+func Length[T any](t *testing.T, expected int) func(actual []T) E.Either[error, []T] {
+	return func(actual []T) E.Either[error, []T] {
+		ok := assert.Len(t, actual, expected)
+		if ok {
+			return E.Of[error](actual)
+		}
+		return E.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] {
+			assert.NoError(t, e)
+			return E.Left[T](e)
+		}, func(value T) E.Either[error, T] {
+			assert.NoError(t, nil)
+			return E.Right[error](value)
+		})
+	}
+}
+
+// ArrayContains tests if a value is contained in an array
+func ArrayContains[T any](t *testing.T, expected T) func(actual []T) E.Either[error, []T] {
+	return func(actual []T) E.Either[error, []T] {
+		ok := assert.Contains(t, actual, expected)
+		if ok {
+			return E.Of[error](actual)
+		}
+		return E.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] {
+		ok := assert.Contains(t, actual, expected)
+		if ok {
+			return E.Of[error](actual)
+		}
+		return E.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] {
+		ok := assert.NotContains(t, actual, expected)
+		if ok {
+			return E.Of[error](actual)
+		}
+		return E.Left[map[K]T](errTest)
+	}
+}

v2/boolean/boolean.go

@@ -0,0 +1,59 @@
+// 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 boolean
+
+import (
+	"github.com/IBM/fp-go/v2/eq"
+	"github.com/IBM/fp-go/v2/monoid"
+	"github.com/IBM/fp-go/v2/ord"
+)
+
+var (
+	// MonoidAny is the boolean [monoid.Monoid] under disjunction
+	MonoidAny = monoid.MakeMonoid(
+		func(l, r bool) bool {
+			return l || r
+		},
+		false,
+	)
+
+	// MonoidAll is the boolean [monoid.Monoid] under conjuction
+	MonoidAll = monoid.MakeMonoid(
+		func(l, r bool) bool {
+			return l && r
+		},
+		true,
+	)
+
+	// Eq is the equals predicate for boolean
+	Eq = eq.FromStrictEquals[bool]()
+
+	// Ord is the strict ordering for boolean
+	Ord = ord.MakeOrd(func(l, r bool) int {
+		if l {
+			if r {
+				return 0
+			}
+			return +1
+		}
+		if r {
+			return -1
+		}
+		return 0
+	}, func(l, r bool) bool {
+		return l == r
+	})
+)

v2/boolean/boolean_test.go

@@ -0,0 +1,246 @@
+// 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 boolean
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMonoidAny(t *testing.T) {
+	t.Run("identity element is false", func(t *testing.T) {
+		assert.Equal(t, false, MonoidAny.Empty())
+	})
+
+	t.Run("false OR false = false", func(t *testing.T) {
+		result := MonoidAny.Concat(false, false)
+		assert.Equal(t, false, result)
+	})
+
+	t.Run("false OR true = true", func(t *testing.T) {
+		result := MonoidAny.Concat(false, true)
+		assert.Equal(t, true, result)
+	})
+
+	t.Run("true OR false = true", func(t *testing.T) {
+		result := MonoidAny.Concat(true, false)
+		assert.Equal(t, true, result)
+	})
+
+	t.Run("true OR true = true", func(t *testing.T) {
+		result := MonoidAny.Concat(true, true)
+		assert.Equal(t, true, result)
+	})
+
+	t.Run("left identity: empty OR x = x", func(t *testing.T) {
+		assert.Equal(t, true, MonoidAny.Concat(MonoidAny.Empty(), true))
+		assert.Equal(t, false, MonoidAny.Concat(MonoidAny.Empty(), false))
+	})
+
+	t.Run("right identity: x OR empty = x", func(t *testing.T) {
+		assert.Equal(t, true, MonoidAny.Concat(true, MonoidAny.Empty()))
+		assert.Equal(t, false, MonoidAny.Concat(false, MonoidAny.Empty()))
+	})
+
+	t.Run("associativity: (a OR b) OR c = a OR (b OR c)", func(t *testing.T) {
+		a, b, c := true, false, true
+		left := MonoidAny.Concat(MonoidAny.Concat(a, b), c)
+		right := MonoidAny.Concat(a, MonoidAny.Concat(b, c))
+		assert.Equal(t, left, right)
+	})
+}
+
+func TestMonoidAll(t *testing.T) {
+	t.Run("identity element is true", func(t *testing.T) {
+		assert.Equal(t, true, MonoidAll.Empty())
+	})
+
+	t.Run("false AND false = false", func(t *testing.T) {
+		result := MonoidAll.Concat(false, false)
+		assert.Equal(t, false, result)
+	})
+
+	t.Run("false AND true = false", func(t *testing.T) {
+		result := MonoidAll.Concat(false, true)
+		assert.Equal(t, false, result)
+	})
+
+	t.Run("true AND false = false", func(t *testing.T) {
+		result := MonoidAll.Concat(true, false)
+		assert.Equal(t, false, result)
+	})
+
+	t.Run("true AND true = true", func(t *testing.T) {
+		result := MonoidAll.Concat(true, true)
+		assert.Equal(t, true, result)
+	})
+
+	t.Run("left identity: empty AND x = x", func(t *testing.T) {
+		assert.Equal(t, true, MonoidAll.Concat(MonoidAll.Empty(), true))
+		assert.Equal(t, false, MonoidAll.Concat(MonoidAll.Empty(), false))
+	})
+
+	t.Run("right identity: x AND empty = x", func(t *testing.T) {
+		assert.Equal(t, true, MonoidAll.Concat(true, MonoidAll.Empty()))
+		assert.Equal(t, false, MonoidAll.Concat(false, MonoidAll.Empty()))
+	})
+
+	t.Run("associativity: (a AND b) AND c = a AND (b AND c)", func(t *testing.T) {
+		a, b, c := true, false, true
+		left := MonoidAll.Concat(MonoidAll.Concat(a, b), c)
+		right := MonoidAll.Concat(a, MonoidAll.Concat(b, c))
+		assert.Equal(t, left, right)
+	})
+}
+
+func TestEq(t *testing.T) {
+	t.Run("true equals true", func(t *testing.T) {
+		assert.True(t, Eq.Equals(true, true))
+	})
+
+	t.Run("false equals false", func(t *testing.T) {
+		assert.True(t, Eq.Equals(false, false))
+	})
+
+	t.Run("true not equals false", func(t *testing.T) {
+		assert.False(t, Eq.Equals(true, false))
+	})
+
+	t.Run("false not equals true", func(t *testing.T) {
+		assert.False(t, Eq.Equals(false, true))
+	})
+
+	t.Run("reflexivity: x equals x", func(t *testing.T) {
+		assert.True(t, Eq.Equals(true, true))
+		assert.True(t, Eq.Equals(false, false))
+	})
+
+	t.Run("symmetry: if x equals y then y equals x", func(t *testing.T) {
+		assert.Equal(t, Eq.Equals(true, false), Eq.Equals(false, true))
+		assert.Equal(t, Eq.Equals(true, true), Eq.Equals(true, true))
+	})
+
+	t.Run("transitivity: if x equals y and y equals z then x equals z", func(t *testing.T) {
+		x, y, z := true, true, true
+		if Eq.Equals(x, y) && Eq.Equals(y, z) {
+			assert.True(t, Eq.Equals(x, z))
+		}
+	})
+}
+
+func TestOrd(t *testing.T) {
+	t.Run("false < true", func(t *testing.T) {
+		result := Ord.Compare(false, true)
+		assert.Equal(t, -1, result)
+	})
+
+	t.Run("true > false", func(t *testing.T) {
+		result := Ord.Compare(true, false)
+		assert.Equal(t, 1, result)
+	})
+
+	t.Run("true == true", func(t *testing.T) {
+		result := Ord.Compare(true, true)
+		assert.Equal(t, 0, result)
+	})
+
+	t.Run("false == false", func(t *testing.T) {
+		result := Ord.Compare(false, false)
+		assert.Equal(t, 0, result)
+	})
+
+	t.Run("Equals method works", func(t *testing.T) {
+		assert.True(t, Ord.Equals(true, true))
+		assert.True(t, Ord.Equals(false, false))
+		assert.False(t, Ord.Equals(true, false))
+		assert.False(t, Ord.Equals(false, true))
+	})
+
+	t.Run("reflexivity: x <= x", func(t *testing.T) {
+		assert.True(t, Ord.Compare(true, true) == 0)
+		assert.True(t, Ord.Compare(false, false) == 0)
+	})
+
+	t.Run("antisymmetry: if x <= y and y <= x then x == y", func(t *testing.T) {
+		x, y := true, true
+		if Ord.Compare(x, y) <= 0 && Ord.Compare(y, x) <= 0 {
+			assert.Equal(t, 0, Ord.Compare(x, y))
+		}
+	})
+
+	t.Run("transitivity: if x <= y and y <= z then x <= z", func(t *testing.T) {
+		x, y, z := false, true, true
+		if Ord.Compare(x, y) <= 0 && Ord.Compare(y, z) <= 0 {
+			assert.True(t, Ord.Compare(x, z) <= 0)
+		}
+	})
+
+	t.Run("totality: x <= y or y <= x", func(t *testing.T) {
+		assert.True(t, Ord.Compare(true, false) >= 0 || Ord.Compare(false, true) >= 0)
+		assert.True(t, Ord.Compare(false, true) <= 0 || Ord.Compare(true, false) <= 0)
+	})
+}
+
+// Example tests that also serve as documentation
+func ExampleMonoidAny() {
+	// Combine booleans with OR
+	result := MonoidAny.Concat(false, true)
+	println(result) // true
+
+	// Identity element
+	identity := MonoidAny.Empty()
+	println(identity) // false
+
+	// Output:
+}
+
+func ExampleMonoidAll() {
+	// Combine booleans with AND
+	result := MonoidAll.Concat(true, true)
+	println(result) // true
+
+	// Identity element
+	identity := MonoidAll.Empty()
+	println(identity) // true
+
+	// Output:
+}
+
+func ExampleEq() {
+	// Check equality
+	equal := Eq.Equals(true, true)
+	println(equal) // true
+
+	notEqual := Eq.Equals(true, false)
+	println(notEqual) // false
+
+	// Output:
+}
+
+func ExampleOrd() {
+	// Compare booleans (false < true)
+	cmp := Ord.Compare(false, true)
+	println(cmp) // -1
+
+	cmp2 := Ord.Compare(true, false)
+	println(cmp2) // 1
+
+	cmp3 := Ord.Compare(true, true)
+	println(cmp3) // 0
+
+	// Output:
+}

v2/boolean/doc.go

@@ -0,0 +1,138 @@
+// 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 boolean provides functional programming utilities for working with boolean values.
+//
+// This package offers algebraic structures (Monoid, Eq, Ord) for boolean values,
+// enabling functional composition and reasoning about boolean operations.
+//
+// # Monoids
+//
+// The package provides two monoid instances for booleans:
+//
+//   - MonoidAny: Combines booleans using logical OR (disjunction), with false as identity
+//   - MonoidAll: Combines booleans using logical AND (conjunction), with true as identity
+//
+// # MonoidAny - Logical OR
+//
+// MonoidAny implements the boolean monoid under disjunction (OR operation).
+// The identity element is false, meaning false OR x = x for any boolean x.
+//
+// Example:
+//
+//	import "github.com/IBM/fp-go/v2/boolean"
+//
+//	// Combine multiple booleans with OR
+//	result := boolean.MonoidAny.Concat(false, true)  // true
+//	result2 := boolean.MonoidAny.Concat(false, false) // false
+//
+//	// Identity element
+//	identity := boolean.MonoidAny.Empty() // false
+//
+//	// Check if any value in a collection is true
+//	import "github.com/IBM/fp-go/v2/array"
+//	values := []bool{false, false, true, false}
+//	anyTrue := array.Fold(boolean.MonoidAny)(values) // true
+//
+// # MonoidAll - Logical AND
+//
+// MonoidAll implements the boolean monoid under conjunction (AND operation).
+// The identity element is true, meaning true AND x = x for any boolean x.
+//
+// Example:
+//
+//	import "github.com/IBM/fp-go/v2/boolean"
+//
+//	// Combine multiple booleans with AND
+//	result := boolean.MonoidAll.Concat(true, true)   // true
+//	result2 := boolean.MonoidAll.Concat(true, false) // false
+//
+//	// Identity element
+//	identity := boolean.MonoidAll.Empty() // true
+//
+//	// Check if all values in a collection are true
+//	import "github.com/IBM/fp-go/v2/array"
+//	values := []bool{true, true, true}
+//	allTrue := array.Fold(boolean.MonoidAll)(values) // true
+//
+// # Equality
+//
+// The Eq instance provides structural equality for booleans:
+//
+//	import "github.com/IBM/fp-go/v2/boolean"
+//
+//	equal := boolean.Eq.Equals(true, true)   // true
+//	equal2 := boolean.Eq.Equals(true, false) // false
+//
+// # Ordering
+//
+// The Ord instance provides a total ordering for booleans where false < true:
+//
+//	import "github.com/IBM/fp-go/v2/boolean"
+//
+//	cmp := boolean.Ord.Compare(false, true) // -1 (false < true)
+//	cmp2 := boolean.Ord.Compare(true, false) // +1 (true > false)
+//	cmp3 := boolean.Ord.Compare(true, true)  // 0 (equal)
+//
+// # Use Cases
+//
+// The boolean package is particularly useful for:
+//
+//   - Combining multiple boolean conditions functionally
+//   - Implementing validation logic that accumulates results
+//   - Working with predicates in a composable way
+//   - Folding collections of boolean values
+//
+// Example - Validation:
+//
+//	import (
+//	    "github.com/IBM/fp-go/v2/array"
+//	    "github.com/IBM/fp-go/v2/boolean"
+//	)
+//
+//	type User struct {
+//	    Name  string
+//	    Email string
+//	    Age   int
+//	}
+//
+//	// Define validation predicates
+//	validations := []func(User) bool{
+//	    func(u User) bool { return len(u.Name) > 0 },
+//	    func(u User) bool { return len(u.Email) > 0 },
+//	    func(u User) bool { return u.Age >= 18 },
+//	}
+//
+//	// Check if user passes all validations
+//	user := User{"Alice", "alice@example.com", 25}
+//	results := array.Map(func(v func(User) bool) bool {
+//	    return v(user)
+//	})(validations)
+//	allValid := array.Fold(boolean.MonoidAll)(results) // true
+//
+// Example - Any Match:
+//
+//	import (
+//	    "github.com/IBM/fp-go/v2/array"
+//	    "github.com/IBM/fp-go/v2/boolean"
+//	)
+//
+//	// Check if any number is even
+//	numbers := []int{1, 3, 5, 7, 8, 9}
+//	checks := array.Map(func(n int) bool {
+//	    return n%2 == 0
+//	})(numbers)
+//	hasEven := array.Fold(boolean.MonoidAny)(checks) // true
+package boolean

v2/boolean/types.go

@@ -0,0 +1,22 @@
+// 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 boolean
+
+import "github.com/IBM/fp-go/v2/monoid"
+
+type (
+	Monoid = monoid.Monoid[bool]
+)

v2/bounded/bounded.go

@@ -0,0 +1,62 @@
+// 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 bounded
+
+import "github.com/IBM/fp-go/v2/ord"
+
+type Bounded[T any] interface {
+	ord.Ord[T]
+	Top() T
+	Bottom() T
+}
+
+type bounded[T any] struct {
+	c func(x, y T) int
+	e func(x, y T) bool
+	t T
+	b T
+}
+
+func (b bounded[T]) Equals(x, y T) bool {
+	return b.e(x, y)
+}
+
+func (b bounded[T]) Compare(x, y T) int {
+	return b.c(x, y)
+}
+
+func (b bounded[T]) Top() T {
+	return b.t
+}
+
+func (b bounded[T]) Bottom() T {
+	return b.b
+}
+
+// MakeBounded creates an instance of a bounded type
+func MakeBounded[T any](o ord.Ord[T], t, b T) Bounded[T] {
+	return bounded[T]{c: o.Compare, e: o.Equals, t: t, b: b}
+}
+
+// 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())
+}
+
+// Reverse reverses the ordering and swaps the bounds
+func Reverse[T any](b Bounded[T]) Bounded[T] {
+	return MakeBounded(ord.Reverse(b), b.Bottom(), b.Top())
+}

v2/bounded/bounded_test.go

@@ -0,0 +1,212 @@
+// 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 bounded
+
+import (
+	"testing"
+
+	"github.com/IBM/fp-go/v2/ord"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMakeBounded(t *testing.T) {
+	t.Run("creates bounded instance with correct top and bottom", func(t *testing.T) {
+		b := MakeBounded(ord.FromStrictCompare[int](), 100, 0)
+
+		assert.Equal(t, 100, b.Top())
+		assert.Equal(t, 0, b.Bottom())
+	})
+
+	t.Run("preserves ordering from Ord", func(t *testing.T) {
+		b := MakeBounded(ord.FromStrictCompare[int](), 100, 0)
+
+		assert.Equal(t, -1, b.Compare(5, 10))
+		assert.Equal(t, 0, b.Compare(5, 5))
+		assert.Equal(t, 1, b.Compare(10, 5))
+	})
+
+	t.Run("preserves equality from Ord", func(t *testing.T) {
+		b := MakeBounded(ord.FromStrictCompare[int](), 100, 0)
+
+		assert.True(t, b.Equals(5, 5))
+		assert.False(t, b.Equals(5, 10))
+	})
+}
+
+func TestClamp(t *testing.T) {
+	t.Run("returns value within bounds unchanged", func(t *testing.T) {
+		b := MakeBounded(ord.FromStrictCompare[int](), 100, 0)
+		clamp := Clamp(b)
+
+		assert.Equal(t, 50, clamp(50))
+		assert.Equal(t, 0, clamp(0))
+		assert.Equal(t, 100, clamp(100))
+	})
+
+	t.Run("clamps value above top to top", func(t *testing.T) {
+		b := MakeBounded(ord.FromStrictCompare[int](), 100, 0)
+		clamp := Clamp(b)
+
+		assert.Equal(t, 100, clamp(150))
+		assert.Equal(t, 100, clamp(200))
+	})
+
+	t.Run("clamps value below bottom to bottom", func(t *testing.T) {
+		b := MakeBounded(ord.FromStrictCompare[int](), 100, 0)
+		clamp := Clamp(b)
+
+		assert.Equal(t, 0, clamp(-10))
+		assert.Equal(t, 0, clamp(-100))
+	})
+
+	t.Run("works with float64", func(t *testing.T) {
+		b := MakeBounded(ord.FromStrictCompare[float64](), 1.0, 0.0)
+		clamp := Clamp(b)
+
+		assert.Equal(t, 0.5, clamp(0.5))
+		assert.Equal(t, 1.0, clamp(1.5))
+		assert.Equal(t, 0.0, clamp(-0.5))
+	})
+
+	t.Run("works with strings", func(t *testing.T) {
+		b := MakeBounded(ord.FromStrictCompare[string](), "z", "a")
+		clamp := Clamp(b)
+
+		assert.Equal(t, "m", clamp("m"))
+		assert.Equal(t, "z", clamp("zzz"))
+		assert.Equal(t, "a", clamp("A"))
+	})
+}
+
+func TestReverse(t *testing.T) {
+	t.Run("reverses the ordering", func(t *testing.T) {
+		original := MakeBounded(ord.FromStrictCompare[int](), 100, 0)
+		reversed := Reverse(original)
+
+		// In original: 5 < 10, so Compare(5, 10) = -1
+		assert.Equal(t, -1, original.Compare(5, 10))
+
+		// In reversed: 5 > 10, so Compare(5, 10) = 1
+		assert.Equal(t, 1, reversed.Compare(5, 10))
+	})
+
+	t.Run("swaps top and bottom values", func(t *testing.T) {
+		original := MakeBounded(ord.FromStrictCompare[int](), 100, 0)
+		reversed := Reverse(original)
+
+		// Reverse swaps the bounds
+		assert.Equal(t, original.Bottom(), reversed.Top())
+		assert.Equal(t, original.Top(), reversed.Bottom())
+	})
+
+	t.Run("double reverse returns to original ordering", func(t *testing.T) {
+		original := MakeBounded(ord.FromStrictCompare[int](), 100, 0)
+		reversed := Reverse(original)
+		doubleReversed := Reverse(reversed)
+
+		assert.Equal(t, original.Compare(5, 10), doubleReversed.Compare(5, 10))
+		assert.Equal(t, original.Compare(10, 5), doubleReversed.Compare(10, 5))
+	})
+
+	t.Run("preserves equality", func(t *testing.T) {
+		original := MakeBounded(ord.FromStrictCompare[int](), 100, 0)
+		reversed := Reverse(original)
+
+		assert.Equal(t, original.Equals(5, 5), reversed.Equals(5, 5))
+		assert.Equal(t, original.Equals(5, 10), reversed.Equals(5, 10))
+	})
+}
+
+func TestBoundedLaws(t *testing.T) {
+	t.Run("bottom is less than or equal to all values", func(t *testing.T) {
+		b := MakeBounded(ord.FromStrictCompare[int](), 100, 0)
+
+		testValues := []int{0, 25, 50, 75, 100}
+		for _, v := range testValues {
+			assert.True(t, b.Compare(b.Bottom(), v) <= 0,
+				"Bottom (%d) should be <= %d", b.Bottom(), v)
+		}
+	})
+
+	t.Run("top is greater than or equal to all values", func(t *testing.T) {
+		b := MakeBounded(ord.FromStrictCompare[int](), 100, 0)
+
+		testValues := []int{0, 25, 50, 75, 100}
+		for _, v := range testValues {
+			assert.True(t, b.Compare(b.Top(), v) >= 0,
+				"Top (%d) should be >= %d", b.Top(), v)
+		}
+	})
+
+	t.Run("bottom is less than or equal to top", func(t *testing.T) {
+		b := MakeBounded(ord.FromStrictCompare[int](), 100, 0)
+
+		assert.True(t, b.Compare(b.Bottom(), b.Top()) <= 0,
+			"Bottom should be <= Top")
+	})
+}
+
+// Example tests
+func ExampleMakeBounded() {
+	// Create a bounded type for percentages (0-100)
+	percentage := MakeBounded(
+		ord.FromStrictCompare[int](),
+		100, // top
+		0,   // bottom
+	)
+
+	println(percentage.Top())    // 100
+	println(percentage.Bottom()) // 0
+
+	// Output:
+}
+
+func ExampleClamp() {
+	// Create bounded type for percentages
+	percentage := MakeBounded(
+		ord.FromStrictCompare[int](),
+		100, // top
+		0,   // bottom
+	)
+
+	clamp := Clamp(percentage)
+
+	println(clamp(50))  // 50 (within bounds)
+	println(clamp(150)) // 100 (clamped to top)
+	println(clamp(-10)) // 0 (clamped to bottom)
+
+	// Output:
+}
+
+func ExampleReverse() {
+	original := MakeBounded(
+		ord.FromStrictCompare[int](),
+		100, // top
+		0,   // bottom
+	)
+
+	reversed := Reverse(original)
+
+	// Ordering is reversed
+	println(original.Compare(5, 10)) // -1 (5 < 10)
+	println(reversed.Compare(5, 10)) // 1 (5 > 10 in reversed)
+
+	// Bounds are swapped
+	println(reversed.Top())    // 0
+	println(reversed.Bottom()) // 100
+
+	// Output:
+}

v2/bounded/doc.go

@@ -0,0 +1,149 @@
+// 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 bounded provides types and functions for working with bounded ordered types.
+//
+// A Bounded type extends Ord with minimum (Bottom) and maximum (Top) values,
+// representing types that have well-defined lower and upper bounds.
+//
+// # Bounded Interface
+//
+// The Bounded interface combines ordering (Ord) with boundary values:
+//
+//	type Bounded[T any] interface {
+//	    ord.Ord[T]
+//	    Top() T    // Maximum value
+//	    Bottom() T // Minimum value
+//	}
+//
+// # Creating Bounded Instances
+//
+// Use MakeBounded to create a Bounded instance from an Ord and boundary values:
+//
+//	import (
+//	    "github.com/IBM/fp-go/v2/bounded"
+//	    "github.com/IBM/fp-go/v2/ord"
+//	)
+//
+//	// Bounded integers from 0 to 100
+//	boundedInt := bounded.MakeBounded(
+//	    ord.FromStrictCompare[int](),
+//	    100, // top
+//	    0,   // bottom
+//	)
+//
+//	top := boundedInt.Top()       // 100
+//	bottom := boundedInt.Bottom() // 0
+//
+// # Clamping Values
+//
+// The Clamp function restricts values to stay within the bounds:
+//
+//	import (
+//	    "github.com/IBM/fp-go/v2/bounded"
+//	    "github.com/IBM/fp-go/v2/ord"
+//	)
+//
+//	// Create bounded type for percentages (0-100)
+//	percentage := bounded.MakeBounded(
+//	    ord.FromStrictCompare[int](),
+//	    100, // top
+//	    0,   // bottom
+//	)
+//
+//	clamp := bounded.Clamp(percentage)
+//
+//	result1 := clamp(50)   // 50 (within bounds)
+//	result2 := clamp(150)  // 100 (clamped to top)
+//	result3 := clamp(-10)  // 0 (clamped to bottom)
+//
+// # Reversing Bounds
+//
+// The Reverse function swaps the ordering and bounds:
+//
+//	import (
+//	    "github.com/IBM/fp-go/v2/bounded"
+//	    "github.com/IBM/fp-go/v2/ord"
+//	)
+//
+//	original := bounded.MakeBounded(
+//	    ord.FromStrictCompare[int](),
+//	    100, // top
+//	    0,   // bottom
+//	)
+//
+//	reversed := bounded.Reverse(original)
+//
+//	// In reversed, ordering is flipped and bounds are swapped
+//	// Compare(10, 20) returns 1 instead of -1
+//	// Top() returns 0 and Bottom() returns 100
+//
+// # Use Cases
+//
+// Bounded types are useful for:
+//
+//   - Representing ranges with well-defined limits (e.g., percentages, grades)
+//   - Implementing safe arithmetic that stays within bounds
+//   - Validating input values against constraints
+//   - Creating domain-specific types with natural boundaries
+//
+// # Example - Temperature Range
+//
+//	import (
+//	    "github.com/IBM/fp-go/v2/bounded"
+//	    "github.com/IBM/fp-go/v2/ord"
+//	)
+//
+//	// Celsius temperature range for a thermostat
+//	thermostat := bounded.MakeBounded(
+//	    ord.FromStrictCompare[float64](),
+//	    30.0, // max temperature
+//	    15.0, // min temperature
+//	)
+//
+//	clampTemp := bounded.Clamp(thermostat)
+//
+//	// User tries to set temperature
+//	desired := 35.0
+//	actual := clampTemp(desired) // 30.0 (clamped to maximum)
+//
+// # Example - Bounded Characters
+//
+//	import (
+//	    "github.com/IBM/fp-go/v2/bounded"
+//	    "github.com/IBM/fp-go/v2/ord"
+//	)
+//
+//	// Lowercase letters only
+//	lowercase := bounded.MakeBounded(
+//	    ord.FromStrictCompare[rune](),
+//	    'z', // top
+//	    'a', // bottom
+//	)
+//
+//	clampChar := bounded.Clamp(lowercase)
+//
+//	result1 := clampChar('m')  // 'm' (within bounds)
+//	result2 := clampChar('A')  // 'a' (clamped to bottom)
+//	result3 := clampChar('~')  // 'z' (clamped to top)
+//
+// # Laws
+//
+// Bounded instances must satisfy the Ord laws plus:
+//
+//   - Bottom is less than or equal to all values: Compare(Bottom(), x) <= 0
+//   - Top is greater than or equal to all values: Compare(Top(), x) >= 0
+//   - Bottom <= Top: Compare(Bottom(), Top()) <= 0
+package bounded

v2/bytes/bytes.go

@@ -0,0 +1,28 @@
+// 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 bytes
+
+func Empty() []byte {
+	return Monoid.Empty()
+}
+
+func ToString(a []byte) string {
+	return string(a)
+}
+
+func Size(as []byte) int {
+	return len(as)
+}

v2/bytes/bytes_test.go

@@ -0,0 +1,221 @@
+// 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 bytes
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestEmpty(t *testing.T) {
+	t.Run("returns empty byte slice", func(t *testing.T) {
+		result := Empty()
+		assert.NotNil(t, result)
+		assert.Equal(t, 0, len(result))
+	})
+
+	t.Run("is identity for Monoid", func(t *testing.T) {
+		data := []byte("test")
+
+		// Left identity: empty + data = data
+		left := Monoid.Concat(Empty(), data)
+		assert.Equal(t, data, left)
+
+		// Right identity: data + empty = data
+		right := Monoid.Concat(data, Empty())
+		assert.Equal(t, data, right)
+	})
+}
+
+func TestToString(t *testing.T) {
+	t.Run("converts byte slice to string", func(t *testing.T) {
+		result := ToString([]byte("hello"))
+		assert.Equal(t, "hello", result)
+	})
+
+	t.Run("handles empty byte slice", func(t *testing.T) {
+		result := ToString([]byte{})
+		assert.Equal(t, "", result)
+	})
+
+	t.Run("handles binary data", func(t *testing.T) {
+		data := []byte{0x48, 0x65, 0x6c, 0x6c, 0x6f} // "Hello"
+		result := ToString(data)
+		assert.Equal(t, "Hello", result)
+	})
+}
+
+func TestSize(t *testing.T) {
+	t.Run("returns size of byte slice", func(t *testing.T) {
+		assert.Equal(t, 0, Size([]byte{}))
+		assert.Equal(t, 5, Size([]byte("hello")))
+		assert.Equal(t, 10, Size([]byte("0123456789")))
+	})
+
+	t.Run("handles binary data", func(t *testing.T) {
+		data := []byte{0x00, 0x01, 0x02, 0x03}
+		assert.Equal(t, 4, Size(data))
+	})
+}
+
+func TestMonoidConcat(t *testing.T) {
+	t.Run("concatenates two byte slices", func(t *testing.T) {
+		result := Monoid.Concat([]byte("Hello"), []byte(" World"))
+		assert.Equal(t, []byte("Hello World"), result)
+	})
+
+	t.Run("handles empty slices", func(t *testing.T) {
+		result1 := Monoid.Concat([]byte{}, []byte("test"))
+		assert.Equal(t, []byte("test"), result1)
+
+		result2 := Monoid.Concat([]byte("test"), []byte{})
+		assert.Equal(t, []byte("test"), result2)
+
+		result3 := Monoid.Concat([]byte{}, []byte{})
+		assert.Equal(t, []byte{}, result3)
+	})
+
+	t.Run("associativity: (a + b) + c = a + (b + c)", func(t *testing.T) {
+		a := []byte("a")
+		b := []byte("b")
+		c := []byte("c")
+
+		left := Monoid.Concat(Monoid.Concat(a, b), c)
+		right := Monoid.Concat(a, Monoid.Concat(b, c))
+
+		assert.Equal(t, left, right)
+	})
+}
+
+func TestConcatAll(t *testing.T) {
+	t.Run("concatenates multiple byte slices", func(t *testing.T) {
+		result := ConcatAll(
+			[]byte("Hello"),
+			[]byte(" "),
+			[]byte("World"),
+			[]byte("!"),
+		)
+		assert.Equal(t, []byte("Hello World!"), result)
+	})
+
+	t.Run("handles empty input", func(t *testing.T) {
+		result := ConcatAll()
+		assert.Equal(t, []byte{}, result)
+	})
+
+	t.Run("handles single slice", func(t *testing.T) {
+		result := ConcatAll([]byte("test"))
+		assert.Equal(t, []byte("test"), result)
+	})
+
+	t.Run("handles slices with empty elements", func(t *testing.T) {
+		result := ConcatAll(
+			[]byte("a"),
+			[]byte{},
+			[]byte("b"),
+			[]byte{},
+			[]byte("c"),
+		)
+		assert.Equal(t, []byte("abc"), result)
+	})
+
+	t.Run("handles binary data", func(t *testing.T) {
+		result := ConcatAll(
+			[]byte{0x01, 0x02},
+			[]byte{0x03, 0x04},
+			[]byte{0x05},
+		)
+		assert.Equal(t, []byte{0x01, 0x02, 0x03, 0x04, 0x05}, result)
+	})
+}
+
+func TestOrd(t *testing.T) {
+	t.Run("compares byte slices lexicographically", func(t *testing.T) {
+		// "abc" < "abd"
+		assert.Equal(t, -1, Ord.Compare([]byte("abc"), []byte("abd")))
+
+		// "abd" > "abc"
+		assert.Equal(t, 1, Ord.Compare([]byte("abd"), []byte("abc")))
+
+		// "abc" == "abc"
+		assert.Equal(t, 0, Ord.Compare([]byte("abc"), []byte("abc")))
+	})
+
+	t.Run("handles different lengths", func(t *testing.T) {
+		// "ab" < "abc"
+		assert.Equal(t, -1, Ord.Compare([]byte("ab"), []byte("abc")))
+
+		// "abc" > "ab"
+		assert.Equal(t, 1, Ord.Compare([]byte("abc"), []byte("ab")))
+	})
+
+	t.Run("handles empty slices", func(t *testing.T) {
+		// "" < "a"
+		assert.Equal(t, -1, Ord.Compare([]byte{}, []byte("a")))
+
+		// "a" > ""
+		assert.Equal(t, 1, Ord.Compare([]byte("a"), []byte{}))
+
+		// "" == ""
+		assert.Equal(t, 0, Ord.Compare([]byte{}, []byte{}))
+	})
+
+	t.Run("Equals method works", func(t *testing.T) {
+		assert.True(t, Ord.Equals([]byte("test"), []byte("test")))
+		assert.False(t, Ord.Equals([]byte("test"), []byte("Test")))
+		assert.True(t, Ord.Equals([]byte{}, []byte{}))
+	})
+
+	t.Run("handles binary data", func(t *testing.T) {
+		assert.Equal(t, -1, Ord.Compare([]byte{0x01}, []byte{0x02}))
+		assert.Equal(t, 1, Ord.Compare([]byte{0x02}, []byte{0x01}))
+		assert.Equal(t, 0, Ord.Compare([]byte{0x01, 0x02}, []byte{0x01, 0x02}))
+	})
+}
+
+// Example tests
+func ExampleEmpty() {
+	empty := Empty()
+	println(len(empty)) // 0
+
+	// Output:
+}
+
+func ExampleToString() {
+	str := ToString([]byte("hello"))
+	println(str) // hello
+
+	// Output:
+}
+
+func ExampleSize() {
+	size := Size([]byte("hello"))
+	println(size) // 5
+
+	// Output:
+}
+
+func ExampleConcatAll() {
+	result := ConcatAll(
+		[]byte("Hello"),
+		[]byte(" "),
+		[]byte("World"),
+	)
+	println(string(result)) // Hello World
+
+	// Output:
+}

v2/bytes/doc.go

@@ -0,0 +1,114 @@
+// 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 bytes provides functional programming utilities for working with byte slices.
+//
+// This package offers algebraic structures (Monoid, Ord) and utility functions
+// for byte slice operations in a functional style.
+//
+// # Monoid
+//
+// The Monoid instance for byte slices combines them through concatenation,
+// with an empty byte slice as the identity element.
+//
+// Example:
+//
+//	import "github.com/IBM/fp-go/v2/bytes"
+//
+//	// Concatenate byte slices
+//	result := bytes.Monoid.Concat([]byte("Hello"), []byte(" World"))
+//	// result: []byte("Hello World")
+//
+//	// Identity element
+//	empty := bytes.Empty() // []byte{}
+//
+// # ConcatAll
+//
+// Efficiently concatenates multiple byte slices into a single slice:
+//
+//	import "github.com/IBM/fp-go/v2/bytes"
+//
+//	result := bytes.ConcatAll(
+//	    []byte("Hello"),
+//	    []byte(" "),
+//	    []byte("World"),
+//	)
+//	// result: []byte("Hello World")
+//
+// # Ordering
+//
+// The Ord instance provides lexicographic ordering for byte slices:
+//
+//	import "github.com/IBM/fp-go/v2/bytes"
+//
+//	cmp := bytes.Ord.Compare([]byte("abc"), []byte("abd"))
+//	// cmp: -1 (abc < abd)
+//
+//	equal := bytes.Ord.Equals([]byte("test"), []byte("test"))
+//	// equal: true
+//
+// # Utility Functions
+//
+// The package provides several utility functions:
+//
+//	// Get empty byte slice
+//	empty := bytes.Empty() // []byte{}
+//
+//	// Convert to string
+//	str := bytes.ToString([]byte("hello")) // "hello"
+//
+//	// Get size
+//	size := bytes.Size([]byte("hello")) // 5
+//
+// # Use Cases
+//
+// The bytes package is particularly useful for:
+//
+//   - Building byte buffers functionally
+//   - Combining multiple byte slices efficiently
+//   - Comparing byte slices lexicographically
+//   - Working with binary data in a functional style
+//
+// # Example - Building a Protocol Message
+//
+//	import (
+//	    "github.com/IBM/fp-go/v2/bytes"
+//	    "encoding/binary"
+//	)
+//
+//	// Build a simple protocol message
+//	header := []byte{0x01, 0x02}
+//	length := make([]byte, 4)
+//	binary.BigEndian.PutUint32(length, 100)
+//	payload := []byte("data")
+//
+//	message := bytes.ConcatAll(header, length, payload)
+//
+// # Example - Sorting Byte Slices
+//
+//	import (
+//	    "github.com/IBM/fp-go/v2/array"
+//	    "github.com/IBM/fp-go/v2/bytes"
+//	)
+//
+//	data := [][]byte{
+//	    []byte("zebra"),
+//	    []byte("apple"),
+//	    []byte("mango"),
+//	}
+//
+//	sorted := array.Sort(bytes.Ord)(data)
+//	// sorted: [[]byte("apple"), []byte("mango"), []byte("zebra")]
+package bytes

v2/bytes/monoid.go

@@ -0,0 +1,34 @@
+// 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 bytes
+
+import (
+	"bytes"
+
+	A "github.com/IBM/fp-go/v2/array"
+	O "github.com/IBM/fp-go/v2/ord"
+)
+
+var (
+	// monoid for byte arrays
+	Monoid = A.Monoid[byte]()
+
+	// ConcatAll concatenates all bytes
+	ConcatAll = A.ArrayConcatAll[byte]
+
+	// Ord implements the default ordering on bytes
+	Ord = O.MakeOrd(bytes.Compare, bytes.Equal)
+)

v2/bytes/monoid_test.go

@@ -0,0 +1,26 @@
+// 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 bytes
+
+import (
+	"testing"
+
+	M "github.com/IBM/fp-go/v2/monoid/testing"
+)
+
+func TestMonoid(t *testing.T) {
+	M.AssertLaws(t, Monoid)([][]byte{[]byte(""), []byte("a"), []byte("some value")})
+}

v2/cli/apply.go

@@ -0,0 +1,432 @@
+// 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 (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"time"
+
+	C "github.com/urfave/cli/v2"
+)
+
+func generateTraverseTuple(f *os.File, i int) {
+	fmt.Fprintf(f, "\n// TraverseTuple%d is a utility function used to implement the sequence operation for higher kinded types based only on map and ap.\n", i)
+	fmt.Fprintf(f, "// The function takes a [Tuple%d] of base types and %d functions that transform these based types into higher higher kinded types. It returns a higher kinded type of a [Tuple%d] with the resolved values.\n", i, i, i)
+	fmt.Fprintf(f, "func TraverseTuple%d[\n", i)
+	// map as the starting point
+	fmt.Fprintf(f, "  MAP ~func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, " ")
+		}
+		fmt.Fprintf(f, "func(T%d)", j+1)
+	}
+	fmt.Fprintf(f, " ")
+	fmt.Fprintf(f, "T.")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, ") func(HKT_T1)")
+	if i > 1 {
+		fmt.Fprintf(f, " HKT_F")
+		for k := 1; k < i; k++ {
+			fmt.Fprintf(f, "_T%d", k+1)
+		}
+	} else {
+		fmt.Fprintf(f, " HKT_TUPLE%d", i)
+	}
+	fmt.Fprintf(f, ",\n")
+	// the applicatives
+	for j := 1; j < i; j++ {
+		fmt.Fprintf(f, "  AP%d ~func(", j)
+		fmt.Fprintf(f, "HKT_T%d) func(", j+1)
+		fmt.Fprintf(f, "HKT_F")
+		for k := j; k < i; k++ {
+			fmt.Fprintf(f, "_T%d", k+1)
+		}
+		fmt.Fprintf(f, ")")
+		if j+1 < i {
+			fmt.Fprintf(f, " HKT_F")
+			for k := j + 1; k < i; k++ {
+				fmt.Fprintf(f, "_T%d", k+1)
+			}
+		} else {
+			fmt.Fprintf(f, " HKT_TUPLE%d", i)
+		}
+		fmt.Fprintf(f, ",\n")
+	}
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, "  F%d ~func(A%d) HKT_T%d,\n", j+1, j+1, j+1)
+	}
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, "  A%d, T%d,\n", j+1, j+1)
+	}
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, "  HKT_T%d, // HKT[T%d]\n", j+1, j+1)
+	}
+	for j := 1; j < i; j++ {
+		fmt.Fprintf(f, "  HKT_F")
+		for k := j; k < i; k++ {
+			fmt.Fprintf(f, "_T%d", k+1)
+		}
+		fmt.Fprintf(f, ", // HKT[")
+		for k := j; k < i; k++ {
+			fmt.Fprintf(f, "func(T%d) ", k+1)
+		}
+		fmt.Fprintf(f, "T.")
+		writeTupleType(f, "T", i)
+		fmt.Fprintf(f, "]\n")
+	}
+	fmt.Fprintf(f, "  HKT_TUPLE%d any, // HKT[", i)
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, "]\n")
+	fmt.Fprintf(f, "](\n")
+
+	// the callbacks
+	fmt.Fprintf(f, "  fmap MAP,\n")
+	for j := 1; j < i; j++ {
+		fmt.Fprintf(f, "  fap%d AP%d,\n", j, j)
+	}
+	// the transformer functions
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, "  f%d F%d,\n", j, j)
+	}
+	// the parameters
+	fmt.Fprintf(f, "  t T.Tuple%d[", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "A%d", j+1)
+	}
+	fmt.Fprintf(f, "],\n")
+	fmt.Fprintf(f, ") HKT_TUPLE%d {\n", i)
+
+	fmt.Fprintf(f, "  return F.Pipe%d(\n", i)
+	fmt.Fprintf(f, "    f1(t.F1),\n")
+	fmt.Fprintf(f, "    fmap(tupleConstructor%d[", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, "]()),\n")
+	for j := 1; j < i; j++ {
+		fmt.Fprintf(f, "    fap%d(f%d(t.F%d)),\n", j, j+1, j+1)
+	}
+	fmt.Fprintf(f, ")\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateSequenceTuple(f *os.File, i int) {
+	fmt.Fprintf(f, "\n// SequenceTuple%d is a utility function used to implement the sequence operation for higher kinded types based only on map and ap.\n", i)
+	fmt.Fprintf(f, "// The function takes a [Tuple%d] of higher higher kinded types and returns a higher kinded type of a [Tuple%d] with the resolved values.\n", i, i)
+	fmt.Fprintf(f, "func SequenceTuple%d[\n", i)
+	// map as the starting point
+	fmt.Fprintf(f, "  MAP ~func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, " ")
+		}
+		fmt.Fprintf(f, "func(T%d)", j+1)
+	}
+	fmt.Fprintf(f, " ")
+	fmt.Fprintf(f, "T.")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, ") func(HKT_T1)")
+	if i > 1 {
+		fmt.Fprintf(f, " HKT_F")
+		for k := 1; k < i; k++ {
+			fmt.Fprintf(f, "_T%d", k+1)
+		}
+	} else {
+		fmt.Fprintf(f, " HKT_TUPLE%d", i)
+	}
+	fmt.Fprintf(f, ",\n")
+	// the applicatives
+	for j := 1; j < i; j++ {
+		fmt.Fprintf(f, "  AP%d ~func(", j)
+		fmt.Fprintf(f, "HKT_T%d) func(", j+1)
+		fmt.Fprintf(f, "HKT_F")
+		for k := j; k < i; k++ {
+			fmt.Fprintf(f, "_T%d", k+1)
+		}
+		fmt.Fprintf(f, ")")
+		if j+1 < i {
+			fmt.Fprintf(f, " HKT_F")
+			for k := j + 1; k < i; k++ {
+				fmt.Fprintf(f, "_T%d", k+1)
+			}
+		} else {
+			fmt.Fprintf(f, " HKT_TUPLE%d", i)
+		}
+		fmt.Fprintf(f, ",\n")
+	}
+
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, "  T%d,\n", j+1)
+	}
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, "  HKT_T%d, // HKT[T%d]\n", j+1, j+1)
+	}
+	for j := 1; j < i; j++ {
+		fmt.Fprintf(f, "  HKT_F")
+		for k := j; k < i; k++ {
+			fmt.Fprintf(f, "_T%d", k+1)
+		}
+		fmt.Fprintf(f, ", // HKT[")
+		for k := j; k < i; k++ {
+			fmt.Fprintf(f, "func(T%d) ", k+1)
+		}
+		fmt.Fprintf(f, "T.")
+		writeTupleType(f, "T", i)
+		fmt.Fprintf(f, "]\n")
+	}
+	fmt.Fprintf(f, "  HKT_TUPLE%d any, // HKT[", i)
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, "]\n")
+	fmt.Fprintf(f, "](\n")
+
+	// the callbacks
+	fmt.Fprintf(f, "  fmap MAP,\n")
+	for j := 1; j < i; j++ {
+		fmt.Fprintf(f, "  fap%d AP%d,\n", j, j)
+	}
+	// the parameters
+	fmt.Fprintf(f, "  t T.Tuple%d[", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "HKT_T%d", j+1)
+	}
+	fmt.Fprintf(f, "],\n")
+	fmt.Fprintf(f, ") HKT_TUPLE%d {\n", i)
+
+	fmt.Fprintf(f, "  return F.Pipe%d(\n", i)
+	fmt.Fprintf(f, "    t.F1,\n")
+	fmt.Fprintf(f, "    fmap(tupleConstructor%d[", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, "]()),\n")
+	for j := 1; j < i; j++ {
+		fmt.Fprintf(f, "    fap%d(t.F%d),\n", j, j+1)
+	}
+	fmt.Fprintf(f, ")\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateSequenceT(f *os.File, i int) {
+	fmt.Fprintf(f, "\n// SequenceT%d is a utility function used to implement the sequence operation for higher kinded types based only on map and ap.\n", i)
+	fmt.Fprintf(f, "// The function takes %d higher higher kinded types and returns a higher kinded type of a [Tuple%d] with the resolved values.\n", i, i)
+	fmt.Fprintf(f, "func SequenceT%d[\n", i)
+	// map as the starting point
+	fmt.Fprintf(f, "  MAP ~func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, " ")
+		}
+		fmt.Fprintf(f, "func(T%d)", j+1)
+	}
+	fmt.Fprintf(f, " ")
+	fmt.Fprintf(f, "T.")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, ") func(HKT_T1)")
+	if i > 1 {
+		fmt.Fprintf(f, " HKT_F")
+		for k := 1; k < i; k++ {
+			fmt.Fprintf(f, "_T%d", k+1)
+		}
+	} else {
+		fmt.Fprintf(f, " HKT_TUPLE%d", i)
+	}
+	fmt.Fprintf(f, ",\n")
+	// the applicatives
+	for j := 1; j < i; j++ {
+		fmt.Fprintf(f, "  AP%d ~func(", j)
+		fmt.Fprintf(f, "HKT_T%d) func(", j+1)
+		fmt.Fprintf(f, "HKT_F")
+		for k := j; k < i; k++ {
+			fmt.Fprintf(f, "_T%d", k+1)
+		}
+		fmt.Fprintf(f, ")")
+		if j+1 < i {
+			fmt.Fprintf(f, " HKT_F")
+			for k := j + 1; k < i; k++ {
+				fmt.Fprintf(f, "_T%d", k+1)
+			}
+		} else {
+			fmt.Fprintf(f, " HKT_TUPLE%d", i)
+		}
+		fmt.Fprintf(f, ",\n")
+	}
+
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, "  T%d,\n", j+1)
+	}
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, "  HKT_T%d, // HKT[T%d]\n", j+1, j+1)
+	}
+	for j := 1; j < i; j++ {
+		fmt.Fprintf(f, "  HKT_F")
+		for k := j; k < i; k++ {
+			fmt.Fprintf(f, "_T%d", k+1)
+		}
+		fmt.Fprintf(f, ", // HKT[")
+		for k := j; k < i; k++ {
+			fmt.Fprintf(f, "func(T%d) ", k+1)
+		}
+		fmt.Fprintf(f, "T.")
+		writeTupleType(f, "T", i)
+		fmt.Fprintf(f, "]\n")
+	}
+	fmt.Fprintf(f, "  HKT_TUPLE%d any, // HKT[", i)
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, "]\n")
+	fmt.Fprintf(f, "](\n")
+
+	// the callbacks
+	fmt.Fprintf(f, "  fmap MAP,\n")
+	for j := 1; j < i; j++ {
+		fmt.Fprintf(f, "  fap%d AP%d,\n", j, j)
+	}
+	// the parameters
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, "  t%d HKT_T%d,\n", j+1, j+1)
+	}
+	fmt.Fprintf(f, ") HKT_TUPLE%d {\n", i)
+
+	fmt.Fprintf(f, "  return F.Pipe%d(\n", i)
+	fmt.Fprintf(f, "    t1,\n")
+	fmt.Fprintf(f, "    fmap(tupleConstructor%d[", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, "]()),\n")
+	for j := 1; j < i; j++ {
+		fmt.Fprintf(f, "    fap%d(t%d),\n", j, j+1)
+	}
+	fmt.Fprintf(f, ")\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateTupleConstructor(f *os.File, i int) {
+	// Create the optionize version
+	fmt.Fprintf(f, "\n// tupleConstructor%d returns a curried version of [T.MakeTuple%d]\n", i, i)
+	fmt.Fprintf(f, "func tupleConstructor%d[", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, " any]()")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, " func(T%d)", j+1)
+	}
+	fmt.Fprintf(f, " T.Tuple%d[", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, "] {\n")
+
+	fmt.Fprintf(f, "  return F.Curry%d(T.MakeTuple%d[", i, i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, "])\n")
+
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateApplyHelpers(filename string, count int) error {
+	dir, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+	absDir, err := filepath.Abs(dir)
+	if err != nil {
+		return err
+	}
+	pkg := filepath.Base(absDir)
+	f, err := os.Create(filepath.Clean(filename))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	// log
+	log.Printf("Generating code in [%s] for package [%s] with [%d] repetitions ...", filename, pkg, count)
+
+	// some header
+	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(f, "// This file was generated by robots at")
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
+
+	fmt.Fprintf(f, "package %s\n\n", pkg)
+
+	// print out some helpers
+	fmt.Fprintf(f, `
+import (
+	F "github.com/IBM/fp-go/v2/function"
+	T "github.com/IBM/fp-go/v2/tuple"
+)
+`)
+
+	for i := 1; i <= count; i++ {
+		// tuple constructor
+		generateTupleConstructor(f, i)
+		// sequenceT
+		generateSequenceT(f, i)
+		// sequenceTuple
+		generateSequenceTuple(f, i)
+		// traverseTuple
+		generateTraverseTuple(f, i)
+	}
+
+	return nil
+}
+
+func ApplyCommand() *C.Command {
+	return &C.Command{
+		Name:  "apply",
+		Usage: "generate code for the sequence operations of apply",
+		Flags: []C.Flag{
+			flagCount,
+			flagFilename,
+		},
+		Action: func(ctx *C.Context) error {
+			return generateApplyHelpers(
+				ctx.String(keyFilename),
+				ctx.Int(keyCount),
+			)
+		},
+	}
+}

v2/cli/bind.go

@@ -0,0 +1,294 @@
+// 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 (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"time"
+
+	C "github.com/urfave/cli/v2"
+)
+
+func createCombinations(n int, all, prev []int) [][]int {
+	l := len(prev)
+	if l == n {
+		return [][]int{prev}
+	}
+	var res [][]int
+	for idx, val := range all {
+		cpy := make([]int, l+1)
+		copy(cpy, prev)
+		cpy[l] = val
+
+		res = append(res, createCombinations(n, all[idx+1:], cpy)...)
+	}
+	return res
+}
+
+func remaining(comb []int, total int) []int {
+	var res []int
+	mp := make(map[int]int)
+	for _, idx := range comb {
+		mp[idx] = idx
+	}
+	for i := 1; i <= total; i++ {
+		_, ok := mp[i]
+		if !ok {
+			res = append(res, i)
+		}
+	}
+	return res
+}
+
+func generateCombSingleBind(f *os.File, comb [][]int, total int) {
+	for _, c := range comb {
+		// remaining indexes
+		rem := remaining(c, total)
+
+		// bind function
+		fmt.Fprintf(f, "\n// Bind")
+		for _, idx := range c {
+			fmt.Fprintf(f, "%d", idx)
+		}
+		fmt.Fprintf(f, "of%d takes a function with %d parameters and returns a new function with %d parameters that will bind these parameters to the positions [", total, total, len(c))
+		for i, idx := range c {
+			if i > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "%d", idx)
+		}
+		fmt.Fprintf(f, "] of the original function.\n// The return value of is a function with the remaining %d parameters at positions [", len(rem))
+		for i, idx := range rem {
+			if i > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "%d", idx)
+		}
+		fmt.Fprintf(f, "] of the original function.\n")
+		fmt.Fprintf(f, "func Bind")
+		for _, idx := range c {
+			fmt.Fprintf(f, "%d", idx)
+		}
+		fmt.Fprintf(f, "of%d[F ~func(", total)
+		for i := 0; i < total; i++ {
+			if i > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "T%d", i+1)
+		}
+		fmt.Fprintf(f, ") R")
+		for i := 0; i < total; i++ {
+			fmt.Fprintf(f, ", T%d", i+1)
+		}
+		fmt.Fprintf(f, ", R any](f F) func(")
+		for i, idx := range c {
+			if i > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "T%d", idx)
+		}
+		fmt.Fprintf(f, ") func(")
+		for i, idx := range rem {
+			if i > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "T%d", idx)
+		}
+		fmt.Fprintf(f, ") R {\n")
+
+		fmt.Fprintf(f, "  return func(")
+
+		for i, idx := range c {
+			if i > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "t%d T%d", idx, idx)
+		}
+		fmt.Fprintf(f, ") func(")
+		for i, idx := range rem {
+			if i > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "T%d", idx)
+		}
+		fmt.Fprintf(f, ") R {\n")
+
+		fmt.Fprintf(f, "    return func(")
+		for i, idx := range rem {
+			if i > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "t%d T%d", idx, idx)
+		}
+		fmt.Fprintf(f, ") R {\n")
+
+		fmt.Fprintf(f, "      return f(")
+		for i := 1; i <= total; i++ {
+			if i > 1 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "t%d", i)
+		}
+		fmt.Fprintf(f, ")\n")
+
+		fmt.Fprintf(f, "    }\n")
+		fmt.Fprintf(f, "  }\n")
+		fmt.Fprintf(f, "}\n")
+
+		// ignore function
+		fmt.Fprintf(f, "\n// Ignore")
+		for _, idx := range c {
+			fmt.Fprintf(f, "%d", idx)
+		}
+		fmt.Fprintf(f, "of%d takes a function with %d parameters and returns a new function with %d parameters that will ignore the values at positions [", total, len(rem), total)
+		for i, idx := range c {
+			if i > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "%d", idx)
+		}
+		fmt.Fprintf(f, "] and pass the remaining %d parameters to the original function\n", len(rem))
+		fmt.Fprintf(f, "func Ignore")
+		for _, idx := range c {
+			fmt.Fprintf(f, "%d", idx)
+		}
+		fmt.Fprintf(f, "of%d[", total)
+		// start with the undefined parameters
+		for i, idx := range c {
+			if i > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "T%d", idx)
+		}
+		if len(c) > 0 {
+			fmt.Fprintf(f, " any, ")
+		}
+		fmt.Fprintf(f, "F ~func(")
+		for i, idx := range rem {
+			if i > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "T%d", idx)
+		}
+		fmt.Fprintf(f, ") R")
+		for _, idx := range rem {
+			fmt.Fprintf(f, ", T%d", idx)
+		}
+		fmt.Fprintf(f, ", R any](f F) func(")
+		for i := 0; i < total; i++ {
+			if i > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "T%d", i+1)
+		}
+		fmt.Fprintf(f, ") R {\n")
+
+		fmt.Fprintf(f, "  return func(")
+		for i := 0; i < total; i++ {
+			if i > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "t%d T%d", i+1, i+1)
+		}
+		fmt.Fprintf(f, ") R {\n")
+		fmt.Fprintf(f, "      return f(")
+		for i, idx := range rem {
+			if i > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "t%d", idx)
+		}
+		fmt.Fprintf(f, ")\n")
+
+		fmt.Fprintf(f, "  }\n")
+		fmt.Fprintf(f, "}\n")
+
+	}
+}
+
+func generateSingleBind(f *os.File, total int) {
+
+	fmt.Fprintf(f, "// Combinations for a total of %d arguments\n", total)
+
+	// construct the indexes
+	all := make([]int, total)
+	for i := 0; i < total; i++ {
+		all[i] = i + 1
+	}
+	// for all permutations of a certain length
+	for j := 0; j < total; j++ {
+		// get combinations of that size
+		comb := createCombinations(j+1, all, []int{})
+		generateCombSingleBind(f, comb, total)
+	}
+}
+
+func generateBind(f *os.File, i int) {
+	for j := 1; j < i; j++ {
+		generateSingleBind(f, j)
+	}
+}
+
+func generateBindHelpers(filename string, count int) error {
+	dir, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+	absDir, err := filepath.Abs(dir)
+	if err != nil {
+		return err
+	}
+	pkg := filepath.Base(absDir)
+	f, err := os.Create(filepath.Clean(filename))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	// log
+	log.Printf("Generating code in [%s] for package [%s] with [%d] repetitions ...", filename, pkg, count)
+
+	// some header
+	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(f, "// This file was generated by robots at")
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
+
+	fmt.Fprintf(f, "package %s\n", pkg)
+
+	generateBind(f, count)
+
+	return nil
+}
+
+func BindCommand() *C.Command {
+	return &C.Command{
+		Name:        "bind",
+		Usage:       "generate code for binder functions etc",
+		Description: "Code generation for bind, etc",
+		Flags: []C.Flag{
+			flagCount,
+			flagFilename,
+		},
+		Action: func(ctx *C.Context) error {
+			return generateBindHelpers(
+				ctx.String(keyFilename),
+				ctx.Int(keyCount),
+			)
+		},
+	}
+}

v2/cli/commands.go

@@ -0,0 +1,39 @@
+// 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 (
+	C "github.com/urfave/cli/v2"
+)
+
+func Commands() []*C.Command {
+	return []*C.Command{
+		PipeCommand(),
+		IdentityCommand(),
+		OptionCommand(),
+		EitherCommand(),
+		TupleCommand(),
+		BindCommand(),
+		ApplyCommand(),
+		ContextReaderIOEitherCommand(),
+		ReaderIOEitherCommand(),
+		ReaderCommand(),
+		IOEitherCommand(),
+		IOCommand(),
+		IOOptionCommand(),
+		DICommand(),
+	}
+}

v2/cli/common.go

@@ -0,0 +1,39 @@
+// 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 (
+	C "github.com/urfave/cli/v2"
+)
+
+const (
+	keyFilename = "filename"
+	keyCount    = "count"
+)
+
+var (
+	flagFilename = &C.StringFlag{
+		Name:  keyFilename,
+		Value: "gen.go",
+		Usage: "Name of the generated file",
+	}
+
+	flagCount = &C.IntFlag{
+		Name:  keyCount,
+		Value: 20,
+		Usage: "Number of variations to create",
+	}
+)

v2/cli/contextreaderioeither.go

@@ -0,0 +1,271 @@
+// 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 (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+
+	A "github.com/IBM/fp-go/v2/array"
+	C "github.com/urfave/cli/v2"
+)
+
+// Deprecated:
+func generateNestedCallbacks(i, total int) string {
+	var buf strings.Builder
+	for j := i; j < total; j++ {
+		if j > i {
+			buf.WriteString(" ")
+		}
+		buf.WriteString(fmt.Sprintf("func(T%d)", j+1))
+	}
+	if i > 0 {
+		buf.WriteString(" ")
+	}
+	buf.WriteString(tupleType("T")(total))
+	return buf.String()
+}
+
+func generateNestedCallbacksPlain(i, total int) string {
+	fs := A.MakeBy(total-i, func(j int) string {
+		return fmt.Sprintf("func(T%d)", j+i+1)
+	})
+	ts := A.Of(tupleTypePlain("T")(total))
+	return joinAll(" ")(fs, ts)
+}
+
+func generateContextReaderIOEitherEitherize(f, fg *os.File, i int) {
+	// non generic version
+	fmt.Fprintf(f, "\n// Eitherize%d converts a function with %d parameters returning a tuple into a function with %d parameters returning a [ReaderIOEither[R]]\n// The inverse function is [Uneitherize%d]\n", i, i, i, i)
+	fmt.Fprintf(f, "func Eitherize%d[F ~func(context.Context", i)
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ") (R, error)")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ", R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	fmt.Fprintf(f, ") ReaderIOEither[R] {\n")
+	fmt.Fprintf(f, "  return G.Eitherize%d[ReaderIOEither[R]](f)\n", i)
+	fmt.Fprintln(f, "}")
+
+	// generic version
+	fmt.Fprintf(fg, "\n// Eitherize%d converts a function with %d parameters returning a tuple into a function with %d parameters returning a [GRA]\n// The inverse function is [Uneitherize%d]\n", i, i, i, i)
+	fmt.Fprintf(fg, "func Eitherize%d[GRA ~func(context.Context) GIOA, F ~func(context.Context", i)
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", T%d", j)
+	}
+	fmt.Fprintf(fg, ") (R, error), GIOA ~func() E.Either[error, R]")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", T%d", j)
+	}
+	fmt.Fprintf(fg, ", R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "T%d", j)
+	}
+	fmt.Fprintf(fg, ") GRA {\n")
+	fmt.Fprintf(fg, "  return RE.Eitherize%d[GRA](f)\n", i)
+	fmt.Fprintln(fg, "}")
+}
+
+func generateContextReaderIOEitherUneitherize(f, fg *os.File, i int) {
+	// non generic version
+	fmt.Fprintf(f, "\n// Uneitherize%d converts a function with %d parameters returning a [ReaderIOEither[R]] into a function with %d parameters returning a tuple.\n// The first parameter is considered to be the [context.Context].\n", i, i+1, i)
+	fmt.Fprintf(f, "func Uneitherize%d[F ~func(", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	fmt.Fprintf(f, ") ReaderIOEither[R]")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ", R any](f F) func(context.Context")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ") (R, error) {\n")
+	fmt.Fprintf(f, "  return G.Uneitherize%d[ReaderIOEither[R]", i)
+
+	fmt.Fprintf(f, ", func(context.Context")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ")(R, error)](f)\n")
+	fmt.Fprintln(f, "}")
+
+	// generic version
+	fmt.Fprintf(fg, "\n// Uneitherize%d converts a function with %d parameters returning a [GRA] into a function with %d parameters returning a tuple.\n// The first parameter is considered to be the [context.Context].\n", i, i, i)
+	fmt.Fprintf(fg, "func Uneitherize%d[GRA ~func(context.Context) GIOA, F ~func(context.Context", i)
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", T%d", j)
+	}
+	fmt.Fprintf(fg, ") (R, error), GIOA ~func() E.Either[error, R]")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", T%d", j)
+	}
+	fmt.Fprintf(fg, ", R any](f func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "T%d", j)
+	}
+	fmt.Fprintf(fg, ") GRA) F {\n")
+
+	fmt.Fprintf(fg, "  return func(c context.Context")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", t%d T%d", j, j)
+	}
+	fmt.Fprintf(fg, ") (R, error) {\n")
+	fmt.Fprintf(fg, "    return E.UnwrapError(f(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "t%d", j)
+	}
+	fmt.Fprintf(fg, ")(c)())\n")
+	fmt.Fprintf(fg, "  }\n")
+	fmt.Fprintf(fg, "}\n")
+}
+
+func nonGenericContextReaderIOEither(param string) string {
+	return fmt.Sprintf("ReaderIOEither[%s]", param)
+}
+
+var extrasContextReaderIOEither = A.Empty[string]()
+
+func generateContextReaderIOEitherSequenceT(f *os.File, i int) {
+	generateGenericSequenceT("", nonGenericContextReaderIOEither, extrasContextReaderIOEither)(f, i)
+	generateGenericSequenceT("Seq", nonGenericContextReaderIOEither, extrasContextReaderIOEither)(f, i)
+	generateGenericSequenceT("Par", nonGenericContextReaderIOEither, extrasContextReaderIOEither)(f, i)
+}
+
+func generateContextReaderIOEitherSequenceTuple(f *os.File, i int) {
+	generateGenericSequenceTuple("", nonGenericContextReaderIOEither, extrasContextReaderIOEither)(f, i)
+	generateGenericSequenceTuple("Seq", nonGenericContextReaderIOEither, extrasContextReaderIOEither)(f, i)
+	generateGenericSequenceTuple("Par", nonGenericContextReaderIOEither, extrasContextReaderIOEither)(f, i)
+}
+
+func generateContextReaderIOEitherTraverseTuple(f *os.File, i int) {
+	generateGenericTraverseTuple("", nonGenericContextReaderIOEither, extrasContextReaderIOEither)(f, i)
+	generateGenericTraverseTuple("Seq", nonGenericContextReaderIOEither, extrasContextReaderIOEither)(f, i)
+	generateGenericTraverseTuple("Par", nonGenericContextReaderIOEither, extrasContextReaderIOEither)(f, i)
+}
+
+func generateContextReaderIOEitherHelpers(filename string, count int) error {
+	dir, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+	absDir, err := filepath.Abs(dir)
+	if err != nil {
+		return err
+	}
+	pkg := filepath.Base(absDir)
+	f, err := os.Create(filepath.Clean(filename))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	// construct subdirectory
+	genFilename := filepath.Join("generic", filename)
+	err = os.MkdirAll("generic", os.ModePerm)
+	if err != nil {
+		return err
+	}
+	fg, err := os.Create(filepath.Clean(genFilename))
+	if err != nil {
+		return err
+	}
+	defer fg.Close()
+
+	// log
+	log.Printf("Generating code in [%s] for package [%s] with [%d] repetitions ...", filename, pkg, count)
+
+	writePackage(f, pkg)
+
+	fmt.Fprintf(f, `
+import (
+	"context"
+
+	G "github.com/IBM/fp-go/v2/context/%s/generic"
+	"github.com/IBM/fp-go/v2/internal/apply"
+	"github.com/IBM/fp-go/v2/tuple"
+)
+`, pkg)
+
+	writePackage(fg, "generic")
+
+	fmt.Fprintf(fg, `
+import (
+	"context"
+
+	E "github.com/IBM/fp-go/v2/either"
+	RE "github.com/IBM/fp-go/v2/readerioeither/generic"
+)
+`)
+
+	generateContextReaderIOEitherEitherize(f, fg, 0)
+	generateContextReaderIOEitherUneitherize(f, fg, 0)
+
+	for i := 1; i <= count; i++ {
+		// eitherize
+		generateContextReaderIOEitherEitherize(f, fg, i)
+		generateContextReaderIOEitherUneitherize(f, fg, i)
+		// sequenceT
+		generateContextReaderIOEitherSequenceT(f, i)
+		// sequenceTuple
+		generateContextReaderIOEitherSequenceTuple(f, i)
+		// traverseTuple
+		generateContextReaderIOEitherTraverseTuple(f, i)
+	}
+
+	return nil
+}
+
+func ContextReaderIOEitherCommand() *C.Command {
+	return &C.Command{
+		Name:  "contextreaderioeither",
+		Usage: "generate code for ContextReaderIOEither",
+		Flags: []C.Flag{
+			flagCount,
+			flagFilename,
+		},
+		Action: func(ctx *C.Context) error {
+			return generateContextReaderIOEitherHelpers(
+				ctx.String(keyFilename),
+				ctx.Int(keyCount),
+			)
+		},
+	}
+}

v2/cli/di.go

@@ -0,0 +1,231 @@
+// 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 (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"time"
+
+	C "github.com/urfave/cli/v2"
+)
+
+func generateMakeProvider(f *os.File, i int) {
+	// non generic version
+	fmt.Fprintf(f, "\n// MakeProvider%d creates a [DIE.Provider] for an [InjectionToken] from a function with %d dependencies\n", i, i)
+	fmt.Fprintf(f, "func MakeProvider%d[", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, " any, R any](\n")
+	fmt.Fprintf(f, "  token InjectionToken[R],\n")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, "  d%d Dependency[T%d],\n", j+1, j+1)
+	}
+	fmt.Fprintf(f, "  f func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, ") IOE.IOEither[error, R],\n")
+	fmt.Fprintf(f, ") DIE.Provider {\n")
+	fmt.Fprint(f, "  return DIE.MakeProvider(\n")
+	fmt.Fprint(f, "    token,\n")
+	fmt.Fprintf(f, "    MakeProviderFactory%d(\n", i)
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, "      d%d,\n", j+1)
+	}
+	fmt.Fprint(f, "      f,\n")
+	fmt.Fprint(f, "  ))\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateMakeTokenWithDefault(f *os.File, i int) {
+	// non generic version
+	fmt.Fprintf(f, "\n// MakeTokenWithDefault%d creates an [InjectionToken] with a default implementation with %d dependencies\n", i, i)
+	fmt.Fprintf(f, "func MakeTokenWithDefault%d[", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, " any, R any](\n")
+	fmt.Fprintf(f, "  name string,\n")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, "  d%d Dependency[T%d],\n", j+1, j+1)
+	}
+	fmt.Fprintf(f, "  f func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, ") IOE.IOEither[error, R],\n")
+	fmt.Fprintf(f, ") InjectionToken[R] {\n")
+	fmt.Fprintf(f, "  return MakeTokenWithDefault[R](name, MakeProviderFactory%d(\n", i)
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, "    d%d,\n", j+1)
+	}
+	fmt.Fprint(f, "    f,\n")
+	fmt.Fprint(f, "  ))\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateMakeProviderFactory(f *os.File, i int) {
+	// non generic version
+	fmt.Fprintf(f, "\n// MakeProviderFactory%d creates a [DIE.ProviderFactory] from a function with %d arguments and %d dependencies\n", i, i, i)
+	fmt.Fprintf(f, "func MakeProviderFactory%d[", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, " any, R any](\n")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, "  d%d Dependency[T%d],\n", j+1, j+1)
+	}
+	fmt.Fprintf(f, "  f func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, ") IOE.IOEither[error, R],\n")
+	fmt.Fprintf(f, ") DIE.ProviderFactory {\n")
+	fmt.Fprint(f, "  return DIE.MakeProviderFactory(\n")
+	fmt.Fprint(f, "    A.From[DIE.Dependency](\n")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, "      d%d,\n", j+1)
+	}
+	fmt.Fprint(f, "    ),\n")
+	fmt.Fprintf(f, "    eraseProviderFactory%d(\n", i)
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, "      d%d,\n", j+1)
+	}
+	fmt.Fprint(f, "      f,\n")
+	fmt.Fprint(f, "    ),\n")
+	fmt.Fprint(f, "  )\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateEraseProviderFactory(f *os.File, i int) {
+	// non generic version
+	fmt.Fprintf(f, "\n// eraseProviderFactory%d creates a function that takes a variadic number of untyped arguments and from a function of %d strongly typed arguments and %d dependencies\n", i, i, i)
+	fmt.Fprintf(f, "func eraseProviderFactory%d[", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, " any, R any](\n")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, "  d%d Dependency[T%d],\n", j+1, j+1)
+	}
+	fmt.Fprintf(f, "  f func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, ") IOE.IOEither[error, R]) func(params ...any) IOE.IOEither[error, any] {\n")
+	fmt.Fprintf(f, "  ft := eraseTuple(T.Tupled%d(f))\n", i)
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, "  t%d := lookupAt[T%d](%d, d%d)\n", j+1, j+1, j, j+1)
+	}
+	fmt.Fprint(f, "  return func(params ...any) IOE.IOEither[error, any] {\n")
+	fmt.Fprintf(f, "    return ft(E.SequenceT%d(\n", i)
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, "      t%d(params),\n", j+1)
+	}
+	fmt.Fprint(f, "    ))\n")
+	fmt.Fprint(f, "  }\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateDIHelpers(filename string, count int) error {
+	dir, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+	absDir, err := filepath.Abs(dir)
+	if err != nil {
+		return err
+	}
+	pkg := filepath.Base(absDir)
+	f, err := os.Create(filepath.Clean(filename))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	// log
+	log.Printf("Generating code in [%s] for package [%s] with [%d] repetitions ...", filename, pkg, count)
+
+	// some header
+	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(f, "// This file was generated by robots at")
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
+
+	fmt.Fprintf(f, "package %s\n\n", pkg)
+
+	fmt.Fprint(f, `
+import (
+	E "github.com/IBM/fp-go/v2/either"
+	IOE "github.com/IBM/fp-go/v2/ioeither"
+	T "github.com/IBM/fp-go/v2/tuple"
+	A "github.com/IBM/fp-go/v2/array"
+	DIE "github.com/IBM/fp-go/v2/di/erasure"
+)
+`)
+
+	for i := 1; i <= count; i++ {
+		generateEraseProviderFactory(f, i)
+		generateMakeProviderFactory(f, i)
+		generateMakeTokenWithDefault(f, i)
+		generateMakeProvider(f, i)
+	}
+
+	return nil
+}
+
+func DICommand() *C.Command {
+	return &C.Command{
+		Name:  "di",
+		Usage: "generate code for the dependency injection package",
+		Flags: []C.Flag{
+			flagCount,
+			flagFilename,
+		},
+		Action: func(ctx *C.Context) error {
+			return generateDIHelpers(
+				ctx.String(keyFilename),
+				ctx.Int(keyCount),
+			)
+		},
+	}
+}

v2/cli/either.go

@@ -0,0 +1,200 @@
+// 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 (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"time"
+
+	C "github.com/urfave/cli/v2"
+)
+
+func eitherHKT(typeE string) func(typeA string) string {
+	return func(typeA string) string {
+		return fmt.Sprintf("Either[%s, %s]", typeE, typeA)
+	}
+}
+
+func generateEitherTraverseTuple(f *os.File, i int) {
+	generateTraverseTuple1(eitherHKT("E"), "E")(f, i)
+}
+
+func generateEitherSequenceTuple(f *os.File, i int) {
+	generateSequenceTuple1(eitherHKT("E"), "E")(f, i)
+}
+
+func generateEitherSequenceT(f *os.File, i int) {
+	generateSequenceT1(eitherHKT("E"), "E")(f, i)
+}
+
+func generateUneitherize(f *os.File, i int) {
+	// Create the optionize version
+	fmt.Fprintf(f, "\n// Uneitherize%d converts a function with %d parameters returning an Either into a function with %d parameters returning a tuple\n// The inverse function is [Eitherize%d]\n", i, i, i, i)
+	fmt.Fprintf(f, "func Uneitherize%d[F ~func(", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	fmt.Fprintf(f, ") Either[error, R]")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ", R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	fmt.Fprintf(f, ") (R, error) {\n")
+	fmt.Fprintf(f, "  return func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t%d T%d", j, j)
+	}
+	fmt.Fprintf(f, ") (R, error) {\n")
+	fmt.Fprintf(f, "    return UnwrapError(f(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t%d", j)
+	}
+	fmt.Fprintln(f, "))")
+	fmt.Fprintln(f, "  }")
+	fmt.Fprintln(f, "}")
+}
+
+func generateEitherize(f *os.File, i int) {
+	// Create the optionize version
+	fmt.Fprintf(f, "\n// Eitherize%d converts a function with %d parameters returning a tuple into a function with %d parameters returning an Either\n// The inverse function is [Uneitherize%d]\n", i, i, i, i)
+	fmt.Fprintf(f, "func Eitherize%d[F ~func(", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	fmt.Fprintf(f, ") (R, error)")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ", R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	fmt.Fprintf(f, ") Either[error, R] {\n")
+	fmt.Fprintf(f, "  return func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t%d T%d", j, j)
+	}
+	fmt.Fprintf(f, ") Either[error, R] {\n")
+	fmt.Fprintf(f, "    return TryCatchError(f(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t%d", j)
+	}
+	fmt.Fprintln(f, "))")
+	fmt.Fprintln(f, "  }")
+	fmt.Fprintln(f, "}")
+}
+
+func generateEitherHelpers(filename string, count int) error {
+	dir, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+	absDir, err := filepath.Abs(dir)
+	if err != nil {
+		return err
+	}
+	pkg := filepath.Base(absDir)
+	f, err := os.Create(filepath.Clean(filename))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	// log
+	log.Printf("Generating code in [%s] for package [%s] with [%d] repetitions ...", filename, pkg, count)
+
+	// some header
+	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(f, "// This file was generated by robots at")
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
+
+	fmt.Fprintf(f, "package %s\n\n", pkg)
+
+	fmt.Fprintf(f, `
+import (
+	A "github.com/IBM/fp-go/v2/internal/apply"
+	T "github.com/IBM/fp-go/v2/tuple"
+)
+`)
+
+	// zero level functions
+
+	// optionize
+	generateEitherize(f, 0)
+	// unoptionize
+	generateUneitherize(f, 0)
+
+	for i := 1; i <= count; i++ {
+		// optionize
+		generateEitherize(f, i)
+		// unoptionize
+		generateUneitherize(f, i)
+		// sequenceT
+		generateEitherSequenceT(f, i)
+		// sequenceTuple
+		generateEitherSequenceTuple(f, i)
+		// traverseTuple
+		generateEitherTraverseTuple(f, i)
+	}
+
+	return nil
+}
+
+func EitherCommand() *C.Command {
+	return &C.Command{
+		Name:  "either",
+		Usage: "generate code for Either",
+		Flags: []C.Flag{
+			flagCount,
+			flagFilename,
+		},
+		Action: func(ctx *C.Context) error {
+			return generateEitherHelpers(
+				ctx.String(keyFilename),
+				ctx.Int(keyCount),
+			)
+		},
+	}
+}

v2/cli/header.go

@@ -0,0 +1,31 @@
+// 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 (
+	"fmt"
+	"os"
+	"time"
+)
+
+func writePackage(f *os.File, pkg string) {
+	// print package
+	fmt.Fprintf(f, "package %s\n\n", pkg)
+	// some header
+	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(f, "// This file was generated by robots at")
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
+}

v2/cli/identity.go

@@ -0,0 +1,103 @@
+// 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 (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"time"
+
+	C "github.com/urfave/cli/v2"
+)
+
+func identityHKT(typeA string) string {
+	return typeA
+}
+
+func generateIdentityTraverseTuple(f *os.File, i int) {
+	generateTraverseTuple1(identityHKT, "")(f, i)
+}
+
+func generateIdentitySequenceTuple(f *os.File, i int) {
+	generateSequenceTuple1(identityHKT, "")(f, i)
+}
+
+func generateIdentitySequenceT(f *os.File, i int) {
+	generateSequenceT1(identityHKT, "")(f, i)
+}
+
+func generateIdentityHelpers(filename string, count int) error {
+	dir, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+	absDir, err := filepath.Abs(dir)
+	if err != nil {
+		return err
+	}
+	pkg := filepath.Base(absDir)
+	f, err := os.Create(filepath.Clean(filename))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	// log
+	log.Printf("Generating code in [%s] for package [%s] with [%d] repetitions ...", filename, pkg, count)
+
+	// some header
+	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(f, "// This file was generated by robots at")
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
+
+	fmt.Fprintf(f, "package %s\n\n", pkg)
+
+	fmt.Fprintf(f, `
+import (
+	A "github.com/IBM/fp-go/v2/internal/apply"
+	T "github.com/IBM/fp-go/v2/tuple"
+)
+`)
+
+	for i := 1; i <= count; i++ {
+		// sequenceT
+		generateIdentitySequenceT(f, i)
+		// sequenceTuple
+		generateIdentitySequenceTuple(f, i)
+		// traverseTuple
+		generateIdentityTraverseTuple(f, i)
+	}
+
+	return nil
+}
+
+func IdentityCommand() *C.Command {
+	return &C.Command{
+		Name:  "identity",
+		Usage: "generate code for Identity",
+		Flags: []C.Flag{
+			flagCount,
+			flagFilename,
+		},
+		Action: func(ctx *C.Context) error {
+			return generateIdentityHelpers(
+				ctx.String(keyFilename),
+				ctx.Int(keyCount),
+			)
+		},
+	}
+}

v2/cli/io.go

@@ -0,0 +1,112 @@
+// 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 (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"time"
+
+	A "github.com/IBM/fp-go/v2/array"
+	C "github.com/urfave/cli/v2"
+)
+
+func nonGenericIO(param string) string {
+	return fmt.Sprintf("IO[%s]", param)
+}
+
+var extrasIO = A.Empty[string]()
+
+func generateIOSequenceT(f *os.File, i int) {
+	generateGenericSequenceT("", nonGenericIO, extrasIO)(f, i)
+	generateGenericSequenceT("Seq", nonGenericIO, extrasIO)(f, i)
+	generateGenericSequenceT("Par", nonGenericIO, extrasIO)(f, i)
+}
+
+func generateIOSequenceTuple(f *os.File, i int) {
+	generateGenericSequenceTuple("", nonGenericIO, extrasIO)(f, i)
+	generateGenericSequenceTuple("Seq", nonGenericIO, extrasIO)(f, i)
+	generateGenericSequenceTuple("Par", nonGenericIO, extrasIO)(f, i)
+}
+
+func generateIOTraverseTuple(f *os.File, i int) {
+	generateGenericTraverseTuple("", nonGenericIO, extrasIO)(f, i)
+	generateGenericTraverseTuple("Seq", nonGenericIO, extrasIO)(f, i)
+	generateGenericTraverseTuple("Par", nonGenericIO, extrasIO)(f, i)
+}
+
+func generateIOHelpers(filename string, count int) error {
+	dir, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+	absDir, err := filepath.Abs(dir)
+	if err != nil {
+		return err
+	}
+	pkg := filepath.Base(absDir)
+	f, err := os.Create(filepath.Clean(filename))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	// log
+	log.Printf("Generating code in [%s] for package [%s] with [%d] repetitions ...", filename, pkg, count)
+
+	// some header
+	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(f, "// This file was generated by robots at")
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
+
+	fmt.Fprintf(f, "package %s\n\n", pkg)
+
+	fmt.Fprintf(f, `
+import (
+	"github.com/IBM/fp-go/v2/tuple"
+	"github.com/IBM/fp-go/v2/internal/apply"
+)
+`)
+
+	for i := 1; i <= count; i++ {
+		// sequenceT
+		generateIOSequenceT(f, i)
+		// sequenceTuple
+		generateIOSequenceTuple(f, i)
+		// traverseTuple
+		generateIOTraverseTuple(f, i)
+	}
+
+	return nil
+}
+
+func IOCommand() *C.Command {
+	return &C.Command{
+		Name:  "io",
+		Usage: "generate code for IO",
+		Flags: []C.Flag{
+			flagCount,
+			flagFilename,
+		},
+		Action: func(ctx *C.Context) error {
+			return generateIOHelpers(
+				ctx.String(keyFilename),
+				ctx.Int(keyCount),
+			)
+		},
+	}
+}

v2/cli/ioeither.go

@@ -0,0 +1,283 @@
+// 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 (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"time"
+
+	A "github.com/IBM/fp-go/v2/array"
+	C "github.com/urfave/cli/v2"
+)
+
+// [GA ~func() ET.Either[E, A], GB ~func() ET.Either[E, B], GTAB ~func() ET.Either[E, T.Tuple2[A, B]], E, A, B any](a GA, b GB) GTAB {
+
+func nonGenericIOEither(param string) string {
+	return fmt.Sprintf("IOEither[E, %s]", param)
+}
+
+var extrasIOEither = A.From("E")
+
+func generateIOEitherSequenceT(f, fg *os.File, i int) {
+	generateGenericSequenceT("", nonGenericIOEither, extrasIOEither)(f, i)
+	generateGenericSequenceT("Seq", nonGenericIOEither, extrasIOEither)(f, i)
+	generateGenericSequenceT("Par", nonGenericIOEither, extrasIOEither)(f, i)
+}
+
+func generateIOEitherSequenceTuple(f, fg *os.File, i int) {
+	generateGenericSequenceTuple("", nonGenericIOEither, extrasIOEither)(f, i)
+	generateGenericSequenceTuple("Seq", nonGenericIOEither, extrasIOEither)(f, i)
+	generateGenericSequenceTuple("Par", nonGenericIOEither, extrasIOEither)(f, i)
+}
+
+func generateIOEitherTraverseTuple(f, fg *os.File, i int) {
+	generateGenericTraverseTuple("", nonGenericIOEither, extrasIOEither)(f, i)
+	generateGenericTraverseTuple("Seq", nonGenericIOEither, extrasIOEither)(f, i)
+	generateGenericTraverseTuple("Par", nonGenericIOEither, extrasIOEither)(f, i)
+}
+
+func generateIOEitherUneitherize(f, fg *os.File, i int) {
+	// non generic version
+	fmt.Fprintf(f, "\n// Uneitherize%d converts a function with %d parameters returning a tuple into a function with %d parameters returning a [IOEither[error, R]]\n", i, i+1, i)
+	fmt.Fprintf(f, "func Uneitherize%d[F ~func(", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, ") IOEither[error, R]")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j+1)
+	}
+	fmt.Fprintf(f, ", R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, ") (R, error) {\n")
+	fmt.Fprintf(f, "  return G.Uneitherize%d[IOEither[error, R]](f)\n", i)
+	fmt.Fprintln(f, "}")
+
+	// generic version
+	fmt.Fprintf(fg, "\n// Uneitherize%d converts a function with %d parameters returning a tuple into a function with %d parameters returning a [GIOA]\n", i, i, i)
+	fmt.Fprintf(fg, "func Uneitherize%d[GIOA ~func() ET.Either[error, R], GTA ~func(", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "T%d", j+1)
+	}
+	fmt.Fprintf(fg, ") GIOA")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", T%d", j+1)
+	}
+	fmt.Fprintf(fg, ", R any](f GTA) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "T%d", j+1)
+	}
+	fmt.Fprintf(fg, ") (R, error) {\n")
+	fmt.Fprintf(fg, "  return func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "t%d T%d", j+1, j+1)
+	}
+	fmt.Fprintf(fg, ") (R, error) {\n")
+	fmt.Fprintf(fg, "    return ET.Unwrap(f(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "t%d", j+1)
+	}
+	fmt.Fprintf(fg, ")())\n")
+	fmt.Fprintf(fg, "  }\n")
+	fmt.Fprintf(fg, "}\n")
+}
+
+func generateIOEitherEitherize(f, fg *os.File, i int) {
+	// non generic version
+	fmt.Fprintf(f, "\n// Eitherize%d converts a function with %d parameters returning a tuple into a function with %d parameters returning a [IOEither[error, R]]\n", i, i+1, i)
+	fmt.Fprintf(f, "func Eitherize%d[F ~func(", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, ") (R, error)")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j+1)
+	}
+	fmt.Fprintf(f, ", R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, ") IOEither[error, R] {\n")
+	fmt.Fprintf(f, "  return G.Eitherize%d[IOEither[error, R]](f)\n", i)
+	fmt.Fprintln(f, "}")
+
+	// generic version
+	fmt.Fprintf(fg, "\n// Eitherize%d converts a function with %d parameters returning a tuple into a function with %d parameters returning a [GIOA]\n", i, i, i)
+	fmt.Fprintf(fg, "func Eitherize%d[GIOA ~func() ET.Either[error, R], F ~func(", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "T%d", j+1)
+	}
+	fmt.Fprintf(fg, ") (R, error)")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", T%d", j+1)
+	}
+	fmt.Fprintf(fg, ", R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "T%d", j+1)
+	}
+	fmt.Fprintf(fg, ") GIOA {\n")
+	fmt.Fprintf(fg, "  e := ET.Eitherize%d(f)\n", i)
+	fmt.Fprintf(fg, "  return func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "t%d T%d", j+1, j+1)
+	}
+	fmt.Fprintf(fg, ") GIOA {\n")
+	fmt.Fprintf(fg, "    return func() ET.Either[error, R] {\n")
+	fmt.Fprintf(fg, "      return e(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "t%d", j+1)
+	}
+	fmt.Fprintf(fg, ")\n")
+	fmt.Fprintf(fg, "    }}\n")
+	fmt.Fprintf(fg, "}\n")
+}
+
+func generateIOEitherHelpers(filename string, count int) error {
+	dir, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+	absDir, err := filepath.Abs(dir)
+	if err != nil {
+		return err
+	}
+	pkg := filepath.Base(absDir)
+	f, err := os.Create(filepath.Clean(filename))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	// construct subdirectory
+	genFilename := filepath.Join("generic", filename)
+	err = os.MkdirAll("generic", os.ModePerm)
+	if err != nil {
+		return err
+	}
+	fg, err := os.Create(filepath.Clean(genFilename))
+	if err != nil {
+		return err
+	}
+	defer fg.Close()
+
+	// log
+	log.Printf("Generating code in [%s] for package [%s] with [%d] repetitions ...", filename, pkg, count)
+
+	// some header
+	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(f, "// This file was generated by robots at")
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
+
+	fmt.Fprintf(f, "package %s\n\n", pkg)
+
+	fmt.Fprintf(f, `
+import (
+	G "github.com/IBM/fp-go/v2/%s/generic"	
+	"github.com/IBM/fp-go/v2/internal/apply"
+	"github.com/IBM/fp-go/v2/tuple"
+)
+`, pkg)
+
+	// some header
+	fmt.Fprintln(fg, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(fg, "// This file was generated by robots at")
+	fmt.Fprintf(fg, "// %s\n", time.Now())
+
+	fmt.Fprintf(fg, "package generic\n\n")
+
+	fmt.Fprintf(fg, `
+import (
+	ET "github.com/IBM/fp-go/v2/either"
+)
+`)
+
+	// eitherize
+	generateIOEitherEitherize(f, fg, 0)
+	// uneitherize
+	generateIOEitherUneitherize(f, fg, 0)
+
+	for i := 1; i <= count; i++ {
+		// eitherize
+		generateIOEitherEitherize(f, fg, i)
+		// uneitherize
+		generateIOEitherUneitherize(f, fg, i)
+		// sequenceT
+		generateIOEitherSequenceT(f, fg, i)
+		// sequenceTuple
+		generateIOEitherSequenceTuple(f, fg, i)
+		// traverseTuple
+		generateIOEitherTraverseTuple(f, fg, i)
+	}
+
+	return nil
+}
+
+func IOEitherCommand() *C.Command {
+	return &C.Command{
+		Name:  "ioeither",
+		Usage: "generate code for IOEither",
+		Flags: []C.Flag{
+			flagCount,
+			flagFilename,
+		},
+		Action: func(ctx *C.Context) error {
+			return generateIOEitherHelpers(
+				ctx.String(keyFilename),
+				ctx.Int(keyCount),
+			)
+		},
+	}
+}

v2/cli/iooption.go

@@ -0,0 +1,117 @@
+// 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 (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"time"
+
+	A "github.com/IBM/fp-go/v2/array"
+	C "github.com/urfave/cli/v2"
+)
+
+func nonGenericIOOption(param string) string {
+	return fmt.Sprintf("IOOption[%s]", param)
+}
+
+func genericIOOption(param string) string {
+	return fmt.Sprintf("func() O.Option[%s]", param)
+}
+
+var extrasIOOption = A.Empty[string]()
+
+func generateIOOptionSequenceT(f *os.File, i int) {
+	generateGenericSequenceT("", nonGenericIOOption, extrasIOOption)(f, i)
+	generateGenericSequenceT("Seq", nonGenericIOOption, extrasIOOption)(f, i)
+	generateGenericSequenceT("Par", nonGenericIOOption, extrasIOOption)(f, i)
+}
+
+func generateIOOptionSequenceTuple(f *os.File, i int) {
+	generateGenericSequenceTuple("", nonGenericIOOption, extrasIOOption)(f, i)
+	generateGenericSequenceTuple("Seq", nonGenericIOOption, extrasIOOption)(f, i)
+	generateGenericSequenceTuple("Par", nonGenericIOOption, extrasIOOption)(f, i)
+}
+
+func generateIOOptionTraverseTuple(f *os.File, i int) {
+	generateGenericTraverseTuple("", nonGenericIOOption, extrasIOOption)(f, i)
+	generateGenericTraverseTuple("Seq", nonGenericIOOption, extrasIOOption)(f, i)
+	generateGenericTraverseTuple("Par", nonGenericIOOption, extrasIOOption)(f, i)
+}
+
+func generateIOOptionHelpers(filename string, count int) error {
+	dir, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+	absDir, err := filepath.Abs(dir)
+	if err != nil {
+		return err
+	}
+	pkg := filepath.Base(absDir)
+	f, err := os.Create(filepath.Clean(filename))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	// log
+	log.Printf("Generating code in [%s] for package [%s] with [%d] repetitions ...", filename, pkg, count)
+
+	// some header
+	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(f, "// This file was generated by robots at")
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
+
+	fmt.Fprintf(f, "package %s\n\n", pkg)
+
+	fmt.Fprintf(f, `
+import (
+	"github.com/IBM/fp-go/v2/tuple"
+	"github.com/IBM/fp-go/v2/internal/apply"
+)
+`)
+
+	for i := 1; i <= count; i++ {
+		// sequenceT
+		generateIOOptionSequenceT(f, i)
+		// sequenceTuple
+		generateIOOptionSequenceTuple(f, i)
+		// traverseTuple
+		generateIOOptionTraverseTuple(f, i)
+	}
+
+	return nil
+}
+
+func IOOptionCommand() *C.Command {
+	return &C.Command{
+		Name:  "iooption",
+		Usage: "generate code for IOOption",
+		Flags: []C.Flag{
+			flagCount,
+			flagFilename,
+		},
+		Action: func(ctx *C.Context) error {
+			return generateIOOptionHelpers(
+				ctx.String(keyFilename),
+				ctx.Int(keyCount),
+			)
+		},
+	}
+}

v2/cli/monad.go

@@ -0,0 +1,376 @@
+// 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 (
+	"fmt"
+	"os"
+	"strings"
+)
+
+// Deprecated:
+func tupleType(name string) func(i int) string {
+	return func(i int) string {
+		var buf strings.Builder
+		buf.WriteString(fmt.Sprintf("T.Tuple%d[", i))
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				buf.WriteString(", ")
+			}
+			buf.WriteString(fmt.Sprintf("%s%d", name, j+1))
+		}
+		buf.WriteString("]")
+
+		return buf.String()
+	}
+}
+
+func tupleTypePlain(name string) func(i int) string {
+	return func(i int) string {
+		var buf strings.Builder
+		buf.WriteString(fmt.Sprintf("tuple.Tuple%d[", i))
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				buf.WriteString(", ")
+			}
+			buf.WriteString(fmt.Sprintf("%s%d", name, j+1))
+		}
+		buf.WriteString("]")
+
+		return buf.String()
+	}
+}
+
+func monadGenerateSequenceTNonGeneric(
+	hkt func(string) string,
+	fmap func(string, string) string,
+	fap func(string, string) string,
+) func(f *os.File, i int) {
+	return func(f *os.File, i int) {
+
+		tuple := tupleType("T")(i)
+
+		fmt.Fprintf(f, "SequenceT%d[", i)
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "T%d", j+1)
+		}
+		fmt.Fprintf(f, "](")
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "t%d %s", j+1, hkt(fmt.Sprintf("T%d", j+1)))
+		}
+		fmt.Fprintf(f, ") %s {", hkt(tuple))
+		// the actual apply callback
+		fmt.Fprintf(f, "  return apply.SequenceT%d(\n", i)
+		// map callback
+
+		curried := func(count int) string {
+			var buf strings.Builder
+			for j := count; j < i; j++ {
+				buf.WriteString(fmt.Sprintf("func(T%d)", j+1))
+			}
+			buf.WriteString(tuple)
+			return buf.String()
+		}
+
+		fmt.Fprintf(f, "    %s,\n", fmap("T1", curried(1)))
+		for j := 1; j < i; j++ {
+			fmt.Fprintf(f, "    %s,\n", fap(curried(j+1), fmt.Sprintf("T%d", j)))
+		}
+
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(f, "    T%d,\n", j+1)
+		}
+
+		fmt.Fprintf(f, "  )\n")
+
+		fmt.Fprintf(f, "}\n")
+
+	}
+}
+
+func monadGenerateSequenceTGeneric(
+	hkt func(string) string,
+	fmap func(string, string) string,
+	fap func(string, string) string,
+) func(f *os.File, i int) {
+	return func(f *os.File, i int) {
+
+		tuple := tupleType("T")(i)
+
+		fmt.Fprintf(f, "SequenceT%d[", i)
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "T%d", j+1)
+		}
+		fmt.Fprintf(f, "](")
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "t%d %s", j+1, hkt(fmt.Sprintf("T%d", j+1)))
+		}
+		fmt.Fprintf(f, ") %s {", hkt(tuple))
+		// the actual apply callback
+		fmt.Fprintf(f, "  return apply.SequenceT%d(\n", i)
+		// map callback
+
+		curried := func(count int) string {
+			var buf strings.Builder
+			for j := count; j < i; j++ {
+				buf.WriteString(fmt.Sprintf("func(T%d)", j+1))
+			}
+			buf.WriteString(tuple)
+			return buf.String()
+		}
+
+		fmt.Fprintf(f, "    %s,\n", fmap("T1", curried(1)))
+		for j := 1; j < i; j++ {
+			fmt.Fprintf(f, "    %s,\n", fap(curried(j+1), fmt.Sprintf("T%d", j)))
+		}
+
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(f, "    T%d,\n", j+1)
+		}
+
+		fmt.Fprintf(f, "  )\n")
+
+		fmt.Fprintf(f, "}\n")
+
+	}
+}
+
+func generateTraverseTuple1(
+	hkt func(string) string,
+	infix string) func(f *os.File, i int) {
+
+	return func(f *os.File, i int) {
+		tuple := tupleType("T")(i)
+
+		fmt.Fprintf(f, "\n// TraverseTuple%d converts a [Tuple%d] of [A] via transformation functions transforming [A] to [%s] into a [%s].\n", i, i, hkt("A"), hkt(fmt.Sprintf("Tuple%d", i)))
+		fmt.Fprintf(f, "func TraverseTuple%d[", i)
+		// functions
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "F%d ~func(A%d) %s", j+1, j+1, hkt(fmt.Sprintf("T%d", j+1)))
+		}
+		if infix != "" {
+			fmt.Fprintf(f, ", %s", infix)
+		}
+		// types
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(f, ", A%d, T%d", j+1, j+1)
+		}
+		fmt.Fprintf(f, " any](")
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "f%d F%d", j+1, j+1)
+		}
+		fmt.Fprintf(f, ") func (T.Tuple%d[", i)
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "A%d", j+1)
+		}
+		fmt.Fprintf(f, "]) %s {\n", hkt(tuple))
+		fmt.Fprintf(f, "  return func(t T.Tuple%d[", i)
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "A%d", j+1)
+		}
+		fmt.Fprintf(f, "]) %s {\n", hkt(tuple))
+		fmt.Fprintf(f, "    return A.TraverseTuple%d(\n", i)
+		// map
+		fmt.Fprintf(f, "      Map[")
+		if infix != "" {
+			fmt.Fprintf(f, "%s, T1,", infix)
+		} else {
+			fmt.Fprintf(f, "T1,")
+		}
+		for j := 1; j < i; j++ {
+			fmt.Fprintf(f, " func(T%d)", j+1)
+		}
+		fmt.Fprintf(f, " %s],\n", tuple)
+		// applicatives
+		for j := 1; j < i; j++ {
+			fmt.Fprintf(f, "      Ap[")
+			for k := j + 1; k < i; k++ {
+				if k > j+1 {
+					fmt.Fprintf(f, " ")
+				}
+				fmt.Fprintf(f, "func(T%d)", k+1)
+			}
+			if j < i-1 {
+				fmt.Fprintf(f, " ")
+			}
+			fmt.Fprintf(f, "%s", tuple)
+			if infix != "" {
+				fmt.Fprintf(f, ", %s", infix)
+			}
+			fmt.Fprintf(f, ", T%d],\n", j+1)
+		}
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(f, "      f%d,\n", j+1)
+		}
+		fmt.Fprintf(f, "      t,\n")
+		fmt.Fprintf(f, "    )\n")
+		fmt.Fprintf(f, "  }\n")
+		fmt.Fprintf(f, "}\n")
+	}
+}
+
+func generateSequenceTuple1(
+	hkt func(string) string,
+	infix string) func(f *os.File, i int) {
+
+	return func(f *os.File, i int) {
+
+		tuple := tupleType("T")(i)
+
+		fmt.Fprintf(f, "\n// SequenceTuple%d converts a [Tuple%d] of [%s] into an [%s].\n", i, i, hkt("T"), hkt(fmt.Sprintf("Tuple%d", i)))
+		fmt.Fprintf(f, "func SequenceTuple%d[", i)
+		if infix != "" {
+			fmt.Fprintf(f, "%s", infix)
+		}
+		for j := 0; j < i; j++ {
+			if infix != "" || j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "T%d", j+1)
+		}
+		fmt.Fprintf(f, " any](t T.Tuple%d[", i)
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "%s", hkt(fmt.Sprintf("T%d", j+1)))
+		}
+		fmt.Fprintf(f, "]) %s {\n", hkt(tuple))
+		fmt.Fprintf(f, "  return A.SequenceTuple%d(\n", i)
+		// map
+		fmt.Fprintf(f, "    Map[")
+		if infix != "" {
+			fmt.Fprintf(f, "%s, T1,", infix)
+		} else {
+			fmt.Fprintf(f, "T1,")
+		}
+		for j := 1; j < i; j++ {
+			fmt.Fprintf(f, " func(T%d)", j+1)
+		}
+		fmt.Fprintf(f, " %s],\n", tuple)
+		// applicatives
+		for j := 1; j < i; j++ {
+			fmt.Fprintf(f, "    Ap[")
+			for k := j + 1; k < i; k++ {
+				if k > j+1 {
+					fmt.Fprintf(f, " ")
+				}
+				fmt.Fprintf(f, "func(T%d)", k+1)
+			}
+			if j < i-1 {
+				fmt.Fprintf(f, " ")
+			}
+			fmt.Fprintf(f, "%s", tuple)
+			if infix != "" {
+				fmt.Fprintf(f, ", %s", infix)
+			}
+			fmt.Fprintf(f, ", T%d],\n", j+1)
+		}
+		fmt.Fprintf(f, "    t,\n")
+		fmt.Fprintf(f, "  )\n")
+		fmt.Fprintf(f, "}\n")
+	}
+}
+
+func generateSequenceT1(
+	hkt func(string) string,
+	infix string) func(f *os.File, i int) {
+
+	return func(f *os.File, i int) {
+
+		tuple := tupleType("T")(i)
+
+		fmt.Fprintf(f, "\n// SequenceT%d converts %d parameters of [%s] into a [%s].\n", i, i, hkt("T"), hkt(fmt.Sprintf("Tuple%d", i)))
+		fmt.Fprintf(f, "func SequenceT%d[", i)
+		if infix != "" {
+			fmt.Fprintf(f, "%s", infix)
+		}
+		for j := 0; j < i; j++ {
+			if infix != "" || j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "T%d", j+1)
+		}
+		fmt.Fprintf(f, " any](")
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "t%d %s", j+1, hkt(fmt.Sprintf("T%d", j+1)))
+		}
+		fmt.Fprintf(f, ") %s {\n", hkt(tuple))
+		fmt.Fprintf(f, "  return A.SequenceT%d(\n", i)
+		// map
+		fmt.Fprintf(f, "    Map[")
+		if infix != "" {
+			fmt.Fprintf(f, "%s, T1,", infix)
+		} else {
+			fmt.Fprintf(f, "T1,")
+		}
+		for j := 1; j < i; j++ {
+			fmt.Fprintf(f, " func(T%d)", j+1)
+		}
+		fmt.Fprintf(f, " %s],\n", tuple)
+		// applicatives
+		for j := 1; j < i; j++ {
+			fmt.Fprintf(f, "    Ap[")
+			for k := j + 1; k < i; k++ {
+				if k > j+1 {
+					fmt.Fprintf(f, " ")
+				}
+				fmt.Fprintf(f, "func(T%d)", k+1)
+			}
+			if j < i-1 {
+				fmt.Fprintf(f, " ")
+			}
+			fmt.Fprintf(f, "%s", tuple)
+			if infix != "" {
+				fmt.Fprintf(f, ", %s", infix)
+			}
+			fmt.Fprintf(f, ", T%d],\n", j+1)
+		}
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(f, "    t%d,\n", j+1)
+		}
+		fmt.Fprintf(f, "  )\n")
+		fmt.Fprintf(f, "}\n")
+	}
+
+}

v2/cli/monad2.go

@@ -0,0 +1,413 @@
+// 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 (
+	"fmt"
+	"os"
+
+	A "github.com/IBM/fp-go/v2/array"
+	F "github.com/IBM/fp-go/v2/function"
+	N "github.com/IBM/fp-go/v2/number"
+	S "github.com/IBM/fp-go/v2/string"
+)
+
+var (
+	concStrgs     = A.Monoid[string]().Concat
+	intercalStrgs = A.Intercalate(S.Monoid)
+	concAllStrgs  = A.ConcatAll(A.Monoid[string]())
+)
+
+func joinAll(middle string) func(all ...[]string) string {
+	ic := intercalStrgs(middle)
+	return func(all ...[]string) string {
+		return ic(concAllStrgs(all))
+	}
+}
+
+// Deprecated:
+func deprecatedGenerateGenericSequenceT(
+	nonGenericType func(string) string,
+	genericType func(string) string,
+	extra []string,
+) func(f, fg *os.File, i int) {
+	return func(f, fg *os.File, i int) {
+		// tuple
+		tuple := tupleType("T")(i)
+		// all types T
+		typesT := A.MakeBy(i, F.Flow2(
+			N.Inc[int],
+			S.Format[int]("T%d"),
+		))
+		// non generic version
+		fmt.Fprintf(f, "\n// SequenceT%d converts %d [%s] into a [%s]\n", i, i, nonGenericType("T"), nonGenericType(tuple))
+		fmt.Fprintf(f, "func SequenceT%d[%s any](\n", i, joinAll(", ")(extra, typesT))
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(f, "  t%d %s,\n", j+1, nonGenericType(fmt.Sprintf("T%d", j+1)))
+		}
+		fmt.Fprintf(f, ") %s {\n", nonGenericType(tuple))
+		fmt.Fprintf(f, "  return G.SequenceT%d[\n", i)
+		fmt.Fprintf(f, "    %s,\n", nonGenericType(tuple))
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(f, "    %s,\n", nonGenericType(fmt.Sprintf("T%d", j+1)))
+		}
+		fmt.Fprintf(f, "  ](")
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "t%d", j+1)
+		}
+		fmt.Fprintf(f, ")\n")
+		fmt.Fprintf(f, "}\n")
+
+		// generic version
+		fmt.Fprintf(fg, "\n// SequenceT%d converts %d [%s] into a [%s]\n", i, i, genericType("T"), genericType(tuple))
+		fmt.Fprintf(fg, "func SequenceT%d[\n", i)
+		fmt.Fprintf(fg, "  G_TUPLE%d ~%s,\n", i, genericType(tuple))
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(fg, "  G_T%d ~%s, \n", j+1, genericType(fmt.Sprintf("T%d", j+1)))
+		}
+		fmt.Fprintf(fg, "  %s any](\n", joinAll(", ")(extra, typesT))
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(fg, "  t%d G_T%d,\n", j+1, j+1)
+		}
+		fmt.Fprintf(fg, ")  G_TUPLE%d {\n", i)
+		fmt.Fprintf(fg, "  return A.SequenceT%d(\n", i)
+		// map call
+		var cio string
+		cb := generateNestedCallbacks(1, i)
+		if i > 1 {
+			cio = genericType(cb)
+		} else {
+			cio = fmt.Sprintf("G_TUPLE%d", i)
+		}
+		fmt.Fprintf(fg, "    Map[%s],\n", joinAll(", ")(A.From("G_T1", cio), extra, A.From("T1", cb)))
+		// the apply calls
+		for j := 1; j < i; j++ {
+			if j < i-1 {
+				cb := generateNestedCallbacks(j+1, i)
+				cio = genericType(cb)
+			} else {
+				cio = fmt.Sprintf("G_TUPLE%d", i)
+			}
+			fmt.Fprintf(fg, "    Ap[%s, %s, G_T%d],\n", cio, genericType(generateNestedCallbacks(j, i)), j+1)
+		}
+		// function parameters
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(fg, "    t%d,\n", j+1)
+		}
+
+		fmt.Fprintf(fg, "  )\n")
+		fmt.Fprintf(fg, "}\n")
+	}
+}
+
+// Deprecated:
+func deprecatedGenerateGenericSequenceTuple(
+	nonGenericType func(string) string,
+	genericType func(string) string,
+	extra []string,
+) func(f, fg *os.File, i int) {
+	return func(f, fg *os.File, i int) {
+		// tuple
+		tuple := tupleType("T")(i)
+		// all types T
+		typesT := A.MakeBy(i, F.Flow2(
+			N.Inc[int],
+			S.Format[int]("T%d"),
+		))
+		// non generic version
+		fmt.Fprintf(f, "\n// SequenceTuple%d converts a [T.Tuple%d[%s]] into a [%s]\n", i, i, nonGenericType("T"), nonGenericType(tuple))
+		fmt.Fprintf(f, "func SequenceTuple%d[%s any](t T.Tuple%d[", i, joinAll(", ")(extra, typesT), i)
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "%s", nonGenericType(fmt.Sprintf("T%d", j+1)))
+		}
+		fmt.Fprintf(f, "]) %s {\n", nonGenericType(tuple))
+		fmt.Fprintf(f, "  return G.SequenceTuple%d[\n", i)
+		fmt.Fprintf(f, "    %s,\n", nonGenericType(tuple))
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(f, "    %s,\n", nonGenericType(fmt.Sprintf("T%d", j+1)))
+		}
+		fmt.Fprintf(f, "  ](t)\n")
+		fmt.Fprintf(f, "}\n")
+
+		// generic version
+		fmt.Fprintf(fg, "\n// SequenceTuple%d converts a [T.Tuple%d[%s]] into a [%s]\n", i, i, genericType("T"), genericType(tuple))
+		fmt.Fprintf(fg, "func SequenceTuple%d[\n", i)
+		fmt.Fprintf(fg, "  G_TUPLE%d ~%s,\n", i, genericType(tuple))
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(fg, "  G_T%d ~%s, \n", j+1, genericType(fmt.Sprintf("T%d", j+1)))
+		}
+		fmt.Fprintf(fg, "  %s any](t T.Tuple%d[", joinAll(", ")(extra, typesT), i)
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(fg, ", ")
+			}
+			fmt.Fprintf(fg, "G_T%d", j+1)
+		}
+		fmt.Fprintf(fg, "])  G_TUPLE%d {\n", i)
+		fmt.Fprintf(fg, "  return A.SequenceTuple%d(\n", i)
+		// map call
+		var cio string
+		cb := generateNestedCallbacks(1, i)
+		if i > 1 {
+			cio = genericType(cb)
+		} else {
+			cio = fmt.Sprintf("G_TUPLE%d", i)
+		}
+		fmt.Fprintf(fg, "    Map[%s],\n", joinAll(", ")(A.From("G_T1", cio), extra, A.From("T1", cb)))
+		// the apply calls
+		for j := 1; j < i; j++ {
+			if j < i-1 {
+				cb := generateNestedCallbacks(j+1, i)
+				cio = genericType(cb)
+			} else {
+				cio = fmt.Sprintf("G_TUPLE%d", i)
+			}
+			fmt.Fprintf(fg, "    Ap[%s, %s, G_T%d],\n", cio, genericType(generateNestedCallbacks(j, i)), j+1)
+		}
+		// function parameters
+		fmt.Fprintf(fg, "    t)\n")
+		fmt.Fprintf(fg, "}\n")
+	}
+}
+
+// Deprecated:
+func deprecatedGenerateGenericTraverseTuple(
+	nonGenericType func(string) string,
+	genericType func(string) string,
+	extra []string,
+) func(f, fg *os.File, i int) {
+	return func(f, fg *os.File, i int) {
+		// tuple
+		tupleT := tupleType("T")(i)
+		tupleA := tupleType("A")(i)
+		// all types T
+		typesT := A.MakeBy(i, F.Flow2(
+			N.Inc[int],
+			S.Format[int]("T%d"),
+		))
+		// all types A
+		typesA := A.MakeBy(i, F.Flow2(
+			N.Inc[int],
+			S.Format[int]("A%d"),
+		))
+		// all function types
+		typesF := A.MakeBy(i, F.Flow2(
+			N.Inc[int],
+			func(j int) string {
+				return fmt.Sprintf("F%d ~func(A%d) %s", j, j, nonGenericType(fmt.Sprintf("T%d", j)))
+			},
+		))
+		// non generic version
+		fmt.Fprintf(f, "\n// TraverseTuple%d converts a [T.Tuple%d[%s]] into a [%s]\n", i, i, nonGenericType("T"), nonGenericType(tupleT))
+		fmt.Fprintf(f, "func TraverseTuple%d[%s any](", i, joinAll(", ")(typesF, extra, typesA, typesT))
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "f%d F%d", j+1, j+1)
+		}
+		fmt.Fprintf(f, ") func(%s) %s {\n", tupleA, nonGenericType(tupleT))
+		fmt.Fprintf(f, "  return G.TraverseTuple%d[%s](", i, nonGenericType(tupleT))
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "f%d", j+1)
+		}
+		fmt.Fprintf(f, ")\n")
+		fmt.Fprintf(f, "}\n")
+
+		// generic version
+		fmt.Fprintf(fg, "\n// TraverseTuple%d converts a [T.Tuple%d[%s]] into a [%s]\n", i, i, genericType("T"), genericType(tupleT))
+		fmt.Fprintf(fg, "func TraverseTuple%d[\n", i)
+		fmt.Fprintf(fg, "  G_TUPLE%d ~%s,\n", i, genericType(tupleT))
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(fg, "  F%d ~func(A%d) G_T%d,\n", j+1, j+1, j+1)
+		}
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(fg, "  G_T%d ~%s, \n", j+1, genericType(fmt.Sprintf("T%d", j+1)))
+		}
+		fmt.Fprintf(fg, "  %s any](", joinAll(", ")(extra, typesA, typesT))
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(fg, ", ")
+			}
+			fmt.Fprintf(fg, "f%d F%d", j+1, j+1)
+		}
+		fmt.Fprintf(fg, ") func(%s) G_TUPLE%d {\n", tupleA, i)
+		fmt.Fprintf(fg, "  return func(t %s) G_TUPLE%d {\n", tupleA, i)
+		fmt.Fprintf(fg, "    return A.TraverseTuple%d(\n", i)
+		// map call
+		var cio string
+		cb := generateNestedCallbacks(1, i)
+		if i > 1 {
+			cio = genericType(cb)
+		} else {
+			cio = fmt.Sprintf("G_TUPLE%d", i)
+		}
+		fmt.Fprintf(fg, "    Map[%s],\n", joinAll(", ")(A.From("G_T1", cio), extra, A.From("T1", cb)))
+		// the apply calls
+		for j := 1; j < i; j++ {
+			if j < i-1 {
+				cb := generateNestedCallbacks(j+1, i)
+				cio = genericType(cb)
+			} else {
+				cio = fmt.Sprintf("G_TUPLE%d", i)
+			}
+			fmt.Fprintf(fg, "    Ap[%s, %s, G_T%d],\n", cio, genericType(generateNestedCallbacks(j, i)), j+1)
+		}
+		// function parameters
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(fg, "    f%d,\n", j+1)
+		}
+		// tuple parameter
+		fmt.Fprintf(fg, "    t)\n")
+		fmt.Fprintf(fg, "   }\n")
+		fmt.Fprintf(fg, "}\n")
+	}
+}
+
+func generateGenericSequenceT(
+	suffix string,
+	nonGenericType func(string) string,
+	extra []string,
+) func(f *os.File, i int) {
+	return func(f *os.File, i int) {
+		// tuple
+		tuple := tupleTypePlain("T")(i)
+		// all types T
+		typesT := A.MakeBy(i, F.Flow2(
+			N.Inc[int],
+			S.Format[int]("T%d"),
+		))
+		// non generic version
+		fmt.Fprintf(f, "\n// Sequence%sT%d converts %d [%s] into a [%s]\n", suffix, i, i, nonGenericType("T"), nonGenericType(tuple))
+		fmt.Fprintf(f, "func Sequence%sT%d[%s any](\n", suffix, i, joinAll(", ")(extra, typesT))
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(f, "  t%d %s,\n", j+1, nonGenericType(fmt.Sprintf("T%d", j+1)))
+		}
+		fmt.Fprintf(f, ") %s {\n", nonGenericType(tuple))
+		fmt.Fprintf(f, "  return apply.SequenceT%d(\n", i)
+		fmt.Fprintf(f, "    Map[%s],\n", joinAll(", ")(extra, A.From("T1", generateNestedCallbacksPlain(1, i))))
+
+		// the apply calls
+		for j := 2; j <= i; j++ {
+			fmt.Fprintf(f, "    Ap%s[%s],\n", suffix, joinAll(", ")(A.Of(generateNestedCallbacksPlain(j, i)), extra, A.Of(fmt.Sprintf("T%d", j))))
+		}
+		// function parameters
+		for j := 1; j <= i; j++ {
+			fmt.Fprintf(f, "    t%d,\n", j)
+		}
+
+		fmt.Fprintf(f, "  )\n")
+		fmt.Fprintf(f, "}\n")
+	}
+}
+
+func generateGenericSequenceTuple(
+	suffix string,
+	nonGenericType func(string) string,
+	extra []string,
+) func(f *os.File, i int) {
+	return func(f *os.File, i int) {
+		// tuple
+		tuple := tupleTypePlain("T")(i)
+		// all types T
+		typesT := A.MakeBy(i, F.Flow2(
+			N.Inc[int],
+			S.Format[int]("T%d"),
+		))
+		// non generic version
+		fmt.Fprintf(f, "\n// Sequence%sTuple%d converts a [tuple.Tuple%d[%s]] into a [%s]\n", suffix, i, i, nonGenericType("T"), nonGenericType(tuple))
+		fmt.Fprintf(f, "func Sequence%sTuple%d[%s any](t tuple.Tuple%d[", suffix, i, joinAll(", ")(extra, typesT), i)
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "%s", nonGenericType(fmt.Sprintf("T%d", j+1)))
+		}
+		fmt.Fprintf(f, "]) %s {\n", nonGenericType(tuple))
+		fmt.Fprintf(f, "  return apply.SequenceTuple%d(\n", i)
+		fmt.Fprintf(f, "    Map[%s],\n", joinAll(", ")(extra, A.From("T1", generateNestedCallbacksPlain(1, i))))
+
+		// the apply calls
+		for j := 2; j <= i; j++ {
+			fmt.Fprintf(f, "    Ap%s[%s],\n", suffix, joinAll(", ")(A.Of(generateNestedCallbacksPlain(j, i)), extra, A.Of(fmt.Sprintf("T%d", j))))
+		}
+
+		// function parameters
+		fmt.Fprintf(f, "    t,\n")
+		// function parameters
+		fmt.Fprintf(f, "  )\n")
+		fmt.Fprintf(f, "}\n")
+	}
+}
+
+func generateGenericTraverseTuple(
+	suffix string,
+	nonGenericType func(string) string,
+	extra []string,
+) func(f *os.File, i int) {
+	return func(f *os.File, i int) {
+		// all types T
+		typesT := A.MakeBy(i, F.Flow2(
+			N.Inc[int],
+			S.Format[int]("T%d"),
+		))
+		// all types A
+		typesA := A.MakeBy(i, F.Flow2(
+			N.Inc[int],
+			S.Format[int]("A%d"),
+		))
+		// function types
+		typesF := A.MakeBy(i, func(j int) string {
+			return fmt.Sprintf("F%d ~func(A%d) %s", j+1, j+1, nonGenericType(fmt.Sprintf("T%d", j+1)))
+		})
+		paramF := A.MakeBy(i, func(j int) string {
+			return fmt.Sprintf("f%d F%d", j+1, j+1)
+		})
+		// return type
+		paramType := fmt.Sprintf("tuple.Tuple%d[%s]", i, joinAll(", ")(typesA))
+		returnType := nonGenericType(fmt.Sprintf("tuple.Tuple%d[%s]", i, joinAll(", ")(typesT)))
+		// non generic version
+		fmt.Fprintf(f, "\n// Traverse%sTuple%d converts a [%s] into a [%s]\n", suffix, i, paramType, returnType)
+		fmt.Fprintf(f, "func Traverse%sTuple%d[%s any](%s) func(%s) %s {\n", suffix, i, joinAll(", ")(extra, typesF, typesT, typesA), joinAll(", ")(paramF), paramType, returnType)
+		fmt.Fprintf(f, "  return func(t %s) %s {\n", paramType, returnType)
+		fmt.Fprintf(f, "    return apply.TraverseTuple%d(\n", i)
+		fmt.Fprintf(f, "      Map[%s],\n", joinAll(", ")(extra, A.From("T1", generateNestedCallbacksPlain(1, i))))
+
+		// the apply calls
+		for j := 2; j <= i; j++ {
+			fmt.Fprintf(f, "      Ap%s[%s],\n", suffix, joinAll(", ")(A.Of(generateNestedCallbacksPlain(j, i)), extra, A.Of(fmt.Sprintf("T%d", j))))
+		}
+		// the function parameters
+		for j := 1; j <= i; j++ {
+			fmt.Fprintf(f, "      f%d,\n", j)
+		}
+		// function parameters
+		fmt.Fprintf(f, "      t,\n")
+		// function parameters
+		fmt.Fprintf(f, "    )\n")
+		fmt.Fprintf(f, "  }\n")
+		fmt.Fprintf(f, "}\n")
+	}
+}

v2/cli/option.go

@@ -0,0 +1,210 @@
+// 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 (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"time"
+
+	C "github.com/urfave/cli/v2"
+)
+
+func optionHKT(typeA string) string {
+	return fmt.Sprintf("Option[%s]", typeA)
+}
+
+func generateOptionTraverseTuple(f *os.File, i int) {
+	generateTraverseTuple1(optionHKT, "")(f, i)
+}
+
+func generateOptionSequenceTuple(f *os.File, i int) {
+	generateSequenceTuple1(optionHKT, "")(f, i)
+}
+
+func generateOptionSequenceT(f *os.File, i int) {
+	generateSequenceT1(optionHKT, "")(f, i)
+}
+
+func generateOptionize(f *os.File, i int) {
+	// Create the optionize version
+	fmt.Fprintf(f, "\n// Optionize%d converts a function with %d parameters returning a tuple of a return value R and a boolean into a function with %d parameters returning an Option[R]\n", i, i, i)
+	fmt.Fprintf(f, "func Optionize%d[F ~func(", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	fmt.Fprintf(f, ") (R, bool)")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ", R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	fmt.Fprintf(f, ") Option[R] {\n")
+	fmt.Fprintf(f, "  return func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t%d T%d", j, j)
+	}
+	fmt.Fprintf(f, ") Option[R] {\n")
+	fmt.Fprintf(f, "    return optionize(func() (R, bool) {\n")
+	fmt.Fprintf(f, "      return f(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t%d", j)
+	}
+	fmt.Fprintln(f, ")")
+	fmt.Fprintln(f, "    })")
+	fmt.Fprintln(f, "  }")
+	fmt.Fprintln(f, "}")
+}
+
+func generateUnoptionize(f *os.File, i int) {
+	// Create the optionize version
+	fmt.Fprintf(f, "\n// Unoptionize%d converts a function with %d parameters returning a tuple of a return value R and a boolean into a function with %d parameters returning an Option[R]\n", i, i, i)
+	fmt.Fprintf(f, "func Unoptionize%d[F ~func(", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	fmt.Fprintf(f, ") Option[R]")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ", R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	fmt.Fprintf(f, ") (R, bool) {\n")
+	fmt.Fprintf(f, "  return func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t%d T%d", j, j)
+	}
+	fmt.Fprintf(f, ") (R, bool) {\n")
+	fmt.Fprintf(f, "    return Unwrap(f(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t%d", j)
+	}
+	fmt.Fprintln(f, "))")
+	fmt.Fprintln(f, "  }")
+	fmt.Fprintln(f, "}")
+}
+
+func generateOptionHelpers(filename string, count int) error {
+	dir, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+	absDir, err := filepath.Abs(dir)
+	if err != nil {
+		return err
+	}
+	pkg := filepath.Base(absDir)
+	f, err := os.Create(filepath.Clean(filename))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	// log
+	log.Printf("Generating code in [%s] for package [%s] with [%d] repetitions ...", filename, pkg, count)
+
+	// some header
+	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(f, "// This file was generated by robots at")
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
+
+	fmt.Fprintf(f, "package %s\n\n", pkg)
+
+	fmt.Fprintf(f, `
+import (
+	A "github.com/IBM/fp-go/v2/internal/apply"
+	T "github.com/IBM/fp-go/v2/tuple"
+)
+`)
+
+	// print out some helpers
+	fmt.Fprintf(f, `// optionize converts a nullary function to an option
+func optionize[R any](f func() (R, bool)) Option[R] {
+	if r, ok := f(); ok {
+		return Some(r)
+	}
+	return None[R]()
+}
+`)
+
+	// zero level functions
+
+	// optionize
+	generateOptionize(f, 0)
+	// unoptionize
+	generateUnoptionize(f, 0)
+
+	for i := 1; i <= count; i++ {
+		// optionize
+		generateOptionize(f, i)
+		// unoptionize
+		generateUnoptionize(f, i)
+		// sequenceT
+		generateOptionSequenceT(f, i)
+		// sequenceTuple
+		generateOptionSequenceTuple(f, i)
+		// traverseTuple
+		generateOptionTraverseTuple(f, i)
+	}
+
+	return nil
+}
+
+func OptionCommand() *C.Command {
+	return &C.Command{
+		Name:  "option",
+		Usage: "generate code for Option",
+		Flags: []C.Flag{
+			flagCount,
+			flagFilename,
+		},
+		Action: func(ctx *C.Context) error {
+			return generateOptionHelpers(
+				ctx.String(keyFilename),
+				ctx.Int(keyCount),
+			)
+		},
+	}
+}

v2/cli/pipe.go

@@ -0,0 +1,433 @@
+// 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 (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"time"
+
+	C "github.com/urfave/cli/v2"
+)
+
+func generateUnsliced(f *os.File, i int) {
+	// Create the optionize version
+	fmt.Fprintf(f, "\n// Unsliced%d converts a function taking a slice parameter into a function with %d parameters\n", i, i)
+	fmt.Fprintf(f, "func Unsliced%d[F ~func([]T) R, T, R any](f F) func(", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T")
+	}
+	fmt.Fprintf(f, ") R {\n")
+	fmt.Fprintf(f, "  return func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t%d", j+1)
+	}
+	if i > 0 {
+		fmt.Fprintf(f, " T")
+	}
+	fmt.Fprintf(f, ") R {\n")
+	fmt.Fprintf(f, "    return f([]T{")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t%d", j+1)
+	}
+	fmt.Fprintln(f, "})")
+	fmt.Fprintln(f, "  }")
+	fmt.Fprintln(f, "}")
+}
+
+func generateVariadic(f *os.File, i int) {
+	// Create the nullary version
+	fmt.Fprintf(f, "\n// Variadic%d converts a function taking %d parameters and a final slice into a function with %d parameters but a final variadic argument\n", i, i, i)
+	fmt.Fprintf(f, "func Variadic%d[", i)
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	if i > 0 {
+		fmt.Fprintf(f, ", ")
+	}
+	fmt.Fprintf(f, "V, R any](f func(")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	if i > 0 {
+		fmt.Fprintf(f, ", ")
+	}
+	fmt.Fprintf(f, "[]V) R) func(")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	if i > 0 {
+		fmt.Fprintf(f, ", ")
+	}
+	fmt.Fprintf(f, "...V) R {\n")
+	fmt.Fprintf(f, "  return func(")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t%d T%d", j, j)
+	}
+	if i > 0 {
+		fmt.Fprintf(f, ", ")
+	}
+	fmt.Fprintf(f, "v ...V) R {\n")
+	fmt.Fprintf(f, "    return f(")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t%d", j)
+	}
+	if i > 0 {
+		fmt.Fprintf(f, ", ")
+	}
+	fmt.Fprintf(f, "v)\n")
+	fmt.Fprintf(f, "  }\n")
+
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateUnvariadic(f *os.File, i int) {
+	// Create the nullary version
+	fmt.Fprintf(f, "\n// Unvariadic%d converts a function taking %d parameters and a final variadic argument into a function with %d parameters but a final slice argument\n", i, i, i)
+	fmt.Fprintf(f, "func Unvariadic%d[", i)
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	if i > 0 {
+		fmt.Fprintf(f, ", ")
+	}
+	fmt.Fprintf(f, "V, R any](f func(")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	if i > 0 {
+		fmt.Fprintf(f, ", ")
+	}
+	fmt.Fprintf(f, "...V) R) func(")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	if i > 0 {
+		fmt.Fprintf(f, ", ")
+	}
+	fmt.Fprintf(f, "[]V) R {\n")
+	fmt.Fprintf(f, "  return func(")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t%d T%d", j, j)
+	}
+	if i > 0 {
+		fmt.Fprintf(f, ", ")
+	}
+	fmt.Fprintf(f, "v []V) R {\n")
+	fmt.Fprintf(f, "    return f(")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t%d", j)
+	}
+	if i > 0 {
+		fmt.Fprintf(f, ", ")
+	}
+	fmt.Fprintf(f, "v...)\n")
+	fmt.Fprintf(f, "  }\n")
+
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateNullary(f *os.File, i int) {
+	// Create the nullary version
+	fmt.Fprintf(f, "\n// Nullary%d creates a parameter less function from a parameter less function and %d functions. When executed the first parameter less function gets executed and then the result is piped through the remaining functions\n", i, i-1)
+	fmt.Fprintf(f, "func Nullary%d[F1 ~func() T1", i)
+	for j := 2; j <= i; j++ {
+		fmt.Fprintf(f, ", F%d ~func(T%d) T%d", j, j-1, j)
+	}
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, " any](f1 F1")
+	for j := 2; j <= i; j++ {
+		fmt.Fprintf(f, ", f%d F%d", j, j)
+	}
+	fmt.Fprintf(f, ") func() T%d {\n", i)
+	fmt.Fprintf(f, "  return func() T%d {\n", i)
+	fmt.Fprintf(f, "    return Pipe%d(f1()", i-1)
+	for j := 2; j <= i; j++ {
+		fmt.Fprintf(f, ", f%d", j)
+	}
+	fmt.Fprintf(f, ")\n")
+	fmt.Fprintln(f, "  }")
+
+	fmt.Fprintln(f, "}")
+}
+
+func generateFlow(f *os.File, i int) {
+	// Create the flow version
+	fmt.Fprintf(f, "\n// Flow%d creates a function that takes an initial value t0 and successively applies %d functions where the input of a function is the return value of the previous function\n// The final return value is the result of the last function application\n", i, i)
+	fmt.Fprintf(f, "func Flow%d[", i)
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "F%d ~func(T%d) T%d", j, j-1, j)
+	}
+	for j := 0; j <= i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, " any](")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "f%d F%d", j, j)
+	}
+	fmt.Fprintf(f, ") func(T0) T%d {\n", i)
+	fmt.Fprintf(f, "  return func(t0 T0) T%d {\n", i)
+	fmt.Fprintf(f, "    return Pipe%d(t0", i)
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, ", f%d", j)
+	}
+	fmt.Fprintf(f, ")\n")
+	fmt.Fprintln(f, "  }")
+
+	fmt.Fprintln(f, "}")
+
+}
+
+func generatePipe(f *os.File, i int) {
+	// Create the pipe version
+	fmt.Fprintf(f, "\n// Pipe%d takes an initial value t0 and successively applies %d functions where the input of a function is the return value of the previous function\n// The final return value is the result of the last function application\n", i, i)
+	fmt.Fprintf(f, "func Pipe%d[", i)
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "F%d ~func(T%d) T%d", j, j-1, j)
+	}
+	if i > 0 {
+		fmt.Fprintf(f, ", ")
+	}
+	for j := 0; j <= i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+
+	fmt.Fprintf(f, " any](t0 T0")
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, ", f%d F%d", j, j)
+	}
+	fmt.Fprintf(f, ") T%d {\n", i)
+	fmt.Fprintf(f, "  return ")
+	for j := i; j >= 1; j-- {
+		fmt.Fprintf(f, "f%d(", j)
+	}
+	fmt.Fprintf(f, "t0")
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, ")")
+	}
+	fmt.Fprintf(f, "\n")
+	fmt.Fprintln(f, "}")
+}
+
+func recurseCurry(f *os.File, indent string, total, count int) {
+	if count == 1 {
+		fmt.Fprintf(f, "%sreturn func(t%d T%d) T%d {\n", indent, total-1, total-1, total)
+		fmt.Fprintf(f, "%s  return f(t0", indent)
+		for i := 1; i < total; i++ {
+			fmt.Fprintf(f, ", t%d", i)
+		}
+		fmt.Fprintf(f, ")\n")
+		fmt.Fprintf(f, "%s}\n", indent)
+	} else {
+		fmt.Fprintf(f, "%sreturn", indent)
+		for i := total - count + 1; i <= total; i++ {
+			fmt.Fprintf(f, " func(t%d T%d)", i-1, i-1)
+		}
+		fmt.Fprintf(f, " T%d {\n", total)
+		recurseCurry(f, fmt.Sprintf("  %s", indent), total, count-1)
+		fmt.Fprintf(f, "%s}\n", indent)
+	}
+}
+
+func generateCurry(f *os.File, i int) {
+	// Create the curry version
+	fmt.Fprintf(f, "\n// Curry%d takes a function with %d parameters and returns a cascade of functions each taking only one parameter.\n// The inverse function is [Uncurry%d]\n", i, i, i)
+	fmt.Fprintf(f, "func Curry%d[FCT ~func(T0", i)
+	for j := 1; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ") T%d", i)
+	// type arguments
+	for j := 0; j <= i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, " any](f FCT) func(T0)")
+	for j := 2; j <= i; j++ {
+		fmt.Fprintf(f, " func(T%d)", j-1)
+	}
+	fmt.Fprintf(f, " T%d {\n", i)
+	recurseCurry(f, "  ", i, i)
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateUncurry(f *os.File, i int) {
+	// Create the uncurry version
+	fmt.Fprintf(f, "\n// Uncurry%d takes a cascade of %d functions each taking only one parameter and returns a function with %d parameters .\n// The inverse function is [Curry%d]\n", i, i, i, i)
+	fmt.Fprintf(f, "func Uncurry%d[FCT ~func(T0)", i)
+	for j := 1; j < i; j++ {
+		fmt.Fprintf(f, " func(T%d)", j)
+	}
+	fmt.Fprintf(f, " T%d", i)
+	// the type parameters
+	for j := 0; j <= i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, " any](f FCT) func(")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j-1)
+	}
+	fmt.Fprintf(f, ") T%d {\n", i)
+	fmt.Fprintf(f, "  return func(")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t%d T%d", j-1, j-1)
+	}
+	fmt.Fprintf(f, ") T%d {\n", i)
+	fmt.Fprintf(f, "    return f")
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, "(t%d)", j-1)
+	}
+	fmt.Fprintln(f)
+
+	fmt.Fprintf(f, "  }\n")
+
+	fmt.Fprintf(f, "}\n")
+}
+
+func generatePipeHelpers(filename string, count int) error {
+	dir, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+	absDir, err := filepath.Abs(dir)
+	if err != nil {
+		return err
+	}
+	pkg := filepath.Base(absDir)
+	f, err := os.Create(filepath.Clean(filename))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	// log
+	log.Printf("Generating code in [%s] for package [%s] with [%d] repetitions ...", filename, pkg, count)
+
+	// some header
+	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(f, "// This file was generated by robots at")
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
+
+	fmt.Fprintf(f, "package %s\n", pkg)
+
+	// pipe
+	generatePipe(f, 0)
+	// variadic
+	generateVariadic(f, 0)
+	// unvariadic
+	generateUnvariadic(f, 0)
+	// unsliced
+	generateUnsliced(f, 0)
+
+	for i := 1; i <= count; i++ {
+
+		// pipe
+		generatePipe(f, i)
+		// flow
+		generateFlow(f, i)
+		// nullary
+		generateNullary(f, i)
+		// curry
+		generateCurry(f, i)
+		// uncurry
+		generateUncurry(f, i)
+		// variadic
+		generateVariadic(f, i)
+		// unvariadic
+		generateUnvariadic(f, i)
+		// unsliced
+		generateUnsliced(f, i)
+	}
+
+	return nil
+}
+
+func PipeCommand() *C.Command {
+	return &C.Command{
+		Name:        "pipe",
+		Usage:       "generate code for pipe, flow, curry, etc",
+		Description: "Code generation for pipe, flow, curry, etc",
+		Flags: []C.Flag{
+			flagCount,
+			flagFilename,
+		},
+		Action: func(ctx *C.Context) error {
+			return generatePipeHelpers(
+				ctx.String(keyFilename),
+				ctx.Int(keyCount),
+			)
+		},
+	}
+}

v2/cli/reader.go

@@ -0,0 +1,164 @@
+// 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 (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"time"
+
+	C "github.com/urfave/cli/v2"
+)
+
+func generateReaderFrom(f, fg *os.File, i int) {
+	// non generic version
+	fmt.Fprintf(f, "\n// From%d converts a function with %d parameters returning a [R] into a function with %d parameters returning a [Reader[C, R]]\n// The first parameter is considered to be the context [C] of the reader\n", i, i+1, i)
+	fmt.Fprintf(f, "func From%d[F ~func(C", i)
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ") R")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ", C, R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	fmt.Fprintf(f, ") Reader[C, R] {\n")
+	fmt.Fprintf(f, "  return G.From%d[Reader[C, R]](f)\n", i)
+	fmt.Fprintln(f, "}")
+
+	// generic version
+	fmt.Fprintf(fg, "\n// From%d converts a function with %d parameters returning a [R] into a function with %d parameters returning a [GRA]\n// The first parameter is considered to be the context [C].\n", i, i+1, i)
+	fmt.Fprintf(fg, "func From%d[GRA ~func(C) R, F ~func(C", i)
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", T%d", j)
+	}
+	fmt.Fprintf(fg, ") R")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", T%d", j)
+	}
+	fmt.Fprintf(fg, ", C, R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "T%d", j)
+	}
+	fmt.Fprintf(fg, ") GRA {\n")
+
+	fmt.Fprintf(fg, "  return func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "t%d T%d", j, j)
+	}
+	fmt.Fprintf(fg, ") GRA {\n")
+	fmt.Fprintf(fg, "    return MakeReader[GRA](func(r C) R {\n")
+	fmt.Fprintf(fg, "      return f(r")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", t%d", j)
+	}
+	fmt.Fprintf(fg, ")\n")
+	fmt.Fprintf(fg, "    })\n")
+	fmt.Fprintf(fg, "  }\n")
+	fmt.Fprintf(fg, "}\n")
+}
+
+func generateReaderHelpers(filename string, count int) error {
+	dir, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+	absDir, err := filepath.Abs(dir)
+	if err != nil {
+		return err
+	}
+	pkg := filepath.Base(absDir)
+	f, err := os.Create(filepath.Clean(filename))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	// construct subdirectory
+	genFilename := filepath.Join("generic", filename)
+	err = os.MkdirAll("generic", os.ModePerm)
+	if err != nil {
+		return err
+	}
+	fg, err := os.Create(filepath.Clean(genFilename))
+	if err != nil {
+		return err
+	}
+	defer fg.Close()
+
+	// log
+	log.Printf("Generating code in [%s] for package [%s] with [%d] repetitions ...", filename, pkg, count)
+
+	// some header
+	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(f, "// This file was generated by robots at")
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
+
+	fmt.Fprintf(f, "package %s\n\n", pkg)
+
+	fmt.Fprintf(f, `
+import (
+	G "github.com/IBM/fp-go/v2/%s/generic"	
+)
+`, pkg)
+
+	// some header
+	fmt.Fprintln(fg, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(fg, "// This file was generated by robots at")
+	fmt.Fprintf(fg, "// %s\n", time.Now())
+
+	fmt.Fprintf(fg, "package generic\n\n")
+
+	// from
+	generateReaderFrom(f, fg, 0)
+
+	for i := 1; i <= count; i++ {
+		// from
+		generateReaderFrom(f, fg, i)
+	}
+
+	return nil
+}
+
+func ReaderCommand() *C.Command {
+	return &C.Command{
+		Name:  "reader",
+		Usage: "generate code for Reader",
+		Flags: []C.Flag{
+			flagCount,
+			flagFilename,
+		},
+		Action: func(ctx *C.Context) error {
+			return generateReaderHelpers(
+				ctx.String(keyFilename),
+				ctx.Int(keyCount),
+			)
+		},
+	}
+}

v2/cli/readerioeither.go

@@ -0,0 +1,294 @@
+// 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 (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"time"
+
+	C "github.com/urfave/cli/v2"
+)
+
+func generateReaderIOEitherFrom(f, fg *os.File, i int) {
+	// non generic version
+	fmt.Fprintf(f, "\n// From%d converts a function with %d parameters returning a tuple into a function with %d parameters returning a [ReaderIOEither[R]]\n// The first parameter is considered to be the context [C].\n", i, i+1, i)
+	fmt.Fprintf(f, "func From%d[F ~func(C", i)
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ") func() (R, error)")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ", C, R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	fmt.Fprintf(f, ") ReaderIOEither[C, error, R] {\n")
+	fmt.Fprintf(f, "  return G.From%d[ReaderIOEither[C, error, R]](f)\n", i)
+	fmt.Fprintln(f, "}")
+
+	// generic version
+	fmt.Fprintf(fg, "\n// From%d converts a function with %d parameters returning a tuple into a function with %d parameters returning a [GRA]\n// The first parameter is considerd to be the context [C].\n", i, i+1, i)
+	fmt.Fprintf(fg, "func From%d[GRA ~func(C) GIOA, F ~func(C", i)
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", T%d", j)
+	}
+	fmt.Fprintf(fg, ") func() (R, error), GIOA ~func() E.Either[error, R]")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", T%d", j)
+	}
+	fmt.Fprintf(fg, ", C, R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "T%d", j)
+	}
+	fmt.Fprintf(fg, ") GRA {\n")
+
+	fmt.Fprintf(fg, "  return RD.From%d[GRA](func(r C", i)
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", t%d T%d", j, j)
+	}
+	fmt.Fprintf(fg, ") GIOA {\n")
+	fmt.Fprintf(fg, "    return E.Eitherize0(f(r")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", t%d", j)
+	}
+	fmt.Fprintf(fg, "))\n")
+	fmt.Fprintf(fg, "  })\n")
+	fmt.Fprintf(fg, "}\n")
+}
+
+func generateReaderIOEitherEitherize(f, fg *os.File, i int) {
+	// non generic version
+	fmt.Fprintf(f, "\n// Eitherize%d converts a function with %d parameters returning a tuple into a function with %d parameters returning a [ReaderIOEither[C, error, R]]\n// The first parameter is considered to be the context [C].\n", i, i+1, i)
+	fmt.Fprintf(f, "func Eitherize%d[F ~func(C", i)
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ") (R, error)")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ", C, R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	fmt.Fprintf(f, ") ReaderIOEither[C, error, R] {\n")
+	fmt.Fprintf(f, "  return G.Eitherize%d[ReaderIOEither[C, error, R]](f)\n", i)
+	fmt.Fprintln(f, "}")
+
+	// generic version
+	fmt.Fprintf(fg, "\n// Eitherize%d converts a function with %d parameters returning a tuple into a function with %d parameters returning a [GRA]\n// The first parameter is considered to be the context [C].\n", i, i, i)
+	fmt.Fprintf(fg, "func Eitherize%d[GRA ~func(C) GIOA, F ~func(C", i)
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", T%d", j)
+	}
+	fmt.Fprintf(fg, ") (R, error), GIOA ~func() E.Either[error, R]")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", T%d", j)
+	}
+	fmt.Fprintf(fg, ", C, R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "T%d", j)
+	}
+	fmt.Fprintf(fg, ") GRA {\n")
+
+	fmt.Fprintf(fg, "  return From%d[GRA](func(r C", i)
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", t%d T%d", j, j)
+	}
+	fmt.Fprintf(fg, ") func() (R, error) {\n")
+	fmt.Fprintf(fg, "    return func() (R, error) {\n")
+	fmt.Fprintf(fg, "      return f(r")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", t%d", j)
+	}
+	fmt.Fprintf(fg, ")\n")
+	fmt.Fprintf(fg, "    }})\n")
+	fmt.Fprintf(fg, "}\n")
+}
+
+func generateReaderIOEitherUneitherize(f, fg *os.File, i int) {
+	// non generic version
+	fmt.Fprintf(f, "\n// Uneitherize%d converts a function with %d parameters returning a [ReaderIOEither[C, error, R]] into a function with %d parameters returning a tuple.\n// The first parameter is considered to be the context [C].\n", i, i+1, i)
+	fmt.Fprintf(f, "func Uneitherize%d[F ~func(", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	fmt.Fprintf(f, ") ReaderIOEither[C, error, R]")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ", C, R any](f F) func(C")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ") (R, error) {\n")
+	fmt.Fprintf(f, "  return G.Uneitherize%d[ReaderIOEither[C, error, R]", i)
+
+	fmt.Fprintf(f, ", func(C")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ")(R, error)](f)\n")
+	fmt.Fprintln(f, "}")
+
+	// generic version
+	fmt.Fprintf(fg, "\n// Uneitherize%d converts a function with %d parameters returning a [GRA] into a function with %d parameters returning a tuple.\n// The first parameter is considered to be the context [C].\n", i, i, i)
+	fmt.Fprintf(fg, "func Uneitherize%d[GRA ~func(C) GIOA, F ~func(C", i)
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", T%d", j)
+	}
+	fmt.Fprintf(fg, ") (R, error), GIOA ~func() E.Either[error, R]")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", T%d", j)
+	}
+	fmt.Fprintf(fg, ", C, R any](f func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "T%d", j)
+	}
+	fmt.Fprintf(fg, ") GRA) F {\n")
+
+	fmt.Fprintf(fg, "  return func(c C")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", t%d T%d", j, j)
+	}
+	fmt.Fprintf(fg, ") (R, error) {\n")
+	fmt.Fprintf(fg, "    return E.UnwrapError(f(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "t%d", j)
+	}
+	fmt.Fprintf(fg, ")(c)())\n")
+	fmt.Fprintf(fg, "  }\n")
+	fmt.Fprintf(fg, "}\n")
+}
+
+func generateReaderIOEitherHelpers(filename string, count int) error {
+	dir, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+	absDir, err := filepath.Abs(dir)
+	if err != nil {
+		return err
+	}
+	pkg := filepath.Base(absDir)
+	f, err := os.Create(filepath.Clean(filename))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	// construct subdirectory
+	genFilename := filepath.Join("generic", filename)
+	err = os.MkdirAll("generic", os.ModePerm)
+	if err != nil {
+		return err
+	}
+	fg, err := os.Create(filepath.Clean(genFilename))
+	if err != nil {
+		return err
+	}
+	defer fg.Close()
+
+	// log
+	log.Printf("Generating code in [%s] for package [%s] with [%d] repetitions ...", filename, pkg, count)
+
+	// some header
+	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(f, "// This file was generated by robots at")
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
+
+	fmt.Fprintf(f, "package %s\n\n", pkg)
+
+	fmt.Fprintf(f, `
+import (
+	G "github.com/IBM/fp-go/v2/%s/generic"	
+)
+`, pkg)
+
+	// some header
+	fmt.Fprintln(fg, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(fg, "// This file was generated by robots at")
+	fmt.Fprintf(fg, "// %s\n", time.Now())
+
+	fmt.Fprintf(fg, "package generic\n\n")
+
+	fmt.Fprintf(fg, `
+import (
+	E "github.com/IBM/fp-go/v2/either"
+	RD "github.com/IBM/fp-go/v2/reader/generic"
+)
+`)
+
+	// from
+	generateReaderIOEitherFrom(f, fg, 0)
+	// eitherize
+	generateReaderIOEitherEitherize(f, fg, 0)
+	// uneitherize
+	generateReaderIOEitherUneitherize(f, fg, 0)
+
+	for i := 1; i <= count; i++ {
+		// from
+		generateReaderIOEitherFrom(f, fg, i)
+		// eitherize
+		generateReaderIOEitherEitherize(f, fg, i)
+		// uneitherize
+		generateReaderIOEitherUneitherize(f, fg, i)
+	}
+
+	return nil
+}
+
+func ReaderIOEitherCommand() *C.Command {
+	return &C.Command{
+		Name:  "readerioeither",
+		Usage: "generate code for ReaderIOEither",
+		Flags: []C.Flag{
+			flagCount,
+			flagFilename,
+		},
+		Action: func(ctx *C.Context) error {
+			return generateReaderIOEitherHelpers(
+				ctx.String(keyFilename),
+				ctx.Int(keyCount),
+			)
+		},
+	}
+}

v2/cli/templates/functions.go

@@ -0,0 +1,15 @@
+package templates
+
+import (
+	"text/template"
+
+	E "github.com/IBM/fp-go/v2/either"
+)
+
+var (
+	templateFunctions = template.FuncMap{}
+)
+
+func Parse(name, tmpl string) E.Either[error, *template.Template] {
+	return E.TryCatchError(template.New(name).Funcs(templateFunctions).Parse(tmpl))
+}

v2/cli/tuple.go

@@ -0,0 +1,625 @@
+// 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 (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	C "github.com/urfave/cli/v2"
+)
+
+func writeTupleType(f *os.File, symbol string, i int) {
+	fmt.Fprintf(f, "Tuple%d[", i)
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "%s%d", symbol, j)
+	}
+	fmt.Fprintf(f, "]")
+}
+
+func makeTupleType(name string) func(i int) string {
+	return func(i int) string {
+		var buf strings.Builder
+		buf.WriteString(fmt.Sprintf("Tuple%d[", i))
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				buf.WriteString(", ")
+			}
+			buf.WriteString(fmt.Sprintf("%s%d", name, j+1))
+		}
+		buf.WriteString("]")
+
+		return buf.String()
+	}
+}
+
+func generatePush(f *os.File, i int) {
+	tuple1 := makeTupleType("T")(i)
+	tuple2 := makeTupleType("T")(i + 1)
+	// Create the replicate version
+	fmt.Fprintf(f, "\n// Push%d creates a [Tuple%d] from a [Tuple%d] by appending a constant value\n", i, i+1, i)
+	fmt.Fprintf(f, "func Push%d[", i)
+	// function prototypes
+	for j := 0; j <= i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, " any](value T%d) func(%s) %s {\n", i+1, tuple1, tuple2)
+	fmt.Fprintf(f, "  return func(t %s) %s {\n", tuple1, tuple2)
+	fmt.Fprintf(f, "    return MakeTuple%d(", i+1)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t.F%d", j+1)
+	}
+	fmt.Fprintf(f, ", value)\n")
+	fmt.Fprintf(f, "  }\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateReplicate(f *os.File, i int) {
+	// Create the replicate version
+	fmt.Fprintf(f, "\n// Replicate%d creates a [Tuple%d] with all fields set to the input value `t`\n", i, i)
+	fmt.Fprintf(f, "func Replicate%d[T any](t T) Tuple%d[", i, i)
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T")
+	}
+	fmt.Fprintf(f, "] {\n")
+	// execute the mapping
+	fmt.Fprintf(f, "  return MakeTuple%d(", i)
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t")
+	}
+	fmt.Fprintf(f, ")\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateMap(f *os.File, i int) {
+	// Create the optionize version
+	fmt.Fprintf(f, "\n// Map%d maps each value of a [Tuple%d] via a mapping function\n", i, i)
+	fmt.Fprintf(f, "func Map%d[", i)
+	// function prototypes
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "F%d ~func(T%d) R%d", j, j, j)
+	}
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, ", T%d, R%d", j, j)
+	}
+	fmt.Fprintf(f, " any](")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "f%d F%d", j, j)
+	}
+	fmt.Fprintf(f, ") func(")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, ") ")
+	writeTupleType(f, "R", i)
+	fmt.Fprintf(f, " {\n")
+
+	fmt.Fprintf(f, " return func(t ")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, ") ")
+	writeTupleType(f, "R", i)
+	fmt.Fprintf(f, " {\n")
+
+	// execute the mapping
+	fmt.Fprintf(f, "    return MakeTuple%d(\n", i)
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, "      f%d(t.F%d),\n", j, j)
+	}
+	fmt.Fprintf(f, "    )\n")
+
+	fmt.Fprintf(f, " }\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateMonoid(f *os.File, i int) {
+	// Create the optionize version
+	fmt.Fprintf(f, "\n// Monoid%d creates a [Monoid] for a [Tuple%d] based on %d monoids for the contained types\n", i, i, i)
+	fmt.Fprintf(f, "func Monoid%d[", i)
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	fmt.Fprintf(f, " any](")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "m%d M.Monoid[T%d]", j, j)
+	}
+	fmt.Fprintf(f, ") M.Monoid[")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, "] {\n")
+
+	fmt.Fprintf(f, "  return M.MakeMonoid(func(l, r ")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, ") ")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, "{\n")
+
+	fmt.Fprintf(f, "    return MakeTuple%d(", i)
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "m%d.Concat(l.F%d, r.F%d)", j, j, j)
+	}
+	fmt.Fprintf(f, ")\n")
+	fmt.Fprintf(f, "  }, MakeTuple%d(", i)
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "m%d.Empty()", j)
+	}
+	fmt.Fprintf(f, "))\n")
+
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateOrd(f *os.File, i int) {
+	// Create the optionize version
+	fmt.Fprintf(f, "\n// Ord%d creates n [Ord] for a [Tuple%d] based on %d [Ord]s for the contained types\n", i, i, i)
+	fmt.Fprintf(f, "func Ord%d[", i)
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	fmt.Fprintf(f, " any](")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "o%d O.Ord[T%d]", j, j)
+	}
+	fmt.Fprintf(f, ") O.Ord[")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, "] {\n")
+
+	fmt.Fprintf(f, "  return O.MakeOrd(func(l, r ")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, ") int {\n")
+
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, "    if c:= o%d.Compare(l.F%d, r.F%d); c != 0 {return c}\n", j, j, j)
+	}
+	fmt.Fprintf(f, "    return 0\n")
+	fmt.Fprintf(f, "  }, func(l, r ")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, ") bool {\n")
+	fmt.Fprintf(f, "    return ")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, " && ")
+		}
+		fmt.Fprintf(f, "o%d.Equals(l.F%d, r.F%d)", j, j, j)
+	}
+	fmt.Fprintf(f, "\n")
+	fmt.Fprintf(f, "  })\n")
+
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateTupleType(f *os.File, i int) {
+	// Create the optionize version
+	fmt.Fprintf(f, "\n// Tuple%d is a struct that carries %d independently typed values\n", i, i)
+	fmt.Fprintf(f, "type Tuple%d[", i)
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	fmt.Fprintf(f, " any] struct {\n")
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, "  F%d T%d\n", j, j)
+	}
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateMakeTupleType(f *os.File, i int) {
+	// Create the optionize version
+	fmt.Fprintf(f, "\n// MakeTuple%d is a function that converts its %d parameters into a [Tuple%d]\n", i, i, i)
+	fmt.Fprintf(f, "func MakeTuple%d[", i)
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	fmt.Fprintf(f, " any](")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t%d T%d", j, j)
+	}
+	fmt.Fprintf(f, ") ")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, " {\n")
+	fmt.Fprintf(f, "  return Tuple%d[", i)
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	fmt.Fprintf(f, "]{")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t%d", j)
+	}
+	fmt.Fprintf(f, "}\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateUntupled(f *os.File, i int) {
+	// Create the optionize version
+	fmt.Fprintf(f, "\n// Untupled%d converts a function with a [Tuple%d] parameter into a function with %d parameters\n// The inverse function is [Tupled%d]\n", i, i, i, i)
+	fmt.Fprintf(f, "func Untupled%d[F ~func(Tuple%d[", i, i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, "]) R")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j+1)
+	}
+	fmt.Fprintf(f, ", R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, ") R {\n")
+	fmt.Fprintf(f, "  return func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t%d T%d", j+1, j+1)
+	}
+	fmt.Fprintf(f, ") R {\n")
+	fmt.Fprintf(f, "    return f(MakeTuple%d(", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t%d", j+1)
+	}
+	fmt.Fprintln(f, "))")
+	fmt.Fprintln(f, "  }")
+	fmt.Fprintln(f, "}")
+}
+
+func generateTupled(f *os.File, i int) {
+	// Create the optionize version
+	fmt.Fprintf(f, "\n// Tupled%d converts a function with %d parameters into a function taking a Tuple%d\n// The inverse function is [Untupled%d]\n", i, i, i, i)
+	fmt.Fprintf(f, "func Tupled%d[F ~func(", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, ") R")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j+1)
+	}
+	fmt.Fprintf(f, ", R any](f F) func(Tuple%d[", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, "]) R {\n")
+	fmt.Fprintf(f, "  return func(t Tuple%d[", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, "]) R {\n")
+	fmt.Fprintf(f, "    return f(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t.F%d", j+1)
+	}
+	fmt.Fprintf(f, ")\n")
+	fmt.Fprintf(f, "  }\n")
+	fmt.Fprintln(f, "}")
+}
+
+func generateTupleHelpers(filename string, count int) error {
+	dir, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+	absDir, err := filepath.Abs(dir)
+	if err != nil {
+		return err
+	}
+	pkg := filepath.Base(absDir)
+	f, err := os.Create(filepath.Clean(filename))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	// log
+	log.Printf("Generating code in [%s] for package [%s] with [%d] repetitions ...", filename, pkg, count)
+
+	// some header
+	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(f, "// This file was generated by robots at")
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
+
+	fmt.Fprintf(f, "package %s\n\n", pkg)
+
+	fmt.Fprintf(f, `
+import (
+	M "github.com/IBM/fp-go/v2/monoid"
+	O "github.com/IBM/fp-go/v2/ord"	
+)
+`)
+
+	for i := 1; i <= count; i++ {
+		// tuple type
+		generateTupleType(f, i)
+	}
+
+	for i := 1; i <= count; i++ {
+		// tuple generator
+		generateMakeTupleType(f, i)
+		// tupled wrapper
+		generateTupled(f, i)
+		// untupled wrapper
+		generateUntupled(f, i)
+		// monoid
+		generateMonoid(f, i)
+		// generate order
+		generateOrd(f, i)
+		// generate map
+		generateMap(f, i)
+		// generate replicate
+		generateReplicate(f, i)
+		// generate tuple functions such as string and fmt
+		generateTupleString(f, i)
+		// generate json support
+		generateTupleMarshal(f, i)
+		// generate json support
+		generateTupleUnmarshal(f, i)
+		// generate toArray
+		generateToArray(f, i)
+		// generate fromArray
+		generateFromArray(f, i)
+		// generate push
+		if i < count {
+			generatePush(f, i)
+		}
+	}
+
+	return nil
+}
+
+func generateTupleMarshal(f *os.File, i int) {
+	// Create the stringify version
+	fmt.Fprintf(f, "\n// MarshalJSON marshals the [Tuple%d] into a JSON array\n", i)
+	fmt.Fprintf(f, "func (t ")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, ") MarshalJSON() ([]byte, error) {\n")
+	fmt.Fprintf(f, "  return tupleMarshalJSON(")
+	// function prototypes
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t.F%d", j)
+	}
+	fmt.Fprintf(f, ")\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateTupleUnmarshal(f *os.File, i int) {
+	// Create the stringify version
+	fmt.Fprintf(f, "\n// UnmarshalJSON unmarshals a JSON array into a [Tuple%d]\n", i)
+	fmt.Fprintf(f, "func (t *")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, ") UnmarshalJSON(data []byte) error {\n")
+	fmt.Fprintf(f, "  return tupleUnmarshalJSON(data")
+	// function prototypes
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, ", &t.F%d", j)
+	}
+	fmt.Fprintf(f, ")\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateToArray(f *os.File, i int) {
+	// Create the stringify version
+	fmt.Fprintf(f, "\n// ToArray converts the [Tuple%d] into an array of type [R] using %d transformation functions from [T] to [R]\n// The inverse function is [FromArray%d]\n", i, i, i)
+	fmt.Fprintf(f, "func ToArray%d[", i)
+	// function prototypes
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "F%d ~func(T%d) R", j, j)
+	}
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ", R any](")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "f%d F%d", j, j)
+	}
+	fmt.Fprintf(f, ") func(t ")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, ") []R {\n")
+	fmt.Fprintf(f, "  return func(t ")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, ") []R {\n")
+	fmt.Fprintf(f, "    return []R{\n")
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, "      f%d(t.F%d),\n", j, j)
+	}
+	fmt.Fprintf(f, "    }\n")
+	fmt.Fprintf(f, "  }\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateFromArray(f *os.File, i int) {
+	// Create the stringify version
+	fmt.Fprintf(f, "\n// FromArray converts an array of [R] into a [Tuple%d] using %d functions from [R] to [T]\n// The inverse function is [ToArray%d]\n", i, i, i)
+	fmt.Fprintf(f, "func FromArray%d[", i)
+	// function prototypes
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "F%d ~func(R) T%d", j, j)
+	}
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ", R any](")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "f%d F%d", j, j)
+	}
+	fmt.Fprintf(f, ") func(r []R) ")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, " {\n")
+	fmt.Fprintf(f, "  return func(r []R) ")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, " {\n")
+	fmt.Fprintf(f, "    return MakeTuple%d(\n", i)
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, "      f%d(r[%d]),\n", j, j-1)
+	}
+	fmt.Fprintf(f, "    )\n")
+	fmt.Fprintf(f, "  }\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateTupleString(f *os.File, i int) {
+	// Create the stringify version
+	fmt.Fprintf(f, "\n// String prints some debug info for the [Tuple%d]\n", i)
+	fmt.Fprintf(f, "func (t ")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, ") String() string {\n")
+	// convert to string
+	fmt.Fprint(f, "  return tupleString(")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t.F%d", j)
+	}
+	fmt.Fprintf(f, ")\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+// func generateTupleJson(f *os.File, i int) {
+// 	// Create the stringify version
+// 	fmt.Fprintf(f, "\n// MarshalJSON converts the [Tuple%d] into a JSON byte stream\n", i)
+// 	fmt.Fprintf(f, "func (t ")
+// 	writeTupleType(f, "T", i)
+// 	fmt.Fprintf(f, ") MarshalJSON() ([]byte, error) {\n")
+// 	// convert to string
+// 	fmt.Fprintf(f, "  return fmt.Sprintf(\"Tuple%d[", i)
+// 	for j := 1; j <= i; j++ {
+// 		if j > 1 {
+// 			fmt.Fprintf(f, ", ")
+// 		}
+// 		fmt.Fprintf(f, "%s", "%T")
+// 	}
+// 	fmt.Fprintf(f, "](")
+// 	for j := 1; j <= i; j++ {
+// 		if j > 1 {
+// 			fmt.Fprintf(f, ", ")
+// 		}
+// 		fmt.Fprintf(f, "%s", "%v")
+// 	}
+// 	fmt.Fprintf(f, ")\", ")
+// 	for j := 1; j <= i; j++ {
+// 		if j > 1 {
+// 			fmt.Fprintf(f, ", ")
+// 		}
+// 		fmt.Fprintf(f, "t.F%d", j)
+// 	}
+// 	for j := 1; j <= i; j++ {
+// 		fmt.Fprintf(f, ", t.F%d", j)
+// 	}
+// 	fmt.Fprintf(f, ")\n")
+// 	fmt.Fprintf(f, "}\n")
+// }
+
+func TupleCommand() *C.Command {
+	return &C.Command{
+		Name:  "tuple",
+		Usage: "generate code for Tuple",
+		Flags: []C.Flag{
+			flagCount,
+			flagFilename,
+		},
+		Action: func(ctx *C.Context) error {
+			return generateTupleHelpers(
+				ctx.String(keyFilename),
+				ctx.Int(keyCount),
+			)
+		},
+	}
+}

v2/constant/const.go

@@ -0,0 +1,59 @@
+// 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 constant
+
+import (
+	F "github.com/IBM/fp-go/v2/function"
+	M "github.com/IBM/fp-go/v2/monoid"
+	S "github.com/IBM/fp-go/v2/semigroup"
+)
+
+type Const[E, A any] struct {
+	value E
+}
+
+func Make[E, A any](e E) Const[E, A] {
+	return Const[E, A]{value: e}
+}
+
+func Unwrap[E, A any](c Const[E, A]) E {
+	return c.value
+}
+
+func Of[E, A any](m M.Monoid[E]) func(A) Const[E, A] {
+	return F.Constant1[A](Make[E, A](m.Empty()))
+}
+
+func MonadMap[E, A, B any](fa Const[E, A], _ func(A) B) Const[E, B] {
+	return Make[E, B](fa.value)
+}
+
+func MonadAp[E, A, B any](s S.Semigroup[E]) func(fab Const[E, func(A) B], fa Const[E, A]) Const[E, B] {
+	return func(fab Const[E, func(A) B], fa Const[E, A]) Const[E, B] {
+		return Make[E, B](s.Concat(fab.value, fa.value))
+	}
+}
+
+func Map[E, A, B any](f func(A) B) func(fa Const[E, A]) Const[E, B] {
+	return F.Bind2nd(MonadMap[E, A, B], f)
+}
+
+func Ap[E, A, B any](s S.Semigroup[E]) func(fa Const[E, A]) func(fab Const[E, func(A) B]) Const[E, B] {
+	monadap := MonadAp[E, A, B](s)
+	return func(fa Const[E, A]) func(fab Const[E, func(A) B]) Const[E, B] {
+		return F.Bind2nd(monadap, fa)
+	}
+}

v2/constant/const_test.go

@@ -0,0 +1,40 @@
+// 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 constant
+
+import (
+	"testing"
+
+	F "github.com/IBM/fp-go/v2/function"
+	"github.com/IBM/fp-go/v2/internal/utils"
+	S "github.com/IBM/fp-go/v2/string"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMap(t *testing.T) {
+	fa := Make[string, int]("foo")
+	assert.Equal(t, fa, F.Pipe1(fa, Map[string, int](utils.Double)))
+}
+
+func TestOf(t *testing.T) {
+	assert.Equal(t, Make[string, int](""), Of[string, int](S.Monoid)(1))
+}
+
+func TestAp(t *testing.T) {
+	fab := Make[string, int]("bar")
+	assert.Equal(t, Make[string, int]("foobar"), Ap[string, int, int](S.Monoid)(fab)(Make[string, func(int) int]("foo")))
+}

v2/constraints/constraints.go

@@ -0,0 +1,40 @@
+// 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 constraints
+
+type Ordered interface {
+	Integer | Float | ~string
+}
+
+type Signed interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64
+}
+
+type Unsigned interface {
+	~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr
+}
+
+type Integer interface {
+	Signed | Unsigned
+}
+
+type Float interface {
+	~float32 | ~float64
+}
+
+type Complex interface {
+	~complex64 | ~complex128
+}

v2/context/doc.go

@@ -0,0 +1,17 @@
+// 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 context contains versions of reader IO monads that work with a golang [context.Context]
+package context

v2/context/ioeither/generic/ioeither.go

@@ -0,0 +1,33 @@
+// 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 generic
+
+import (
+	"context"
+
+	E "github.com/IBM/fp-go/v2/either"
+	IOE "github.com/IBM/fp-go/v2/ioeither/generic"
+)
+
+// WithContext wraps an existing IOEither and performs a context check for cancellation before delegating
+func WithContext[GIO ~func() E.Either[error, A], A any](ctx context.Context, ma GIO) GIO {
+	return IOE.MakeIO[GIO](func() E.Either[error, A] {
+		if err := context.Cause(ctx); err != nil {
+			return E.Left[A](err)
+		}
+		return ma()
+	})
+}

v2/context/ioeither/ioeither.go

@@ -0,0 +1,33 @@
+// 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 ioeither
+
+import (
+	"context"
+
+	"github.com/IBM/fp-go/v2/either"
+	IOE "github.com/IBM/fp-go/v2/ioeither"
+)
+
+// 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] {
+		if err := context.Cause(ctx); err != nil {
+			return either.Left[A](err)
+		}
+		return ma()
+	}
+}

v2/context/readereither/array.go

@@ -0,0 +1,33 @@
+// 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 "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] {
+	return readereither.TraverseArray(f)
+}
+
+// TraverseArrayWithIndex transforms an array
+func TraverseArrayWithIndex[A, B any](f func(int, A) ReaderEither[B]) func([]A) ReaderEither[[]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] {
+	return readereither.SequenceArray(ma)
+}

v2/context/readereither/bind.go

@@ -0,0 +1,68 @@
+// 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/readereither/bind_test.go

@@ -0,0 +1,58 @@
+// 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"
+	"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"
+	"github.com/stretchr/testify/assert"
+)
+
+func getLastName(s utils.Initial) ReaderEither[string] {
+	return Of("Doe")
+}
+
+func getGivenName(s utils.WithLastName) ReaderEither[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(context.Background()), 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(context.Background()), E.Of[error]("John Doe"))
+}

v2/context/readereither/cancel.go

@@ -0,0 +1,32 @@
+// 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"
+
+	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] {
+	return func(ctx context.Context) E.Either[error, A] {
+		if err := context.Cause(ctx); err != nil {
+			return E.Left[A](err)
+		}
+		return ma(ctx)
+	}
+}

v2/context/readereither/curry.go

@@ -0,0 +1,53 @@
+// 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"
+
+	"github.com/IBM/fp-go/v2/readereither"
+)
+
+// 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] {
+	return readereither.Curry0(f)
+}
+
+func Curry1[T1, A any](f func(context.Context, T1) (A, error)) func(T1) ReaderEither[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] {
+	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] {
+	return readereither.Curry3(f)
+}
+
+func Uncurry1[T1, A any](f func(T1) ReaderEither[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) {
+	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) {
+	return readereither.Uncurry3(f)
+}

v2/context/readereither/exec/exec.go

@@ -0,0 +1,39 @@
+// 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 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"
+)
+
+var (
+	// Command executes a command
+	// use this version if the command does not produce any side effect, i.e. if the output is uniquely determined by by the input
+	// typically you'd rather use the ReaderIOEither version of the command
+	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))
+	}
+}

v2/context/readereither/from.go

@@ -0,0 +1,41 @@
+// 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"
+
+	"github.com/IBM/fp-go/v2/readereither"
+)
+
+// 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] {
+	return readereither.From0(f)
+}
+
+func From1[T1, A any](f func(context.Context, T1) (A, error)) func(T1) ReaderEither[A] {
+	return readereither.From1(f)
+}
+
+func From2[T1, T2, A any](f func(context.Context, T1, T2) (A, error)) func(T1, T2) ReaderEither[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] {
+	return readereither.From3(f)
+}

v2/context/readereither/reader.go

@@ -0,0 +1,94 @@
+// 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"
+
+	"github.com/IBM/fp-go/v2/readereither"
+)
+
+func FromEither[A any](e Either[A]) ReaderEither[A] {
+	return readereither.FromEither[context.Context](e)
+}
+
+func Left[A any](l error) ReaderEither[A] {
+	return readereither.Left[context.Context, A](l)
+}
+
+func Right[A any](r A) ReaderEither[A] {
+	return readereither.Right[context.Context, error](r)
+}
+
+func MonadMap[A, B any](fa ReaderEither[A], f func(A) B) ReaderEither[B] {
+	return readereither.MonadMap(fa, f)
+}
+
+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] {
+	return readereither.MonadChain(ma, f)
+}
+
+func Chain[A, B any](f func(A) ReaderEither[B]) Operator[A, B] {
+	return readereither.Chain(f)
+}
+
+func Of[A any](a A) ReaderEither[A] {
+	return readereither.Of[context.Context, error](a)
+}
+
+func MonadAp[A, B any](fab ReaderEither[func(A) B], fa ReaderEither[A]) ReaderEither[B] {
+	return readereither.MonadAp(fab, fa)
+}
+
+func Ap[A, B any](fa ReaderEither[A]) func(ReaderEither[func(A) B]) ReaderEither[B] {
+	return readereither.Ap[B](fa)
+}
+
+func FromPredicate[A any](pred func(A) bool, onFalse func(A) error) func(A) ReaderEither[A] {
+	return readereither.FromPredicate[context.Context](pred, onFalse)
+}
+
+func OrElse[A any](onLeft func(error) ReaderEither[A]) func(ReaderEither[A]) ReaderEither[A] {
+	return readereither.OrElse(onLeft)
+}
+
+func Ask() ReaderEither[context.Context] {
+	return readereither.Ask[context.Context, error]()
+}
+
+func MonadChainEitherK[A, B any](ma ReaderEither[A], f func(A) Either[B]) ReaderEither[B] {
+	return readereither.MonadChainEitherK(ma, f)
+}
+
+func ChainEitherK[A, B any](f func(A) Either[B]) func(ma ReaderEither[A]) ReaderEither[B] {
+	return readereither.ChainEitherK[context.Context](f)
+}
+
+func ChainOptionK[A, B any](onNone func() error) func(func(A) Option[B]) Operator[A, B] {
+	return readereither.ChainOptionK[context.Context, A, B](onNone)
+}
+
+func MonadFlap[B, A any](fab ReaderEither[func(A) B], a A) ReaderEither[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)
+}

v2/context/readereither/sequence.go

@@ -0,0 +1,39 @@
+// 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 (
+	"github.com/IBM/fp-go/v2/readereither"
+	"github.com/IBM/fp-go/v2/tuple"
+)
+
+// 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]] {
+	return readereither.SequenceT1(a)
+}
+
+func SequenceT2[A, B any](a ReaderEither[A], b ReaderEither[B]) ReaderEither[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]] {
+	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]] {
+	return readereither.SequenceT4(a, b, c, d)
+}

v2/context/readereither/type.go

@@ -0,0 +1,35 @@
+// 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 implements a specialization of the Reader monad assuming a golang context as the context of the monad and a standard golang error
+package readereither
+
+import (
+	"context"
+
+	"github.com/IBM/fp-go/v2/either"
+	"github.com/IBM/fp-go/v2/option"
+	"github.com/IBM/fp-go/v2/reader"
+	"github.com/IBM/fp-go/v2/readereither"
+)
+
+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]
+
+	Operator[A, B any] = reader.Reader[ReaderEither[A], ReaderEither[B]]
+)

v2/context/readerioeither/bind.go

@@ -0,0 +1,89 @@
+// 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/bind_test.go

@@ -0,0 +1,58 @@
+// 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"
+	"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"
+	"github.com/stretchr/testify/assert"
+)
+
+func getLastName(s utils.Initial) ReaderIOEither[string] {
+	return Of("Doe")
+}
+
+func getGivenName(s utils.WithLastName) ReaderIOEither[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(context.Background())(), 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(context.Background())(), E.Of[error]("John Doe"))
+}

v2/context/readerioeither/bracket.go

@@ -0,0 +1,44 @@
+// 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"
+
+	"github.com/IBM/fp-go/v2/internal/bracket"
+	"github.com/IBM/fp-go/v2/readerio"
+)
+
+// Bracket makes sure that a resource is cleaned up in the event of an error. The release action is called regardless of
+// whether the body action returns and error or not.
+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,
+	)
+}

v2/context/readerioeither/cancel.go

@@ -0,0 +1,42 @@
+// 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"
+
+	CIOE "github.com/IBM/fp-go/v2/context/ioeither"
+	"github.com/IBM/fp-go/v2/ioeither"
+)
+
+// WithContext wraps an existing [ReaderIOEither] 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
+//
+// Returns a ReaderIOEither that checks for cancellation before executing.
+func WithContext[A any](ma ReaderIOEither[A]) ReaderIOEither[A] {
+	return func(ctx context.Context) IOEither[A] {
+		if err := context.Cause(ctx); err != nil {
+			return ioeither.Left[A](err)
+		}
+		return CIOE.WithContext(ctx, ma(ctx))
+	}
+}