Merge pull request #66 from IBM/cleue-add-try-catch-for-single-value-return

fix: remove File.GetName and add Join for convenience

.github/workflows/build.yml

@@ -29,7 +29,7 @@ jobs:
         go-version: [ '1.20.x', '1.21.x' ]
     steps:
       # full checkout for semantic-release
-      - uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9 # v3.5.3
+      - uses: actions/checkout@8ade135a41bc03ea155e62e844d188df1ea18608 # v4.1.0
         with:
           fetch-depth: 0
       - name: Set up go ${{ matrix.go-version }}
@@ -55,7 +55,7 @@ jobs:
     steps:
       # full checkout for semantic-release
       - name: Full checkout
-        uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9 # v3.5.3
+        uses: actions/checkout@8ade135a41bc03ea155e62e844d188df1ea18608 # v4.1.0
         with:
           fetch-depth: 0
 

array/array.go

@@ -308,3 +308,11 @@ func Fold[A any](m M.Monoid[A]) func([]A) A {
 func Push[A any](a A) func([]A) []A {
 	return G.Push[[]A](a)
 }
+
+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)
+}
+
+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)
+}

array/generic/array.go

@@ -18,6 +18,7 @@ package generic
 import (
 	F "github.com/IBM/fp-go/function"
 	"github.com/IBM/fp-go/internal/array"
+	FC "github.com/IBM/fp-go/internal/functor"
 	M "github.com/IBM/fp-go/monoid"
 	O "github.com/IBM/fp-go/option"
 	"github.com/IBM/fp-go/tuple"
@@ -187,6 +188,14 @@ 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) {
@@ -242,3 +251,11 @@ func Fold[AS ~[]A, A any](m M.Monoid[A]) func(AS) A {
 func Push[GA ~[]A, A any](a A) func(GA) GA {
 	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 F.Bind2nd(MonadFlap[FAB, GFAB, GB, A, B], a)
+}

array/nonempty/array.go

@@ -0,0 +1,124 @@
+// Copyright (c) 2023 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/array/generic"
+	F "github.com/IBM/fp-go/function"
+	"github.com/IBM/fp-go/internal/array"
+	S "github.com/IBM/fp-go/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](as NonEmptyArray[A]) bool {
+	return false
+}
+
+func IsNonEmpty[A any](as 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 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))
+	}
+}

cli/pipe.go

@@ -25,6 +25,40 @@ import (
 	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)
@@ -83,7 +117,7 @@ func generateVariadic(f *os.File, i int) {
 	fmt.Fprintf(f, "v)\n")
 	fmt.Fprintf(f, "  }\n")
 
-	fmt.Fprintf(f, "}")
+	fmt.Fprintf(f, "}\n")
 }
 
 func generateUnvariadic(f *os.File, i int) {
@@ -144,7 +178,7 @@ func generateUnvariadic(f *os.File, i int) {
 	fmt.Fprintf(f, "v...)\n")
 	fmt.Fprintf(f, "  }\n")
 
-	fmt.Fprintf(f, "}")
+	fmt.Fprintf(f, "}\n")
 }
 
 func generateNullary(f *os.File, i int) {
@@ -347,6 +381,8 @@ func generatePipeHelpers(filename string, count int) error {
 	generateVariadic(f, 0)
 	// unvariadic
 	generateUnvariadic(f, 0)
+	// unsliced
+	generateUnsliced(f, 0)
 
 	for i := 1; i <= count; i++ {
 
@@ -364,6 +400,8 @@ func generatePipeHelpers(filename string, count int) error {
 		generateVariadic(f, i)
 		// unvariadic
 		generateUnvariadic(f, i)
+		// unsliced
+		generateUnsliced(f, i)
 	}
 
 	return nil

cli/tuple.go

@@ -338,7 +338,7 @@ func generateUntupled(f *os.File, i int) {
 
 func generateTupled(f *os.File, i int) {
 	// Create the optionize version
-	fmt.Fprintf(f, "\n// Tupled%d converts a function with %d parameters returning into a function taking a Tuple%d\n// The inverse function is [Untupled%d]\n", i, i, i, i)
+	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 {

context/reader/array.go

@@ -24,6 +24,11 @@ func TraverseArray[A, B any](f func(A) Reader[B]) func([]A) Reader[[]B] {
 	return R.TraverseArray[Reader[B], Reader[[]B], []A](f)
 }
 
+// TraverseArrayWithIndex transforms an array
+func TraverseArrayWithIndex[A, B any](f func(int, A) Reader[B]) func([]A) Reader[[]B] {
+	return R.TraverseArrayWithIndex[Reader[B], Reader[[]B], []A](f)
+}
+
 // SequenceArray converts a homogeneous sequence of either into an either of sequence
 func SequenceArray[A any](ma []Reader[A]) Reader[[]A] {
 	return R.SequenceArray[Reader[A], Reader[[]A]](ma)

context/readereither/array.go

@@ -24,6 +24,11 @@ func TraverseArray[A, B any](f func(A) ReaderEither[B]) func([]A) ReaderEither[[
 	return RE.TraverseArray[ReaderEither[B], ReaderEither[[]B], []A](f)
 }
 
+// TraverseArrayWithIndex transforms an array
+func TraverseArrayWithIndex[A, B any](f func(int, A) ReaderEither[B]) func([]A) ReaderEither[[]B] {
+	return RE.TraverseArrayWithIndex[ReaderEither[B], ReaderEither[[]B], []A](f)
+}
+
 // SequenceArray converts a homogeneous sequence of either into an either of sequence
 func SequenceArray[A any](ma []ReaderEither[A]) ReaderEither[[]A] {
 	return RE.SequenceArray[ReaderEither[A], ReaderEither[[]A]](ma)

context/readerio/array.go

@@ -25,6 +25,11 @@ func TraverseArray[A, B any](f func(A) ReaderIO[B]) func([]A) ReaderIO[[]B] {
 	return R.TraverseArray[ReaderIO[B], ReaderIO[[]B], IO.IO[B], IO.IO[[]B], []A](f)
 }
 
+// TraverseArrayWithIndex transforms an array
+func TraverseArrayWithIndex[A, B any](f func(int, A) ReaderIO[B]) func([]A) ReaderIO[[]B] {
+	return R.TraverseArrayWithIndex[ReaderIO[B], ReaderIO[[]B], IO.IO[B], IO.IO[[]B], []A](f)
+}
+
 // SequenceArray converts a homogeneous sequence of either into an either of sequence
 func SequenceArray[A any](ma []ReaderIO[A]) ReaderIO[[]A] {
 	return R.SequenceArray[ReaderIO[A], ReaderIO[[]A]](ma)

context/readerio/reader.go

@@ -18,6 +18,8 @@ package readerio
 import (
 	"context"
 
+	IO "github.com/IBM/fp-go/io"
+	L "github.com/IBM/fp-go/lazy"
 	R "github.com/IBM/fp-go/readerio/generic"
 )
 
@@ -37,6 +39,22 @@ func Chain[A, B any](f func(A) ReaderIO[B]) func(ReaderIO[A]) ReaderIO[B] {
 	return R.Chain[ReaderIO[A]](f)
 }
 
+func MonadChainIOK[A, B any](fa ReaderIO[A], f func(A) IO.IO[B]) ReaderIO[B] {
+	return R.MonadChainIOK[ReaderIO[A], ReaderIO[B]](fa, f)
+}
+
+func ChainIOK[A, B any](f func(A) IO.IO[B]) func(ReaderIO[A]) ReaderIO[B] {
+	return R.ChainIOK[ReaderIO[A], ReaderIO[B]](f)
+}
+
+func MonadChainFirstIOK[A, B any](fa ReaderIO[A], f func(A) IO.IO[B]) ReaderIO[A] {
+	return R.MonadChainFirstIOK[ReaderIO[A], ReaderIO[B]](fa, f)
+}
+
+func ChainFirstIOK[A, B any](f func(A) IO.IO[B]) func(ReaderIO[A]) ReaderIO[A] {
+	return R.ChainFirstIOK[ReaderIO[A], ReaderIO[B]](f)
+}
+
 func Of[A any](a A) ReaderIO[A] {
 	return R.Of[ReaderIO[A]](a)
 }
@@ -54,6 +72,18 @@ func Ask() ReaderIO[context.Context] {
 }
 
 // Defer creates an IO by creating a brand new IO via a generator function, each time
-func Defer[A any](gen func() ReaderIO[A]) ReaderIO[A] {
+func Defer[A any](gen L.Lazy[ReaderIO[A]]) ReaderIO[A] {
 	return R.Defer[ReaderIO[A]](gen)
 }
+
+// Memoize computes the value of the provided [ReaderIO] monad lazily but exactly once
+// The context used to compute the value is the context of the first call, so do not use this
+// method if the value has a functional dependency on the content of the context
+func Memoize[A any](rdr ReaderIO[A]) ReaderIO[A] {
+	return R.Memoize[ReaderIO[A]](rdr)
+}
+
+// Flatten converts a nested [ReaderIO] into a [ReaderIO]
+func Flatten[A any](mma ReaderIO[ReaderIO[A]]) ReaderIO[A] {
+	return R.Flatten[ReaderIO[A]](mma)
+}

context/readerioeither/file/file.go

@@ -25,25 +25,31 @@ import (
 	F "github.com/IBM/fp-go/function"
 	"github.com/IBM/fp-go/internal/file"
 	IOE "github.com/IBM/fp-go/ioeither"
+	IOEF "github.com/IBM/fp-go/ioeither/file"
 )
 
 var (
-	openIOE = IOE.Eitherize1(os.Open)
 	// Open opens a file for reading within the given context
 	Open = F.Flow3(
-		openIOE,
+		IOEF.Open,
 		RIOE.FromIOEither[*os.File],
 		RIOE.WithContext[*os.File],
 	)
+
+	// Remove removes a file by name
+	Remove = F.Flow2(
+		IOEF.Remove,
+		RIOE.FromIOEither[string],
+	)
 )
 
 // Close closes an object
 func Close[C io.Closer](c C) RIOE.ReaderIOEither[any] {
-	return RIOE.FromIOEither(func() ET.Either[error, any] {
-		return ET.TryCatchError(func() (any, error) {
-			return c, c.Close()
-		})
-	})
+	return F.Pipe2(
+		c,
+		IOEF.Close[C],
+		RIOE.FromIOEither[any],
+	)
 }
 
 // ReadFile reads a file in the scope of a context

context/readerioeither/file/tempfile.go

@@ -0,0 +1,52 @@
+// Copyright (c) 2023 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 file
+
+import (
+	"os"
+
+	RIOE "github.com/IBM/fp-go/context/readerioeither"
+	F "github.com/IBM/fp-go/function"
+	IO "github.com/IBM/fp-go/io"
+	IOF "github.com/IBM/fp-go/io/file"
+	IOEF "github.com/IBM/fp-go/ioeither/file"
+)
+
+var (
+	// onCreateTempFile creates a temp file with sensible defaults
+	onCreateTempFile = CreateTemp("", "*")
+	// destroy handler
+	onReleaseTempFile = F.Flow4(
+		IOF.Close[*os.File],
+		IO.Map((*os.File).Name),
+		RIOE.FromIO[string],
+		RIOE.Chain(Remove),
+	)
+)
+
+// CreateTemp created a temp file with proper parametrization
+func CreateTemp(dir, pattern string) RIOE.ReaderIOEither[*os.File] {
+	return F.Pipe2(
+		IOEF.CreateTemp(dir, pattern),
+		RIOE.FromIOEither[*os.File],
+		RIOE.WithContext[*os.File],
+	)
+}
+
+// WithTempFile creates a temporary file, then invokes a callback to create a resource based on the file, then close and remove the temp file
+func WithTempFile[A any](f func(*os.File) RIOE.ReaderIOEither[A]) RIOE.ReaderIOEither[A] {
+	return RIOE.WithResource[A](onCreateTempFile, onReleaseTempFile)(f)
+}

context/readerioeither/file/tempfile_test.go

@@ -0,0 +1,47 @@
+// Copyright (c) 2023 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 file
+
+import (
+	"context"
+	"os"
+	"testing"
+
+	RIOE "github.com/IBM/fp-go/context/readerioeither"
+	E "github.com/IBM/fp-go/either"
+	F "github.com/IBM/fp-go/function"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestWithTempFile(t *testing.T) {
+
+	res := WithTempFile(onWriteAll[*os.File]([]byte("Carsten")))
+
+	assert.Equal(t, E.Of[error]([]byte("Carsten")), res(context.Background())())
+}
+
+func TestWithTempFileOnClosedFile(t *testing.T) {
+
+	res := WithTempFile(func(f *os.File) RIOE.ReaderIOEither[[]byte] {
+		return F.Pipe2(
+			f,
+			onWriteAll[*os.File]([]byte("Carsten")),
+			RIOE.ChainFirst(F.Constant1[[]byte](Close(f))),
+		)
+	})
+
+	assert.Equal(t, E.Of[error]([]byte("Carsten")), res(context.Background())())
+}

context/readerioeither/file/write.go

@@ -0,0 +1,57 @@
+// Copyright (c) 2023 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 file
+
+import (
+	"context"
+	"io"
+
+	RIOE "github.com/IBM/fp-go/context/readerioeither"
+	F "github.com/IBM/fp-go/function"
+)
+
+func onWriteAll[W io.Writer](data []byte) func(w W) RIOE.ReaderIOEither[[]byte] {
+	return func(w W) RIOE.ReaderIOEither[[]byte] {
+		return F.Pipe1(
+			RIOE.TryCatch(func(ctx context.Context) func() ([]byte, error) {
+				return func() ([]byte, error) {
+					_, err := w.Write(data)
+					return data, err
+				}
+			}),
+			RIOE.WithContext[[]byte],
+		)
+	}
+}
+
+// WriteAll uses a generator function to create a stream, writes data to it and closes it
+func WriteAll[W io.WriteCloser](data []byte) func(acquire RIOE.ReaderIOEither[W]) RIOE.ReaderIOEither[[]byte] {
+	onWrite := onWriteAll[W](data)
+	return func(onCreate RIOE.ReaderIOEither[W]) RIOE.ReaderIOEither[[]byte] {
+		return RIOE.WithResource[[]byte](
+			onCreate,
+			Close[W])(
+			onWrite,
+		)
+	}
+}
+
+// Write uses a generator function to create a stream, writes data to it and closes it
+func Write[R any, W io.WriteCloser](acquire RIOE.ReaderIOEither[W]) func(use func(W) RIOE.ReaderIOEither[R]) RIOE.ReaderIOEither[R] {
+	return RIOE.WithResource[R](
+		acquire,
+		Close[W])
+}

context/readerioeither/gen.go

@@ -2,7 +2,7 @@ package readerioeither
 
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-08-17 22:58:56.457404 +0200 CEST m=+0.024265101
+// 2023-09-12 13:44:14.1022311 +0200 CEST m=+0.017763401
 
 import (
 	"context"

context/readerioeither/generic/gen.go

@@ -2,7 +2,7 @@ package generic
 
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-08-17 22:58:56.457404 +0200 CEST m=+0.024265101
+// 2023-09-12 13:44:14.1036885 +0200 CEST m=+0.019220801
 
 import (
 	"context"

context/readerioeither/generic/monoid.go

@@ -0,0 +1,56 @@
+//   Copyright (c) 2023 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"
+
+	ET "github.com/IBM/fp-go/either"
+	M "github.com/IBM/fp-go/monoid"
+)
+
+func ApplicativeMonoid[GRA ~func(context.Context) GIOA, GRFA ~func(context.Context) GIOFA, GIOA ~func() ET.Either[error, A], GIOFA ~func() ET.Either[error, func(A) A], A any](
+	m M.Monoid[A],
+) M.Monoid[GRA] {
+	return M.ApplicativeMonoid(
+		Of[GRA],
+		MonadMap[GRA, GRFA],
+		MonadAp[GRA, GRA, GRFA],
+		m,
+	)
+}
+
+func ApplicativeMonoidSeq[GRA ~func(context.Context) GIOA, GRFA ~func(context.Context) GIOFA, GIOA ~func() ET.Either[error, A], GIOFA ~func() ET.Either[error, func(A) A], A any](
+	m M.Monoid[A],
+) M.Monoid[GRA] {
+	return M.ApplicativeMonoid(
+		Of[GRA],
+		MonadMap[GRA, GRFA],
+		MonadApSeq[GRA, GRA, GRFA],
+		m,
+	)
+}
+
+func ApplicativeMonoidPar[GRA ~func(context.Context) GIOA, GRFA ~func(context.Context) GIOFA, GIOA ~func() ET.Either[error, A], GIOFA ~func() ET.Either[error, func(A) A], A any](
+	m M.Monoid[A],
+) M.Monoid[GRA] {
+	return M.ApplicativeMonoid(
+		Of[GRA],
+		MonadMap[GRA, GRFA],
+		MonadApPar[GRA, GRA, GRFA],
+		m,
+	)
+}

context/readerioeither/generic/reader.go

@@ -100,6 +100,28 @@ func Map[
 	return RIE.Map[GRA, GRB](f)
 }
 
+func MonadMapTo[
+	GRA ~func(context.Context) GIOA,
+	GRB ~func(context.Context) GIOB,
+
+	GIOA ~func() E.Either[error, A],
+	GIOB ~func() E.Either[error, B],
+
+	A, B any](fa GRA, b B) GRB {
+	return RIE.MonadMapTo[GRA, GRB](fa, b)
+}
+
+func MapTo[
+	GRA ~func(context.Context) GIOA,
+	GRB ~func(context.Context) GIOB,
+
+	GIOA ~func() E.Either[error, A],
+	GIOB ~func() E.Either[error, B],
+
+	A, B any](b B) func(GRA) GRB {
+	return RIE.MapTo[GRA, GRB](b)
+}
+
 func MonadChain[
 	GRA ~func(context.Context) GIOA,
 	GRB ~func(context.Context) GIOB,
@@ -458,6 +480,34 @@ func ChainIOK[
 	return RIE.ChainIOK[GRA, GRB](f)
 }
 
+func MonadChainReaderIOK[
+	GRB ~func(context.Context) GIOB,
+	GRA ~func(context.Context) GIOA,
+	GRIO ~func(context.Context) GIO,
+
+	GIOA ~func() E.Either[error, A],
+	GIOB ~func() E.Either[error, B],
+
+	GIO ~func() B,
+
+	A, B any](ma GRA, f func(A) GRIO) GRB {
+	return RIE.MonadChainReaderIOK[GRA, GRB](ma, f)
+}
+
+func ChainReaderIOK[
+	GRB ~func(context.Context) GIOB,
+	GRA ~func(context.Context) GIOA,
+	GRIO ~func(context.Context) GIO,
+
+	GIOA ~func() E.Either[error, A],
+	GIOB ~func() E.Either[error, B],
+
+	GIO ~func() B,
+
+	A, B any](f func(A) GRIO) func(ma GRA) GRB {
+	return RIE.ChainReaderIOK[GRA, GRB](f)
+}
+
 func MonadChainFirstIOK[
 	GRA ~func(context.Context) GIOA,
 	GIOA ~func() E.Either[error, A],
@@ -543,3 +593,74 @@ func TryCatch[
 	A any](f func(context.Context) func() (A, error)) GRA {
 	return RIE.TryCatch[GRA](f, ER.IdentityError)
 }
+
+func MonadAlt[LAZY ~func() GEA, GEA ~func(context.Context) GIOA, GIOA ~func() E.Either[error, A], A any](first GEA, second LAZY) GEA {
+	return RIE.MonadAlt(first, second)
+}
+
+func Alt[LAZY ~func() GEA, GEA ~func(context.Context) GIOA, GIOA ~func() E.Either[error, A], A any](second LAZY) func(GEA) GEA {
+	return RIE.Alt(second)
+}
+
+// Memoize computes the value of the provided monad lazily but exactly once
+// The context used to compute the value is the context of the first call, so do not use this
+// method if the value has a functional dependency on the content of the context
+func Memoize[
+	GRA ~func(context.Context) GIOA,
+	GIOA ~func() E.Either[error, A],
+	A any](rdr GRA) GRA {
+	return RIE.Memoize[GRA](rdr)
+}
+
+func Flatten[
+	GGRA ~func(context.Context) GGIOA,
+	GGIOA ~func() E.Either[error, GRA],
+	GRA ~func(context.Context) GIOA,
+	GIOA ~func() E.Either[error, A],
+	A any](rdr GGRA) GRA {
+	return RIE.Flatten[GRA](rdr)
+}
+
+func MonadFromReaderIO[
+	GRIOEA ~func(context.Context) GIOEA,
+	GIOEA ~func() E.Either[error, A],
+
+	GRIOA ~func(context.Context) GIOA,
+	GIOA ~func() A,
+
+	A any](a A, f func(A) GRIOA) GRIOEA {
+	return RIE.MonadFromReaderIO[GRIOEA](a, f)
+}
+
+func FromReaderIO[
+	GRIOEA ~func(context.Context) GIOEA,
+	GIOEA ~func() E.Either[error, A],
+
+	GRIOA ~func(context.Context) GIOA,
+	GIOA ~func() A,
+
+	A any](f func(A) GRIOA) func(A) GRIOEA {
+	return RIE.FromReaderIO[GRIOEA](f)
+}
+
+func RightReaderIO[
+	GRIOEA ~func(context.Context) GIOEA,
+	GIOEA ~func() E.Either[error, A],
+
+	GRIOA ~func(context.Context) GIOA,
+	GIOA ~func() A,
+
+	A any](ma GRIOA) GRIOEA {
+	return RIE.RightReaderIO[GRIOEA](ma)
+}
+
+func LeftReaderIO[
+	GRIOEA ~func(context.Context) GIOEA,
+	GIOEA ~func() E.Either[error, A],
+
+	GRIOE ~func(context.Context) GIOE,
+	GIOE ~func() error,
+
+	A any](ma GRIOE) GRIOEA {
+	return RIE.LeftReaderIO[GRIOEA](ma)
+}

context/readerioeither/generic/semigroup.go

@@ -0,0 +1,29 @@
+//   Copyright (c) 2023 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"
+
+	ET "github.com/IBM/fp-go/either"
+	S "github.com/IBM/fp-go/semigroup"
+)
+
+func AltSemigroup[GRA ~func(context.Context) GIOA, GIOA ~func() ET.Either[error, A], A any]() S.Semigroup[GRA] {
+	return S.AltSemigroup(
+		MonadAlt[func() GRA],
+	)
+}

context/readerioeither/generic/traverse.go

@@ -62,6 +62,25 @@ func TraverseArray[
 	)
 }
 
+// TraverseArrayWithIndex transforms an array
+func TraverseArrayWithIndex[
+	AS ~[]A,
+	GRBS ~func(context.Context) GIOBS,
+	GRB ~func(context.Context) GIOB,
+	GIOBS ~func() E.Either[error, BS],
+	GIOB ~func() E.Either[error, B],
+	BS ~[]B,
+	A, B any](f func(int, A) GRB) func(AS) GRBS {
+
+	return RA.TraverseWithIndex[AS](
+		Of[GRBS, GIOBS, BS],
+		Map[GRBS, func(context.Context) func() E.Either[error, func(B) BS], GIOBS, func() E.Either[error, func(B) BS], BS, func(B) BS],
+		Ap[GRBS, func(context.Context) func() E.Either[error, func(B) BS], GRB],
+
+		f,
+	)
+}
+
 // SequenceArray converts a homogeneous sequence of either into an either of sequence
 func SequenceArray[
 	AS ~[]A,
@@ -115,6 +134,26 @@ func TraverseRecord[K comparable,
 	)
 }
 
+// TraverseRecordWithIndex transforms a record
+func TraverseRecordWithIndex[K comparable,
+	AS ~map[K]A,
+	GRBS ~func(context.Context) GIOBS,
+	GRB ~func(context.Context) GIOB,
+	GIOBS ~func() E.Either[error, BS],
+	GIOB ~func() E.Either[error, B],
+	BS ~map[K]B,
+
+	A, B any](f func(K, A) GRB) func(AS) GRBS {
+
+	return RR.TraverseWithIndex[AS](
+		Of[GRBS, GIOBS, BS],
+		Map[GRBS, func(context.Context) func() E.Either[error, func(B) BS], GIOBS, func() E.Either[error, func(B) BS], BS, func(B) BS],
+		Ap[GRBS, func(context.Context) func() E.Either[error, func(B) BS], GRB],
+
+		f,
+	)
+}
+
 // SequenceRecord converts a homogeneous sequence of either into an either of sequence
 func SequenceRecord[K comparable,
 	AS ~map[K]A,

context/readerioeither/http/request_test.go

@@ -21,6 +21,13 @@ import (
 	"testing"
 
 	H "net/http"
+
+	R "github.com/IBM/fp-go/context/readerioeither"
+	E "github.com/IBM/fp-go/either"
+	"github.com/IBM/fp-go/errors"
+	F "github.com/IBM/fp-go/function"
+	IOE "github.com/IBM/fp-go/ioeither"
+	"github.com/stretchr/testify/assert"
 )
 
 type PostItem struct {
@@ -30,6 +37,47 @@ type PostItem struct {
 	Body   string `json:"body"`
 }
 
+func getTitle(item PostItem) string {
+	return item.Title
+}
+
+type simpleRequestBuilder struct {
+	method  string
+	url     string
+	headers H.Header
+}
+
+func requestBuilder() simpleRequestBuilder {
+	return simpleRequestBuilder{method: "GET"}
+}
+
+func (b simpleRequestBuilder) WithURL(url string) simpleRequestBuilder {
+	b.url = url
+	return b
+}
+
+func (b simpleRequestBuilder) WithHeader(key, value string) simpleRequestBuilder {
+	if b.headers == nil {
+		b.headers = make(H.Header)
+	} else {
+		b.headers = b.headers.Clone()
+	}
+	b.headers.Set(key, value)
+	return b
+}
+
+func (b simpleRequestBuilder) Build() R.ReaderIOEither[*H.Request] {
+	return func(ctx context.Context) IOE.IOEither[error, *H.Request] {
+		return IOE.TryCatchError(func() (*H.Request, error) {
+			req, err := H.NewRequestWithContext(ctx, b.method, b.url, nil)
+			if err == nil {
+				req.Header = b.headers
+			}
+			return req, err
+		})
+	}
+}
+
 func TestSendSingleRequest(t *testing.T) {
 
 	client := MakeClient(H.DefaultClient)
@@ -40,7 +88,70 @@ func TestSendSingleRequest(t *testing.T) {
 
 	resp1 := readItem(req1)
 
-	resE := resp1(context.Background())()
+	resE := resp1(context.TODO())()
 
 	fmt.Println(resE)
 }
+
+// setHeaderUnsafe updates a header value in a request object by mutating the request object
+func setHeaderUnsafe(key, value string) func(*H.Request) *H.Request {
+	return func(req *H.Request) *H.Request {
+		req.Header.Set(key, value)
+		return req
+	}
+}
+
+func TestSendSingleRequestWithHeaderUnsafe(t *testing.T) {
+
+	client := MakeClient(H.DefaultClient)
+
+	// this is not safe from a puristic perspective, because the map call mutates the request object
+	req1 := F.Pipe2(
+		"https://jsonplaceholder.typicode.com/posts/1",
+		MakeGetRequest,
+		R.Map(setHeaderUnsafe("Content-Type", "text/html")),
+	)
+
+	readItem := ReadJson[PostItem](client)
+
+	resp1 := F.Pipe2(
+		req1,
+		readItem,
+		R.Map(getTitle),
+	)
+
+	res := F.Pipe1(
+		resp1(context.TODO())(),
+		E.GetOrElse(errors.ToString),
+	)
+
+	assert.Equal(t, "sunt aut facere repellat provident occaecati excepturi optio reprehenderit", res)
+}
+
+func TestSendSingleRequestWithHeaderSafe(t *testing.T) {
+
+	client := MakeClient(H.DefaultClient)
+
+	// the request builder assembles config values to construct
+	// the final http request. Each `With` step creates a copy of the settings
+	// so the flow is pure
+	request := requestBuilder().
+		WithURL("https://jsonplaceholder.typicode.com/posts/1").
+		WithHeader("Content-Type", "text/html").
+		Build()
+
+	readItem := ReadJson[PostItem](client)
+
+	response := F.Pipe2(
+		request,
+		readItem,
+		R.Map(getTitle),
+	)
+
+	res := F.Pipe1(
+		response(context.TODO())(),
+		E.GetOrElse(errors.ToString),
+	)
+
+	assert.Equal(t, "sunt aut facere repellat provident occaecati excepturi optio reprehenderit", res)
+}

context/readerioeither/monoid.go

@@ -0,0 +1,56 @@
+//   Copyright (c) 2023 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 (
+	G "github.com/IBM/fp-go/context/readerioeither/generic"
+	L "github.com/IBM/fp-go/lazy"
+	M "github.com/IBM/fp-go/monoid"
+)
+
+// ApplicativeMonoid returns a [Monoid] that concatenates [ReaderIOEither] instances via their applicative
+func ApplicativeMonoid[A any](m M.Monoid[A]) M.Monoid[ReaderIOEither[A]] {
+	return G.ApplicativeMonoid[ReaderIOEither[A], ReaderIOEither[func(A) A]](m)
+}
+
+// ApplicativeMonoidSeq returns a [Monoid] that concatenates [ReaderIOEither] instances via their applicative
+func ApplicativeMonoidSeq[A any](m M.Monoid[A]) M.Monoid[ReaderIOEither[A]] {
+	return G.ApplicativeMonoidSeq[ReaderIOEither[A], ReaderIOEither[func(A) A]](m)
+}
+
+// ApplicativeMonoidPar returns a [Monoid] that concatenates [ReaderIOEither] instances via their applicative
+func ApplicativeMonoidPar[A any](m M.Monoid[A]) M.Monoid[ReaderIOEither[A]] {
+	return G.ApplicativeMonoidPar[ReaderIOEither[A], ReaderIOEither[func(A) A]](m)
+}
+
+// AlternativeMonoid is the alternative [Monoid] for [ReaderIOEither]
+func AlternativeMonoid[A any](m M.Monoid[A]) M.Monoid[ReaderIOEither[A]] {
+	return M.AlternativeMonoid(
+		Of[A],
+		MonadMap[A, func(A) A],
+		MonadAp[A, A],
+		MonadAlt[A],
+		m,
+	)
+}
+
+// AltMonoid is the alternative [Monoid] for an [ReaderIOEither]
+func AltMonoid[A any](zero L.Lazy[ReaderIOEither[A]]) M.Monoid[ReaderIOEither[A]] {
+	return M.AltMonoid(
+		zero,
+		MonadAlt[A],
+	)
+}

context/readerioeither/reader.go

@@ -25,6 +25,7 @@ import (
 	ET "github.com/IBM/fp-go/either"
 	IO "github.com/IBM/fp-go/io"
 	IOE "github.com/IBM/fp-go/ioeither"
+	L "github.com/IBM/fp-go/lazy"
 	O "github.com/IBM/fp-go/option"
 )
 
@@ -60,6 +61,14 @@ func Map[A, B any](f func(A) B) func(ReaderIOEither[A]) ReaderIOEither[B] {
 	return G.Map[ReaderIOEither[A], ReaderIOEither[B]](f)
 }
 
+func MonadMapTo[A, B any](fa ReaderIOEither[A], b B) ReaderIOEither[B] {
+	return G.MonadMapTo[ReaderIOEither[A], ReaderIOEither[B]](fa, b)
+}
+
+func MapTo[A, B any](b B) func(ReaderIOEither[A]) ReaderIOEither[B] {
+	return G.MapTo[ReaderIOEither[A], ReaderIOEither[B]](b)
+}
+
 func MonadChain[A, B any](ma ReaderIOEither[A], f func(A) ReaderIOEither[B]) ReaderIOEither[B] {
 	return G.MonadChain(ma, f)
 }
@@ -146,11 +155,23 @@ func FromIO[A any](t IO.IO[A]) ReaderIOEither[A] {
 	return G.FromIO[ReaderIOEither[A]](t)
 }
 
+func FromLazy[A any](t L.Lazy[A]) ReaderIOEither[A] {
+	return G.FromIO[ReaderIOEither[A]](t)
+}
+
 // Never returns a 'ReaderIOEither' that never returns, except if its context gets canceled
 func Never[A any]() ReaderIOEither[A] {
 	return G.Never[ReaderIOEither[A]]()
 }
 
+func MonadChainReaderIOK[A, B any](ma ReaderIOEither[A], f func(A) RIO.ReaderIO[B]) ReaderIOEither[B] {
+	return G.MonadChainReaderIOK[ReaderIOEither[B], ReaderIOEither[A]](ma, f)
+}
+
+func ChainReaderIOK[A, B any](f func(A) RIO.ReaderIO[B]) func(ma ReaderIOEither[A]) ReaderIOEither[B] {
+	return G.ChainReaderIOK[ReaderIOEither[B], ReaderIOEither[A]](f)
+}
+
 func MonadChainIOK[A, B any](ma ReaderIOEither[A], f func(A) IO.IO[B]) ReaderIOEither[B] {
 	return G.MonadChainIOK[ReaderIOEither[B], ReaderIOEither[A]](ma, f)
 }
@@ -182,7 +203,7 @@ func Timer(delay time.Duration) ReaderIOEither[time.Time] {
 }
 
 // Defer creates an IO by creating a brand new IO via a generator function, each time
-func Defer[A any](gen func() ReaderIOEither[A]) ReaderIOEither[A] {
+func Defer[A any](gen L.Lazy[ReaderIOEither[A]]) ReaderIOEither[A] {
 	return G.Defer[ReaderIOEither[A]](gen)
 }
 
@@ -190,3 +211,42 @@ func Defer[A any](gen func() ReaderIOEither[A]) ReaderIOEither[A] {
 func TryCatch[A any](f func(context.Context) func() (A, error)) ReaderIOEither[A] {
 	return G.TryCatch[ReaderIOEither[A]](f)
 }
+
+// MonadAlt identifies an associative operation on a type constructor
+func MonadAlt[A any](first ReaderIOEither[A], second L.Lazy[ReaderIOEither[A]]) ReaderIOEither[A] {
+	return G.MonadAlt(first, second)
+}
+
+// Alt identifies an associative operation on a type constructor
+func Alt[A any](second L.Lazy[ReaderIOEither[A]]) func(ReaderIOEither[A]) ReaderIOEither[A] {
+	return G.Alt(second)
+}
+
+// Memoize computes the value of the provided [ReaderIOEither] monad lazily but exactly once
+// The context used to compute the value is the context of the first call, so do not use this
+// method if the value has a functional dependency on the content of the context
+func Memoize[A any](rdr ReaderIOEither[A]) ReaderIOEither[A] {
+	return G.Memoize[ReaderIOEither[A]](rdr)
+}
+
+// Flatten converts a nested [ReaderIOEither] into a [ReaderIOEither]
+func Flatten[
+	A any](rdr ReaderIOEither[ReaderIOEither[A]]) ReaderIOEither[A] {
+	return G.Flatten[ReaderIOEither[ReaderIOEither[A]]](rdr)
+}
+
+func MonadFromReaderIO[A any](a A, f func(A) RIO.ReaderIO[A]) ReaderIOEither[A] {
+	return G.MonadFromReaderIO[ReaderIOEither[A]](a, f)
+}
+
+func FromReaderIO[A any](f func(A) RIO.ReaderIO[A]) func(A) ReaderIOEither[A] {
+	return G.FromReaderIO[ReaderIOEither[A]](f)
+}
+
+func RightReaderIO[A any](ma RIO.ReaderIO[A]) ReaderIOEither[A] {
+	return G.RightReaderIO[ReaderIOEither[A]](ma)
+}
+
+func LeftReaderIO[A any](ma RIO.ReaderIO[error]) ReaderIOEither[A] {
+	return G.LeftReaderIO[ReaderIOEither[A]](ma)
+}

context/readerioeither/reader_test.go

@@ -162,3 +162,125 @@ func TestRegularApply(t *testing.T) {
 	res := applied(context.Background())()
 	assert.Equal(t, E.Of[error]("CARSTEN"), res)
 }
+
+func TestWithResourceNoErrors(t *testing.T) {
+	var countAcquire, countBody, countRelease int
+
+	acquire := FromLazy(func() int {
+		countAcquire++
+		return countAcquire
+	})
+
+	release := func(int) ReaderIOEither[int] {
+		return FromLazy(func() int {
+			countRelease++
+			return countRelease
+		})
+	}
+
+	body := func(int) ReaderIOEither[int] {
+		return FromLazy(func() int {
+			countBody++
+			return countBody
+		})
+	}
+
+	resRIOE := WithResource[int](acquire, release)(body)
+
+	res := resRIOE(context.Background())()
+
+	assert.Equal(t, 1, countAcquire)
+	assert.Equal(t, 1, countBody)
+	assert.Equal(t, 1, countRelease)
+	assert.Equal(t, E.Of[error](1), res)
+}
+
+func TestWithResourceErrorInBody(t *testing.T) {
+	var countAcquire, countBody, countRelease int
+
+	acquire := FromLazy(func() int {
+		countAcquire++
+		return countAcquire
+	})
+
+	release := func(int) ReaderIOEither[int] {
+		return FromLazy(func() int {
+			countRelease++
+			return countRelease
+		})
+	}
+
+	err := fmt.Errorf("error in body")
+	body := func(int) ReaderIOEither[int] {
+		return Left[int](err)
+	}
+
+	resRIOE := WithResource[int](acquire, release)(body)
+
+	res := resRIOE(context.Background())()
+
+	assert.Equal(t, 1, countAcquire)
+	assert.Equal(t, 0, countBody)
+	assert.Equal(t, 1, countRelease)
+	assert.Equal(t, E.Left[int](err), res)
+}
+
+func TestWithResourceErrorInAcquire(t *testing.T) {
+	var countAcquire, countBody, countRelease int
+
+	err := fmt.Errorf("error in acquire")
+	acquire := Left[int](err)
+
+	release := func(int) ReaderIOEither[int] {
+		return FromLazy(func() int {
+			countRelease++
+			return countRelease
+		})
+	}
+
+	body := func(int) ReaderIOEither[int] {
+		return FromLazy(func() int {
+			countBody++
+			return countBody
+		})
+	}
+
+	resRIOE := WithResource[int](acquire, release)(body)
+
+	res := resRIOE(context.Background())()
+
+	assert.Equal(t, 0, countAcquire)
+	assert.Equal(t, 0, countBody)
+	assert.Equal(t, 0, countRelease)
+	assert.Equal(t, E.Left[int](err), res)
+}
+
+func TestWithResourceErrorInRelease(t *testing.T) {
+	var countAcquire, countBody, countRelease int
+
+	acquire := FromLazy(func() int {
+		countAcquire++
+		return countAcquire
+	})
+
+	err := fmt.Errorf("error in release")
+	release := func(int) ReaderIOEither[int] {
+		return Left[int](err)
+	}
+
+	body := func(int) ReaderIOEither[int] {
+		return FromLazy(func() int {
+			countBody++
+			return countBody
+		})
+	}
+
+	resRIOE := WithResource[int](acquire, release)(body)
+
+	res := resRIOE(context.Background())()
+
+	assert.Equal(t, 1, countAcquire)
+	assert.Equal(t, 1, countBody)
+	assert.Equal(t, 0, countRelease)
+	assert.Equal(t, E.Left[int](err), res)
+}

context/readerioeither/semigroup.go

@@ -0,0 +1,26 @@
+//   Copyright (c) 2023 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 (
+	G "github.com/IBM/fp-go/context/readerioeither/generic"
+	S "github.com/IBM/fp-go/semigroup"
+)
+
+// AltSemigroup is a [Semigroup] that tries the first item and then the second one using an alternative
+func AltSemigroup[A any]() S.Semigroup[ReaderIOEither[A]] {
+	return G.AltSemigroup[ReaderIOEither[A]]()
+}

context/readerioeither/traverse.go

@@ -24,6 +24,11 @@ func TraverseArray[A, B any](f func(A) ReaderIOEither[B]) func([]A) ReaderIOEith
 	return G.TraverseArray[[]A, ReaderIOEither[[]B]](f)
 }
 
+// TraverseArrayWithIndex uses transforms an array [[]A] into [[]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[[]B]]
+func TraverseArrayWithIndex[A, B any](f func(int, A) ReaderIOEither[B]) func([]A) ReaderIOEither[[]B] {
+	return G.TraverseArrayWithIndex[[]A, ReaderIOEither[[]B]](f)
+}
+
 // SequenceArray converts a homogeneous sequence of either into an either of sequence
 func SequenceArray[A any](ma []ReaderIOEither[A]) ReaderIOEither[[]A] {
 	return G.SequenceArray[[]A, []ReaderIOEither[A], ReaderIOEither[[]A]](ma)
@@ -34,6 +39,11 @@ func TraverseRecord[K comparable, A, B any](f func(A) ReaderIOEither[B]) func(ma
 	return G.TraverseRecord[K, map[K]A, ReaderIOEither[map[K]B]](f)
 }
 
+// TraverseRecordWithIndex uses transforms a record [map[K]A] into [map[K]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[map[K]B]]
+func TraverseRecordWithIndex[K comparable, A, B any](f func(K, A) ReaderIOEither[B]) func(map[K]A) ReaderIOEither[map[K]B] {
+	return G.TraverseRecordWithIndex[K, map[K]A, ReaderIOEither[map[K]B]](f)
+}
+
 // SequenceRecord converts a homogeneous sequence of either into an either of sequence
 func SequenceRecord[K comparable, A any](ma map[K]ReaderIOEither[A]) ReaderIOEither[map[K]A] {
 	return G.SequenceRecord[K, map[K]A, map[K]ReaderIOEither[A], ReaderIOEither[map[K]A]](ma)

coverage.bat

@@ -0,0 +1,2 @@
+@echo off
+go tool cover -html=build/cover.out -o build/cover.html

either/apply.go

@@ -24,6 +24,7 @@ func ApplySemigroup[E, A any](s S.Semigroup[A]) S.Semigroup[Either[E, A]] {
 	return S.ApplySemigroup(MonadMap[E, A, func(A) A], MonadAp[A, E, A], s)
 }
 
+// ApplicativeMonoid returns a [Monoid] that concatenates [Either] instances via their applicative
 func ApplicativeMonoid[E, A any](m M.Monoid[A]) M.Monoid[Either[E, A]] {
 	return M.ApplicativeMonoid(Of[E, A], MonadMap[E, A, func(A) A], MonadAp[A, E, A], m)
 }

either/array.go

@@ -20,7 +20,7 @@ import (
 	RA "github.com/IBM/fp-go/internal/array"
 )
 
-// TraverseArray transforms an array
+// TraverseArrayG transforms an array
 func TraverseArrayG[GA ~[]A, GB ~[]B, E, A, B any](f func(A) Either[E, B]) func(GA) Either[E, GB] {
 	return RA.Traverse[GA](
 		Of[E, GB],
@@ -36,6 +36,22 @@ func TraverseArray[E, A, B any](f func(A) Either[E, B]) func([]A) Either[E, []B]
 	return TraverseArrayG[[]A, []B](f)
 }
 
+// TraverseArrayWithIndexG transforms an array
+func TraverseArrayWithIndexG[GA ~[]A, GB ~[]B, E, A, B any](f func(int, A) Either[E, B]) func(GA) Either[E, GB] {
+	return RA.TraverseWithIndex[GA](
+		Of[E, GB],
+		Map[E, GB, func(B) GB],
+		Ap[GB, E, B],
+
+		f,
+	)
+}
+
+// TraverseArrayWithIndex transforms an array
+func TraverseArrayWithIndex[E, A, B any](f func(int, A) Either[E, B]) func([]A) Either[E, []B] {
+	return TraverseArrayWithIndexG[[]A, []B](f)
+}
+
 func SequenceArrayG[GA ~[]A, GOA ~[]Either[E, A], E, A any](ma GOA) Either[E, GA] {
 	return TraverseArrayG[GOA, GA](F.Identity[Either[E, A]])(ma)
 }
@@ -44,3 +60,15 @@ func SequenceArrayG[GA ~[]A, GOA ~[]Either[E, A], E, A any](ma GOA) Either[E, GA
 func SequenceArray[E, A any](ma []Either[E, A]) Either[E, []A] {
 	return SequenceArrayG[[]A](ma)
 }
+
+// CompactArrayG discards the none values and keeps the some values
+func CompactArrayG[A1 ~[]Either[E, A], A2 ~[]A, E, A any](fa A1) A2 {
+	return RA.Reduce(fa, func(out A2, value Either[E, A]) A2 {
+		return MonadFold(value, F.Constant1[E](out), F.Bind1st(RA.Append[A2, A], out))
+	}, make(A2, len(fa)))
+}
+
+// CompactArray discards the none values and keeps the some values
+func CompactArray[E, A any](fa []Either[E, A]) []A {
+	return CompactArrayG[[]Either[E, A], []A](fa)
+}

either/either.go

@@ -22,6 +22,8 @@ package either
 import (
 	E "github.com/IBM/fp-go/errors"
 	F "github.com/IBM/fp-go/function"
+	FC "github.com/IBM/fp-go/internal/functor"
+	L "github.com/IBM/fp-go/lazy"
 	O "github.com/IBM/fp-go/option"
 )
 
@@ -91,12 +93,12 @@ func MonadChainTo[E, A, B any](ma Either[E, A], mb Either[E, B]) Either[E, B] {
 	return mb
 }
 
-func MonadChainOptionK[E, A, B any](onNone func() E, ma Either[E, A], f func(A) O.Option[B]) Either[E, B] {
-	return MonadChain(ma, F.Flow2(f, FromOption[E, B](onNone)))
+func MonadChainOptionK[A, B, E any](onNone func() E, ma Either[E, A], f func(A) O.Option[B]) Either[E, B] {
+	return MonadChain(ma, F.Flow2(f, FromOption[B](onNone)))
 }
 
-func ChainOptionK[E, A, B any](onNone func() E) func(func(A) O.Option[B]) func(Either[E, A]) Either[E, B] {
-	from := FromOption[E, B](onNone)
+func ChainOptionK[A, B, E any](onNone func() E) func(func(A) O.Option[B]) func(Either[E, A]) Either[E, B] {
+	from := FromOption[B](onNone)
 	return func(f func(A) O.Option[B]) func(Either[E, A]) Either[E, B] {
 		return Chain(F.Flow2(f, from))
 	}
@@ -142,7 +144,7 @@ func Sequence3[E, T1, T2, T3, R any](f func(T1, T2, T3) Either[E, R]) func(Eithe
 	}
 }
 
-func FromOption[E, A any](onNone func() E) func(O.Option[A]) Either[E, A] {
+func FromOption[A, E any](onNone func() E) func(O.Option[A]) Either[E, A] {
 	return O.Fold(F.Nullary2(onNone, Left[A, E]), Right[E, A])
 }
 
@@ -197,11 +199,11 @@ func Reduce[E, A, B any](f func(B, A) B, initial B) func(Either[E, A]) B {
 	)
 }
 
-func AltW[E, E1, A any](that func() Either[E1, A]) func(Either[E, A]) Either[E1, A] {
+func AltW[E, E1, A any](that L.Lazy[Either[E1, A]]) func(Either[E, A]) Either[E1, A] {
 	return Fold(F.Ignore1of1[E](that), Right[E1, A])
 }
 
-func Alt[E, A any](that func() Either[E, A]) func(Either[E, A]) Either[E, A] {
+func Alt[E, A any](that L.Lazy[Either[E, A]]) func(Either[E, A]) Either[E, A] {
 	return AltW[E](that)
 }
 
@@ -209,7 +211,7 @@ func OrElse[E, A any](onLeft func(e E) Either[E, A]) func(Either[E, A]) Either[E
 	return Fold(onLeft, Of[E, A])
 }
 
-func ToType[E, A any](onError func(any) E) func(any) Either[E, A] {
+func ToType[A, E any](onError func(any) E) func(any) Either[E, A] {
 	return func(value any) Either[E, A] {
 		return F.Pipe2(
 			value,
@@ -245,3 +247,15 @@ func MonadSequence3[E, T1, T2, T3, R any](e1 Either[E, T1], e2 Either[E, T2], e3
 func Swap[E, A any](val Either[E, A]) Either[A, E] {
 	return MonadFold(val, Right[A, E], Left[E, A])
 }
+
+func MonadFlap[E, B, A any](fab Either[E, func(A) B], a A) Either[E, B] {
+	return FC.MonadFlap(MonadMap[E, func(A) B, B], fab, a)
+}
+
+func Flap[E, B, A any](a A) func(Either[E, func(A) B]) Either[E, B] {
+	return F.Bind2nd(MonadFlap[E, B, A], a)
+}
+
+func MonadAlt[E, A any](fa Either[E, A], that L.Lazy[Either[E, A]]) Either[E, A] {
+	return MonadFold(fa, F.Ignore1of1[E](that), Of[E, A])
+}

either/either_test.go

@@ -100,7 +100,7 @@ func TestChainFirst(t *testing.T) {
 }
 
 func TestChainOptionK(t *testing.T) {
-	f := ChainOptionK[string, int, int](F.Constant("a"))(func(n int) O.Option[int] {
+	f := ChainOptionK[int, int](F.Constant("a"))(func(n int) O.Option[int] {
 		if n > 0 {
 			return O.Some(n)
 		}
@@ -112,6 +112,6 @@ func TestChainOptionK(t *testing.T) {
 }
 
 func TestFromOption(t *testing.T) {
-	assert.Equal(t, Left[int]("none"), FromOption[string, int](F.Constant("none"))(O.None[int]()))
-	assert.Equal(t, Right[string](1), FromOption[string, int](F.Constant("none"))(O.Some(1)))
+	assert.Equal(t, Left[int]("none"), FromOption[int](F.Constant("none"))(O.None[int]()))
+	assert.Equal(t, Right[string](1), FromOption[int](F.Constant("none"))(O.Some(1)))
 }

either/exec/exec.go

@@ -27,7 +27,7 @@ import (
 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 IOEither version of the command
+	// typically you'd rather use the [IOEither] version of the command
 	Command = F.Curry3(command)
 )
 

either/gen.go

@@ -1,6 +1,6 @@
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-08-17 22:58:57.9925506 +0200 CEST m=+0.033401101
+// 2023-09-12 13:44:15.6356542 +0200 CEST m=+0.009418901
 
 package either
 

either/monoid.go

@@ -0,0 +1,40 @@
+// Copyright (c) 2023 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 either
+
+import (
+	L "github.com/IBM/fp-go/lazy"
+	M "github.com/IBM/fp-go/monoid"
+)
+
+// AlternativeMonoid is the alternative [Monoid] for an [Either]
+func AlternativeMonoid[E, A any](m M.Monoid[A]) M.Monoid[Either[E, A]] {
+	return M.AlternativeMonoid(
+		Of[E, A],
+		MonadMap[E, A, func(A) A],
+		MonadAp[A, E, A],
+		MonadAlt[E, A],
+		m,
+	)
+}
+
+// AltMonoid is the alternative [Monoid] for an [Either]
+func AltMonoid[E, A any](zero L.Lazy[Either[E, A]]) M.Monoid[Either[E, A]] {
+	return M.AltMonoid(
+		zero,
+		MonadAlt[E, A],
+	)
+}

either/record.go

@@ -20,7 +20,7 @@ import (
 	RR "github.com/IBM/fp-go/internal/record"
 )
 
-// TraverseRecord transforms a record of options into an option of a record
+// TraverseRecordG transforms a record of options into an option of a record
 func TraverseRecordG[GA ~map[K]A, GB ~map[K]B, K comparable, E, A, B any](f func(A) Either[E, B]) func(GA) Either[E, GB] {
 	return RR.Traverse[GA](
 		Of[E, GB],
@@ -35,6 +35,21 @@ func TraverseRecord[K comparable, E, A, B any](f func(A) Either[E, B]) func(map[
 	return TraverseRecordG[map[K]A, map[K]B](f)
 }
 
+// TraverseRecordWithIndexG transforms a record of options into an option of a record
+func TraverseRecordWithIndexG[GA ~map[K]A, GB ~map[K]B, K comparable, E, A, B any](f func(K, A) Either[E, B]) func(GA) Either[E, GB] {
+	return RR.TraverseWithIndex[GA](
+		Of[E, GB],
+		Map[E, GB, func(B) GB],
+		Ap[GB, E, B],
+		f,
+	)
+}
+
+// TraverseRecordWithIndex transforms a record of eithers into an either of a record
+func TraverseRecordWithIndex[K comparable, E, A, B any](f func(K, A) Either[E, B]) func(map[K]A) Either[E, map[K]B] {
+	return TraverseRecordWithIndexG[map[K]A, map[K]B](f)
+}
+
 func SequenceRecordG[GA ~map[K]A, GOA ~map[K]Either[E, A], K comparable, E, A any](ma GOA) Either[E, GA] {
 	return TraverseRecordG[GOA, GA](F.Identity[Either[E, A]])(ma)
 }
@@ -43,3 +58,24 @@ func SequenceRecordG[GA ~map[K]A, GOA ~map[K]Either[E, A], K comparable, E, A an
 func SequenceRecord[K comparable, E, A any](ma map[K]Either[E, A]) Either[E, map[K]A] {
 	return SequenceRecordG[map[K]A](ma)
 }
+
+func upsertAtReadWrite[M ~map[K]V, K comparable, V any](r M, k K, v V) M {
+	r[k] = v
+	return r
+}
+
+// CompactRecordG discards the noe values and keeps the some values
+func CompactRecordG[M1 ~map[K]Either[E, A], M2 ~map[K]A, K comparable, E, A any](m M1) M2 {
+	out := make(M2)
+	onLeft := F.Constant1[E](out)
+	return RR.ReduceWithIndex(m, func(key K, _ M2, value Either[E, A]) M2 {
+		return MonadFold(value, onLeft, func(v A) M2 {
+			return upsertAtReadWrite(out, key, v)
+		})
+	}, out)
+}
+
+// CompactRecord discards all none values and keeps the somes
+func CompactRecord[K comparable, E, A any](m map[K]Either[E, A]) map[K]A {
+	return CompactRecordG[map[K]Either[E, A], map[K]A](m)
+}

either/record_test.go

@@ -0,0 +1,37 @@
+// Copyright (c) 2023 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 either
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCompactRecord(t *testing.T) {
+	// make the map
+	m := make(map[string]Either[string, int])
+	m["foo"] = Left[int]("error")
+	m["bar"] = Right[string](1)
+	// compact it
+	m1 := CompactRecord(m)
+	// check expected
+	exp := map[string]int{
+		"bar": 1,
+	}
+
+	assert.Equal(t, exp, m1)
+}

either/semigroup.go

@@ -13,17 +13,15 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package file
+package either
 
 import (
-	"io"
-
-	IOE "github.com/IBM/fp-go/ioeither"
+	S "github.com/IBM/fp-go/semigroup"
 )
 
-// onClose closes a closeable resource
-func onClose[R io.Closer](r R) IOE.IOEither[error, R] {
-	return IOE.TryCatchError(func() (R, error) {
-		return r, r.Close()
-	})
+// AltSemigroup is the alternative [Semigroup] for an [Either]
+func AltSemigroup[E, A any]() S.Semigroup[Either[E, A]] {
+	return S.AltSemigroup(
+		MonadAlt[E, A],
+	)
 }

either/traverse.go

@@ -27,13 +27,13 @@ HKTRB = HKT<Either[B]>
 HKTA = HKT<A>
 HKTB = HKT<B>
 */
-func traverse[E, A, B, HKTA, HKTB, HKTRB any](
-	_of func(Either[E, B]) HKTRB,
-	_map func(HKTB, func(B) Either[E, B]) HKTRB,
+func traverse[E, A, B, HKTB, HKTRB any](
+	mof func(Either[E, B]) HKTRB,
+	mmap func(func(B) Either[E, B]) func(HKTB) HKTRB,
 ) func(Either[E, A], func(A) HKTB) HKTRB {
 
-	left := F.Flow2(Left[B, E], _of)
-	right := F.Bind2nd(_map, Right[E, B])
+	left := F.Flow2(Left[B, E], mof)
+	right := mmap(Right[E, B])
 
 	return func(ta Either[E, A], f func(A) HKTB) HKTRB {
 		return MonadFold(ta,
@@ -43,27 +43,21 @@ func traverse[E, A, B, HKTA, HKTB, HKTRB any](
 	}
 }
 
-func Traverse[E, A, B, HKTA, HKTB, HKTRB any](
-	_of func(Either[E, B]) HKTRB,
-	_map func(HKTB, func(B) Either[E, B]) HKTRB,
+// Traverse converts an [Either] of some higher kinded type into the higher kinded type of an [Either]
+func Traverse[A, E, B, HKTB, HKTRB any](
+	mof func(Either[E, B]) HKTRB,
+	mmap func(func(B) Either[E, B]) func(HKTB) HKTRB,
 ) func(func(A) HKTB) func(Either[E, A]) HKTRB {
-	delegate := traverse[E, A, B, HKTA](_of, _map)
+	delegate := traverse[E, A, B](mof, mmap)
 	return func(f func(A) HKTB) func(Either[E, A]) HKTRB {
 		return F.Bind2nd(delegate, f)
 	}
 }
 
-/*
-*
-We need to pass the members of the applicative explicitly, because golang does neither support higher kinded types nor template methods on structs or interfaces
-
-HKTRA = HKT<Either[A]>
-HKTA = HKT<A>
-HKTB = HKT<B>
-*/
+// Sequence converts an [Either] of some higher kinded type into the higher kinded type of an [Either]
 func Sequence[E, A, HKTA, HKTRA any](
-	_of func(Either[E, A]) HKTRA,
-	_map func(HKTA, func(A) Either[E, A]) HKTRA,
+	mof func(Either[E, A]) HKTRA,
+	mmap func(func(A) Either[E, A]) func(HKTA) HKTRA,
 ) func(Either[E, HKTA]) HKTRA {
-	return Fold(F.Flow2(Left[A, E], _of), F.Bind2nd(_map, Right[E, A]))
+	return Fold(F.Flow2(Left[A, E], mof), mmap(Right[E, A]))
 }

either/traverse_test.go

@@ -30,9 +30,9 @@ func TestTraverse(t *testing.T) {
 		}
 		return O.None[int]()
 	}
-	trav := Traverse[string, int, int, O.Option[Either[string, int]]](
+	trav := Traverse[int](
 		O.Of[Either[string, int]],
-		O.MonadMap[int, Either[string, int]],
+		O.Map[int, Either[string, int]],
 	)(f)
 
 	assert.Equal(t, O.Of(Left[int]("a")), F.Pipe1(Left[int]("a"), trav))
@@ -44,7 +44,7 @@ func TestSequence(t *testing.T) {
 
 	seq := Sequence(
 		O.Of[Either[string, int]],
-		O.MonadMap[int, Either[string, int]],
+		O.Map[int, Either[string, int]],
 	)
 
 	assert.Equal(t, O.Of(Right[string](1)), seq(Right[string](O.Of(1))))

exec/exec.go

@@ -20,11 +20,14 @@ import (
 )
 
 type (
-	// command output
+	// CommandOutput represents the output of executing a command. The first field in the [Tuple2] is
+	// stdout, the second one is stderr. Use [StdOut] and [StdErr] to access these fields
 	CommandOutput = T.Tuple2[[]byte, []byte]
 )
 
 var (
+	// StdOut returns the field of a [CommandOutput] representing `stdout`
 	StdOut = T.First[[]byte, []byte]
+	// StdErr returns the field of a [CommandOutput] representing `stderr`
 	StdErr = T.Second[[]byte, []byte]
 )

file/getters.go

@@ -15,9 +15,11 @@
 
 package file
 
-import "os"
+import "path/filepath"
 
-// GetName is the getter for the `Name` property of [os.File]
-func GetName(f *os.File) string {
-	return f.Name()
+// Join appends a filename to a root path
+func Join(name string) func(root string) string {
+	return func(root string) string {
+		return filepath.Join(root, name)
+	}
 }

function/bind.go

@@ -26,6 +26,7 @@ func Bind2nd[T1, T2, R any](f func(T1, T2) R, t2 T2) func(T1) R {
 	}
 }
 
+// SK function (SKI combinator calculus).
 func SK[T1, T2 any](_ T1, t2 T2) T2 {
 	return t2
 }

function/binds.go

@@ -1,6 +1,6 @@
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-08-17 22:59:01.9404821 +0200 CEST m=+0.161366801
+// 2023-09-12 13:44:23.4226437 +0200 CEST m=+0.011841001
 
 package function
 

function/cache.go

@@ -0,0 +1,30 @@
+// Copyright (c) 2023 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 function
+
+import (
+	G "github.com/IBM/fp-go/function/generic"
+)
+
+// Memoize converts a unary function into a unary function that caches the value depending on the parameter
+func Memoize[K comparable, T any](f func(K) T) func(K) T {
+	return G.Memoize(f)
+}
+
+// ContramapMemoize converts a unary function into a unary function that caches the value depending on the parameter
+func ContramapMemoize[A any, K comparable, T any](kf func(A) K) func(func(A) T) func(A) T {
+	return G.ContramapMemoize[func(A) T](kf)
+}

function/cache_test.go

@@ -0,0 +1,50 @@
+// Copyright (c) 2023 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 function
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCache(t *testing.T) {
+	var count int
+
+	withSideEffect := func(n int) int {
+		count++
+		return n
+	}
+
+	cached := Memoize(withSideEffect)
+
+	assert.Equal(t, 0, count)
+
+	assert.Equal(t, 10, cached(10))
+	assert.Equal(t, 1, count)
+
+	assert.Equal(t, 10, cached(10))
+	assert.Equal(t, 1, count)
+
+	assert.Equal(t, 20, cached(20))
+	assert.Equal(t, 2, count)
+
+	assert.Equal(t, 20, cached(20))
+	assert.Equal(t, 2, count)
+
+	assert.Equal(t, 10, cached(10))
+	assert.Equal(t, 2, count)
+}

function/function.go

@@ -62,6 +62,7 @@ func First[T1, T2 any](t1 T1, _ T2) T1 {
 }
 
 // Second returns the second out of two input values
+// Identical to [SK]
 func Second[T1, T2 any](_ T1, t2 T2) T2 {
 	return t2
 }

function/gen.go

@@ -1,6 +1,6 @@
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-08-17 22:58:59.8663985 +0200 CEST m=+0.103744101
+// 2023-09-12 13:44:17.0002767 +0200 CEST m=+0.008233101
 
 package function
 
@@ -24,6 +24,13 @@ func Unvariadic0[V, R any](f func(...V) R) func([]V) R {
 	}
 }
 
+// Unsliced0 converts a function taking a slice parameter into a function with 0 parameters
+func Unsliced0[F ~func([]T) R, T, R any](f F) func() R {
+	return func() R {
+		return f([]T{})
+	}
+}
+
 // Pipe1 takes an initial value t0 and successively applies 1 functions where the input of a function is the return value of the previous function
 // The final return value is the result of the last function application
 func Pipe1[F1 ~func(T0) T1, T0, T1 any](t0 T0, f1 F1) T1 {
@@ -76,6 +83,13 @@ func Unvariadic1[T1, V, R any](f func(T1, ...V) R) func(T1, []V) R {
 	}
 }
 
+// Unsliced1 converts a function taking a slice parameter into a function with 1 parameters
+func Unsliced1[F ~func([]T) R, T, R any](f F) func(T) R {
+	return func(t1 T) R {
+		return f([]T{t1})
+	}
+}
+
 // Pipe2 takes an initial value t0 and successively applies 2 functions where the input of a function is the return value of the previous function
 // The final return value is the result of the last function application
 func Pipe2[F1 ~func(T0) T1, F2 ~func(T1) T2, T0, T1, T2 any](t0 T0, f1 F1, f2 F2) T2 {
@@ -131,6 +145,13 @@ func Unvariadic2[T1, T2, V, R any](f func(T1, T2, ...V) R) func(T1, T2, []V) R {
 	}
 }
 
+// Unsliced2 converts a function taking a slice parameter into a function with 2 parameters
+func Unsliced2[F ~func([]T) R, T, R any](f F) func(T, T) R {
+	return func(t1, t2 T) R {
+		return f([]T{t1, t2})
+	}
+}
+
 // Pipe3 takes an initial value t0 and successively applies 3 functions where the input of a function is the return value of the previous function
 // The final return value is the result of the last function application
 func Pipe3[F1 ~func(T0) T1, F2 ~func(T1) T2, F3 ~func(T2) T3, T0, T1, T2, T3 any](t0 T0, f1 F1, f2 F2, f3 F3) T3 {
@@ -189,6 +210,13 @@ func Unvariadic3[T1, T2, T3, V, R any](f func(T1, T2, T3, ...V) R) func(T1, T2,
 	}
 }
 
+// Unsliced3 converts a function taking a slice parameter into a function with 3 parameters
+func Unsliced3[F ~func([]T) R, T, R any](f F) func(T, T, T) R {
+	return func(t1, t2, t3 T) R {
+		return f([]T{t1, t2, t3})
+	}
+}
+
 // Pipe4 takes an initial value t0 and successively applies 4 functions where the input of a function is the return value of the previous function
 // The final return value is the result of the last function application
 func Pipe4[F1 ~func(T0) T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4, T0, T1, T2, T3, T4 any](t0 T0, f1 F1, f2 F2, f3 F3, f4 F4) T4 {
@@ -250,6 +278,13 @@ func Unvariadic4[T1, T2, T3, T4, V, R any](f func(T1, T2, T3, T4, ...V) R) func(
 	}
 }
 
+// Unsliced4 converts a function taking a slice parameter into a function with 4 parameters
+func Unsliced4[F ~func([]T) R, T, R any](f F) func(T, T, T, T) R {
+	return func(t1, t2, t3, t4 T) R {
+		return f([]T{t1, t2, t3, t4})
+	}
+}
+
 // Pipe5 takes an initial value t0 and successively applies 5 functions where the input of a function is the return value of the previous function
 // The final return value is the result of the last function application
 func Pipe5[F1 ~func(T0) T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4, F5 ~func(T4) T5, T0, T1, T2, T3, T4, T5 any](t0 T0, f1 F1, f2 F2, f3 F3, f4 F4, f5 F5) T5 {
@@ -314,6 +349,13 @@ func Unvariadic5[T1, T2, T3, T4, T5, V, R any](f func(T1, T2, T3, T4, T5, ...V)
 	}
 }
 
+// Unsliced5 converts a function taking a slice parameter into a function with 5 parameters
+func Unsliced5[F ~func([]T) R, T, R any](f F) func(T, T, T, T, T) R {
+	return func(t1, t2, t3, t4, t5 T) R {
+		return f([]T{t1, t2, t3, t4, t5})
+	}
+}
+
 // Pipe6 takes an initial value t0 and successively applies 6 functions where the input of a function is the return value of the previous function
 // The final return value is the result of the last function application
 func Pipe6[F1 ~func(T0) T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4, F5 ~func(T4) T5, F6 ~func(T5) T6, T0, T1, T2, T3, T4, T5, T6 any](t0 T0, f1 F1, f2 F2, f3 F3, f4 F4, f5 F5, f6 F6) T6 {
@@ -381,6 +423,13 @@ func Unvariadic6[T1, T2, T3, T4, T5, T6, V, R any](f func(T1, T2, T3, T4, T5, T6
 	}
 }
 
+// Unsliced6 converts a function taking a slice parameter into a function with 6 parameters
+func Unsliced6[F ~func([]T) R, T, R any](f F) func(T, T, T, T, T, T) R {
+	return func(t1, t2, t3, t4, t5, t6 T) R {
+		return f([]T{t1, t2, t3, t4, t5, t6})
+	}
+}
+
 // Pipe7 takes an initial value t0 and successively applies 7 functions where the input of a function is the return value of the previous function
 // The final return value is the result of the last function application
 func Pipe7[F1 ~func(T0) T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4, F5 ~func(T4) T5, F6 ~func(T5) T6, F7 ~func(T6) T7, T0, T1, T2, T3, T4, T5, T6, T7 any](t0 T0, f1 F1, f2 F2, f3 F3, f4 F4, f5 F5, f6 F6, f7 F7) T7 {
@@ -451,6 +500,13 @@ func Unvariadic7[T1, T2, T3, T4, T5, T6, T7, V, R any](f func(T1, T2, T3, T4, T5
 	}
 }
 
+// Unsliced7 converts a function taking a slice parameter into a function with 7 parameters
+func Unsliced7[F ~func([]T) R, T, R any](f F) func(T, T, T, T, T, T, T) R {
+	return func(t1, t2, t3, t4, t5, t6, t7 T) R {
+		return f([]T{t1, t2, t3, t4, t5, t6, t7})
+	}
+}
+
 // Pipe8 takes an initial value t0 and successively applies 8 functions where the input of a function is the return value of the previous function
 // The final return value is the result of the last function application
 func Pipe8[F1 ~func(T0) T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4, F5 ~func(T4) T5, F6 ~func(T5) T6, F7 ~func(T6) T7, F8 ~func(T7) T8, T0, T1, T2, T3, T4, T5, T6, T7, T8 any](t0 T0, f1 F1, f2 F2, f3 F3, f4 F4, f5 F5, f6 F6, f7 F7, f8 F8) T8 {
@@ -524,6 +580,13 @@ func Unvariadic8[T1, T2, T3, T4, T5, T6, T7, T8, V, R any](f func(T1, T2, T3, T4
 	}
 }
 
+// Unsliced8 converts a function taking a slice parameter into a function with 8 parameters
+func Unsliced8[F ~func([]T) R, T, R any](f F) func(T, T, T, T, T, T, T, T) R {
+	return func(t1, t2, t3, t4, t5, t6, t7, t8 T) R {
+		return f([]T{t1, t2, t3, t4, t5, t6, t7, t8})
+	}
+}
+
 // Pipe9 takes an initial value t0 and successively applies 9 functions where the input of a function is the return value of the previous function
 // The final return value is the result of the last function application
 func Pipe9[F1 ~func(T0) T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4, F5 ~func(T4) T5, F6 ~func(T5) T6, F7 ~func(T6) T7, F8 ~func(T7) T8, F9 ~func(T8) T9, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9 any](t0 T0, f1 F1, f2 F2, f3 F3, f4 F4, f5 F5, f6 F6, f7 F7, f8 F8, f9 F9) T9 {
@@ -600,6 +663,13 @@ func Unvariadic9[T1, T2, T3, T4, T5, T6, T7, T8, T9, V, R any](f func(T1, T2, T3
 	}
 }
 
+// Unsliced9 converts a function taking a slice parameter into a function with 9 parameters
+func Unsliced9[F ~func([]T) R, T, R any](f F) func(T, T, T, T, T, T, T, T, T) R {
+	return func(t1, t2, t3, t4, t5, t6, t7, t8, t9 T) R {
+		return f([]T{t1, t2, t3, t4, t5, t6, t7, t8, t9})
+	}
+}
+
 // Pipe10 takes an initial value t0 and successively applies 10 functions where the input of a function is the return value of the previous function
 // The final return value is the result of the last function application
 func Pipe10[F1 ~func(T0) T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4, F5 ~func(T4) T5, F6 ~func(T5) T6, F7 ~func(T6) T7, F8 ~func(T7) T8, F9 ~func(T8) T9, F10 ~func(T9) T10, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10 any](t0 T0, f1 F1, f2 F2, f3 F3, f4 F4, f5 F5, f6 F6, f7 F7, f8 F8, f9 F9, f10 F10) T10 {
@@ -679,6 +749,13 @@ func Unvariadic10[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, V, R any](f func(T1,
 	}
 }
 
+// Unsliced10 converts a function taking a slice parameter into a function with 10 parameters
+func Unsliced10[F ~func([]T) R, T, R any](f F) func(T, T, T, T, T, T, T, T, T, T) R {
+	return func(t1, t2, t3, t4, t5, t6, t7, t8, t9, t10 T) R {
+		return f([]T{t1, t2, t3, t4, t5, t6, t7, t8, t9, t10})
+	}
+}
+
 // Pipe11 takes an initial value t0 and successively applies 11 functions where the input of a function is the return value of the previous function
 // The final return value is the result of the last function application
 func Pipe11[F1 ~func(T0) T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4, F5 ~func(T4) T5, F6 ~func(T5) T6, F7 ~func(T6) T7, F8 ~func(T7) T8, F9 ~func(T8) T9, F10 ~func(T9) T10, F11 ~func(T10) T11, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11 any](t0 T0, f1 F1, f2 F2, f3 F3, f4 F4, f5 F5, f6 F6, f7 F7, f8 F8, f9 F9, f10 F10, f11 F11) T11 {
@@ -761,6 +838,13 @@ func Unvariadic11[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, V, R any](f func
 	}
 }
 
+// Unsliced11 converts a function taking a slice parameter into a function with 11 parameters
+func Unsliced11[F ~func([]T) R, T, R any](f F) func(T, T, T, T, T, T, T, T, T, T, T) R {
+	return func(t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11 T) R {
+		return f([]T{t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11})
+	}
+}
+
 // Pipe12 takes an initial value t0 and successively applies 12 functions where the input of a function is the return value of the previous function
 // The final return value is the result of the last function application
 func Pipe12[F1 ~func(T0) T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4, F5 ~func(T4) T5, F6 ~func(T5) T6, F7 ~func(T6) T7, F8 ~func(T7) T8, F9 ~func(T8) T9, F10 ~func(T9) T10, F11 ~func(T10) T11, F12 ~func(T11) T12, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12 any](t0 T0, f1 F1, f2 F2, f3 F3, f4 F4, f5 F5, f6 F6, f7 F7, f8 F8, f9 F9, f10 F10, f11 F11, f12 F12) T12 {
@@ -846,6 +930,13 @@ func Unvariadic12[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, V, R any](f
 	}
 }
 
+// Unsliced12 converts a function taking a slice parameter into a function with 12 parameters
+func Unsliced12[F ~func([]T) R, T, R any](f F) func(T, T, T, T, T, T, T, T, T, T, T, T) R {
+	return func(t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12 T) R {
+		return f([]T{t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12})
+	}
+}
+
 // Pipe13 takes an initial value t0 and successively applies 13 functions where the input of a function is the return value of the previous function
 // The final return value is the result of the last function application
 func Pipe13[F1 ~func(T0) T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4, F5 ~func(T4) T5, F6 ~func(T5) T6, F7 ~func(T6) T7, F8 ~func(T7) T8, F9 ~func(T8) T9, F10 ~func(T9) T10, F11 ~func(T10) T11, F12 ~func(T11) T12, F13 ~func(T12) T13, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13 any](t0 T0, f1 F1, f2 F2, f3 F3, f4 F4, f5 F5, f6 F6, f7 F7, f8 F8, f9 F9, f10 F10, f11 F11, f12 F12, f13 F13) T13 {
@@ -934,6 +1025,13 @@ func Unvariadic13[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, V, R a
 	}
 }
 
+// Unsliced13 converts a function taking a slice parameter into a function with 13 parameters
+func Unsliced13[F ~func([]T) R, T, R any](f F) func(T, T, T, T, T, T, T, T, T, T, T, T, T) R {
+	return func(t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13 T) R {
+		return f([]T{t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13})
+	}
+}
+
 // Pipe14 takes an initial value t0 and successively applies 14 functions where the input of a function is the return value of the previous function
 // The final return value is the result of the last function application
 func Pipe14[F1 ~func(T0) T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4, F5 ~func(T4) T5, F6 ~func(T5) T6, F7 ~func(T6) T7, F8 ~func(T7) T8, F9 ~func(T8) T9, F10 ~func(T9) T10, F11 ~func(T10) T11, F12 ~func(T11) T12, F13 ~func(T12) T13, F14 ~func(T13) T14, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14 any](t0 T0, f1 F1, f2 F2, f3 F3, f4 F4, f5 F5, f6 F6, f7 F7, f8 F8, f9 F9, f10 F10, f11 F11, f12 F12, f13 F13, f14 F14) T14 {
@@ -1025,6 +1123,13 @@ func Unvariadic14[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, V
 	}
 }
 
+// Unsliced14 converts a function taking a slice parameter into a function with 14 parameters
+func Unsliced14[F ~func([]T) R, T, R any](f F) func(T, T, T, T, T, T, T, T, T, T, T, T, T, T) R {
+	return func(t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14 T) R {
+		return f([]T{t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14})
+	}
+}
+
 // Pipe15 takes an initial value t0 and successively applies 15 functions where the input of a function is the return value of the previous function
 // The final return value is the result of the last function application
 func Pipe15[F1 ~func(T0) T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4, F5 ~func(T4) T5, F6 ~func(T5) T6, F7 ~func(T6) T7, F8 ~func(T7) T8, F9 ~func(T8) T9, F10 ~func(T9) T10, F11 ~func(T10) T11, F12 ~func(T11) T12, F13 ~func(T12) T13, F14 ~func(T13) T14, F15 ~func(T14) T15, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15 any](t0 T0, f1 F1, f2 F2, f3 F3, f4 F4, f5 F5, f6 F6, f7 F7, f8 F8, f9 F9, f10 F10, f11 F11, f12 F12, f13 F13, f14 F14, f15 F15) T15 {
@@ -1119,6 +1224,13 @@ func Unvariadic15[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T
 	}
 }
 
+// Unsliced15 converts a function taking a slice parameter into a function with 15 parameters
+func Unsliced15[F ~func([]T) R, T, R any](f F) func(T, T, T, T, T, T, T, T, T, T, T, T, T, T, T) R {
+	return func(t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14, t15 T) R {
+		return f([]T{t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14, t15})
+	}
+}
+
 // Pipe16 takes an initial value t0 and successively applies 16 functions where the input of a function is the return value of the previous function
 // The final return value is the result of the last function application
 func Pipe16[F1 ~func(T0) T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4, F5 ~func(T4) T5, F6 ~func(T5) T6, F7 ~func(T6) T7, F8 ~func(T7) T8, F9 ~func(T8) T9, F10 ~func(T9) T10, F11 ~func(T10) T11, F12 ~func(T11) T12, F13 ~func(T12) T13, F14 ~func(T13) T14, F15 ~func(T14) T15, F16 ~func(T15) T16, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16 any](t0 T0, f1 F1, f2 F2, f3 F3, f4 F4, f5 F5, f6 F6, f7 F7, f8 F8, f9 F9, f10 F10, f11 F11, f12 F12, f13 F13, f14 F14, f15 F15, f16 F16) T16 {
@@ -1216,6 +1328,13 @@ func Unvariadic16[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T
 	}
 }
 
+// Unsliced16 converts a function taking a slice parameter into a function with 16 parameters
+func Unsliced16[F ~func([]T) R, T, R any](f F) func(T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T) R {
+	return func(t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14, t15, t16 T) R {
+		return f([]T{t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14, t15, t16})
+	}
+}
+
 // Pipe17 takes an initial value t0 and successively applies 17 functions where the input of a function is the return value of the previous function
 // The final return value is the result of the last function application
 func Pipe17[F1 ~func(T0) T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4, F5 ~func(T4) T5, F6 ~func(T5) T6, F7 ~func(T6) T7, F8 ~func(T7) T8, F9 ~func(T8) T9, F10 ~func(T9) T10, F11 ~func(T10) T11, F12 ~func(T11) T12, F13 ~func(T12) T13, F14 ~func(T13) T14, F15 ~func(T14) T15, F16 ~func(T15) T16, F17 ~func(T16) T17, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17 any](t0 T0, f1 F1, f2 F2, f3 F3, f4 F4, f5 F5, f6 F6, f7 F7, f8 F8, f9 F9, f10 F10, f11 F11, f12 F12, f13 F13, f14 F14, f15 F15, f16 F16, f17 F17) T17 {
@@ -1316,6 +1435,13 @@ func Unvariadic17[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T
 	}
 }
 
+// Unsliced17 converts a function taking a slice parameter into a function with 17 parameters
+func Unsliced17[F ~func([]T) R, T, R any](f F) func(T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T) R {
+	return func(t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14, t15, t16, t17 T) R {
+		return f([]T{t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14, t15, t16, t17})
+	}
+}
+
 // Pipe18 takes an initial value t0 and successively applies 18 functions where the input of a function is the return value of the previous function
 // The final return value is the result of the last function application
 func Pipe18[F1 ~func(T0) T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4, F5 ~func(T4) T5, F6 ~func(T5) T6, F7 ~func(T6) T7, F8 ~func(T7) T8, F9 ~func(T8) T9, F10 ~func(T9) T10, F11 ~func(T10) T11, F12 ~func(T11) T12, F13 ~func(T12) T13, F14 ~func(T13) T14, F15 ~func(T14) T15, F16 ~func(T15) T16, F17 ~func(T16) T17, F18 ~func(T17) T18, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18 any](t0 T0, f1 F1, f2 F2, f3 F3, f4 F4, f5 F5, f6 F6, f7 F7, f8 F8, f9 F9, f10 F10, f11 F11, f12 F12, f13 F13, f14 F14, f15 F15, f16 F16, f17 F17, f18 F18) T18 {
@@ -1419,6 +1545,13 @@ func Unvariadic18[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T
 	}
 }
 
+// Unsliced18 converts a function taking a slice parameter into a function with 18 parameters
+func Unsliced18[F ~func([]T) R, T, R any](f F) func(T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T) R {
+	return func(t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14, t15, t16, t17, t18 T) R {
+		return f([]T{t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14, t15, t16, t17, t18})
+	}
+}
+
 // Pipe19 takes an initial value t0 and successively applies 19 functions where the input of a function is the return value of the previous function
 // The final return value is the result of the last function application
 func Pipe19[F1 ~func(T0) T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4, F5 ~func(T4) T5, F6 ~func(T5) T6, F7 ~func(T6) T7, F8 ~func(T7) T8, F9 ~func(T8) T9, F10 ~func(T9) T10, F11 ~func(T10) T11, F12 ~func(T11) T12, F13 ~func(T12) T13, F14 ~func(T13) T14, F15 ~func(T14) T15, F16 ~func(T15) T16, F17 ~func(T16) T17, F18 ~func(T17) T18, F19 ~func(T18) T19, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19 any](t0 T0, f1 F1, f2 F2, f3 F3, f4 F4, f5 F5, f6 F6, f7 F7, f8 F8, f9 F9, f10 F10, f11 F11, f12 F12, f13 F13, f14 F14, f15 F15, f16 F16, f17 F17, f18 F18, f19 F19) T19 {
@@ -1525,6 +1658,13 @@ func Unvariadic19[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T
 	}
 }
 
+// Unsliced19 converts a function taking a slice parameter into a function with 19 parameters
+func Unsliced19[F ~func([]T) R, T, R any](f F) func(T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T) R {
+	return func(t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14, t15, t16, t17, t18, t19 T) R {
+		return f([]T{t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14, t15, t16, t17, t18, t19})
+	}
+}
+
 // Pipe20 takes an initial value t0 and successively applies 20 functions where the input of a function is the return value of the previous function
 // The final return value is the result of the last function application
 func Pipe20[F1 ~func(T0) T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4, F5 ~func(T4) T5, F6 ~func(T5) T6, F7 ~func(T6) T7, F8 ~func(T7) T8, F9 ~func(T8) T9, F10 ~func(T9) T10, F11 ~func(T10) T11, F12 ~func(T11) T12, F13 ~func(T12) T13, F14 ~func(T13) T14, F15 ~func(T14) T15, F16 ~func(T15) T16, F17 ~func(T16) T17, F18 ~func(T17) T18, F19 ~func(T18) T19, F20 ~func(T19) T20, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20 any](t0 T0, f1 F1, f2 F2, f3 F3, f4 F4, f5 F5, f6 F6, f7 F7, f8 F8, f9 F9, f10 F10, f11 F11, f12 F12, f13 F13, f14 F14, f15 F15, f16 F16, f17 F17, f18 F18, f19 F19, f20 F20) T20 {
@@ -1633,3 +1773,10 @@ func Unvariadic20[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T
 		return f(t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14, t15, t16, t17, t18, t19, t20, v...)
 	}
 }
+
+// Unsliced20 converts a function taking a slice parameter into a function with 20 parameters
+func Unsliced20[F ~func([]T) R, T, R any](f F) func(T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T) R {
+	return func(t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14, t15, t16, t17, t18, t19, t20 T) R {
+		return f([]T{t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14, t15, t16, t17, t18, t19, t20})
+	}
+}

function/generic/cache.go

@@ -0,0 +1,65 @@
+// Copyright (c) 2023 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 (
+	"sync"
+
+	L "github.com/IBM/fp-go/internal/lazy"
+)
+
+// Memoize converts a unary function into a unary function that caches the value depending on the parameter
+func Memoize[F ~func(K) T, K comparable, T any](f F) F {
+	return ContramapMemoize[F](func(k K) K { return k })(f)
+}
+
+// ContramapMemoize converts a unary function into a unary function that caches the value depending on the parameter
+func ContramapMemoize[F ~func(A) T, KF func(A) K, A any, K comparable, T any](kf KF) func(F) F {
+	return CacheCallback[F](kf, getOrCreate[K, T]())
+}
+
+// getOrCreate is a naive implementation of a cache, without bounds
+func getOrCreate[K comparable, T any]() func(K, func() func() T) func() T {
+	cache := make(map[K]func() T)
+	var l sync.Mutex
+
+	return func(k K, cb func() func() T) func() T {
+		// only lock to access a lazy accessor to the value
+		l.Lock()
+		existing, ok := cache[k]
+		if !ok {
+			existing = cb()
+			cache[k] = existing
+		}
+		l.Unlock()
+		// compute the value outside of the lock
+		return existing
+	}
+}
+
+// CacheCallback converts a unary function into a unary function that caches the value depending on the parameter
+func CacheCallback[F ~func(A) T, KF func(A) K, C ~func(K, func() func() T) func() T, A any, K comparable, T any](kf KF, getOrCreate C) func(F) F {
+	return func(f F) F {
+		return func(a A) T {
+			// cache entry
+			return getOrCreate(kf(a), func() func() T {
+				return L.Memoize[func() T](func() T {
+					return f(a)
+				})
+			})()
+		}
+	}
+}

function/unvariadic_test.go

@@ -0,0 +1,45 @@
+// Copyright (c) 2023 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 function
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func fromLibrary(data ...string) string {
+	return strings.Join(data, "-")
+}
+
+func TestUnvariadic(t *testing.T) {
+
+	res := Pipe1(
+		[]string{"A", "B"},
+		Unvariadic0(fromLibrary),
+	)
+
+	assert.Equal(t, "A-B", res)
+}
+
+func TestVariadicArity(t *testing.T) {
+
+	f := Unsliced2(Unvariadic0(fromLibrary))
+
+	res := f("A", "B")
+	assert.Equal(t, "A-B", res)
+}

http/utils.go

@@ -57,7 +57,7 @@ var (
 			GetHeader,
 			R.Lookup[H.Header](HeaderContentType),
 			O.Chain(A.First[string]),
-			E.FromOption[error, string](errors.OnNone("unable to access the [%s] header", HeaderContentType)),
+			E.FromOption[string](errors.OnNone("unable to access the [%s] header", HeaderContentType)),
 			E.ChainFirst(validateJsonContentTypeString),
 		)))
 )

identity/gen.go

@@ -1,6 +1,6 @@
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-08-17 22:59:06.2987136 +0200 CEST m=+0.049156901
+// 2023-09-12 13:44:24.9409324 +0200 CEST m=+0.008573601
 
 package identity
 

identity/generic/identity.go

@@ -18,6 +18,7 @@ package generic
 import (
 	F "github.com/IBM/fp-go/function"
 	C "github.com/IBM/fp-go/internal/chain"
+	FC "github.com/IBM/fp-go/internal/functor"
 )
 
 func MonadAp[GAB ~func(A) B, B, A any](fab GAB, fa A) B {
@@ -51,3 +52,11 @@ func MonadChainFirst[GAB ~func(A) B, A, B any](fa A, f GAB) A {
 func ChainFirst[GAB ~func(A) B, A, B any](f GAB) func(A) A {
 	return C.ChainFirst(MonadChain[func(A) A, A, A], MonadMap[func(B) A, B, A], f)
 }
+
+func MonadFlap[GAB ~func(A) B, A, B any](fab GAB, a A) B {
+	return FC.MonadFlap(MonadMap[func(GAB) B, GAB, B], fab, a)
+}
+
+func Flap[GAB ~func(A) B, A, B any](a A) func(GAB) B {
+	return F.Bind2nd(MonadFlap[GAB, A, B], a)
+}

identity/identity.go

@@ -63,3 +63,11 @@ func MonadChainFirst[A, B any](fa A, f func(A) B) A {
 func ChainFirst[A, B any](f func(A) B) func(A) A {
 	return G.ChainFirst(f)
 }
+
+func MonadFlap[B, A any](fab func(A) B, a A) B {
+	return G.MonadFlap[func(A) B](fab, a)
+}
+
+func Flap[B, A any](a A) func(func(A) B) B {
+	return G.Flap[func(A) B](a)
+}

internal/apply/gen.go

@@ -1,6 +1,6 @@
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-08-17 22:59:08.1313362 +0200 CEST m=+0.111171801
+// 2023-09-12 13:44:26.2499883 +0200 CEST m=+0.007601301
 
 package apply
 

internal/array/traverse.go

@@ -37,6 +37,24 @@ func MonadTraverse[GA ~[]A, GB ~[]B, A, B, HKTB, HKTAB, HKTRB any](
 	return MonadTraverseReduce(fof, fmap, fap, ta, f, Append[GB, B], Empty[GB]())
 }
 
+/*
+*
+We need to pass the members of the applicative explicitly, because golang does neither support higher kinded types nor template methods on structs or interfaces
+
+HKTRB = HKT<GB>
+HKTB = HKT<B>
+HKTAB = HKT<func(A)B>
+*/
+func MonadTraverseWithIndex[GA ~[]A, GB ~[]B, A, B, HKTB, HKTAB, HKTRB any](
+	fof func(GB) HKTRB,
+	fmap func(func(GB) func(B) GB) func(HKTRB) HKTAB,
+	fap func(HKTB) func(HKTAB) HKTRB,
+
+	ta GA,
+	f func(int, A) HKTB) HKTRB {
+	return MonadTraverseReduceWithIndex(fof, fmap, fap, ta, f, Append[GB, B], Empty[GB]())
+}
+
 func Traverse[GA ~[]A, GB ~[]B, A, B, HKTB, HKTAB, HKTRB any](
 	fof func(GB) HKTRB,
 	fmap func(func(GB) func(B) GB) func(HKTRB) HKTAB,
@@ -49,6 +67,18 @@ func Traverse[GA ~[]A, GB ~[]B, A, B, HKTB, HKTAB, HKTRB any](
 	}
 }
 
+func TraverseWithIndex[GA ~[]A, GB ~[]B, A, B, HKTB, HKTAB, HKTRB any](
+	fof func(GB) HKTRB,
+	fmap func(func(GB) func(B) GB) func(HKTRB) HKTAB,
+	fap func(HKTB) func(HKTAB) HKTRB,
+
+	f func(int, A) HKTB) func(GA) HKTRB {
+
+	return func(ma GA) HKTRB {
+		return MonadTraverseWithIndex(fof, fmap, fap, ma, f)
+	}
+}
+
 func MonadTraverseReduce[GA ~[]A, GB, A, B, HKTB, HKTAB, HKTRB any](
 	fof func(GB) HKTRB,
 	fmap func(func(GB) func(B) GB) func(HKTRB) HKTAB,
@@ -71,6 +101,28 @@ func MonadTraverseReduce[GA ~[]A, GB, A, B, HKTB, HKTAB, HKTRB any](
 	}, fof(initial))
 }
 
+func MonadTraverseReduceWithIndex[GA ~[]A, GB, A, B, HKTB, HKTAB, HKTRB any](
+	fof func(GB) HKTRB,
+	fmap func(func(GB) func(B) GB) func(HKTRB) HKTAB,
+	fap func(HKTB) func(HKTAB) HKTRB,
+
+	ta GA,
+
+	transform func(int, A) HKTB,
+	reduce func(GB, B) GB,
+	initial GB,
+) HKTRB {
+	mmap := fmap(F.Curry2(reduce))
+
+	return ReduceWithIndex(ta, func(idx int, r HKTRB, a A) HKTRB {
+		return F.Pipe2(
+			r,
+			mmap,
+			fap(transform(idx, a)),
+		)
+	}, fof(initial))
+}
+
 func TraverseReduce[GA ~[]A, GB, A, B, HKTB, HKTAB, HKTRB any](
 	fof func(GB) HKTRB,
 	fmap func(func(GB) func(B) GB) func(HKTRB) HKTAB,
@@ -84,3 +136,17 @@ func TraverseReduce[GA ~[]A, GB, A, B, HKTB, HKTAB, HKTRB any](
 		return MonadTraverseReduce(fof, fmap, fap, ta, transform, reduce, initial)
 	}
 }
+
+func TraverseReduceWithIndex[GA ~[]A, GB, A, B, HKTB, HKTAB, HKTRB any](
+	fof func(GB) HKTRB,
+	fmap func(func(GB) func(B) GB) func(HKTRB) HKTAB,
+	fap func(HKTB) func(HKTAB) HKTRB,
+
+	transform func(int, A) HKTB,
+	reduce func(GB, B) GB,
+	initial GB,
+) func(GA) HKTRB {
+	return func(ta GA) HKTRB {
+		return MonadTraverseReduceWithIndex(fof, fmap, fap, ta, transform, reduce, initial)
+	}
+}

internal/eithert/either.go

@@ -22,6 +22,16 @@ import (
 	FC "github.com/IBM/fp-go/internal/functor"
 )
 
+func MonadAlt[LAZY ~func() HKTFA, E, A, HKTFA any](
+	fof func(ET.Either[E, A]) HKTFA,
+	fchain func(HKTFA, func(ET.Either[E, A]) HKTFA) HKTFA,
+
+	first HKTFA,
+	second LAZY) HKTFA {
+
+	return fchain(first, ET.Fold(F.Ignore1of1[E](second), F.Flow2(ET.Of[E, A], fof)))
+}
+
 // HKTFA = HKT<F, Either<E, A>>
 // HKTFB = HKT<F, Either<E, B>>
 func MonadMap[E, A, B, HKTFA, HKTFB any](fmap func(HKTFA, func(ET.Either[E, A]) ET.Either[E, B]) HKTFB, fa HKTFA, f func(A) B) HKTFB {

internal/fromeither/either.go

@@ -22,8 +22,8 @@ import (
 	O "github.com/IBM/fp-go/option"
 )
 
-func FromOption[E, A, HKTEA any](fromEither func(ET.Either[E, A]) HKTEA, onNone func() E) func(ma O.Option[A]) HKTEA {
-	return F.Flow2(ET.FromOption[E, A](onNone), fromEither)
+func FromOption[A, HKTEA, E any](fromEither func(ET.Either[E, A]) HKTEA, onNone func() E) func(ma O.Option[A]) HKTEA {
+	return F.Flow2(ET.FromOption[A](onNone), fromEither)
 }
 
 func FromPredicate[E, A, HKTEA any](fromEither func(ET.Either[E, A]) HKTEA, pred func(A) bool, onFalse func(A) E) func(A) HKTEA {
@@ -45,7 +45,7 @@ func MonadFromOption[E, A, HKTEA any](
 	)
 }
 
-func FromOptionK[E, A, B, HKTEB any](
+func FromOptionK[A, E, B, HKTEB any](
 	fromEither func(ET.Either[E, B]) HKTEB,
 	onNone func() E) func(f func(A) O.Option[B]) func(A) HKTEB {
 	// helper
@@ -65,7 +65,7 @@ func ChainOptionK[A, E, B, HKTEA, HKTEB any](
 	fromEither func(ET.Either[E, B]) HKTEB,
 	onNone func() E,
 ) func(f func(A) O.Option[B]) func(ma HKTEA) HKTEB {
-	return F.Flow2(FromOptionK[E, A](fromEither, onNone), F.Bind1st(F.Bind2nd[HKTEA, func(A) HKTEB, HKTEB], mchain))
+	return F.Flow2(FromOptionK[A](fromEither, onNone), F.Bind1st(F.Bind2nd[HKTEA, func(A) HKTEB, HKTEB], mchain))
 }
 
 func MonadChainFirstEitherK[A, E, B, HKTEA, HKTEB any](

internal/functor/flap.go

@@ -0,0 +1,37 @@
+// Copyright (c) 2023 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 functor
+
+func MonadFlap[FAB ~func(A) B, A, B, HKTFAB, HKTB any](
+	fmap func(HKTFAB, func(FAB) B) HKTB,
+
+	fab HKTFAB,
+	a A,
+) HKTB {
+	return fmap(fab, func(f FAB) B {
+		return f(a)
+	})
+}
+
+func Flap[FAB ~func(A) B, A, B, HKTFAB, HKTB any](
+	fmap func(HKTFAB, func(FAB) B) HKTB,
+
+	a A,
+) func(HKTFAB) HKTB {
+	return func(fab HKTFAB) HKTB {
+		return MonadFlap(fmap, fab, a)
+	}
+}

internal/lazy/memoize.go

@@ -0,0 +1,34 @@
+// Copyright (c) 2023 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 lazy
+
+import "sync"
+
+// Memoize computes the value of the provided IO monad lazily but exactly once
+func Memoize[GA ~func() A, A any](ma GA) GA {
+	// synchronization primitives
+	var once sync.Once
+	var result A
+	// callback
+	gen := func() {
+		result = ma()
+	}
+	// returns our memoized wrapper
+	return func() A {
+		once.Do(gen)
+		return result
+	}
+}

io/gen.go

@@ -1,6 +1,6 @@
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-08-17 22:59:10.1040409 +0200 CEST m=+0.089470201
+// 2023-09-12 13:44:27.9813739 +0200 CEST m=+0.011088001
 
 package io
 

io/generic/gen.go

@@ -1,6 +1,6 @@
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-08-17 22:59:10.1132645 +0200 CEST m=+0.098693801
+// 2023-09-12 13:44:27.9813739 +0200 CEST m=+0.011088001
 package generic
 
 import (

io/generic/io.go

@@ -16,11 +16,12 @@
 package generic
 
 import (
-	"sync"
 	"time"
 
 	F "github.com/IBM/fp-go/function"
 	C "github.com/IBM/fp-go/internal/chain"
+	FC "github.com/IBM/fp-go/internal/functor"
+	L "github.com/IBM/fp-go/internal/lazy"
 )
 
 // type IO[A any] = func() A
@@ -119,18 +120,7 @@ func Flatten[GA ~func() A, GAA ~func() GA, A any](mma GAA) GA {
 
 // Memoize computes the value of the provided IO monad lazily but exactly once
 func Memoize[GA ~func() A, A any](ma GA) GA {
-	// synchronization primitives
-	var once sync.Once
-	var result A
-	// callback
-	gen := func() {
-		result = ma()
-	}
-	// returns our memoized wrapper
-	return func() A {
-		once.Do(gen)
-		return result
-	}
+	return L.Memoize[GA, A](ma)
 }
 
 // Delay creates an operation that passes in the value after some delay
@@ -154,3 +144,11 @@ func Defer[GA ~func() A, A any](gen func() GA) GA {
 		return gen()()
 	})
 }
+
+func MonadFlap[FAB ~func(A) B, GFAB ~func() FAB, GB ~func() B, A, B any](fab GFAB, a A) GB {
+	return FC.MonadFlap(MonadMap[GFAB, GB, FAB, B], fab, a)
+}
+
+func Flap[FAB ~func(A) B, GFAB ~func() FAB, GB ~func() B, A, B any](a A) func(GFAB) GB {
+	return F.Bind2nd(MonadFlap[FAB, GFAB, GB, A, B], a)
+}

io/generic/traverse.go

@@ -42,6 +42,16 @@ func TraverseArray[GB ~func() B, GBS ~func() BBS, AAS ~[]A, BBS ~[]B, A, B any](
 	)
 }
 
+func TraverseArrayWithIndex[GB ~func() B, GBS ~func() BBS, AAS ~[]A, BBS ~[]B, A, B any](f func(int, A) GB) func(AAS) GBS {
+	return RA.TraverseWithIndex[AAS](
+		Of[GBS, BBS],
+		Map[GBS, func() func(B) BBS, BBS, func(B) BBS],
+		Ap[GBS, func() func(B) BBS, GB],
+
+		f,
+	)
+}
+
 func SequenceArray[GA ~func() A, GAS ~func() AAS, AAS ~[]A, GAAS ~[]GA, A any](tas GAAS) GAS {
 	return MonadTraverseArray[GA, GAS](tas, F.Identity[GA])
 }
@@ -66,6 +76,16 @@ func TraverseRecord[GB ~func() B, GBS ~func() MB, MA ~map[K]A, MB ~map[K]B, K co
 	)
 }
 
+// TraverseRecordWithIndex transforms a record using an IO transform an IO of a record
+func TraverseRecordWithIndex[GB ~func() B, GBS ~func() MB, MA ~map[K]A, MB ~map[K]B, K comparable, A, B any](f func(K, A) GB) func(MA) GBS {
+	return RR.TraverseWithIndex[MA](
+		Of[GBS, MB],
+		Map[GBS, func() func(B) MB, MB, func(B) MB],
+		Ap[GBS, func() func(B) MB, GB],
+		f,
+	)
+}
+
 func SequenceRecord[GA ~func() A, GAS ~func() AAS, AAS ~map[K]A, GAAS ~map[K]GA, K comparable, A any](tas GAAS) GAS {
 	return MonadTraverseRecord[GA, GAS](tas, F.Identity[GA])
 }

io/io.go

@@ -84,7 +84,7 @@ func Flatten[A any](mma IO[IO[A]]) IO[A] {
 	return G.Flatten(mma)
 }
 
-// Memoize computes the value of the provided IO monad lazily but exactly once
+// Memoize computes the value of the provided [IO] monad lazily but exactly once
 func Memoize[A any](ma IO[A]) IO[A] {
 	return G.Memoize(ma)
 }
@@ -138,3 +138,11 @@ var Now = G.Now[IO[time.Time]]()
 func Defer[A any](gen func() IO[A]) IO[A] {
 	return G.Defer[IO[A]](gen)
 }
+
+func MonadFlap[B, A any](fab IO[func(A) B], a A) IO[B] {
+	return G.MonadFlap[func(A) B, IO[func(A) B], IO[B], A, B](fab, a)
+}
+
+func Flap[FAB ~func(A) B, GFAB ~func() FAB, GB ~func() B, A, B any](a A) func(IO[func(A) B]) IO[B] {
+	return G.Flap[func(A) B, IO[func(A) B], IO[B], A, B](a)
+}

io/traverse.go

@@ -29,6 +29,12 @@ func TraverseArray[A, B any](f func(A) IO[B]) func([]A) IO[[]B] {
 	return G.TraverseArray[IO[B], IO[[]B], []A](f)
 }
 
+// TraverseArrayWithIndex applies a function returning an [IO] to all elements in an array and the
+// transforms this into an [IO] of that array
+func TraverseArrayWithIndex[A, B any](f func(int, A) IO[B]) func([]A) IO[[]B] {
+	return G.TraverseArrayWithIndex[IO[B], IO[[]B], []A](f)
+}
+
 // SequenceArray converts an array of [IO] to an [IO] of an array
 func SequenceArray[A any](tas []IO[A]) IO[[]A] {
 	return G.SequenceArray[IO[A], IO[[]A]](tas)
@@ -38,12 +44,18 @@ func MonadTraverseRecord[K comparable, A, B any](tas map[K]A, f func(A) IO[B]) I
 	return G.MonadTraverseRecord[IO[B], IO[map[K]B]](tas, f)
 }
 
-// TraverseArray applies a function returning an [IO] to all elements in a record and the
+// TraverseRecord applies a function returning an [IO] to all elements in a record and the
 // transforms this into an [IO] of that record
 func TraverseRecord[K comparable, A, B any](f func(A) IO[B]) func(map[K]A) IO[map[K]B] {
 	return G.TraverseRecord[IO[B], IO[map[K]B], map[K]A](f)
 }
 
+// TraverseRecordWithIndex applies a function returning an [IO] to all elements in a record and the
+// transforms this into an [IO] of that record
+func TraverseRecordWithIndex[K comparable, A, B any](f func(K, A) IO[B]) func(map[K]A) IO[map[K]B] {
+	return G.TraverseRecordWithIndex[IO[B], IO[map[K]B], map[K]A](f)
+}
+
 // SequenceRecord converts a record of [IO] to an [IO] of a record
 func SequenceRecord[K comparable, A any](tas map[K]IO[A]) IO[map[K]A] {
 	return G.SequenceRecord[IO[A], IO[map[K]A]](tas)

ioeither/file/file.go

@@ -16,6 +16,7 @@
 package file
 
 import (
+	"io"
 	"os"
 
 	IOE "github.com/IBM/fp-go/ioeither"
@@ -45,3 +46,10 @@ func Remove(name string) IOE.IOEither[error, string] {
 		return name, os.Remove(name)
 	})
 }
+
+// Close closes an object
+func Close[C io.Closer](c C) IOE.IOEither[error, any] {
+	return IOE.TryCatchError(func() (any, error) {
+		return c, c.Close()
+	})
+}

ioeither/file/readall.go

@@ -31,7 +31,7 @@ func onReadAll[R io.Reader](r R) IOE.IOEither[error, []byte] {
 func ReadAll[R io.ReadCloser](acquire IOE.IOEither[error, R]) IOE.IOEither[error, []byte] {
 	return IOE.WithResource[[]byte](
 		acquire,
-		onClose[R])(
+		Close[R])(
 		onReadAll[R],
 	)
 }

ioeither/file/tempfile.go

@@ -18,7 +18,6 @@ package file
 import (
 	"os"
 
-	FL "github.com/IBM/fp-go/file"
 	F "github.com/IBM/fp-go/function"
 	IO "github.com/IBM/fp-go/io"
 	IOF "github.com/IBM/fp-go/io/file"
@@ -33,7 +32,7 @@ var (
 	// destroy handler
 	onReleaseTempFile = F.Flow4(
 		IOF.Close[*os.File],
-		IO.Map(FL.GetName),
+		IO.Map((*os.File).Name),
 		IOE.FromIO[error, string],
 		IOE.Chain(Remove),
 	)

ioeither/file/tempfile_test.go

@@ -38,7 +38,7 @@ func TestWithTempFileOnClosedFile(t *testing.T) {
 		return F.Pipe2(
 			f,
 			onWriteAll[*os.File]([]byte("Carsten")),
-			IOE.ChainFirst(F.Constant1[[]byte](onClose(f))),
+			IOE.ChainFirst(F.Constant1[[]byte](Close(f))),
 		)
 	})
 

ioeither/file/write.go

@@ -36,7 +36,7 @@ func WriteAll[W io.WriteCloser](data []byte) func(acquire IOE.IOEither[error, W]
 	return func(onCreate IOE.IOEither[error, W]) IOE.IOEither[error, []byte] {
 		return IOE.WithResource[[]byte](
 			onCreate,
-			onClose[W])(
+			Close[W])(
 			onWrite,
 		)
 	}
@@ -46,5 +46,5 @@ func WriteAll[W io.WriteCloser](data []byte) func(acquire IOE.IOEither[error, W]
 func Write[R any, W io.WriteCloser](acquire IOE.IOEither[error, W]) func(use func(W) IOE.IOEither[error, R]) IOE.IOEither[error, R] {
 	return IOE.WithResource[R](
 		acquire,
-		onClose[W])
+		Close[W])
 }

ioeither/gen.go

@@ -1,6 +1,6 @@
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-08-17 22:59:12.0033119 +0200 CEST m=+0.096740401
+// 2023-09-12 13:44:29.4935658 +0200 CEST m=+0.015377401
 
 package ioeither
 

ioeither/generic/gen.go

@@ -1,6 +1,6 @@
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-08-17 22:59:12.0246635 +0200 CEST m=+0.118092001
+// 2023-09-12 13:44:29.4935658 +0200 CEST m=+0.015377401
 package generic
 
 import (

ioeither/generic/ioeither.go

@@ -290,3 +290,17 @@ func FromImpure[GA ~func() ET.Either[E, any], IMP ~func(), E any](f IMP) GA {
 func Defer[GEA ~func() ET.Either[E, A], E, A any](gen func() GEA) GEA {
 	return IO.Defer[GEA](gen)
 }
+
+func MonadAlt[LAZY ~func() GIOA, GIOA ~func() ET.Either[E, A], E, A any](first GIOA, second LAZY) GIOA {
+	return eithert.MonadAlt(
+		IO.Of[GIOA],
+		IO.MonadChain[GIOA, GIOA],
+
+		first,
+		second,
+	)
+}
+
+func Alt[LAZY ~func() GIOA, GIOA ~func() ET.Either[E, A], E, A any](second LAZY) func(GIOA) GIOA {
+	return F.Bind2nd(MonadAlt[LAZY], second)
+}

ioeither/generic/monoid.go

@@ -0,0 +1,54 @@
+//   Copyright (c) 2023 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 (
+	ET "github.com/IBM/fp-go/either"
+	M "github.com/IBM/fp-go/monoid"
+)
+
+func ApplicativeMonoid[GEA ~func() ET.Either[E, A], GEFA ~func() ET.Either[E, func(A) A], E, A any](
+	m M.Monoid[A],
+) M.Monoid[GEA] {
+	return M.ApplicativeMonoid(
+		MonadOf[GEA],
+		MonadMap[GEA, GEFA],
+		MonadAp[GEA, GEFA, GEA],
+		m,
+	)
+}
+
+func ApplicativeMonoidSeq[GEA ~func() ET.Either[E, A], GEFA ~func() ET.Either[E, func(A) A], E, A any](
+	m M.Monoid[A],
+) M.Monoid[GEA] {
+	return M.ApplicativeMonoid(
+		MonadOf[GEA],
+		MonadMap[GEA, GEFA],
+		MonadApSeq[GEA, GEFA, GEA],
+		m,
+	)
+}
+
+func ApplicativeMonoidPar[GEA ~func() ET.Either[E, A], GEFA ~func() ET.Either[E, func(A) A], E, A any](
+	m M.Monoid[A],
+) M.Monoid[GEA] {
+	return M.ApplicativeMonoid(
+		MonadOf[GEA],
+		MonadMap[GEA, GEFA],
+		MonadApPar[GEA, GEFA, GEA],
+		m,
+	)
+}

ioeither/generic/semigroup.go

@@ -0,0 +1,27 @@
+//   Copyright (c) 2023 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 (
+	ET "github.com/IBM/fp-go/either"
+	S "github.com/IBM/fp-go/semigroup"
+)
+
+func AltSemigroup[GIOA ~func() ET.Either[E, A], E, A any]() S.Semigroup[GIOA] {
+	return S.AltSemigroup(
+		MonadAlt[func() GIOA],
+	)
+}

ioeither/generic/traverse.go

@@ -45,6 +45,29 @@ func TraverseArray[GB ~func() ET.Either[E, B], GBS ~func() ET.Either[E, BBS], AA
 	)
 }
 
+// MonadTraverseArrayWithIndex transforms an array
+func MonadTraverseArrayWithIndex[GB ~func() ET.Either[E, B], GBS ~func() ET.Either[E, BBS], AAS ~[]A, BBS ~[]B, E, A, B any](tas AAS, f func(int, A) GB) GBS {
+	return RA.MonadTraverseWithIndex[AAS](
+		Of[GBS, E, BBS],
+		Map[GBS, func() ET.Either[E, func(B) BBS], E, BBS, func(B) BBS],
+		Ap[GBS, func() ET.Either[E, func(B) BBS], GB],
+
+		tas,
+		f,
+	)
+}
+
+// TraverseArrayWithIndex transforms an array
+func TraverseArrayWithIndex[GB ~func() ET.Either[E, B], GBS ~func() ET.Either[E, BBS], AAS ~[]A, BBS ~[]B, E, A, B any](f func(int, A) GB) func(AAS) GBS {
+	return RA.TraverseWithIndex[AAS](
+		Of[GBS, E, BBS],
+		Map[GBS, func() ET.Either[E, func(B) BBS], E, BBS, func(B) BBS],
+		Ap[GBS, func() ET.Either[E, func(B) BBS], GB],
+
+		f,
+	)
+}
+
 // SequenceArray converts a homogeneous sequence of either into an either of sequence
 func SequenceArray[GA ~func() ET.Either[E, A], GAS ~func() ET.Either[E, AAS], AAS ~[]A, GAAS ~[]GA, E, A any](tas GAAS) GAS {
 	return MonadTraverseArray[GA, GAS](tas, F.Identity[GA])
@@ -73,6 +96,17 @@ func TraverseRecord[GB ~func() ET.Either[E, B], GBS ~func() ET.Either[E, BBS], A
 	)
 }
 
+// TraverseRecordWithIndex transforms an array
+func TraverseRecordWithIndex[GB ~func() ET.Either[E, B], GBS ~func() ET.Either[E, BBS], AAS ~map[K]A, BBS ~map[K]B, K comparable, E, A, B any](f func(K, A) GB) func(AAS) GBS {
+	return RR.TraverseWithIndex[AAS](
+		Of[GBS, E, BBS],
+		Map[GBS, func() ET.Either[E, func(B) BBS], E, BBS, func(B) BBS],
+		Ap[GBS, func() ET.Either[E, func(B) BBS], GB],
+
+		f,
+	)
+}
+
 // SequenceRecord converts a homogeneous sequence of either into an either of sequence
 func SequenceRecord[GA ~func() ET.Either[E, A], GAS ~func() ET.Either[E, AAS], AAS ~map[K]A, GAAS ~map[K]GA, K comparable, E, A any](tas GAAS) GAS {
 	return MonadTraverseRecord[GA, GAS](tas, F.Identity[GA])

ioeither/ioeither.go

@@ -19,6 +19,7 @@ import (
 	ET "github.com/IBM/fp-go/either"
 	I "github.com/IBM/fp-go/io"
 	G "github.com/IBM/fp-go/ioeither/generic"
+	L "github.com/IBM/fp-go/lazy"
 	O "github.com/IBM/fp-go/option"
 )
 
@@ -74,10 +75,20 @@ func ChainIOK[E, A, B any](f func(A) I.IO[B]) func(IOEither[E, A]) IOEither[E, B
 	return G.ChainIOK[IOEither[E, A], IOEither[E, B]](f)
 }
 
+func ChainLazyK[E, A, B any](f func(A) L.Lazy[B]) func(IOEither[E, A]) IOEither[E, B] {
+	return G.ChainIOK[IOEither[E, A], IOEither[E, B]](f)
+}
+
+// FromIO creates an [IOEither] from an [IO] instance, invoking [IO] for each invocation of [IOEither]
 func FromIO[E, A any](mr I.IO[A]) IOEither[E, A] {
 	return G.FromIO[IOEither[E, A]](mr)
 }
 
+// FromLazy creates an [IOEither] from a [Lazy] instance, invoking [Lazy] for each invocation of [IOEither]
+func FromLazy[E, A any](mr L.Lazy[A]) IOEither[E, A] {
+	return G.FromIO[IOEither[E, A]](mr)
+}
+
 func MonadMap[E, A, B any](fa IOEither[E, A], f func(A) B) IOEither[E, B] {
 	return G.MonadMap[IOEither[E, A], IOEither[E, B]](fa, f)
 }
@@ -166,27 +177,27 @@ func MonadChainTo[E, A, B any](fa IOEither[E, A], fb IOEither[E, B]) IOEither[E,
 	return G.MonadChainTo(fa, fb)
 }
 
-// ChainTo composes to the second monad ignoring the return value of the first
+// ChainTo composes to the second [IOEither] monad ignoring the return value of the first
 func ChainTo[E, A, B any](fb IOEither[E, B]) func(IOEither[E, A]) IOEither[E, B] {
 	return G.ChainTo[IOEither[E, A]](fb)
 }
 
-// MonadChainFirst runs the monad returned by the function but returns the result of the original monad
+// MonadChainFirst runs the [IOEither] monad returned by the function but returns the result of the original monad
 func MonadChainFirst[E, A, B any](ma IOEither[E, A], f func(A) IOEither[E, B]) IOEither[E, A] {
 	return G.MonadChainFirst(ma, f)
 }
 
-// ChainFirst runs the monad returned by the function but returns the result of the original monad
+// ChainFirst runs the [IOEither] monad returned by the function but returns the result of the original monad
 func ChainFirst[E, A, B any](f func(A) IOEither[E, B]) func(IOEither[E, A]) IOEither[E, A] {
 	return G.ChainFirst[IOEither[E, A]](f)
 }
 
-// MonadChainFirstIOK runs the monad returned by the function but returns the result of the original monad
+// MonadChainFirstIOK runs [IO] the monad returned by the function but returns the result of the original monad
 func MonadChainFirstIOK[E, A, B any](ma IOEither[E, A], f func(A) I.IO[B]) IOEither[E, A] {
 	return G.MonadChainFirstIOK(ma, f)
 }
 
-// ChainFirsIOKt runs the monad returned by the function but returns the result of the original monad
+// ChainFirstIOK runs the [IO] monad returned by the function but returns the result of the original monad
 func ChainFirstIOK[E, A, B any](f func(A) I.IO[B]) func(IOEither[E, A]) IOEither[E, A] {
 	return G.ChainFirstIOK[IOEither[E, A]](f)
 }
@@ -207,6 +218,16 @@ func FromImpure[E any](f func()) IOEither[E, any] {
 }
 
 // Defer creates an IO by creating a brand new IO via a generator function, each time
-func Defer[E, A any](gen func() IOEither[E, A]) IOEither[E, A] {
+func Defer[E, A any](gen L.Lazy[IOEither[E, A]]) IOEither[E, A] {
 	return G.Defer[IOEither[E, A]](gen)
 }
+
+// MonadAlt identifies an associative operation on a type constructor
+func MonadAlt[E, A any](first IOEither[E, A], second L.Lazy[IOEither[E, A]]) IOEither[E, A] {
+	return G.MonadAlt(first, second)
+}
+
+// Alt identifies an associative operation on a type constructor
+func Alt[E, A any](second L.Lazy[IOEither[E, A]]) func(IOEither[E, A]) IOEither[E, A] {
+	return G.Alt(second)
+}

ioeither/monoid.go

@@ -0,0 +1,42 @@
+//   Copyright (c) 2023 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 (
+	G "github.com/IBM/fp-go/ioeither/generic"
+	M "github.com/IBM/fp-go/monoid"
+)
+
+// ApplicativeMonoid returns a [Monoid] that concatenates [IOEither] instances via their applicative
+func ApplicativeMonoid[E, A any](
+	m M.Monoid[A],
+) M.Monoid[IOEither[E, A]] {
+	return G.ApplicativeMonoid[IOEither[E, A], IOEither[E, func(A) A]](m)
+}
+
+// ApplicativeMonoid returns a [Monoid] that concatenates [IOEither] instances via their applicative
+func ApplicativeMonoidSeq[E, A any](
+	m M.Monoid[A],
+) M.Monoid[IOEither[E, A]] {
+	return G.ApplicativeMonoidSeq[IOEither[E, A], IOEither[E, func(A) A]](m)
+}
+
+// ApplicativeMonoid returns a [Monoid] that concatenates [IOEither] instances via their applicative
+func ApplicativeMonoidPar[E, A any](
+	m M.Monoid[A],
+) M.Monoid[IOEither[E, A]] {
+	return G.ApplicativeMonoid[IOEither[E, A], IOEither[E, func(A) A]](m)
+}

ioeither/monoid_test.go

@@ -0,0 +1,42 @@
+//   Copyright (c) 2023 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 (
+	"fmt"
+	"testing"
+
+	E "github.com/IBM/fp-go/either"
+	S "github.com/IBM/fp-go/string"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestApplicativeMonoid(t *testing.T) {
+	m := ApplicativeMonoid[error](S.Monoid)
+
+	// good cases
+	assert.Equal(t, E.Of[error]("ab"), m.Concat(Of[error]("a"), Of[error]("b"))())
+	assert.Equal(t, E.Of[error]("a"), m.Concat(Of[error]("a"), m.Empty())())
+	assert.Equal(t, E.Of[error]("b"), m.Concat(m.Empty(), Of[error]("b"))())
+
+	// bad cases
+	e1 := fmt.Errorf("e1")
+	e2 := fmt.Errorf("e1")
+
+	assert.Equal(t, E.Left[string](e1), m.Concat(Left[string](e1), Of[error]("b"))())
+	assert.Equal(t, E.Left[string](e1), m.Concat(Left[string](e1), Left[string](e2))())
+	assert.Equal(t, E.Left[string](e2), m.Concat(Of[error]("a"), Left[string](e2))())
+}

ioeither/semigroup.go

@@ -0,0 +1,26 @@
+// Copyright (c) 2023 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 (
+	G "github.com/IBM/fp-go/ioeither/generic"
+	S "github.com/IBM/fp-go/semigroup"
+)
+
+// AltSemigroup is a [Semigroup] that tries the first item and then the second one using an alternative
+func AltSemigroup[E, A any]() S.Semigroup[IOEither[E, A]] {
+	return G.AltSemigroup[IOEither[E, A]]()
+}

ioeither/traverse.go

@@ -24,6 +24,11 @@ func TraverseArray[E, A, B any](f func(A) IOEither[E, B]) func([]A) IOEither[E,
 	return G.TraverseArray[IOEither[E, B], IOEither[E, []B], []A](f)
 }
 
+// TraverseArrayWithIndex transforms an array
+func TraverseArrayWithIndex[E, A, B any](f func(int, A) IOEither[E, B]) func([]A) IOEither[E, []B] {
+	return G.TraverseArrayWithIndex[IOEither[E, B], IOEither[E, []B], []A](f)
+}
+
 // SequenceArray converts a homogeneous sequence of either into an either of sequence
 func SequenceArray[E, A any](ma []IOEither[E, A]) IOEither[E, []A] {
 	return G.SequenceArray[IOEither[E, A], IOEither[E, []A]](ma)
@@ -34,6 +39,11 @@ func TraverseRecord[K comparable, E, A, B any](f func(A) IOEither[E, B]) func(ma
 	return G.TraverseRecord[IOEither[E, B], IOEither[E, map[K]B], map[K]A](f)
 }
 
+// TraverseRecordWithIndex transforms a record
+func TraverseRecordWithIndex[K comparable, E, A, B any](f func(K, A) IOEither[E, B]) func(map[K]A) IOEither[E, map[K]B] {
+	return G.TraverseRecordWithIndex[IOEither[E, B], IOEither[E, map[K]B], map[K]A](f)
+}
+
 // SequenceRecord converts a homogeneous sequence of either into an either of sequence
 func SequenceRecord[K comparable, E, A any](ma map[K]IOEither[E, A]) IOEither[E, map[K]A] {
 	return G.SequenceRecord[IOEither[E, A], IOEither[E, map[K]A]](ma)

ioeither/traverse_test.go

@@ -0,0 +1,37 @@
+// Copyright (c) 2023 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 (
+	"fmt"
+	"testing"
+
+	A "github.com/IBM/fp-go/array"
+	E "github.com/IBM/fp-go/either"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestTraverseArray(t *testing.T) {
+
+	src := A.From("A", "B")
+
+	trfrm := TraverseArrayWithIndex(func(idx int, data string) IOEither[error, string] {
+		return Of[error](fmt.Sprintf("idx: %d, data: %s", idx, data))
+	})
+
+	assert.Equal(t, E.Of[error](A.From("idx: 0, data: A", "idx: 1, data: B")), trfrm(src)())
+
+}

iooption/array.go

@@ -24,6 +24,11 @@ func TraverseArray[A, B any](f func(A) IOOption[B]) func([]A) IOOption[[]B] {
 	return G.TraverseArray[IOOption[B], IOOption[[]B], []A](f)
 }
 
+// TraverseArrayWithIndex transforms an array
+func TraverseArrayWithIndex[A, B any](f func(int, A) IOOption[B]) func([]A) IOOption[[]B] {
+	return G.TraverseArrayWithIndex[IOOption[B], IOOption[[]B], []A](f)
+}
+
 // SequenceArray converts a homogeneous sequence of either into an either of sequence
 func SequenceArray[A any](ma []IOOption[A]) IOOption[[]A] {
 	return G.SequenceArray[IOOption[A], IOOption[[]A], []IOOption[A], []A, A](ma)

iooption/gen.go

@@ -1,6 +1,6 @@
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-08-17 22:59:14.0582736 +0200 CEST m=+0.248503201
+// 2023-09-12 13:44:32.1514823 +0200 CEST m=+0.098931001
 
 package iooption
 

iooption/generic/gen.go

@@ -1,6 +1,6 @@
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-08-17 22:59:14.0642289 +0200 CEST m=+0.254458501
+// 2023-09-12 13:44:32.1546277 +0200 CEST m=+0.102076401
 package generic
 
 import (

iooption/generic/iooption.go

@@ -18,6 +18,7 @@ package generic
 import (
 	"time"
 
+	ET "github.com/IBM/fp-go/either"
 	F "github.com/IBM/fp-go/function"
 	FI "github.com/IBM/fp-go/internal/fromio"
 	"github.com/IBM/fp-go/internal/optiont"
@@ -55,6 +56,21 @@ func FromOption[GA ~func() O.Option[A], A any](o O.Option[A]) GA {
 	return IO.Of[GA](o)
 }
 
+func FromEither[GA ~func() O.Option[A], E, A any](e ET.Either[E, A]) GA {
+	return F.Pipe2(
+		e,
+		ET.ToOption[E, A],
+		FromOption[GA],
+	)
+}
+
+func FromIOEither[GA ~func() O.Option[A], GEA ~func() ET.Either[E, A], E, A any](ioe GEA) GA {
+	return F.Pipe1(
+		ioe,
+		IO.Map[GEA, GA](ET.ToOption[E, A]),
+	)
+}
+
 func MonadMap[GA ~func() O.Option[A], GB ~func() O.Option[B], A, B any](fa GA, f func(A) B) GB {
 	return optiont.MonadMap(IO.MonadMap[GA, GB, O.Option[A], O.Option[B]], fa, f)
 }

iooption/generic/traverse.go

@@ -28,6 +28,13 @@ func TraverseArray[TB ~func() O.Option[B], TBS ~func() O.Option[GB], GA ~[]A, GB
 	)
 }
 
+func TraverseArrayWithIndex[TB ~func() O.Option[B], TBS ~func() O.Option[GB], GA ~[]A, GB ~[]B, A, B any](f func(int, A) TB) func(GA) TBS {
+	return F.Flow2(
+		I.TraverseArrayWithIndex[TB, func() []O.Option[B], GA](f),
+		I.Map[func() []O.Option[B], TBS](O.SequenceArrayG[GB, []O.Option[B], B]),
+	)
+}
+
 func SequenceArray[TB ~func() O.Option[B], TBS ~func() O.Option[GB], GA ~[]TB, GB ~[]B, A, B any](ma GA) TBS {
 	return TraverseArray[TB, TBS, GA](F.Identity[TB])(ma)
 }

iooption/iooption.go

@@ -16,7 +16,9 @@
 package iooption
 
 import (
+	ET "github.com/IBM/fp-go/either"
 	I "github.com/IBM/fp-go/io"
+	IOE "github.com/IBM/fp-go/ioeither"
 	G "github.com/IBM/fp-go/iooption/generic"
 	O "github.com/IBM/fp-go/option"
 )
@@ -117,7 +119,7 @@ func Memoize[A any](ma IOOption[A]) IOOption[A] {
 	return G.Memoize(ma)
 }
 
-// Fold convers an IOOption into an IO
+// Fold convers an [IOOption] into an [IO]
 func Fold[A, B any](onNone func() I.IO[B], onSome func(A) I.IO[B]) func(IOOption[A]) I.IO[B] {
 	return G.Fold[IOOption[A]](onNone, onSome)
 }
@@ -126,3 +128,13 @@ func Fold[A, B any](onNone func() I.IO[B], onSome func(A) I.IO[B]) func(IOOption
 func Defer[A any](gen func() IOOption[A]) IOOption[A] {
 	return G.Defer[IOOption[A]](gen)
 }
+
+// FromIOEither converts an [IOEither] into an [IOOption]
+func FromIOEither[E, A any](ioe IOE.IOEither[E, A]) IOOption[A] {
+	return G.FromIOEither[IOOption[A]](ioe)
+}
+
+// FromEither converts an [Either] into an [IOOption]
+func FromEither[E, A any](e ET.Either[E, A]) IOOption[A] {
+	return G.FromEither[IOOption[A]](e)
+}

iterator/stateless/benchmark_test.go

@@ -0,0 +1,65 @@
+// Copyright (c) 2023 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 stateless
+
+import (
+	"testing"
+
+	F "github.com/IBM/fp-go/function"
+)
+
+func BenchmarkMulti(b *testing.B) {
+	// run the Fib function b.N times
+	for n := 0; n < b.N; n++ {
+		single()
+	}
+}
+
+func single() int64 {
+
+	length := 10000
+	nums := make([]int, 0, length)
+	for i := 0; i < length; i++ {
+		nums = append(nums, i+1)
+	}
+
+	return F.Pipe6(
+		nums,
+		FromArray[int],
+		Filter(func(n int) bool {
+			return n%2 == 0
+		}),
+		Map(func(t int) int64 {
+			return int64(t)
+		}),
+		Filter(func(t int64) bool {
+			n := t
+			for n/10 != 0 {
+				if n%10 == 4 {
+					return false
+				}
+				n = n / 10
+			}
+			return true
+		}),
+		Map(func(t int64) int {
+			return int(t)
+		}),
+		Reduce(func(n int64, r int) int64 {
+			return n + int64(r)
+		}, int64(0)),
+	)
+}

iterator/stateless/generic/iterator.go

@@ -82,6 +82,7 @@ func Map[GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tuple2[GU,
 			m,
 		)
 	}
+
 	m = O.Map(T.Map2(recurse, f))
 
 	return recurse

lazy/lazy.go

@@ -83,7 +83,7 @@ func Flatten[A any](mma Lazy[Lazy[A]]) Lazy[A] {
 	return G.Flatten(mma)
 }
 
-// Memoize computes the value of the provided IO monad lazily but exactly once
+// Memoize computes the value of the provided [Lazy] monad lazily but exactly once
 func Memoize[A any](ma Lazy[A]) Lazy[A] {
 	return G.Memoize(ma)
 }

lazy/traverse.go

@@ -29,6 +29,12 @@ func TraverseArray[A, B any](f func(A) Lazy[B]) func([]A) Lazy[[]B] {
 	return G.TraverseArray[Lazy[B], Lazy[[]B], []A](f)
 }
 
+// TraverseArrayWithIndex applies a function returning an [IO] to all elements in an array and the
+// transforms this into an [IO] of that array
+func TraverseArrayWithIndex[A, B any](f func(int, A) Lazy[B]) func([]A) Lazy[[]B] {
+	return G.TraverseArrayWithIndex[Lazy[B], Lazy[[]B], []A](f)
+}
+
 // SequenceArray converts an array of [IO] to an [IO] of an array
 func SequenceArray[A any](tas []Lazy[A]) Lazy[[]A] {
 	return G.SequenceArray[Lazy[A], Lazy[[]A]](tas)
@@ -38,12 +44,18 @@ func MonadTraverseRecord[K comparable, A, B any](tas map[K]A, f func(A) Lazy[B])
 	return G.MonadTraverseRecord[Lazy[B], Lazy[map[K]B]](tas, f)
 }
 
-// TraverseArray applies a function returning an [IO] to all elements in a record and the
+// TraverseRecord applies a function returning an [IO] to all elements in a record and the
 // transforms this into an [IO] of that record
 func TraverseRecord[K comparable, A, B any](f func(A) Lazy[B]) func(map[K]A) Lazy[map[K]B] {
 	return G.TraverseRecord[Lazy[B], Lazy[map[K]B], map[K]A](f)
 }
 
+// TraverseRecord applies a function returning an [IO] to all elements in a record and the
+// transforms this into an [IO] of that record
+func TraverseRecordWithIndex[K comparable, A, B any](f func(K, A) Lazy[B]) func(map[K]A) Lazy[map[K]B] {
+	return G.TraverseRecordWithIndex[Lazy[B], Lazy[map[K]B], map[K]A](f)
+}
+
 // SequenceRecord converts a record of [IO] to an [IO] of a record
 func SequenceRecord[K comparable, A any](tas map[K]Lazy[A]) Lazy[map[K]A] {
 	return G.SequenceRecord[Lazy[A], Lazy[map[K]A]](tas)

monoid/alt.go

@@ -0,0 +1,58 @@
+// Copyright (c) 2023 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 monoid
+
+import (
+	S "github.com/IBM/fp-go/semigroup"
+)
+
+func AlternativeMonoid[A, HKTA, HKTFA any, LAZYHKTA ~func() HKTA](
+	fof func(A) HKTA,
+
+	fmap func(HKTA, func(A) func(A) A) HKTFA,
+	fap func(HKTFA, HKTA) HKTA,
+
+	falt func(HKTA, LAZYHKTA) HKTA,
+
+	m Monoid[A],
+
+) Monoid[HKTA] {
+
+	sg := ApplicativeMonoid(fof, fmap, fap, m)
+
+	return MakeMonoid(
+		func(first, second HKTA) HKTA {
+			snd := func() HKTA { return second }
+
+			return falt(sg.Concat(first, second), func() HKTA {
+				return falt(first, snd)
+			})
+		},
+		sg.Empty(),
+	)
+}
+
+func AltMonoid[HKTA any, LAZYHKTA ~func() HKTA](
+	fzero LAZYHKTA,
+	falt func(HKTA, LAZYHKTA) HKTA,
+
+) Monoid[HKTA] {
+
+	return MakeMonoid(
+		S.AltSemigroup(falt).Concat,
+		fzero(),
+	)
+}

monoid/apply.go

@@ -20,15 +20,15 @@ import (
 )
 
 func ApplicativeMonoid[A, HKTA, HKTFA any](
-	_of func(A) HKTA,
-	_map func(HKTA, func(A) func(A) A) HKTFA,
-	_ap func(HKTFA, HKTA) HKTA,
+	fof func(A) HKTA,
+	fmap func(HKTA, func(A) func(A) A) HKTFA,
+	fap func(HKTFA, HKTA) HKTA,
 
 	m Monoid[A],
 ) Monoid[HKTA] {
 
 	return MakeMonoid(
-		S.ApplySemigroup[A](_map, _ap, m).Concat,
-		_of(m.Empty()),
+		S.ApplySemigroup[A](fmap, fap, m).Concat,
+		fof(m.Empty()),
 	)
 }

number/integer/string.go

@@ -0,0 +1,23 @@
+// Copyright (c) 2023 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 integer
+
+import "strconv"
+
+var (
+	// ToString converts an integer to a string
+	ToString = strconv.Itoa
+)

number/magma.go

@@ -24,3 +24,9 @@ func MagmaSub[A Number]() M.Magma[A] {
 		return first - second
 	})
 }
+
+func MagmaDiv[A Number]() M.Magma[A] {
+	return M.MakeMagma(func(first A, second A) A {
+		return first / second
+	})
+}

number/monoid.go

@@ -19,6 +19,7 @@ import (
 	M "github.com/IBM/fp-go/monoid"
 )
 
+// MonoidSum is the [Monoid] that adds elements with a zero empty element
 func MonoidSum[A Number]() M.Monoid[A] {
 	s := SemigroupSum[A]()
 	return M.MakeMonoid(
@@ -26,3 +27,12 @@ func MonoidSum[A Number]() M.Monoid[A] {
 		0,
 	)
 }
+
+// MonoidProduct is the [Monoid] that multiplies elements with a one empty element
+func MonoidProduct[A Number]() M.Monoid[A] {
+	s := SemigroupProduct[A]()
+	return M.MakeMonoid(
+		s.Concat,
+		1,
+	)
+}

number/semigroup.go

@@ -24,3 +24,9 @@ func SemigroupSum[A Number]() S.Semigroup[A] {
 		return first + second
 	})
 }
+
+func SemigroupProduct[A Number]() S.Semigroup[A] {
+	return S.MakeSemigroup(func(first A, second A) A {
+		return first * second
+	})
+}

number/utils.go

@@ -24,16 +24,30 @@ type Number interface {
 }
 
 // Add is a curried function used to add two numbers
-func Add[T Number](left T) func(T) T {
-	return func(right T) T {
+func Add[T Number](right T) func(T) T {
+	return func(left T) T {
 		return left + right
 	}
 }
 
-// Mul is a curried function used to add two numbers
-func Mul[T Number](coeff T) func(T) T {
-	return func(value T) T {
-		return coeff * value
+// Sub is a curried function used to subtract two numbers
+func Sub[T Number](right T) func(T) T {
+	return func(left T) T {
+		return left - right
+	}
+}
+
+// Mul is a curried function used to multiply two numbers
+func Mul[T Number](right T) func(T) T {
+	return func(left T) T {
+		return left * right
+	}
+}
+
+// Div is a curried function used to divide two numbers
+func Div[T Number](right T) func(T) T {
+	return func(left T) T {
+		return left / right
 	}
 }
 

optics/iso/iso.go

@@ -67,7 +67,7 @@ func Modify[S, A any](f func(A) A) func(Iso[S, A]) func(S) S {
 }
 
 // Wrap wraps the value
-func Unwrap[S, A any](s S) func(Iso[S, A]) A {
+func Unwrap[A, S any](s S) func(Iso[S, A]) A {
 	return func(sa Iso[S, A]) A {
 		return sa.Get(s)
 	}
@@ -81,8 +81,8 @@ func Wrap[S, A any](a A) func(Iso[S, A]) S {
 }
 
 // From wraps the value
-func To[S, A any](s S) func(Iso[S, A]) A {
-	return Unwrap[S, A](s)
+func To[A, S any](s S) func(Iso[S, A]) A {
+	return Unwrap[A, S](s)
 }
 
 // To unwraps the value