fix: add WithLock to limit concurrency

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

.github/workflows/build.yml

@@ -17,22 +17,25 @@ on:
 env:
   # Currently no way to detect automatically
   DEFAULT_BRANCH: main
-  GO_VERSION: 1.20.5 # renovate: datasource=golang-version depName=golang
+  GO_VERSION: 1.20.6 # renovate: datasource=golang-version depName=golang
   NODE_VERSION: 18
   DRY_RUN: true
 
 jobs:
   build:
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        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 ${{env.GO_VERSION}}
+      - name: Set up go ${{ matrix.go-version }}
         uses: actions/setup-go@v4
         with:
-          go-version: ${{env.GO_VERSION}}
+          go-version: ${{ matrix.go-version }}
       -
         name: Tests
         run: |
@@ -52,7 +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
 

README.md

@@ -1,6 +1,6 @@
 # Functional programming library for golang
 
-**🚧 Work in progress! 🚧** Despite major version 1 because of https://github.com/semantic-release/semantic-release/issues/1507. Trying to not make breaking changes, but devil is in the details. 
+**🚧 Work in progress! 🚧** Despite major version 1 because of <https://github.com/semantic-release/semantic-release/issues/1507>. Trying to not make breaking changes, but devil is in the details.
 
 ![logo](resources/images/logo.png)
 
@@ -12,7 +12,9 @@ This library is strongly influenced by the awesome [fp-ts](https://github.com/gc
 go get github.com/IBM/fp-go
 ```
 
-Refer to the [samples](./samples/). 
+Refer to the [samples](./samples/).
+
+Find API documentation [here](https://pkg.go.dev/github.com/IBM/fp-go)
 
 ## Design Goal
 
@@ -65,7 +67,7 @@ This library aims to provide a set of data types and functions that make it easy
 
 #### 🧘🏽 Moderation is a virtue
 
-✔️ The library does not implement its own goroutines and also does not require any expensive synchronization primitives. Coordination of IO operations is implemented via atomic counters without additional primitives. 
+✔️ The library does not implement its own goroutines and also does not require any expensive synchronization primitives. Coordination of IO operations is implemented via atomic counters without additional primitives.
 
 #### 🧘🏽 Maintainability counts
 
@@ -73,6 +75,40 @@ This library aims to provide a set of data types and functions that make it easy
 
 The library itself also comprises many small functions, but it's admittedly harder to maintain than code that uses it. However this asymmetry is intended because it offloads complexity from users into a central component.
 
+## Comparison to Idiomatic Go
+
+In this section we discuss how the functional APIs differ from idiomatic go function signatures and how to convert back and forth.
+
+### Pure functions
+
+Pure functions are functions that take input parameters and that compute an output without changing any global state and without mutating the input parameters. They will always return the same output for the same input.
+
+#### Without Errors
+
+If your pure function does not return an error, the idiomatic signature is just fine and no changes are required.
+
+#### With Errors
+
+If your pure function can return an error, then it will have a `(T, error)` return value in idiomatic go. In functional style the return value is [Either[error, T]](https://pkg.go.dev/github.com/IBM/fp-go/either) because function composition is easier with such a return type. Use the `EitherizeXXX` methods in ["github.com/IBM/fp-go/either"](https://pkg.go.dev/github.com/IBM/fp-go/either) to convert from idiomatic to functional style and `UneitherizeXXX` to convert from functional to idiomatic style.
+
+### Effectful functions
+
+An effectful function (or function with a side effect) is one that changes data outside the scope of the function or that does not always produce the same output for the same input (because it depends on some external, mutable state). There is no special way in idiomatic go to identify such a function other than documentation. In functional style we represent them as functions that do not take an input but that produce an output. The base type for these functions is [IO[T]](https://pkg.go.dev/github.com/IBM/fp-go/io) because in many cases such functions represent `I/O` operations.
+
+#### Without Errors
+
+If your effectful function does not return an error, the functional signature is [IO[T]](https://pkg.go.dev/github.com/IBM/fp-go/io)
+
+#### With Errors
+
+If your effectful function can return an error, the functional signature is [IOEither[error, T]](https://pkg.go.dev/github.com/IBM/fp-go/ioeither). Use `EitherizeXXX` from ["github.com/IBM/fp-go/ioeither"](https://pkg.go.dev/github.com/IBM/fp-go/ioeither) to convert an idiomatic go function to functional style.
+
+### Go Context
+
+Functions that take a [context](https://pkg.go.dev/context) are per definition effectful because they depend on the context parameter that is designed to be mutable (it can e.g. be used to cancel a running operation). Furthermore in idiomatic go the parameter is typically passed as the first parameter to a function.
+
+In functional style we isolate the [context](https://pkg.go.dev/context) and represent the nature of the effectful function as an [IOEither[error, T]](https://pkg.go.dev/github.com/IBM/fp-go/ioeither). The resulting type is [ReaderIOEither[T]](https://pkg.go.dev/github.com/IBM/fp-go/context/readerioeither), a function taking a [context](https://pkg.go.dev/context) that returns a function without parameters returning an [Either[error, T]](https://pkg.go.dev/github.com/IBM/fp-go/either). Use the `EitherizeXXX` methods from ["github.com/IBM/fp-go/context/readerioeither"](https://pkg.go.dev/github.com/IBM/fp-go/context/readerioeither) to convert an idiomatic go function with a [context](https://pkg.go.dev/context) to functional style.
+
 ## Implementation Notes
 
 ### Generics
@@ -147,7 +183,7 @@ The `Map` operation for `ReaderIOEither` is defined as:
 func Map[R, E, A, B any](f func(A) B) func(fa ReaderIOEither[R, E, A]) ReaderIOEither[R, E, B]
 ```
 
-and in fact the equivalent operations for all other mondas follow the same pattern, we could try to introduce a new type for `ReaderIOEither` (without a parameter) as a HKT, e.g. like so (made-up syntax, does not work in go):
+and in fact the equivalent operations for all other monads follow the same pattern, we could try to introduce a new type for `ReaderIOEither` (without a parameter) as a HKT, e.g. like so (made-up syntax, does not work in go):
 
 ```go
 func Map[HKT, R, E, A, B any](f func(A) B) func(HKT[R, E, A]) HKT[R, E, B]
@@ -158,3 +194,14 @@ this would be the completely generic method signature for all possible monads. I
 This FP library addresses this by introducing the HKTs as individual types, e.g. `HKT[A]` would be represented as a new generic type `HKTA`. This loses the correlation to the type `A` but allows to implement generic algorithms, at the price of readability.
 
 For that reason these implementations are kept in the `internal` package. These are meant to be used by the library itself or by extensions, not by end users.
+
+## Map/Ap/Flap
+
+The following table lists the relationship between some selected operators
+
+| Opertator | Parameter        | Monad           | Result   |
+| --------  | ---------------- | --------------- | -------- |
+| Map       | `func(A) B`      | `HKT[A]`        | `HKT[B]` |
+| Chain     | `func(A) HKT[B]` | `HKT[A]` | `HKT[B]` |
+| Ap        | `HKT[A]`         | `HKT[func(A)B]` | `HKT[B]` |
+| Flap      | `A`              | `HKT[func(A)B]` | `HKT[B]` |

array/array.go

@@ -108,10 +108,16 @@ func MonadFilterMap[A, B any](fa []A, f func(a A) O.Option[B]) []B {
 	return G.MonadFilterMap[[]A, []B](fa, f)
 }
 
+// FilterChain maps an array with an iterating function that returns an [O.Option] and it keeps only the Some values discarding the Nones.
 func FilterMap[A, B any](f func(a A) O.Option[B]) func([]A) []B {
 	return G.FilterMap[[]A, []B](f)
 }
 
+// FilterChain maps an array with an iterating function that returns an [O.Option] of an array. It keeps only the Some values discarding the Nones and then flattens the result.
+func FilterChain[A, B any](f func(A) O.Option[[]B]) func([]A) []B {
+	return G.FilterChain[[]A](f)
+}
+
 func FilterMapRef[A, B any](pred func(a *A) bool, f func(a *A) B) func([]A) []B {
 	return func(fa []A) []B {
 		return filterMapRef(fa, pred, f)
@@ -230,14 +236,14 @@ func Intersperse[A any](middle A) func([]A) []A {
 }
 
 func Intercalate[A any](m M.Monoid[A]) func(A) func([]A) A {
-	concatAll := ConcatAll[A](m)(m.Empty())
+	concatAll := ConcatAll[A](m)
 	return func(middle A) func([]A) A {
 		return Match(m.Empty, F.Flow2(Intersperse(middle), concatAll))
 	}
 }
 
 func Flatten[A any](mma [][]A) []A {
-	return MonadChain(mma, F.Identity[[]A])
+	return G.Flatten(mma)
 }
 
 func Slice[A any](low, high int) func(as []A) []A {
@@ -280,3 +286,33 @@ func IsNonNil[A any](as []A) bool {
 func ConstNil[A any]() []A {
 	return array.ConstNil[[]A]()
 }
+
+func SliceRight[A any](start int) func([]A) []A {
+	return G.SliceRight[[]A](start)
+}
+
+func Copy[A any](b []A) []A {
+	return G.Copy(b)
+}
+
+// FoldMap maps and folds an array. Map the Array passing each value to the iterating function. Then fold the results using the provided Monoid.
+func FoldMap[A, B any](m M.Monoid[B]) func(func(A) B) func([]A) B {
+	return G.FoldMap[[]A](m)
+}
+
+// Fold folds the array using the provided Monoid.
+func Fold[A any](m M.Monoid[A]) func([]A) A {
+	return G.Fold[[]A](m)
+}
+
+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/array_test.go

@@ -16,6 +16,7 @@
 package array
 
 import (
+	"fmt"
 	"strings"
 	"testing"
 
@@ -142,3 +143,52 @@ func TestPartition(t *testing.T) {
 	assert.Equal(t, T.MakeTuple2(Empty[int](), Empty[int]()), Partition(pred)(Empty[int]()))
 	assert.Equal(t, T.MakeTuple2(From(1), From(3)), Partition(pred)(From(1, 3)))
 }
+
+func TestFilterChain(t *testing.T) {
+	src := From(1, 2, 3)
+
+	f := func(i int) O.Option[[]string] {
+		if i%2 != 0 {
+			return O.Of(From(fmt.Sprintf("a%d", i), fmt.Sprintf("b%d", i)))
+		}
+		return O.None[[]string]()
+	}
+
+	res := FilterChain(f)(src)
+
+	assert.Equal(t, From("a1", "b1", "a3", "b3"), res)
+}
+
+func TestFilterMap(t *testing.T) {
+	src := From(1, 2, 3)
+
+	f := func(i int) O.Option[string] {
+		if i%2 != 0 {
+			return O.Of(fmt.Sprintf("a%d", i))
+		}
+		return O.None[string]()
+	}
+
+	res := FilterMap(f)(src)
+
+	assert.Equal(t, From("a1", "a3"), res)
+}
+
+func TestFoldMap(t *testing.T) {
+	src := From("a", "b", "c")
+
+	fold := FoldMap[string](S.Monoid)(strings.ToUpper)
+
+	assert.Equal(t, "ABC", fold(src))
+}
+
+func ExampleFoldMap() {
+	src := From("a", "b", "c")
+
+	fold := FoldMap[string](S.Monoid)(strings.ToUpper)
+
+	fmt.Println(fold(src))
+
+	// Output: ABC
+
+}

array/examples_basic_test.go

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

array/examples_sort_test.go

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

array/generic/array.go

@@ -18,6 +18,8 @@ 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"
 )
@@ -27,6 +29,14 @@ func Of[GA ~[]A, A any](value A) GA {
 	return GA{value}
 }
 
+func Reduce[GA ~[]A, A, B any](fa GA, f func(B, A) B, initial B) B {
+	return array.Reduce(fa, f, initial)
+}
+
+func ReduceWithIndex[GA ~[]A, A, B any](fa GA, f func(int, B, A) B, initial B) B {
+	return array.ReduceWithIndex(fa, f, initial)
+}
+
 // From constructs an array from a set of variadic arguments
 func From[GA ~[]A, A any](data ...A) GA {
 	return data
@@ -104,6 +114,10 @@ func MonadMap[GA ~[]A, GB ~[]B, A, B any](as GA, f func(a A) B) GB {
 	return array.MonadMap[GA, GB](as, f)
 }
 
+func Map[GA ~[]A, GB ~[]B, A, B any](f func(a A) B) func(GA) GB {
+	return F.Bind2nd(MonadMap[GA, GB, A, B], f)
+}
+
 func Size[GA ~[]A, A any](as GA) int {
 	return len(as)
 }
@@ -118,6 +132,17 @@ func MonadFilterMap[GA ~[]A, GB ~[]B, A, B any](fa GA, f func(a A) O.Option[B])
 	return filterMap[GA, GB](fa, f)
 }
 
+func FilterChain[GA ~[]A, GB ~[]B, A, B any](f func(a A) O.Option[GB]) func(GA) GB {
+	return F.Flow2(
+		FilterMap[GA, []GB](f),
+		Flatten[[]GB],
+	)
+}
+
+func Flatten[GAA ~[]GA, GA ~[]A, A any](mma GAA) GA {
+	return MonadChain(mma, F.Identity[GA])
+}
+
 func FilterMap[GA ~[]A, GB ~[]B, A, B any](f func(a A) O.Option[B]) func(GA) GB {
 	return F.Bind2nd(MonadFilterMap[GA, GB, A, B], f)
 }
@@ -163,6 +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) {
@@ -180,3 +213,49 @@ func MatchLeft[AS ~[]A, A, B any](onEmpty func() B, onNonEmpty func(A, AS) B) fu
 		return onNonEmpty(as[0], as[1:])
 	}
 }
+
+func Slice[AS ~[]A, A any](start int, end int) func(AS) AS {
+	return func(a AS) AS {
+		return a[start:end]
+	}
+}
+
+func SliceRight[AS ~[]A, A any](start int) func(AS) AS {
+	return func(a AS) AS {
+		return a[start:]
+	}
+}
+
+func Copy[AS ~[]A, A any](b AS) AS {
+	buf := make(AS, len(b))
+	copy(buf, b)
+	return buf
+}
+
+func FoldMap[AS ~[]A, A, B any](m M.Monoid[B]) func(func(A) B) func(AS) B {
+	return func(f func(A) B) func(AS) B {
+		return func(as AS) B {
+			return array.Reduce(as, func(cur B, a A) B {
+				return m.Concat(cur, f(a))
+			}, m.Empty())
+		}
+	}
+}
+
+func Fold[AS ~[]A, A any](m M.Monoid[A]) func(AS) A {
+	return func(as AS) A {
+		return array.Reduce(as, m.Concat, m.Empty())
+	}
+}
+
+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/generic/sort.go

@@ -18,11 +18,17 @@ package generic
 import (
 	"sort"
 
+	F "github.com/IBM/fp-go/function"
 	O "github.com/IBM/fp-go/ord"
 )
 
 // Sort implements a stable sort on the array given the provided ordering
 func Sort[GA ~[]T, T any](ord O.Ord[T]) func(ma GA) GA {
+	return SortByKey[GA](ord, F.Identity[T])
+}
+
+// SortByKey implements a stable sort on the array given the provided ordering on an extracted key
+func SortByKey[GA ~[]T, K, T any](ord O.Ord[K], f func(T) K) func(ma GA) GA {
 
 	return func(ma GA) GA {
 		// nothing to sort
@@ -34,8 +40,17 @@ func Sort[GA ~[]T, T any](ord O.Ord[T]) func(ma GA) GA {
 		cpy := make(GA, l)
 		copy(cpy, ma)
 		sort.Slice(cpy, func(i, j int) bool {
-			return ord.Compare(cpy[i], cpy[j]) < 0
+			return ord.Compare(f(cpy[i]), f(cpy[j])) < 0
 		})
 		return cpy
 	}
 }
+
+// SortBy implements a stable sort on the array given the provided ordering
+func SortBy[GA ~[]T, GO ~[]O.Ord[T], T any](ord GO) func(ma GA) GA {
+	return F.Pipe2(
+		ord,
+		Fold[GO](O.Monoid[T]()),
+		Sort[GA, T],
+	)
+}

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

array/magma.go

@@ -16,10 +16,9 @@
 package array
 
 import (
-	F "github.com/IBM/fp-go/function"
-	M "github.com/IBM/fp-go/magma"
+	M "github.com/IBM/fp-go/monoid"
 )
 
-func ConcatAll[A any](m M.Magma[A]) func(A) func([]A) A {
-	return F.Bind1st(Reduce[A, A], m.Concat)
+func ConcatAll[A any](m M.Monoid[A]) func([]A) A {
+	return Reduce(m.Concat, m.Empty())
 }

array/magma_test.go

@@ -20,16 +20,16 @@ import (
 
 	"github.com/stretchr/testify/assert"
 
-	M "github.com/IBM/fp-go/magma"
+	M "github.com/IBM/fp-go/monoid"
 )
 
-var subInt = M.MakeMagma(func(first int, second int) int {
+var subInt = M.MakeMonoid(func(first int, second int) int {
 	return first - second
-})
+}, 0)
 
 func TestConcatAll(t *testing.T) {
 
-	var subAll = ConcatAll(subInt)(0)
+	var subAll = ConcatAll(subInt)
 
 	assert.Equal(t, subAll([]int{1, 2, 3}), -6)
 

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))
+	}
+}

array/sort.go

@@ -24,3 +24,13 @@ import (
 func Sort[T any](ord O.Ord[T]) func(ma []T) []T {
 	return G.Sort[[]T](ord)
 }
+
+// SortByKey implements a stable sort on the array given the provided ordering on an extracted key
+func SortByKey[K, T any](ord O.Ord[K], f func(T) K) func(ma []T) []T {
+	return G.SortByKey[[]T](ord, f)
+}
+
+// SortBy implements a stable sort on the array given the provided ordering
+func SortBy[T any](ord []O.Ord[T]) func(ma []T) []T {
+	return G.SortBy[[]T, []O.Ord[T]](ord)
+}

array/zip.go

@@ -0,0 +1,38 @@
+// 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 array
+
+import (
+	G "github.com/IBM/fp-go/array/generic"
+	T "github.com/IBM/fp-go/tuple"
+)
+
+// ZipWith applies a function to pairs of elements at the same index in two arrays, collecting the results in a new array. If one
+// input array is short, excess elements of the longer array are discarded.
+func ZipWith[FCT ~func(A, B) C, A, B, C any](fa []A, fb []B, f FCT) []C {
+	return G.ZipWith[[]A, []B, []C, FCT](fa, fb, f)
+}
+
+// Zip takes two arrays and returns an array of corresponding pairs. If one input array is short, excess elements of the
+// longer array are discarded
+func Zip[A, B any](fb []B) func([]A) []T.Tuple2[A, B] {
+	return G.Zip[[]A, []B, []T.Tuple2[A, B]](fb)
+}
+
+// Unzip is the function is reverse of [Zip]. Takes an array of pairs and return two corresponding arrays
+func Unzip[A, B any](cs []T.Tuple2[A, B]) T.Tuple2[[]A, []B] {
+	return G.Unzip[[]A, []B, []T.Tuple2[A, B]](cs)
+}

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

boolean/boolean.go

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

cli/apply.go

@@ -388,7 +388,7 @@ func generateApplyHelpers(filename string, count int) error {
 	// some header
 	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
 	fmt.Fprintln(f, "// This file was generated by robots at")
-	fmt.Fprintf(f, "// %s\n", time.Now())
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
 
 	fmt.Fprintf(f, "package %s\n\n", pkg)
 

cli/bind.go

@@ -266,7 +266,7 @@ func generateBindHelpers(filename string, count int) error {
 	// some header
 	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
 	fmt.Fprintln(f, "// This file was generated by robots at")
-	fmt.Fprintf(f, "// %s\n", time.Now())
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
 
 	fmt.Fprintf(f, "package %s\n", pkg)
 

cli/commands.go

@@ -31,5 +31,8 @@ func Commands() []*C.Command {
 		ContextReaderIOEitherCommand(),
 		ReaderIOEitherCommand(),
 		ReaderCommand(),
+		IOEitherCommand(),
+		IOCommand(),
+		IOOptionCommand(),
 	}
 }

cli/either.go

@@ -150,7 +150,7 @@ func generateEitherHelpers(filename string, count int) error {
 	// some header
 	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
 	fmt.Fprintln(f, "// This file was generated by robots at")
-	fmt.Fprintf(f, "// %s\n", time.Now())
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
 
 	fmt.Fprintf(f, "package %s\n\n", pkg)
 

cli/header.go

@@ -27,5 +27,5 @@ func writePackage(f *os.File, pkg string) {
 	// some header
 	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
 	fmt.Fprintln(f, "// This file was generated by robots at")
-	fmt.Fprintf(f, "// %s\n", time.Now())
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
 }

cli/identity.go

@@ -62,7 +62,7 @@ func generateIdentityHelpers(filename string, count int) error {
 	// some header
 	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
 	fmt.Fprintln(f, "// This file was generated by robots at")
-	fmt.Fprintf(f, "// %s\n", time.Now())
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
 
 	fmt.Fprintf(f, "package %s\n\n", pkg)
 

cli/io.go

@@ -0,0 +1,136 @@
+// 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 cli
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"time"
+
+	A "github.com/IBM/fp-go/array"
+	C "github.com/urfave/cli/v2"
+)
+
+func nonGenericIO(param string) string {
+	return fmt.Sprintf("IO[%s]", param)
+}
+
+func genericIO(param string) string {
+	return fmt.Sprintf("func() %s", param)
+}
+
+var extrasIO = A.Empty[string]()
+
+func generateIOSequenceT(f, fg *os.File, i int) {
+	generateGenericSequenceT(nonGenericIO, genericIO, extrasIO)(f, fg, i)
+}
+
+func generateIOSequenceTuple(f, fg *os.File, i int) {
+	generateGenericSequenceTuple(nonGenericIO, genericIO, extrasIO)(f, fg, i)
+}
+
+func generateIOTraverseTuple(f, fg *os.File, i int) {
+	generateGenericTraverseTuple(nonGenericIO, genericIO, extrasIO)(f, fg, i)
+}
+
+func generateIOHelpers(filename string, count int) error {
+	dir, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+	absDir, err := filepath.Abs(dir)
+	if err != nil {
+		return err
+	}
+	pkg := filepath.Base(absDir)
+	f, err := os.Create(filepath.Clean(filename))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	// construct subdirectory
+	genFilename := filepath.Join("generic", filename)
+	err = os.MkdirAll("generic", os.ModePerm)
+	if err != nil {
+		return err
+	}
+	fg, err := os.Create(filepath.Clean(genFilename))
+	if err != nil {
+		return err
+	}
+	defer fg.Close()
+
+	// log
+	log.Printf("Generating code in [%s] for package [%s] with [%d] repetitions ...", filename, pkg, count)
+
+	// some header
+	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(f, "// This file was generated by robots at")
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
+
+	fmt.Fprintf(f, "package %s\n\n", pkg)
+
+	fmt.Fprintf(f, `
+import (
+	G "github.com/IBM/fp-go/%s/generic"	
+	T "github.com/IBM/fp-go/tuple"
+)
+`, pkg)
+
+	// some header
+	fmt.Fprintln(fg, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(fg, "// This file was generated by robots at")
+	fmt.Fprintf(fg, "// %s\n", time.Now())
+
+	fmt.Fprintf(fg, "package generic\n\n")
+
+	fmt.Fprintf(fg, `
+import (
+	T "github.com/IBM/fp-go/tuple"
+	A "github.com/IBM/fp-go/internal/apply"
+)
+`)
+
+	for i := 1; i <= count; i++ {
+		// sequenceT
+		generateIOSequenceT(f, fg, i)
+		// sequenceTuple
+		generateIOSequenceTuple(f, fg, i)
+		// traverseTuple
+		generateIOTraverseTuple(f, fg, i)
+	}
+
+	return nil
+}
+
+func IOCommand() *C.Command {
+	return &C.Command{
+		Name:  "io",
+		Usage: "generate code for IO",
+		Flags: []C.Flag{
+			flagCount,
+			flagFilename,
+		},
+		Action: func(ctx *C.Context) error {
+			return generateIOHelpers(
+				ctx.String(keyFilename),
+				ctx.Int(keyCount),
+			)
+		},
+	}
+}

cli/ioeither.go

@@ -0,0 +1,282 @@
+// 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 cli
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"time"
+
+	A "github.com/IBM/fp-go/array"
+	C "github.com/urfave/cli/v2"
+)
+
+// [GA ~func() ET.Either[E, A], GB ~func() ET.Either[E, B], GTAB ~func() ET.Either[E, T.Tuple2[A, B]], E, A, B any](a GA, b GB) GTAB {
+
+func nonGenericIOEither(param string) string {
+	return fmt.Sprintf("IOEither[E, %s]", param)
+}
+
+func genericIOEither(param string) string {
+	return fmt.Sprintf("func() ET.Either[E, %s]", param)
+}
+
+var extrasIOEither = A.From("E")
+
+func generateIOEitherSequenceT(f, fg *os.File, i int) {
+	generateGenericSequenceT(nonGenericIOEither, genericIOEither, extrasIOEither)(f, fg, i)
+}
+
+func generateIOEitherSequenceTuple(f, fg *os.File, i int) {
+	generateGenericSequenceTuple(nonGenericIOEither, genericIOEither, extrasIOEither)(f, fg, i)
+}
+
+func generateIOEitherTraverseTuple(f, fg *os.File, i int) {
+	generateGenericTraverseTuple(nonGenericIOEither, genericIOEither, extrasIOEither)(f, fg, i)
+}
+
+func generateIOEitherUneitherize(f, fg *os.File, i int) {
+	// non generic version
+	fmt.Fprintf(f, "\n// Uneitherize%d converts a function with %d parameters returning a tuple into a function with %d parameters returning a [IOEither[error, R]]\n", i, i+1, i)
+	fmt.Fprintf(f, "func Uneitherize%d[F ~func(", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, ") IOEither[error, R]")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j+1)
+	}
+	fmt.Fprintf(f, ", R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, ") (R, error) {\n")
+	fmt.Fprintf(f, "  return G.Uneitherize%d[IOEither[error, R]](f)\n", i)
+	fmt.Fprintln(f, "}")
+
+	// generic version
+	fmt.Fprintf(fg, "\n// Uneitherize%d converts a function with %d parameters returning a tuple into a function with %d parameters returning a [GIOA]\n", i, i, i)
+	fmt.Fprintf(fg, "func Uneitherize%d[GIOA ~func() ET.Either[error, R], GTA ~func(", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "T%d", j+1)
+	}
+	fmt.Fprintf(fg, ") GIOA")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", T%d", j+1)
+	}
+	fmt.Fprintf(fg, ", R any](f GTA) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "T%d", j+1)
+	}
+	fmt.Fprintf(fg, ") (R, error) {\n")
+	fmt.Fprintf(fg, "  return func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "t%d T%d", j+1, j+1)
+	}
+	fmt.Fprintf(fg, ") (R, error) {\n")
+	fmt.Fprintf(fg, "    return ET.Unwrap(f(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "t%d", j+1)
+	}
+	fmt.Fprintf(fg, ")())\n")
+	fmt.Fprintf(fg, "  }\n")
+	fmt.Fprintf(fg, "}\n")
+}
+
+func generateIOEitherEitherize(f, fg *os.File, i int) {
+	// non generic version
+	fmt.Fprintf(f, "\n// Eitherize%d converts a function with %d parameters returning a tuple into a function with %d parameters returning a [IOEither[error, R]]\n", i, i+1, i)
+	fmt.Fprintf(f, "func Eitherize%d[F ~func(", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, ") (R, error)")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j+1)
+	}
+	fmt.Fprintf(f, ", R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, ") IOEither[error, R] {\n")
+	fmt.Fprintf(f, "  return G.Eitherize%d[IOEither[error, R]](f)\n", i)
+	fmt.Fprintln(f, "}")
+
+	// generic version
+	fmt.Fprintf(fg, "\n// Eitherize%d converts a function with %d parameters returning a tuple into a function with %d parameters returning a [GIOA]\n", i, i, i)
+	fmt.Fprintf(fg, "func Eitherize%d[GIOA ~func() ET.Either[error, R], F ~func(", i)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "T%d", j+1)
+	}
+	fmt.Fprintf(fg, ") (R, error)")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", T%d", j+1)
+	}
+	fmt.Fprintf(fg, ", R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "T%d", j+1)
+	}
+	fmt.Fprintf(fg, ") GIOA {\n")
+	fmt.Fprintf(fg, "  e := ET.Eitherize%d(f)\n", i)
+	fmt.Fprintf(fg, "  return func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "t%d T%d", j+1, j+1)
+	}
+	fmt.Fprintf(fg, ") GIOA {\n")
+	fmt.Fprintf(fg, "    return func() ET.Either[error, R] {\n")
+	fmt.Fprintf(fg, "      return e(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "t%d", j+1)
+	}
+	fmt.Fprintf(fg, ")\n")
+	fmt.Fprintf(fg, "    }}\n")
+	fmt.Fprintf(fg, "}\n")
+}
+
+func generateIOEitherHelpers(filename string, count int) error {
+	dir, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+	absDir, err := filepath.Abs(dir)
+	if err != nil {
+		return err
+	}
+	pkg := filepath.Base(absDir)
+	f, err := os.Create(filepath.Clean(filename))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	// construct subdirectory
+	genFilename := filepath.Join("generic", filename)
+	err = os.MkdirAll("generic", os.ModePerm)
+	if err != nil {
+		return err
+	}
+	fg, err := os.Create(filepath.Clean(genFilename))
+	if err != nil {
+		return err
+	}
+	defer fg.Close()
+
+	// log
+	log.Printf("Generating code in [%s] for package [%s] with [%d] repetitions ...", filename, pkg, count)
+
+	// some header
+	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(f, "// This file was generated by robots at")
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
+
+	fmt.Fprintf(f, "package %s\n\n", pkg)
+
+	fmt.Fprintf(f, `
+import (
+	G "github.com/IBM/fp-go/%s/generic"	
+	T "github.com/IBM/fp-go/tuple"
+)
+`, pkg)
+
+	// some header
+	fmt.Fprintln(fg, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(fg, "// This file was generated by robots at")
+	fmt.Fprintf(fg, "// %s\n", time.Now())
+
+	fmt.Fprintf(fg, "package generic\n\n")
+
+	fmt.Fprintf(fg, `
+import (
+	ET "github.com/IBM/fp-go/either"
+	T "github.com/IBM/fp-go/tuple"
+	A "github.com/IBM/fp-go/internal/apply"
+)
+`)
+
+	// eitherize
+	generateIOEitherEitherize(f, fg, 0)
+	// uneitherize
+	generateIOEitherUneitherize(f, fg, 0)
+
+	for i := 1; i <= count; i++ {
+		// eitherize
+		generateIOEitherEitherize(f, fg, i)
+		// uneitherize
+		generateIOEitherUneitherize(f, fg, i)
+		// sequenceT
+		generateIOEitherSequenceT(f, fg, i)
+		// sequenceTuple
+		generateIOEitherSequenceTuple(f, fg, i)
+		// traverseTuple
+		generateIOEitherTraverseTuple(f, fg, i)
+	}
+
+	return nil
+}
+
+func IOEitherCommand() *C.Command {
+	return &C.Command{
+		Name:  "ioeither",
+		Usage: "generate code for IOEither",
+		Flags: []C.Flag{
+			flagCount,
+			flagFilename,
+		},
+		Action: func(ctx *C.Context) error {
+			return generateIOEitherHelpers(
+				ctx.String(keyFilename),
+				ctx.Int(keyCount),
+			)
+		},
+	}
+}

cli/iooption.go

@@ -0,0 +1,137 @@
+// 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 cli
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"time"
+
+	A "github.com/IBM/fp-go/array"
+	C "github.com/urfave/cli/v2"
+)
+
+func nonGenericIOOption(param string) string {
+	return fmt.Sprintf("IOOption[%s]", param)
+}
+
+func genericIOOption(param string) string {
+	return fmt.Sprintf("func() O.Option[%s]", param)
+}
+
+var extrasIOOption = A.Empty[string]()
+
+func generateIOOptionSequenceT(f, fg *os.File, i int) {
+	generateGenericSequenceT(nonGenericIOOption, genericIOOption, extrasIOOption)(f, fg, i)
+}
+
+func generateIOOptionSequenceTuple(f, fg *os.File, i int) {
+	generateGenericSequenceTuple(nonGenericIOOption, genericIOOption, extrasIOOption)(f, fg, i)
+}
+
+func generateIOOptionTraverseTuple(f, fg *os.File, i int) {
+	generateGenericTraverseTuple(nonGenericIOOption, genericIOOption, extrasIOOption)(f, fg, i)
+}
+
+func generateIOOptionHelpers(filename string, count int) error {
+	dir, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+	absDir, err := filepath.Abs(dir)
+	if err != nil {
+		return err
+	}
+	pkg := filepath.Base(absDir)
+	f, err := os.Create(filepath.Clean(filename))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	// construct subdirectory
+	genFilename := filepath.Join("generic", filename)
+	err = os.MkdirAll("generic", os.ModePerm)
+	if err != nil {
+		return err
+	}
+	fg, err := os.Create(filepath.Clean(genFilename))
+	if err != nil {
+		return err
+	}
+	defer fg.Close()
+
+	// log
+	log.Printf("Generating code in [%s] for package [%s] with [%d] repetitions ...", filename, pkg, count)
+
+	// some header
+	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(f, "// This file was generated by robots at")
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
+
+	fmt.Fprintf(f, "package %s\n\n", pkg)
+
+	fmt.Fprintf(f, `
+import (
+	G "github.com/IBM/fp-go/%s/generic"	
+	T "github.com/IBM/fp-go/tuple"
+)
+`, pkg)
+
+	// some header
+	fmt.Fprintln(fg, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(fg, "// This file was generated by robots at")
+	fmt.Fprintf(fg, "// %s\n", time.Now())
+
+	fmt.Fprintf(fg, "package generic\n\n")
+
+	fmt.Fprintf(fg, `
+import (
+	T "github.com/IBM/fp-go/tuple"
+	O "github.com/IBM/fp-go/option"
+	A "github.com/IBM/fp-go/internal/apply"
+)
+`)
+
+	for i := 1; i <= count; i++ {
+		// sequenceT
+		generateIOOptionSequenceT(f, fg, i)
+		// sequenceTuple
+		generateIOOptionSequenceTuple(f, fg, i)
+		// traverseTuple
+		generateIOOptionTraverseTuple(f, fg, i)
+	}
+
+	return nil
+}
+
+func IOOptionCommand() *C.Command {
+	return &C.Command{
+		Name:  "iooption",
+		Usage: "generate code for IOOption",
+		Flags: []C.Flag{
+			flagCount,
+			flagFilename,
+		},
+		Action: func(ctx *C.Context) error {
+			return generateIOOptionHelpers(
+				ctx.String(keyFilename),
+				ctx.Int(keyCount),
+			)
+		},
+	}
+}

cli/monad2.go

@@ -0,0 +1,284 @@
+// 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 cli
+
+import (
+	"fmt"
+	"os"
+
+	A "github.com/IBM/fp-go/array"
+	F "github.com/IBM/fp-go/function"
+	N "github.com/IBM/fp-go/number"
+	S "github.com/IBM/fp-go/string"
+)
+
+var (
+	concStrgs     = A.Monoid[string]().Concat
+	intercalStrgs = A.Intercalate(S.Monoid)
+	concAllStrgs  = A.ConcatAll(A.Monoid[string]())
+)
+
+func joinAll(middle string) func(all ...[]string) string {
+	ic := intercalStrgs(middle)
+	return func(all ...[]string) string {
+		return ic(concAllStrgs(all))
+	}
+}
+
+func generateGenericSequenceT(
+	nonGenericType func(string) string,
+	genericType func(string) string,
+	extra []string,
+) func(f, fg *os.File, i int) {
+	return func(f, fg *os.File, i int) {
+		// tuple
+		tuple := tupleType("T")(i)
+		// all types T
+		typesT := A.MakeBy(i, F.Flow2(
+			N.Inc[int],
+			S.Format[int]("T%d"),
+		))
+		// non generic version
+		fmt.Fprintf(f, "\n// SequenceT%d converts %d [%s] into a [%s]\n", i, i, nonGenericType("T"), nonGenericType(tuple))
+		fmt.Fprintf(f, "func SequenceT%d[%s any](\n", i, joinAll(", ")(extra, typesT))
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(f, "  t%d %s,\n", j+1, nonGenericType(fmt.Sprintf("T%d", j+1)))
+		}
+		fmt.Fprintf(f, ") %s {\n", nonGenericType(tuple))
+		fmt.Fprintf(f, "  return G.SequenceT%d[\n", i)
+		fmt.Fprintf(f, "    %s,\n", nonGenericType(tuple))
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(f, "    %s,\n", nonGenericType(fmt.Sprintf("T%d", j+1)))
+		}
+		fmt.Fprintf(f, "  ](")
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "t%d", j+1)
+		}
+		fmt.Fprintf(f, ")\n")
+		fmt.Fprintf(f, "}\n")
+
+		// generic version
+		fmt.Fprintf(fg, "\n// SequenceT%d converts %d [%s] into a [%s]\n", i, i, genericType("T"), genericType(tuple))
+		fmt.Fprintf(fg, "func SequenceT%d[\n", i)
+		fmt.Fprintf(fg, "  G_TUPLE%d ~%s,\n", i, genericType(tuple))
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(fg, "  G_T%d ~%s, \n", j+1, genericType(fmt.Sprintf("T%d", j+1)))
+		}
+		fmt.Fprintf(fg, "  %s any](\n", joinAll(", ")(extra, typesT))
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(fg, "  t%d G_T%d,\n", j+1, j+1)
+		}
+		fmt.Fprintf(fg, ")  G_TUPLE%d {\n", i)
+		fmt.Fprintf(fg, "  return A.SequenceT%d(\n", i)
+		// map call
+		var cio string
+		cb := generateNestedCallbacks(1, i)
+		if i > 1 {
+			cio = genericType(cb)
+		} else {
+			cio = fmt.Sprintf("G_TUPLE%d", i)
+		}
+		fmt.Fprintf(fg, "    Map[%s],\n", joinAll(", ")(A.From("G_T1", cio), extra, A.From("T1", cb)))
+		// the apply calls
+		for j := 1; j < i; j++ {
+			if j < i-1 {
+				cb := generateNestedCallbacks(j+1, i)
+				cio = genericType(cb)
+			} else {
+				cio = fmt.Sprintf("G_TUPLE%d", i)
+			}
+			fmt.Fprintf(fg, "    Ap[%s, %s, G_T%d],\n", cio, genericType(generateNestedCallbacks(j, i)), j+1)
+		}
+		// function parameters
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(fg, "    t%d,\n", j+1)
+		}
+
+		fmt.Fprintf(fg, "  )\n")
+		fmt.Fprintf(fg, "}\n")
+	}
+}
+
+func generateGenericSequenceTuple(
+	nonGenericType func(string) string,
+	genericType func(string) string,
+	extra []string,
+) func(f, fg *os.File, i int) {
+	return func(f, fg *os.File, i int) {
+		// tuple
+		tuple := tupleType("T")(i)
+		// all types T
+		typesT := A.MakeBy(i, F.Flow2(
+			N.Inc[int],
+			S.Format[int]("T%d"),
+		))
+		// non generic version
+		fmt.Fprintf(f, "\n// SequenceTuple%d converts a [T.Tuple%d[%s]] into a [%s]\n", i, i, nonGenericType("T"), nonGenericType(tuple))
+		fmt.Fprintf(f, "func SequenceTuple%d[%s any](t T.Tuple%d[", i, joinAll(", ")(extra, typesT), i)
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "%s", nonGenericType(fmt.Sprintf("T%d", j+1)))
+		}
+		fmt.Fprintf(f, "]) %s {\n", nonGenericType(tuple))
+		fmt.Fprintf(f, "  return G.SequenceTuple%d[\n", i)
+		fmt.Fprintf(f, "    %s,\n", nonGenericType(tuple))
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(f, "    %s,\n", nonGenericType(fmt.Sprintf("T%d", j+1)))
+		}
+		fmt.Fprintf(f, "  ](t)\n")
+		fmt.Fprintf(f, "}\n")
+
+		// generic version
+		fmt.Fprintf(fg, "\n// SequenceTuple%d converts a [T.Tuple%d[%s]] into a [%s]\n", i, i, genericType("T"), genericType(tuple))
+		fmt.Fprintf(fg, "func SequenceTuple%d[\n", i)
+		fmt.Fprintf(fg, "  G_TUPLE%d ~%s,\n", i, genericType(tuple))
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(fg, "  G_T%d ~%s, \n", j+1, genericType(fmt.Sprintf("T%d", j+1)))
+		}
+		fmt.Fprintf(fg, "  %s any](t T.Tuple%d[", joinAll(", ")(extra, typesT), i)
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(fg, ", ")
+			}
+			fmt.Fprintf(fg, "G_T%d", j+1)
+		}
+		fmt.Fprintf(fg, "])  G_TUPLE%d {\n", i)
+		fmt.Fprintf(fg, "  return A.SequenceTuple%d(\n", i)
+		// map call
+		var cio string
+		cb := generateNestedCallbacks(1, i)
+		if i > 1 {
+			cio = genericType(cb)
+		} else {
+			cio = fmt.Sprintf("G_TUPLE%d", i)
+		}
+		fmt.Fprintf(fg, "    Map[%s],\n", joinAll(", ")(A.From("G_T1", cio), extra, A.From("T1", cb)))
+		// the apply calls
+		for j := 1; j < i; j++ {
+			if j < i-1 {
+				cb := generateNestedCallbacks(j+1, i)
+				cio = genericType(cb)
+			} else {
+				cio = fmt.Sprintf("G_TUPLE%d", i)
+			}
+			fmt.Fprintf(fg, "    Ap[%s, %s, G_T%d],\n", cio, genericType(generateNestedCallbacks(j, i)), j+1)
+		}
+		// function parameters
+		fmt.Fprintf(fg, "    t)\n")
+		fmt.Fprintf(fg, "}\n")
+	}
+}
+
+func generateGenericTraverseTuple(
+	nonGenericType func(string) string,
+	genericType func(string) string,
+	extra []string,
+) func(f, fg *os.File, i int) {
+	return func(f, fg *os.File, i int) {
+		// tuple
+		tupleT := tupleType("T")(i)
+		tupleA := tupleType("A")(i)
+		// all types T
+		typesT := A.MakeBy(i, F.Flow2(
+			N.Inc[int],
+			S.Format[int]("T%d"),
+		))
+		// all types A
+		typesA := A.MakeBy(i, F.Flow2(
+			N.Inc[int],
+			S.Format[int]("A%d"),
+		))
+		// all function types
+		typesF := A.MakeBy(i, F.Flow2(
+			N.Inc[int],
+			func(j int) string {
+				return fmt.Sprintf("F%d ~func(A%d) %s", j, j, nonGenericType(fmt.Sprintf("T%d", j)))
+			},
+		))
+		// non generic version
+		fmt.Fprintf(f, "\n// TraverseTuple%d converts a [T.Tuple%d[%s]] into a [%s]\n", i, i, nonGenericType("T"), nonGenericType(tupleT))
+		fmt.Fprintf(f, "func TraverseTuple%d[%s any](", i, joinAll(", ")(typesF, extra, typesA, typesT))
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "f%d F%d", j+1, j+1)
+		}
+		fmt.Fprintf(f, ") func(%s) %s {\n", tupleA, nonGenericType(tupleT))
+		fmt.Fprintf(f, "  return G.TraverseTuple%d[%s](", i, nonGenericType(tupleT))
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(f, ", ")
+			}
+			fmt.Fprintf(f, "f%d", j+1)
+		}
+		fmt.Fprintf(f, ")\n")
+		fmt.Fprintf(f, "}\n")
+
+		// generic version
+		fmt.Fprintf(fg, "\n// TraverseTuple%d converts a [T.Tuple%d[%s]] into a [%s]\n", i, i, genericType("T"), genericType(tupleT))
+		fmt.Fprintf(fg, "func TraverseTuple%d[\n", i)
+		fmt.Fprintf(fg, "  G_TUPLE%d ~%s,\n", i, genericType(tupleT))
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(fg, "  F%d ~func(A%d) G_T%d,\n", j+1, j+1, j+1)
+		}
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(fg, "  G_T%d ~%s, \n", j+1, genericType(fmt.Sprintf("T%d", j+1)))
+		}
+		fmt.Fprintf(fg, "  %s any](", joinAll(", ")(extra, typesA, typesT))
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				fmt.Fprintf(fg, ", ")
+			}
+			fmt.Fprintf(fg, "f%d F%d", j+1, j+1)
+		}
+		fmt.Fprintf(fg, ") func(%s) G_TUPLE%d {\n", tupleA, i)
+		fmt.Fprintf(fg, "  return func(t %s) G_TUPLE%d {\n", tupleA, i)
+		fmt.Fprintf(fg, "    return A.TraverseTuple%d(\n", i)
+		// map call
+		var cio string
+		cb := generateNestedCallbacks(1, i)
+		if i > 1 {
+			cio = genericType(cb)
+		} else {
+			cio = fmt.Sprintf("G_TUPLE%d", i)
+		}
+		fmt.Fprintf(fg, "    Map[%s],\n", joinAll(", ")(A.From("G_T1", cio), extra, A.From("T1", cb)))
+		// the apply calls
+		for j := 1; j < i; j++ {
+			if j < i-1 {
+				cb := generateNestedCallbacks(j+1, i)
+				cio = genericType(cb)
+			} else {
+				cio = fmt.Sprintf("G_TUPLE%d", i)
+			}
+			fmt.Fprintf(fg, "    Ap[%s, %s, G_T%d],\n", cio, genericType(generateNestedCallbacks(j, i)), j+1)
+		}
+		// function parameters
+		for j := 0; j < i; j++ {
+			fmt.Fprintf(fg, "    f%d,\n", j+1)
+		}
+		// tuple parameter
+		fmt.Fprintf(fg, "    t)\n")
+		fmt.Fprintf(fg, "   }\n")
+		fmt.Fprintf(fg, "}\n")
+	}
+}

cli/option.go

@@ -148,7 +148,7 @@ func generateOptionHelpers(filename string, count int) error {
 	// some header
 	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
 	fmt.Fprintln(f, "// This file was generated by robots at")
-	fmt.Fprintf(f, "// %s\n", time.Now())
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
 
 	fmt.Fprintf(f, "package %s\n\n", pkg)
 

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) {
@@ -337,7 +371,7 @@ func generatePipeHelpers(filename string, count int) error {
 	// some header
 	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
 	fmt.Fprintln(f, "// This file was generated by robots at")
-	fmt.Fprintf(f, "// %s\n", time.Now())
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
 
 	fmt.Fprintf(f, "package %s\n", pkg)
 
@@ -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/reader.go

@@ -12,6 +12,7 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
+
 package cli
 
 import (
@@ -117,7 +118,7 @@ func generateReaderHelpers(filename string, count int) error {
 	// some header
 	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
 	fmt.Fprintln(f, "// This file was generated by robots at")
-	fmt.Fprintf(f, "// %s\n", time.Now())
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
 
 	fmt.Fprintf(f, "package %s\n\n", pkg)
 

cli/readerioeither.go

@@ -169,7 +169,7 @@ func generateReaderIOEitherHelpers(filename string, count int) error {
 	// some header
 	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
 	fmt.Fprintln(f, "// This file was generated by robots at")
-	fmt.Fprintf(f, "// %s\n", time.Now())
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
 
 	fmt.Fprintf(f, "package %s\n\n", pkg)
 

cli/tuple.go

@@ -20,6 +20,7 @@ import (
 	"log"
 	"os"
 	"path/filepath"
+	"strings"
 	"time"
 
 	C "github.com/urfave/cli/v2"
@@ -36,8 +37,51 @@ func writeTupleType(f *os.File, symbol string, i int) {
 	fmt.Fprintf(f, "]")
 }
 
+func makeTupleType(name string) func(i int) string {
+	return func(i int) string {
+		var buf strings.Builder
+		buf.WriteString(fmt.Sprintf("Tuple%d[", i))
+		for j := 0; j < i; j++ {
+			if j > 0 {
+				buf.WriteString(", ")
+			}
+			buf.WriteString(fmt.Sprintf("%s%d", name, j+1))
+		}
+		buf.WriteString("]")
+
+		return buf.String()
+	}
+}
+
+func generatePush(f *os.File, i int) {
+	tuple1 := makeTupleType("T")(i)
+	tuple2 := makeTupleType("T")(i + 1)
+	// Create the replicate version
+	fmt.Fprintf(f, "\n// Push%d creates a [Tuple%d] from a [Tuple%d] by appending a constant value\n", i, i+1, i)
+	fmt.Fprintf(f, "func Push%d[", i)
+	// function prototypes
+	for j := 0; j <= i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j+1)
+	}
+	fmt.Fprintf(f, " any](value T%d) func(%s) %s {\n", i+1, tuple1, tuple2)
+	fmt.Fprintf(f, "  return func(t %s) %s {\n", tuple1, tuple2)
+	fmt.Fprintf(f, "    return MakeTuple%d(", i+1)
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t.F%d", j+1)
+	}
+	fmt.Fprintf(f, ", value)\n")
+	fmt.Fprintf(f, "  }\n")
+	fmt.Fprintf(f, "}\n")
+}
+
 func generateReplicate(f *os.File, i int) {
-	// Create the optionize version
+	// Create the replicate version
 	fmt.Fprintf(f, "\n// Replicate%d creates a [Tuple%d] with all fields set to the input value `t`\n", i, i)
 	fmt.Fprintf(f, "func Replicate%d[T any](t T) Tuple%d[", i, i)
 	for j := 1; j <= i; j++ {
@@ -294,7 +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 {
@@ -355,14 +399,16 @@ func generateTupleHelpers(filename string, count int) error {
 	// some header
 	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
 	fmt.Fprintln(f, "// This file was generated by robots at")
-	fmt.Fprintf(f, "// %s\n", time.Now())
+	fmt.Fprintf(f, "// %s\n\n", time.Now())
 
 	fmt.Fprintf(f, "package %s\n\n", pkg)
 
 	fmt.Fprintf(f, `
 import (
+	"fmt"
+	"encoding/json"
 	M "github.com/IBM/fp-go/monoid"
-	O "github.com/IBM/fp-go/ord"
+	O "github.com/IBM/fp-go/ord"	
 )
 `)
 
@@ -386,11 +432,207 @@ import (
 		generateMap(f, i)
 		// generate replicate
 		generateReplicate(f, i)
+		// generate tuple functions such as string and fmt
+		generateTupleString(f, i)
+		// generate json support
+		generateTupleMarshal(f, i)
+		// generate json support
+		generateTupleUnmarshal(f, i)
+		// generate toArray
+		generateToArray(f, i)
+		// generate fromArray
+		generateFromArray(f, i)
+		// generate push
+		if i < count {
+			generatePush(f, i)
+		}
 	}
 
 	return nil
 }
 
+func generateTupleMarshal(f *os.File, i int) {
+	// Create the stringify version
+	fmt.Fprintf(f, "\n// MarshalJSON marshals the [Tuple%d] into a JSON array\n", i)
+	fmt.Fprintf(f, "func (t ")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, ") MarshalJSON() ([]byte, error) {\n")
+	fmt.Fprintf(f, "  return json.Marshal([]any{")
+	// function prototypes
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t.F%d", j)
+	}
+	fmt.Fprintf(f, "})\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateTupleUnmarshal(f *os.File, i int) {
+	// Create the stringify version
+	fmt.Fprintf(f, "\n// UnmarshalJSON unmarshals a JSON array into a [Tuple%d]\n", i)
+	fmt.Fprintf(f, "func (t *")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, ") UnmarshalJSON(data []byte) error {\n")
+	fmt.Fprintf(f, "  var tmp []json.RawMessage\n")
+	fmt.Fprintf(f, "  if err := json.Unmarshal(data, &tmp); err != nil {return err}\n")
+	fmt.Fprintf(f, "  l := len(tmp)\n")
+	// unmarshal fields
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, "  if l > %d {\n", j-1)
+		fmt.Fprintf(f, "  if err := json.Unmarshal(tmp[%d], &t.F%d); err != nil {return err}\n", j-1, j)
+	}
+	fmt.Fprintf(f, "  ")
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, "}")
+	}
+	fmt.Fprintf(f, "\n  return nil\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateToArray(f *os.File, i int) {
+	// Create the stringify version
+	fmt.Fprintf(f, "\n// ToArray converts the [Tuple%d] into an array of type [R] using %d transformation functions from [T] to [R]\n// The inverse function is [FromArray%d]\n", i, i, i)
+	fmt.Fprintf(f, "func ToArray%d[", i)
+	// function prototypes
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "F%d ~func(T%d) R", j, j)
+	}
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ", R any](")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "f%d F%d", j, j)
+	}
+	fmt.Fprintf(f, ") func(t ")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, ") []R {\n")
+	fmt.Fprintf(f, "  return func(t ")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, ") []R {\n")
+	fmt.Fprintf(f, "    return []R{\n")
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, "      f%d(t.F%d),\n", j, j)
+	}
+	fmt.Fprintf(f, "    }\n")
+	fmt.Fprintf(f, "  }\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateFromArray(f *os.File, i int) {
+	// Create the stringify version
+	fmt.Fprintf(f, "\n// FromArray converts an array of [R] into a [Tuple%d] using %d functions from [R] to [T]\n// The inverse function is [ToArray%d]\n", i, i, i)
+	fmt.Fprintf(f, "func FromArray%d[", i)
+	// function prototypes
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "F%d ~func(R) T%d", j, j)
+	}
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ", R any](")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "f%d F%d", j, j)
+	}
+	fmt.Fprintf(f, ") func(r []R) ")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, " {\n")
+	fmt.Fprintf(f, "  return func(r []R) ")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, " {\n")
+	fmt.Fprintf(f, "    return MakeTuple%d(\n", i)
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, "      f%d(r[%d]),\n", j, j-1)
+	}
+	fmt.Fprintf(f, "    )\n")
+	fmt.Fprintf(f, "  }\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+func generateTupleString(f *os.File, i int) {
+	// Create the stringify version
+	fmt.Fprintf(f, "\n// String prints some debug info for the [Tuple%d]\n", i)
+	fmt.Fprintf(f, "func (t ")
+	writeTupleType(f, "T", i)
+	fmt.Fprintf(f, ") String() string {\n")
+	// convert to string
+	fmt.Fprintf(f, "  return fmt.Sprintf(\"Tuple%d[", i)
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "%s", "%T")
+	}
+	fmt.Fprintf(f, "](")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "%s", "%v")
+	}
+	fmt.Fprintf(f, ")\", ")
+	for j := 1; j <= i; j++ {
+		if j > 1 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "t.F%d", j)
+	}
+	for j := 1; j <= i; j++ {
+		fmt.Fprintf(f, ", t.F%d", j)
+	}
+	fmt.Fprintf(f, ")\n")
+	fmt.Fprintf(f, "}\n")
+}
+
+// func generateTupleJson(f *os.File, i int) {
+// 	// Create the stringify version
+// 	fmt.Fprintf(f, "\n// MarshalJSON converts the [Tuple%d] into a JSON byte stream\n", i)
+// 	fmt.Fprintf(f, "func (t ")
+// 	writeTupleType(f, "T", i)
+// 	fmt.Fprintf(f, ") MarshalJSON() ([]byte, error) {\n")
+// 	// convert to string
+// 	fmt.Fprintf(f, "  return fmt.Sprintf(\"Tuple%d[", i)
+// 	for j := 1; j <= i; j++ {
+// 		if j > 1 {
+// 			fmt.Fprintf(f, ", ")
+// 		}
+// 		fmt.Fprintf(f, "%s", "%T")
+// 	}
+// 	fmt.Fprintf(f, "](")
+// 	for j := 1; j <= i; j++ {
+// 		if j > 1 {
+// 			fmt.Fprintf(f, ", ")
+// 		}
+// 		fmt.Fprintf(f, "%s", "%v")
+// 	}
+// 	fmt.Fprintf(f, ")\", ")
+// 	for j := 1; j <= i; j++ {
+// 		if j > 1 {
+// 			fmt.Fprintf(f, ", ")
+// 		}
+// 		fmt.Fprintf(f, "t.F%d", j)
+// 	}
+// 	for j := 1; j <= i; j++ {
+// 		fmt.Fprintf(f, ", t.F%d", j)
+// 	}
+// 	fmt.Fprintf(f, ")\n")
+// 	fmt.Fprintf(f, "}\n")
+// }
+
 func TupleCommand() *C.Command {
 	return &C.Command{
 		Name:  "tuple",

constraints/constraints.go

@@ -34,3 +34,7 @@ type Integer interface {
 type Float interface {
 	~float32 | ~float64
 }
+
+type Complex interface {
+	~complex64 | ~complex128
+}

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/reader/reader.go

@@ -56,3 +56,11 @@ func Ask() Reader[context.Context] {
 func Asks[A any](r Reader[A]) Reader[A] {
 	return R.Asks(r)
 }
+
+func MonadFlap[B, A any](fab Reader[func(A) B], a A) Reader[B] {
+	return R.MonadFlap[Reader[func(A) B], Reader[B]](fab, a)
+}
+
+func Flap[B, A any](a A) func(Reader[func(A) B]) Reader[B] {
+	return R.Flap[Reader[func(A) B], Reader[B]](a)
+}

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/readereither/reader.go

@@ -119,3 +119,11 @@ func ChainEitherK[A, B any](f func(A) ET.Either[error, B]) func(ma ReaderEither[
 func ChainOptionK[A, B any](onNone func() error) func(func(A) O.Option[B]) func(ReaderEither[A]) ReaderEither[B] {
 	return RE.ChainOptionK[ReaderEither[A], ReaderEither[B]](onNone)
 }
+
+func MonadFlap[B, A any](fab ReaderEither[func(A) B], a A) ReaderEither[B] {
+	return RE.MonadFlap[ReaderEither[func(A) B], ReaderEither[B]](fab, a)
+}
+
+func Flap[B, A any](a A) func(ReaderEither[func(A) B]) ReaderEither[B] {
+	return RE.Flap[ReaderEither[func(A) B], ReaderEither[B]](a)
+}

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

@@ -18,9 +18,16 @@ 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"
 )
 
+// FromIO converts an [IO.IO] to a [ReaderIO]
+func FromIO[A any](a IO.IO[A]) ReaderIO[A] {
+	return R.FromIO[ReaderIO[A]](a)
+}
+
 func MonadMap[A, B any](fa ReaderIO[A], f func(A) B) ReaderIO[B] {
 	return R.MonadMap[ReaderIO[A], ReaderIO[B]](fa, f)
 }
@@ -37,6 +44,22 @@ 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 +77,26 @@ 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)
+}
+
+func MonadFlap[B, A any](fab ReaderIO[func(A) B], a A) ReaderIO[B] {
+	return R.MonadFlap[ReaderIO[func(A) B], ReaderIO[B]](fab, a)
+}
+
+func Flap[B, A any](a A) func(ReaderIO[func(A) B]) ReaderIO[B] {
+	return R.Flap[ReaderIO[func(A) B], ReaderIO[B]](a)
+}

context/readerioeither/bracket.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 readerioeither
+
+import (
+	G "github.com/IBM/fp-go/context/readerioeither/generic"
+	E "github.com/IBM/fp-go/either"
+)
+
+// Bracket makes sure that a resource is cleaned up in the event of an error. The release action is called regardless of
+// whether the body action returns and error or not.
+func Bracket[
+	A, B, ANY any](
+
+	acquire ReaderIOEither[A],
+	use func(A) ReaderIOEither[B],
+	release func(A, E.Either[error, B]) ReaderIOEither[ANY],
+) ReaderIOEither[B] {
+	return G.Bracket[ReaderIOEither[A], ReaderIOEither[B], ReaderIOEither[ANY]](
+		acquire,
+		use,
+		release,
+	)
+}

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

@@ -1,23 +1,8 @@
-// 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
 
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-07-21 10:22:43.4901011 +0200 CEST m=+0.009264601
+// 2023-09-12 13:44:14.1022311 +0200 CEST m=+0.017763401
 
 import (
 	"context"

context/readerioeither/generic/bracket.go

@@ -0,0 +1,53 @@
+// 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"
+
+	E "github.com/IBM/fp-go/either"
+	G "github.com/IBM/fp-go/internal/bracket"
+	I "github.com/IBM/fp-go/readerio/generic"
+)
+
+// Bracket makes sure that a resource is cleaned up in the event of an error. The release action is called regardless of
+// whether the body action returns and error or not.
+func Bracket[
+	GA ~func(context.Context) TA,
+	GB ~func(context.Context) TB,
+	GANY ~func(context.Context) TANY,
+
+	TA ~func() E.Either[error, A],
+	TB ~func() E.Either[error, B],
+	TANY ~func() E.Either[error, ANY],
+
+	A, B, ANY any](
+
+	acquire GA,
+	use func(A) GB,
+	release func(A, E.Either[error, B]) GANY,
+) GB {
+	return G.Bracket[GA, GB, GANY, E.Either[error, B], A, B](
+		I.Of[GB, TB, context.Context, E.Either[error, B]],
+		MonadChain[GA, GB, TA, TB, A, B],
+		I.MonadChain[GB, GB, TB, TB, context.Context, E.Either[error, B], E.Either[error, B]],
+		MonadChain[GANY, GB, TANY, TB, ANY, B],
+
+		acquire,
+		use,
+		release,
+	)
+}

context/readerioeither/generic/gen.go

@@ -1,23 +1,8 @@
-// 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
 
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-07-21 10:22:43.4901011 +0200 CEST m=+0.009264601
+// 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,
@@ -220,7 +242,7 @@ func MonadApPar[
 			fabIOE := withCancelCauseFunc(cancelSub, cfab(ctxSub))
 			faIOE := withCancelCauseFunc(cancelSub, cfa(ctxSub))
 
-			return IOE.MonadApPar[GIOA, GIOB, GIOAB](fabIOE, faIOE)()
+			return IOE.MonadApPar[GIOB, GIOAB](fabIOE, faIOE)()
 		}
 	}
 }
@@ -410,10 +432,10 @@ func FromIOEither[
 
 func FromIO[
 	GRA ~func(context.Context) GIOA,
-	GIOA ~func() E.Either[error, A],
-
 	GIOB ~func() A,
 
+	GIOA ~func() E.Either[error, A],
+
 	A any](t GIOB) GRA {
 	return RIE.FromIO[GRA](t)
 }
@@ -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],
@@ -521,7 +571,7 @@ func Timer[
 ](delay time.Duration) GRA {
 	return F.Pipe2(
 		IO.Now[func() time.Time](),
-		FromIO[GRA, GIOA, func() time.Time],
+		FromIO[GRA, func() time.Time],
 		Delay[GRA](delay),
 	)
 }
@@ -543,3 +593,82 @@ 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)
+}
+
+func MonadFlap[GREAB ~func(context.Context) GEAB, GREB ~func(context.Context) GEB, GEAB ~func() E.Either[error, func(A) B], GEB ~func() E.Either[error, B], B, A any](fab GREAB, a A) GREB {
+	return RIE.MonadFlap[GREAB, GREB](fab, a)
+}
+
+func Flap[GREAB ~func(context.Context) GEAB, GREB ~func(context.Context) GEB, GEAB ~func() E.Either[error, func(A) B], GEB ~func() E.Either[error, B], B, A any](a A) func(GREAB) GREB {
+	return RIE.Flap[GREAB, GREB](a)
+}

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/sync.go

@@ -0,0 +1,44 @@
+// 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"
+
+	E "github.com/IBM/fp-go/either"
+	F "github.com/IBM/fp-go/function"
+	IO "github.com/IBM/fp-go/io/generic"
+)
+
+// WithLock executes the provided IO operation in the scope of a lock
+func WithLock[
+	GRA ~func(context.Context) GIOA,
+	GIOA ~func() E.Either[error, A],
+	GRCANCEL ~func(context.Context) GIOCANCEL,
+	GIOCANCEL ~func() E.Either[error, context.CancelFunc],
+	A any](lock GRCANCEL) func(fa GRA) GRA {
+
+	type GRANY func(ctx context.Context) func() E.Either[error, any]
+	type IOANY func() any
+
+	return F.Flow2(
+		F.Constant1[context.CancelFunc, GRA],
+		WithResource[GRA, GRCANCEL, GRANY](lock, F.Flow2(
+			IO.FromImpure[IOANY, context.CancelFunc],
+			FromIO[GRANY, IOANY],
+		)),
+	)
+}

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 +211,50 @@ 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)
+}
+
+func MonadFlap[B, A any](fab ReaderIOEither[func(A) B], a A) ReaderIOEither[B] {
+	return G.MonadFlap[ReaderIOEither[func(A) B], ReaderIOEither[B]](fab, a)
+}
+
+func Flap[B, A any](a A) func(ReaderIOEither[func(A) B]) ReaderIOEither[B] {
+	return G.Flap[ReaderIOEither[func(A) B], ReaderIOEither[B]](a)
+}

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/sync.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 readerioeither
+
+import (
+	"context"
+
+	G "github.com/IBM/fp-go/context/readerioeither/generic"
+)
+
+// WithLock executes the provided IO operation in the scope of a lock
+func WithLock[A any](lock ReaderIOEither[context.CancelFunc]) func(fa ReaderIOEither[A]) ReaderIOEither[A] {
+	return G.WithLock[ReaderIOEither[A]](lock)
+}

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

@@ -0,0 +1,74 @@
+// 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 (
+	F "github.com/IBM/fp-go/function"
+	RA "github.com/IBM/fp-go/internal/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],
+		Map[E, GB, func(B) GB],
+		Ap[GB, E, B],
+
+		f,
+	)
+}
+
+// TraverseArray transforms an array
+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)
+}
+
+// SequenceArray converts a homogeneous sequence of either into an either of sequence
+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/doc.go

@@ -13,6 +13,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// Package option defines the [Either] datastructure and its monadic operations
 package either
 
 //go:generate go run .. either --count 10 --filename gen.go

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))
 	}
@@ -142,12 +144,12 @@ 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])
 }
 
-func ToOption[E, A any]() func(Either[E, A]) O.Option[A] {
-	return Fold(F.Ignore1of1[E](O.None[A]), O.Some[A])
+func ToOption[E, A any](ma Either[E, A]) O.Option[A] {
+	return MonadFold(ma, F.Ignore1of1[E](O.None[A]), O.Some[A])
 }
 
 func FromError[A any](f func(a A) error) func(A) Either[error, A] {
@@ -182,7 +184,7 @@ func FromPredicate[E, A any](pred func(A) bool, onFalse func(A) E) func(A) Eithe
 	}
 }
 
-func FromNillable[E, A any](e E) func(*A) Either[E, *A] {
+func FromNillable[A, E any](e E) func(*A) Either[E, *A] {
 	return FromPredicate(F.IsNonNil[A], F.Constant1[*A](e))
 }
 
@@ -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/examples_create_test.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 either
+
+import (
+	"fmt"
+
+	"github.com/IBM/fp-go/errors"
+)
+
+func ExampleEither_creation() {
+	// Build an Either
+	leftValue := Left[string](fmt.Errorf("some error"))
+	rightValue := Right[error]("value")
+
+	// Build from a value
+	fromNillable := FromNillable[string](fmt.Errorf("value was nil"))
+	leftFromNil := fromNillable(nil)
+	value := "value"
+	rightFromPointer := fromNillable(&value)
+
+	// some predicate
+	isEven := func(num int) bool {
+		return num%2 == 0
+	}
+	fromEven := FromPredicate(isEven, errors.OnSome[int]("%d is an odd number"))
+	leftFromPred := fromEven(3)
+	rightFromPred := fromEven(4)
+
+	fmt.Println(leftValue)
+	fmt.Println(rightValue)
+	fmt.Println(leftFromNil)
+	fmt.Println(IsRight(rightFromPointer))
+	fmt.Println(leftFromPred)
+	fmt.Println(rightFromPred)
+
+	// Output:
+	// Left[*errors.errorString, string](some error)
+	// Right[<nil>, string](value)
+	// Left[*errors.errorString, *string](value was nil)
+	// true
+	// Left[*errors.errorString, int](3 is an odd number)
+	// Right[<nil>, int](4)
+
+}

either/examples_extract_test.go

@@ -0,0 +1,64 @@
+// 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 (
+	"fmt"
+
+	F "github.com/IBM/fp-go/function"
+	N "github.com/IBM/fp-go/number"
+)
+
+func ExampleEither_extraction() {
+	leftValue := Left[int](fmt.Errorf("Division by Zero!"))
+	rightValue := Right[error](10)
+
+	// Convert Either[E, A] to A with a default value
+	leftWithDefault := GetOrElse(F.Constant1[error](0))(leftValue)   // 0
+	rightWithDefault := GetOrElse(F.Constant1[error](0))(rightValue) // 10
+
+	// Apply a different function on Left(...)/Right(...)
+	doubleOrZero := Fold(F.Constant1[error](0), N.Mul(2)) // func(Either[error, int]) int
+	doubleFromLeft := doubleOrZero(leftValue)             // 0
+	doubleFromRight := doubleOrZero(rightValue)           // 20
+
+	// Pro-tip: Fold is short for the following:
+	doubleOrZeroBis := F.Flow2(
+		Map[error](N.Mul(2)),
+		GetOrElse(F.Constant1[error](0)),
+	)
+	doubleFromLeftBis := doubleOrZeroBis(leftValue)   // 0
+	doubleFromRightBis := doubleOrZeroBis(rightValue) // 20
+
+	fmt.Println(leftValue)
+	fmt.Println(rightValue)
+	fmt.Println(leftWithDefault)
+	fmt.Println(rightWithDefault)
+	fmt.Println(doubleFromLeft)
+	fmt.Println(doubleFromRight)
+	fmt.Println(doubleFromLeftBis)
+	fmt.Println(doubleFromRightBis)
+
+	// Output:
+	// Left[*errors.errorString, int](Division by Zero!)
+	// Right[<nil>, int](10)
+	// 0
+	// 10
+	// 0
+	// 20
+	// 0
+	// 20
+}

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

@@ -1,21 +1,7 @@
-// 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.
-
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-07-21 10:22:45.2674057 +0200 CEST m=+0.015622601
+// 2023-09-12 13:44:15.6356542 +0200 CEST m=+0.009418901
+
 package either
 
 import (

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

@@ -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 either
+
+import (
+	S "github.com/IBM/fp-go/semigroup"
+)
+
+// 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))))

endomorphism/monoid.go

@@ -21,16 +21,12 @@ import (
 	S "github.com/IBM/fp-go/semigroup"
 )
 
-func concat[A any](first, second func(A) A) func(A) A {
-	return F.Flow2(first, second)
-}
-
 // Semigroup for the Endomorphism where the `concat` operation is the usual function composition.
 func Semigroup[A any]() S.Semigroup[func(A) A] {
-	return S.MakeSemigroup(concat[A])
+	return S.MakeSemigroup(F.Flow2[func(A) A, func(A) A])
 }
 
 // Monoid for the Endomorphism where the `concat` operation is the usual function composition.
 func Monoid[A any]() M.Monoid[func(A) A] {
-	return M.MakeMonoid(concat[A], F.Identity[A])
+	return M.MakeMonoid(F.Flow2[func(A) A, func(A) A], F.Identity[A])
 }

errors/messages.go

@@ -28,6 +28,22 @@ func OnNone(msg string, args ...any) func() error {
 	}
 }
 
+// OnSome generates a unary function that produces a formatted error
+func OnSome[T any](msg string, args ...any) func(T) error {
+	l := len(args)
+	if l == 0 {
+		return func(value T) error {
+			return fmt.Errorf(msg, value)
+		}
+	}
+	return func(value T) error {
+		data := make([]any, l)
+		copy(data[1:], args)
+		data[0] = value
+		return fmt.Errorf(msg, data...)
+	}
+}
+
 // OnError generates a unary function that produces a formatted error. The argument
 // to that function is the root cause of the error and the message will be augmented with
 // a format string containing %w

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

@@ -15,14 +15,11 @@
 
 package file
 
-import (
-	"io"
+import "path/filepath"
 
-	IOE "github.com/IBM/fp-go/ioeither"
-)
-
-func onClose[R io.Closer](r R) IOE.IOEither[error, R] {
-	return IOE.TryCatchError(func() (R, error) {
-		return r, r.Close()
-	})
+// 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

@@ -1,21 +1,7 @@
-// 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.
-
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-07-21 10:22:49.808764 +0200 CEST m=+0.064638701
+// 2023-09-12 13:44:23.4226437 +0200 CEST m=+0.011841001
+
 package function
 
 // Combinations for a total of 1 arguments

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/doc.go

@@ -13,6 +13,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// Package function implements function composition primitives, most prominently [Pipe2] and [Flow2]
 package function
 
 //go:generate go run .. pipe --count 20 --filename gen.go

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

@@ -1,21 +1,7 @@
-// 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.
-
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-07-21 10:22:47.675104 +0200 CEST m=+0.112962501
+// 2023-09-12 13:44:17.0002767 +0200 CEST m=+0.008233101
+
 package function
 
 // Pipe0 takes an initial value t0 and successively applies 0 functions where the input of a function is the return value of the previous function
@@ -38,6 +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 {
@@ -90,6 +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 {
@@ -145,6 +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 {
@@ -203,6 +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 {
@@ -264,6 +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 {
@@ -328,6 +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 {
@@ -395,6 +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 {
@@ -465,6 +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 {
@@ -538,6 +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 {
@@ -614,6 +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 {
@@ -693,6 +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 {
@@ -775,6 +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 {
@@ -860,6 +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 {
@@ -948,6 +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 {
@@ -1039,6 +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 {
@@ -1133,6 +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 {
@@ -1230,6 +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 {
@@ -1330,6 +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 {
@@ -1433,6 +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 {
@@ -1539,6 +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 {
@@ -1647,3 +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/pipe_test.go

@@ -0,0 +1,62 @@
+// 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 (
+	"fmt"
+)
+
+func addSthg(value int) int {
+	return value + 1
+}
+
+func doSthgElse(value int) int {
+	return value * 2
+}
+
+func doFinalSthg(value int) string {
+	return fmt.Sprintf("final value: %d", value)
+}
+
+func Example() {
+	// start point
+	value := 1
+	// imperative style
+	value1 := addSthg(value)                    // 2
+	value2 := doSthgElse(value1)                // 4
+	finalValueImperative := doFinalSthg(value2) // "final value: 4"
+
+	// the same but inline
+	finalValueInline := doFinalSthg(doSthgElse(addSthg(value)))
+
+	// with pipe
+	finalValuePipe := Pipe3(value, addSthg, doSthgElse, doFinalSthg)
+
+	// with flow
+	transform := Flow3(addSthg, doSthgElse, doFinalSthg)
+	finalValueFlow := transform(value)
+
+	fmt.Println(finalValueImperative)
+	fmt.Println(finalValueInline)
+	fmt.Println(finalValuePipe)
+	fmt.Println(finalValueFlow)
+
+	// Output:
+	// final value: 4
+	// final value: 4
+	// final value: 4
+	// final value: 4
+}

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

@@ -1,21 +1,7 @@
-// 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.
-
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-07-21 10:22:53.6381914 +0200 CEST m=+0.019961301
+// 2023-09-12 13:44:24.9409324 +0200 CEST m=+0.008573601
+
 package identity
 
 import (

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

@@ -1,21 +1,7 @@
-// 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.
-
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-07-21 10:22:55.7987979 +0200 CEST m=+0.076670601
+// 2023-09-12 13:44:26.2499883 +0200 CEST m=+0.007601301
+
 package apply
 
 import (

internal/array/array.go

@@ -42,10 +42,27 @@ func Reduce[GA ~[]A, A, B any](fa GA, f func(B, A) B, initial B) B {
 	return current
 }
 
+func ReduceWithIndex[GA ~[]A, A, B any](fa GA, f func(int, B, A) B, initial B) B {
+	current := initial
+	count := len(fa)
+	for i := 0; i < count; i++ {
+		current = f(i, current, fa[i])
+	}
+	return current
+}
+
 func Append[GA ~[]A, A any](as GA, a A) GA {
 	return append(as, a)
 }
 
+func Push[GA ~[]A, A any](as GA, a A) GA {
+	l := len(as)
+	cpy := make(GA, l+1)
+	copy(cpy, as)
+	cpy[l] = a
+	return cpy
+}
+
 func Empty[GA ~[]A, A any]() GA {
 	return make(GA, 0)
 }

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/bindt/bind.go

@@ -0,0 +1,75 @@
+// 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 bindt
+
+import (
+	F "github.com/IBM/fp-go/function"
+	I "github.com/IBM/fp-go/identity"
+	T "github.com/IBM/fp-go/tuple"
+)
+
+func Bind[SET ~func(B) func(S1) S2, FCT ~func(S1) HKTB, S1, S2, B, HKTS1, HKTS2, HKTB any](
+	mchain func(func(S1) HKTS2) func(HKTS1) HKTS2,
+	mmap func(func(B) S2) func(HKTB) HKTS2,
+	s SET,
+	f FCT,
+) func(HKTS1) HKTS2 {
+	return mchain(F.Flow3(
+		T.Replicate2[S1],
+		T.Map2(F.Flow2(
+			I.Ap[S2, S1],
+			F.Flow2(
+				F.Bind1st(F.Flow2[SET, func(func(S1) S2) S2], s),
+				mmap,
+			)), f),
+		T.Tupled2(I.MonadAp[HKTS2, HKTB]),
+	))
+}
+
+func BindTo[SET ~func(B) S2, S2, B, HKTS2, HKTB any](
+	mmap func(func(B) S2) func(HKTB) HKTS2,
+	s SET,
+) func(HKTB) HKTS2 {
+	return mmap(s)
+}
+
+func ApS[
+	SET ~func(B) func(S1) S2,
+	S1, S2, B, HKTS1S2, HKTS1, HKTS2, HKTB any,
+](
+	ap func(HKTS1) func(HKTS1S2) HKTS2,
+	mmap func(func(B) func(S1) S2) func(HKTB) HKTS1S2,
+	s SET, fb HKTB) func(HKTS1) HKTS2 {
+
+	return F.Flow2(
+		ap,
+		I.Ap[HKTS2, HKTS1S2](mmap(s)(fb)),
+	)
+}
+
+func Let[SET ~func(B) func(S1) S2, FCT ~func(S1) B, S1, S2, B, HKTS1, HKTS2 any](
+	mmap func(func(S1) S2) func(HKTS1) HKTS2,
+	s SET,
+	f FCT,
+) func(HKTS1) HKTS2 {
+	return mmap(F.Flow3(
+		T.Replicate2[S1],
+		T.Map2(F.Flow2(
+			I.Ap[S2, S1],
+			F.Bind1st(F.Flow2[SET, func(func(S1) S2) S2], s)), f),
+		T.Tupled2(I.MonadAp[S2, B]),
+	))
+}

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)
+	}
+}