fix: add WithQueryArg to request builder

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

.github/workflows/build.yml

@@ -33,7 +33,7 @@ jobs:
         with:
           fetch-depth: 0
       - name: Set up go ${{ matrix.go-version }}
-        uses: actions/setup-go@v4
+        uses: actions/setup-go@v5
         with:
           go-version: ${{ matrix.go-version }}
       -
@@ -60,12 +60,12 @@ jobs:
           fetch-depth: 0
 
       - name: Set up Node.js ${{ env.NODE_VERSION }}
-        uses: actions/setup-node@8f152de45cc393bb48ce5d89d36b731f54556e65 # v4.0.0
+        uses: actions/setup-node@b39b52d1213e96004bfcb1c61a8a6fa8ab84f3e8 # v4.0.1
         with:
           node-version: ${{ env.NODE_VERSION }}
 
       - name: Set up go ${{env.GO_VERSION}}
-        uses: actions/setup-go@v4
+        uses: actions/setup-go@v5
         with:
           go-version: ${{env.GO_VERSION}}
 

.gitignore

@@ -1,3 +1,4 @@
 fp-go.exe
 main.exe
-build/
+build/
+.idea

array/any.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 array
+
+import (
+	G "github.com/IBM/fp-go/array/generic"
+)
+
+// AnyWithIndex tests if any of the elements in the array matches the predicate
+func AnyWithIndex[A any](pred func(int, A) bool) func([]A) bool {
+	return G.AnyWithIndex[[]A](pred)
+}
+
+// Any tests if any of the elements in the array matches the predicate
+func Any[A any](pred func(A) bool) func([]A) bool {
+	return G.Any[[]A](pred)
+}

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

array/array.go

@@ -17,6 +17,7 @@ package array
 
 import (
 	G "github.com/IBM/fp-go/array/generic"
+	EM "github.com/IBM/fp-go/endomorphism"
 	F "github.com/IBM/fp-go/function"
 	"github.com/IBM/fp-go/internal/array"
 	M "github.com/IBM/fp-go/monoid"
@@ -52,6 +53,10 @@ func MonadMapRef[A, B any](as []A, f func(a *A) B) []B {
 	return bs
 }
 
+func MapWithIndex[A, B any](f func(int, A) B) func([]A) []B {
+	return G.MapWithIndex[[]A, []B](f)
+}
+
 func Map[A, B any](f func(a A) B) func([]A) []B {
 	return F.Bind2nd(MonadMap[A, B], f)
 }
@@ -60,18 +65,6 @@ func MapRef[A, B any](f func(a *A) B) func([]A) []B {
 	return F.Bind2nd(MonadMapRef[A, B], f)
 }
 
-func filter[A any](fa []A, pred func(A) bool) []A {
-	var result []A
-	count := len(fa)
-	for i := 0; i < count; i++ {
-		a := fa[i]
-		if pred(a) {
-			result = append(result, a)
-		}
-	}
-	return result
-}
-
 func filterRef[A any](fa []A, pred func(a *A) bool) []A {
 	var result []A
 	count := len(fa)
@@ -96,23 +89,38 @@ func filterMapRef[A, B any](fa []A, pred func(a *A) bool, f func(a *A) B) []B {
 	return result
 }
 
-func Filter[A any](pred func(A) bool) func([]A) []A {
-	return F.Bind2nd(filter[A], pred)
+// Filter returns a new array with all elements from the original array that match a predicate
+func Filter[A any](pred func(A) bool) EM.Endomorphism[[]A] {
+	return G.Filter[[]A](pred)
 }
 
-func FilterRef[A any](pred func(*A) bool) func([]A) []A {
+// FilterWithIndex returns a new array with all elements from the original array that match a predicate
+func FilterWithIndex[A any](pred func(int, A) bool) EM.Endomorphism[[]A] {
+	return G.FilterWithIndex[[]A](pred)
+}
+
+func FilterRef[A any](pred func(*A) bool) EM.Endomorphism[[]A] {
 	return F.Bind2nd(filterRef[A], pred)
 }
 
-func MonadFilterMap[A, B any](fa []A, f func(a A) O.Option[B]) []B {
+func MonadFilterMap[A, B any](fa []A, f func(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 {
+func MonadFilterMapWithIndex[A, B any](fa []A, f func(int, A) O.Option[B]) []B {
+	return G.MonadFilterMapWithIndex[[]A, []B](fa, f)
+}
+
+// FilterMap maps an array with an iterating function that returns an [O.Option] and it keeps only the Some values discarding the Nones.
+func FilterMap[A, B any](f func(A) O.Option[B]) func([]A) []B {
 	return G.FilterMap[[]A, []B](f)
 }
 
+// FilterMapWithIndex maps an array with an iterating function that returns an [O.Option] and it keeps only the Some values discarding the Nones.
+func FilterMapWithIndex[A, B any](f func(int, A) O.Option[B]) func([]A) []B {
+	return G.FilterMapWithIndex[[]A, []B](f)
+}
+
 // FilterChain maps an array with an iterating function that returns an [O.Option] of an array. It keeps only the Some values discarding the Nones and then flattens the result.
 func FilterChain[A, B any](f func(A) O.Option[[]B]) func([]A) []B {
 	return G.FilterChain[[]A](f)
@@ -134,9 +142,19 @@ func reduceRef[A, B any](fa []A, f func(B, *A) B, initial B) B {
 }
 
 func Reduce[A, B any](f func(B, A) B, initial B) func([]A) B {
-	return func(as []A) B {
-		return array.Reduce(as, f, initial)
-	}
+	return G.Reduce[[]A](f, initial)
+}
+
+func ReduceWithIndex[A, B any](f func(int, B, A) B, initial B) func([]A) B {
+	return G.ReduceWithIndex[[]A](f, initial)
+}
+
+func ReduceRight[A, B any](f func(A, B) B, initial B) func([]A) B {
+	return G.ReduceRight[[]A](f, initial)
+}
+
+func ReduceRightWithIndex[A, B any](f func(int, A, B) B, initial B) func([]A) B {
+	return G.ReduceRightWithIndex[[]A](f, initial)
 }
 
 func ReduceRef[A, B any](f func(B, *A) B, initial B) func([]A) B {
@@ -210,7 +228,7 @@ func Last[A any](as []A) O.Option[A] {
 	return G.Last(as)
 }
 
-func PrependAll[A any](middle A) func([]A) []A {
+func PrependAll[A any](middle A) EM.Endomorphism[[]A] {
 	return func(as []A) []A {
 		count := len(as)
 		dst := count * 2
@@ -225,7 +243,7 @@ func PrependAll[A any](middle A) func([]A) []A {
 	}
 }
 
-func Intersperse[A any](middle A) func([]A) []A {
+func Intersperse[A any](middle A) EM.Endomorphism[[]A] {
 	prepend := PrependAll(middle)
 	return func(as []A) []A {
 		if IsEmpty(as) {
@@ -254,7 +272,7 @@ func Lookup[A any](idx int) func([]A) O.Option[A] {
 	return G.Lookup[[]A](idx)
 }
 
-func UpsertAt[A any](a A) func([]A) []A {
+func UpsertAt[A any](a A) EM.Endomorphism[[]A] {
 	return G.UpsertAt[[]A](a)
 }
 
@@ -287,26 +305,37 @@ func ConstNil[A any]() []A {
 	return array.ConstNil[[]A]()
 }
 
-func SliceRight[A any](start int) func([]A) []A {
+func SliceRight[A any](start int) EM.Endomorphism[[]A] {
 	return G.SliceRight[[]A](start)
 }
 
+// Copy creates a shallow copy of the array
 func Copy[A any](b []A) []A {
 	return G.Copy(b)
 }
 
+// Clone creates a deep copy of the array using the provided endomorphism to clone the values
+func Clone[A any](f func(A) A) func(as []A) []A {
+	return G.Clone[[]A](f)
+}
+
 // FoldMap maps and folds an array. Map the Array passing each value to the iterating function. Then fold the results using the provided Monoid.
 func FoldMap[A, B any](m M.Monoid[B]) func(func(A) B) func([]A) B {
 	return G.FoldMap[[]A](m)
 }
 
+// FoldMapWithIndex maps and folds an array. Map the Array passing each value to the iterating function. Then fold the results using the provided Monoid.
+func FoldMapWithIndex[A, B any](m M.Monoid[B]) func(func(int, A) B) func([]A) B {
+	return G.FoldMapWithIndex[[]A](m)
+}
+
 // Fold folds the array using the provided Monoid.
 func Fold[A any](m M.Monoid[A]) func([]A) A {
 	return G.Fold[[]A](m)
 }
 
-func Push[A any](a A) func([]A) []A {
-	return G.Push[[]A](a)
+func Push[A any](a A) EM.Endomorphism[[]A] {
+	return G.Push[EM.Endomorphism[[]A]](a)
 }
 
 func MonadFlap[B, A any](fab []func(A) B, a A) []B {
@@ -316,3 +345,7 @@ func MonadFlap[B, A any](fab []func(A) B, a A) []B {
 func Flap[B, A any](a A) func([]func(A) B) []B {
 	return G.Flap[func(A) B, []func(A) B, []B, A, B](a)
 }
+
+func Prepend[A any](head A) EM.Endomorphism[[]A] {
+	return G.Prepend[EM.Endomorphism[[]A]](head)
+}

array/array_test.go

@@ -59,6 +59,17 @@ func TestMap(t *testing.T) {
 	assert.Equal(t, dst, []string{"A", "B", "C"})
 }
 
+func TestReduceRight(t *testing.T) {
+	values := From("a", "b", "c")
+	f := func(a, acc string) string {
+		return fmt.Sprintf("%s%s", acc, a)
+	}
+	b := ""
+
+	assert.Equal(t, "cba", ReduceRight(f, b)(values))
+	assert.Equal(t, "", ReduceRight(f, b)(Empty[string]()))
+}
+
 func TestReduce(t *testing.T) {
 
 	values := MakeBy(101, F.Identity[int])

array/example_any_test.go

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

array/example_find_test.go

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

array/find.go

@@ -0,0 +1,61 @@
+// 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"
+	O "github.com/IBM/fp-go/option"
+)
+
+// FindFirst finds the first element which satisfies a predicate (or a refinement) function
+func FindFirst[A any](pred func(A) bool) func([]A) O.Option[A] {
+	return G.FindFirst[[]A](pred)
+}
+
+// FindFirstWithIndex finds the first element which satisfies a predicate (or a refinement) function
+func FindFirstWithIndex[A any](pred func(int, A) bool) func([]A) O.Option[A] {
+	return G.FindFirstWithIndex[[]A](pred)
+}
+
+// FindFirstMap finds the first element returned by an [O.Option] based selector function
+func FindFirstMap[A, B any](sel func(A) O.Option[B]) func([]A) O.Option[B] {
+	return G.FindFirstMap[[]A](sel)
+}
+
+// FindFirstMapWithIndex finds the first element returned by an [O.Option] based selector function
+func FindFirstMapWithIndex[A, B any](sel func(int, A) O.Option[B]) func([]A) O.Option[B] {
+	return G.FindFirstMapWithIndex[[]A](sel)
+}
+
+// FindLast finds the Last element which satisfies a predicate (or a refinement) function
+func FindLast[A any](pred func(A) bool) func([]A) O.Option[A] {
+	return G.FindLast[[]A](pred)
+}
+
+// FindLastWithIndex finds the Last element which satisfies a predicate (or a refinement) function
+func FindLastWithIndex[A any](pred func(int, A) bool) func([]A) O.Option[A] {
+	return G.FindLastWithIndex[[]A](pred)
+}
+
+// FindLastMap finds the Last element returned by an [O.Option] based selector function
+func FindLastMap[A, B any](sel func(A) O.Option[B]) func([]A) O.Option[B] {
+	return G.FindLastMap[[]A](sel)
+}
+
+// FindLastMapWithIndex finds the Last element returned by an [O.Option] based selector function
+func FindLastMapWithIndex[A, B any](sel func(int, A) O.Option[B]) func([]A) O.Option[B] {
+	return G.FindLastMapWithIndex[[]A](sel)
+}

array/generic/any.go

@@ -0,0 +1,34 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package generic
+
+import (
+	F "github.com/IBM/fp-go/function"
+	O "github.com/IBM/fp-go/option"
+)
+
+// AnyWithIndex tests if any of the elements in the array matches the predicate
+func AnyWithIndex[AS ~[]A, PRED ~func(int, A) bool, A any](pred PRED) func(AS) bool {
+	return F.Flow2(
+		FindFirstWithIndex[AS](pred),
+		O.IsSome[A],
+	)
+}
+
+// Any tests if any of the elements in the array matches the predicate
+func Any[AS ~[]A, PRED ~func(A) bool, A any](pred PRED) func(AS) bool {
+	return AnyWithIndex[AS](F.Ignore1of2[int](pred))
+}

array/generic/array.go

@@ -29,14 +29,46 @@ 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 {
+func Reduce[GA ~[]A, A, B any](f func(B, A) B, initial B) func(GA) B {
+	return func(as GA) B {
+		return MonadReduce[GA](as, f, initial)
+	}
+}
+
+func ReduceWithIndex[GA ~[]A, A, B any](f func(int, B, A) B, initial B) func(GA) B {
+	return func(as GA) B {
+		return MonadReduceWithIndex[GA](as, f, initial)
+	}
+}
+
+func ReduceRight[GA ~[]A, A, B any](f func(A, B) B, initial B) func(GA) B {
+	return func(as GA) B {
+		return MonadReduceRight[GA](as, f, initial)
+	}
+}
+
+func ReduceRightWithIndex[GA ~[]A, A, B any](f func(int, A, B) B, initial B) func(GA) B {
+	return func(as GA) B {
+		return MonadReduceRightWithIndex[GA](as, f, initial)
+	}
+}
+
+func MonadReduce[GA ~[]A, A, B any](fa GA, f func(B, A) B, initial B) B {
 	return array.Reduce(fa, f, initial)
 }
 
-func ReduceWithIndex[GA ~[]A, A, B any](fa GA, f func(int, B, A) B, initial B) B {
+func MonadReduceWithIndex[GA ~[]A, A, B any](fa GA, f func(int, B, A) B, initial B) B {
 	return array.ReduceWithIndex(fa, f, initial)
 }
 
+func MonadReduceRight[GA ~[]A, A, B any](fa GA, f func(A, B) B, initial B) B {
+	return array.ReduceRight(fa, f, initial)
+}
+
+func MonadReduceRightWithIndex[GA ~[]A, A, B any](fa GA, f func(int, A, B) B, initial B) B {
+	return array.ReduceRightWithIndex(fa, f, initial)
+}
+
 // From constructs an array from a set of variadic arguments
 func From[GA ~[]A, A any](data ...A) GA {
 	return data
@@ -118,20 +150,56 @@ 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 MonadMapWithIndex[GA ~[]A, GB ~[]B, A, B any](as GA, f func(int, A) B) GB {
+	return array.MonadMapWithIndex[GA, GB](as, f)
+}
+
+func MapWithIndex[GA ~[]A, GB ~[]B, A, B any](f func(int, A) B) func(GA) GB {
+	return F.Bind2nd(MonadMapWithIndex[GA, GB, A, B], f)
+}
+
 func Size[GA ~[]A, A any](as GA) int {
 	return len(as)
 }
 
-func filterMap[GA ~[]A, GB ~[]B, A, B any](fa GA, f func(a A) O.Option[B]) GB {
+func filterMap[GA ~[]A, GB ~[]B, A, B any](fa GA, f func(A) O.Option[B]) GB {
 	return array.Reduce(fa, func(bs GB, a A) GB {
 		return O.MonadFold(f(a), F.Constant(bs), F.Bind1st(Append[GB, B], bs))
 	}, Empty[GB]())
 }
 
-func MonadFilterMap[GA ~[]A, GB ~[]B, A, B any](fa GA, f func(a A) O.Option[B]) GB {
+func filterMapWithIndex[GA ~[]A, GB ~[]B, A, B any](fa GA, f func(int, A) O.Option[B]) GB {
+	return array.ReduceWithIndex(fa, func(idx int, bs GB, a A) GB {
+		return O.MonadFold(f(idx, a), F.Constant(bs), F.Bind1st(Append[GB, B], bs))
+	}, Empty[GB]())
+}
+
+func MonadFilterMap[GA ~[]A, GB ~[]B, A, B any](fa GA, f func(A) O.Option[B]) GB {
 	return filterMap[GA, GB](fa, f)
 }
 
+func MonadFilterMapWithIndex[GA ~[]A, GB ~[]B, A, B any](fa GA, f func(int, A) O.Option[B]) GB {
+	return filterMapWithIndex[GA, GB](fa, f)
+}
+
+func filterWithIndex[AS ~[]A, PRED ~func(int, A) bool, A any](fa AS, pred PRED) AS {
+	result := make(AS, 0, len(fa))
+	for i, a := range fa {
+		if pred(i, a) {
+			result = append(result, a)
+		}
+	}
+	return result
+}
+
+func FilterWithIndex[AS ~[]A, PRED ~func(int, A) bool, A any](pred PRED) func(AS) AS {
+	return F.Bind2nd(filterWithIndex[AS, PRED, A], pred)
+}
+
+func Filter[AS ~[]A, PRED ~func(A) bool, A any](pred PRED) func(AS) AS {
+	return FilterWithIndex[AS](F.Ignore1of2[int](pred))
+}
+
 func FilterChain[GA ~[]A, GB ~[]B, A, B any](f func(a A) O.Option[GB]) func(GA) GB {
 	return F.Flow2(
 		FilterMap[GA, []GB](f),
@@ -143,10 +211,14 @@ 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 {
+func FilterMap[GA ~[]A, GB ~[]B, A, B any](f func(A) O.Option[B]) func(GA) GB {
 	return F.Bind2nd(MonadFilterMap[GA, GB, A, B], f)
 }
 
+func FilterMapWithIndex[GA ~[]A, GB ~[]B, A, B any](f func(int, A) O.Option[B]) func(GA) GB {
+	return F.Bind2nd(MonadFilterMapWithIndex[GA, GB, A, B], f)
+}
+
 func MonadPartition[GA ~[]A, A any](as GA, pred func(A) bool) tuple.Tuple2[GA, GA] {
 	left := Empty[GA]()
 	right := Empty[GA]()
@@ -232,6 +304,11 @@ func Copy[AS ~[]A, A any](b AS) AS {
 	return buf
 }
 
+func Clone[AS ~[]A, A any](f func(A) A) func(as AS) AS {
+	// implementation assumes that map does not optimize for the empty array
+	return Map[AS, AS](f)
+}
+
 func FoldMap[AS ~[]A, A, B any](m M.Monoid[B]) func(func(A) B) func(AS) B {
 	return func(f func(A) B) func(AS) B {
 		return func(as AS) B {
@@ -242,13 +319,23 @@ func FoldMap[AS ~[]A, A, B any](m M.Monoid[B]) func(func(A) B) func(AS) B {
 	}
 }
 
+func FoldMapWithIndex[AS ~[]A, A, B any](m M.Monoid[B]) func(func(int, A) B) func(AS) B {
+	return func(f func(int, A) B) func(AS) B {
+		return func(as AS) B {
+			return array.ReduceWithIndex(as, func(idx int, cur B, a A) B {
+				return m.Concat(cur, f(idx, 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 {
+func Push[ENDO ~func(GA) GA, GA ~[]A, A any](a A) ENDO {
 	return F.Bind2nd(array.Push[GA, A], a)
 }
 
@@ -259,3 +346,7 @@ func MonadFlap[FAB ~func(A) B, GFAB ~[]FAB, GB ~[]B, A, B any](fab GFAB, a A) GB
 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)
 }
+
+func Prepend[ENDO ~func(AS) AS, AS []A, A any](head A) ENDO {
+	return array.Prepend[ENDO](head)
+}

array/generic/find.go

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

array/generic/uniq.go

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

array/monoid.go

@@ -18,6 +18,7 @@ package array
 import (
 	"github.com/IBM/fp-go/internal/array"
 	M "github.com/IBM/fp-go/monoid"
+	S "github.com/IBM/fp-go/semigroup"
 )
 
 func concat[T any](left, right []T) []T {
@@ -40,6 +41,10 @@ func Monoid[T any]() M.Monoid[[]T] {
 	return M.MakeMonoid(concat[T], Empty[T]())
 }
 
+func Semigroup[T any]() S.Semigroup[[]T] {
+	return S.MakeSemigroup(concat[T])
+}
+
 func addLen[A any](count int, data []A) int {
 	return count + len(data)
 }

array/nonempty/array.go

@@ -17,6 +17,7 @@ package nonempty
 
 import (
 	G "github.com/IBM/fp-go/array/generic"
+	EM "github.com/IBM/fp-go/endomorphism"
 	F "github.com/IBM/fp-go/function"
 	"github.com/IBM/fp-go/internal/array"
 	S "github.com/IBM/fp-go/semigroup"
@@ -65,6 +66,12 @@ func Reduce[A, B any](f func(B, A) B, initial B) func(NonEmptyArray[A]) B {
 	}
 }
 
+func ReduceRight[A, B any](f func(A, B) B, initial B) func(NonEmptyArray[A]) B {
+	return func(as NonEmptyArray[A]) B {
+		return array.ReduceRight(as, f, initial)
+	}
+}
+
 func Tail[A any](as NonEmptyArray[A]) []A {
 	return as[1:]
 }
@@ -122,3 +129,8 @@ func Fold[A any](s S.Semigroup[A]) func(NonEmptyArray[A]) A {
 		return array.Reduce(Tail(as), s.Concat, Head(as))
 	}
 }
+
+// Prepend prepends a single value to an array
+func Prepend[A any](head A) EM.Endomorphism[NonEmptyArray[A]] {
+	return array.Prepend[EM.Endomorphism[NonEmptyArray[A]]](head)
+}

array/uniq.go

@@ -0,0 +1,17 @@
+package array
+
+import (
+	G "github.com/IBM/fp-go/array/generic"
+)
+
+// StrictUniq converts an array of arbitrary items into an array or unique items
+// where uniqueness is determined by the built-in uniqueness constraint
+func StrictUniq[A comparable](as []A) []A {
+	return G.StrictUniq[[]A](as)
+}
+
+// Uniq converts an array of arbitrary items into an array or unique items
+// where uniqueness is determined based on a key extractor function
+func Uniq[A any, K comparable](f func(A) K) func(as []A) []A {
+	return G.Uniq[[]A](f)
+}

array/uniq_test.go

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

cli/commands.go

@@ -34,5 +34,6 @@ func Commands() []*C.Command {
 		IOEitherCommand(),
 		IOCommand(),
 		IOOptionCommand(),
+		DICommand(),
 	}
 }

cli/di.go

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

cli/pipe.go

@@ -295,15 +295,16 @@ func recurseCurry(f *os.File, indent string, total, count int) {
 func generateCurry(f *os.File, i int) {
 	// Create the curry version
 	fmt.Fprintf(f, "\n// Curry%d takes a function with %d parameters and returns a cascade of functions each taking only one parameter.\n// The inverse function is [Uncurry%d]\n", i, i, i)
-	fmt.Fprintf(f, "func Curry%d[T0", i)
-	for j := 1; j <= i; j++ {
+	fmt.Fprintf(f, "func Curry%d[FCT ~func(T0", i)
+	for j := 1; j < i; j++ {
 		fmt.Fprintf(f, ", T%d", j)
 	}
-	fmt.Fprintf(f, " any](f func(T0")
-	for j := 2; j <= i; j++ {
-		fmt.Fprintf(f, ", T%d", j-1)
+	fmt.Fprintf(f, ") T%d", i)
+	// type arguments
+	for j := 0; j <= i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
 	}
-	fmt.Fprintf(f, ") T%d) func(T0)", i)
+	fmt.Fprintf(f, " any](f FCT) func(T0)")
 	for j := 2; j <= i; j++ {
 		fmt.Fprintf(f, " func(T%d)", j-1)
 	}
@@ -315,15 +316,16 @@ func generateCurry(f *os.File, i int) {
 func generateUncurry(f *os.File, i int) {
 	// Create the uncurry version
 	fmt.Fprintf(f, "\n// Uncurry%d takes a cascade of %d functions each taking only one parameter and returns a function with %d parameters .\n// The inverse function is [Curry%d]\n", i, i, i, i)
-	fmt.Fprintf(f, "func Uncurry%d[T0", i)
-	for j := 1; j <= i; j++ {
+	fmt.Fprintf(f, "func Uncurry%d[FCT ~func(T0)", i)
+	for j := 1; j < i; j++ {
+		fmt.Fprintf(f, " func(T%d)", j)
+	}
+	fmt.Fprintf(f, " T%d", i)
+	// the type parameters
+	for j := 0; j <= i; j++ {
 		fmt.Fprintf(f, ", T%d", j)
 	}
-	fmt.Fprintf(f, " any](f")
-	for j := 1; j <= i; j++ {
-		fmt.Fprintf(f, " func(T%d)", j-1)
-	}
-	fmt.Fprintf(f, " T%d) func(", i)
+	fmt.Fprintf(f, " any](f FCT) func(")
 	for j := 1; j <= i; j++ {
 		if j > 1 {
 			fmt.Fprintf(f, ", ")

context/readerioeither/generic/traverse.go

@@ -166,3 +166,289 @@ func SequenceRecord[K comparable,
 
 	return MonadTraverseRecord[K, GAS, GRAS](ma, F.Identity[GRA])
 }
+
+// MonadTraverseArraySeq transforms an array
+func MonadTraverseArraySeq[
+	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](as AS, f func(A) GRB) GRBS {
+
+	return RA.MonadTraverse[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],
+		ApSeq[GRBS, func(context.Context) func() E.Either[error, func(B) BS], GRB],
+
+		as, f,
+	)
+}
+
+// TraverseArraySeq transforms an array
+func TraverseArraySeq[
+	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(A) GRB) func(AS) GRBS {
+
+	return RA.Traverse[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],
+		ApSeq[GRBS, func(context.Context) func() E.Either[error, func(B) BS], GRB],
+
+		f,
+	)
+}
+
+// TraverseArrayWithIndexSeq transforms an array
+func TraverseArrayWithIndexSeq[
+	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],
+		ApSeq[GRBS, func(context.Context) func() E.Either[error, func(B) BS], GRB],
+
+		f,
+	)
+}
+
+// SequenceArraySeq converts a homogeneous sequence of either into an either of sequence
+func SequenceArraySeq[
+	AS ~[]A,
+	GAS ~[]GRA,
+	GRAS ~func(context.Context) GIOAS,
+	GRA ~func(context.Context) GIOA,
+	GIOAS ~func() E.Either[error, AS],
+	GIOA ~func() E.Either[error, A],
+	A any](ma GAS) GRAS {
+
+	return MonadTraverseArraySeq[GAS, GRAS](ma, F.Identity[GRA])
+}
+
+// MonadTraverseRecordSeq transforms a record
+func MonadTraverseRecordSeq[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](ma AS, f func(A) GRB) GRBS {
+
+	return RR.MonadTraverse[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],
+		ApSeq[GRBS, func(context.Context) func() E.Either[error, func(B) BS], GRB],
+
+		ma, f,
+	)
+}
+
+// TraverseRecordSeq transforms a record
+func TraverseRecordSeq[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(A) GRB) func(AS) GRBS {
+
+	return RR.Traverse[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],
+		ApSeq[GRBS, func(context.Context) func() E.Either[error, func(B) BS], GRB],
+
+		f,
+	)
+}
+
+// TraverseRecordWithIndexSeq transforms a record
+func TraverseRecordWithIndexSeq[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],
+		ApSeq[GRBS, func(context.Context) func() E.Either[error, func(B) BS], GRB],
+
+		f,
+	)
+}
+
+// SequenceRecordSeq converts a homogeneous sequence of either into an either of sequence
+func SequenceRecordSeq[K comparable,
+	AS ~map[K]A,
+	GAS ~map[K]GRA,
+	GRAS ~func(context.Context) GIOAS,
+	GRA ~func(context.Context) GIOA,
+	GIOAS ~func() E.Either[error, AS],
+	GIOA ~func() E.Either[error, A],
+	A any](ma GAS) GRAS {
+
+	return MonadTraverseRecordSeq[K, GAS, GRAS](ma, F.Identity[GRA])
+}
+
+// MonadTraverseArrayPar transforms an array
+func MonadTraverseArrayPar[
+	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](as AS, f func(A) GRB) GRBS {
+
+	return RA.MonadTraverse[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],
+		ApPar[GRBS, func(context.Context) func() E.Either[error, func(B) BS], GRB],
+
+		as, f,
+	)
+}
+
+// TraverseArrayPar transforms an array
+func TraverseArrayPar[
+	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(A) GRB) func(AS) GRBS {
+
+	return RA.Traverse[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],
+		ApPar[GRBS, func(context.Context) func() E.Either[error, func(B) BS], GRB],
+
+		f,
+	)
+}
+
+// TraverseArrayWithIndexPar transforms an array
+func TraverseArrayWithIndexPar[
+	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],
+		ApPar[GRBS, func(context.Context) func() E.Either[error, func(B) BS], GRB],
+
+		f,
+	)
+}
+
+// SequenceArrayPar converts a homogeneous sequence of either into an either of sequence
+func SequenceArrayPar[
+	AS ~[]A,
+	GAS ~[]GRA,
+	GRAS ~func(context.Context) GIOAS,
+	GRA ~func(context.Context) GIOA,
+	GIOAS ~func() E.Either[error, AS],
+	GIOA ~func() E.Either[error, A],
+	A any](ma GAS) GRAS {
+
+	return MonadTraverseArrayPar[GAS, GRAS](ma, F.Identity[GRA])
+}
+
+// MonadTraverseRecordPar transforms a record
+func MonadTraverseRecordPar[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](ma AS, f func(A) GRB) GRBS {
+
+	return RR.MonadTraverse[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],
+		ApPar[GRBS, func(context.Context) func() E.Either[error, func(B) BS], GRB],
+
+		ma, f,
+	)
+}
+
+// TraverseRecordPar transforms a record
+func TraverseRecordPar[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(A) GRB) func(AS) GRBS {
+
+	return RR.Traverse[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],
+		ApPar[GRBS, func(context.Context) func() E.Either[error, func(B) BS], GRB],
+
+		f,
+	)
+}
+
+// TraverseRecordWithIndexPar transforms a record
+func TraverseRecordWithIndexPar[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],
+		ApPar[GRBS, func(context.Context) func() E.Either[error, func(B) BS], GRB],
+
+		f,
+	)
+}
+
+// SequenceRecordPar converts a homogeneous sequence of either into an either of sequence
+func SequenceRecordPar[K comparable,
+	AS ~map[K]A,
+	GAS ~map[K]GRA,
+	GRAS ~func(context.Context) GIOAS,
+	GRA ~func(context.Context) GIOA,
+	GIOAS ~func() E.Either[error, AS],
+	GIOA ~func() E.Either[error, A],
+	A any](ma GAS) GRAS {
+
+	return MonadTraverseRecordPar[K, GAS, GRAS](ma, F.Identity[GRA])
+}

context/readerioeither/traverse.go

@@ -48,3 +48,63 @@ func TraverseRecordWithIndex[K comparable, A, B any](f func(K, A) ReaderIOEither
 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)
 }
+
+// TraverseArraySeq uses transforms an array [[]A] into [[]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[[]B]]
+func TraverseArraySeq[A, B any](f func(A) ReaderIOEither[B]) func([]A) ReaderIOEither[[]B] {
+	return G.TraverseArraySeq[[]A, ReaderIOEither[[]B]](f)
+}
+
+// TraverseArrayWithIndexSeq uses transforms an array [[]A] into [[]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[[]B]]
+func TraverseArrayWithIndexSeq[A, B any](f func(int, A) ReaderIOEither[B]) func([]A) ReaderIOEither[[]B] {
+	return G.TraverseArrayWithIndexSeq[[]A, ReaderIOEither[[]B]](f)
+}
+
+// SequenceArraySeq converts a homogeneous sequence of either into an either of sequence
+func SequenceArraySeq[A any](ma []ReaderIOEither[A]) ReaderIOEither[[]A] {
+	return G.SequenceArraySeq[[]A, []ReaderIOEither[A], ReaderIOEither[[]A]](ma)
+}
+
+// TraverseRecordSeq uses transforms a record [map[K]A] into [map[K]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[map[K]B]]
+func TraverseRecordSeq[K comparable, A, B any](f func(A) ReaderIOEither[B]) func(map[K]A) ReaderIOEither[map[K]B] {
+	return G.TraverseRecordSeq[K, map[K]A, ReaderIOEither[map[K]B]](f)
+}
+
+// TraverseRecordWithIndexSeq uses transforms a record [map[K]A] into [map[K]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[map[K]B]]
+func TraverseRecordWithIndexSeq[K comparable, A, B any](f func(K, A) ReaderIOEither[B]) func(map[K]A) ReaderIOEither[map[K]B] {
+	return G.TraverseRecordWithIndexSeq[K, map[K]A, ReaderIOEither[map[K]B]](f)
+}
+
+// SequenceRecordSeq converts a homogeneous sequence of either into an either of sequence
+func SequenceRecordSeq[K comparable, A any](ma map[K]ReaderIOEither[A]) ReaderIOEither[map[K]A] {
+	return G.SequenceRecordSeq[K, map[K]A, map[K]ReaderIOEither[A], ReaderIOEither[map[K]A]](ma)
+}
+
+// TraverseArrayPar uses transforms an array [[]A] into [[]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[[]B]]
+func TraverseArrayPar[A, B any](f func(A) ReaderIOEither[B]) func([]A) ReaderIOEither[[]B] {
+	return G.TraverseArrayPar[[]A, ReaderIOEither[[]B]](f)
+}
+
+// TraverseArrayWithIndexPar uses transforms an array [[]A] into [[]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[[]B]]
+func TraverseArrayWithIndexPar[A, B any](f func(int, A) ReaderIOEither[B]) func([]A) ReaderIOEither[[]B] {
+	return G.TraverseArrayWithIndexPar[[]A, ReaderIOEither[[]B]](f)
+}
+
+// SequenceArrayPar converts a homogeneous sequence of either into an either of sequence
+func SequenceArrayPar[A any](ma []ReaderIOEither[A]) ReaderIOEither[[]A] {
+	return G.SequenceArrayPar[[]A, []ReaderIOEither[A], ReaderIOEither[[]A]](ma)
+}
+
+// TraverseRecordPar uses transforms a record [map[K]A] into [map[K]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[map[K]B]]
+func TraverseRecordPar[K comparable, A, B any](f func(A) ReaderIOEither[B]) func(map[K]A) ReaderIOEither[map[K]B] {
+	return G.TraverseRecordPar[K, map[K]A, ReaderIOEither[map[K]B]](f)
+}
+
+// TraverseRecordWithIndexPar uses transforms a record [map[K]A] into [map[K]ReaderIOEither[B]] and then resolves that into a [ReaderIOEither[map[K]B]]
+func TraverseRecordWithIndexPar[K comparable, A, B any](f func(K, A) ReaderIOEither[B]) func(map[K]A) ReaderIOEither[map[K]B] {
+	return G.TraverseRecordWithIndexPar[K, map[K]A, ReaderIOEither[map[K]B]](f)
+}
+
+// SequenceRecordPar converts a homogeneous sequence of either into an either of sequence
+func SequenceRecordPar[K comparable, A any](ma map[K]ReaderIOEither[A]) ReaderIOEither[map[K]A] {
+	return G.SequenceRecordPar[K, map[K]A, map[K]ReaderIOEither[A], ReaderIOEither[map[K]A]](ma)
+}

di/app.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 di
+
+import (
+	DIE "github.com/IBM/fp-go/di/erasure"
+	F "github.com/IBM/fp-go/function"
+	IO "github.com/IBM/fp-go/io"
+	IOE "github.com/IBM/fp-go/ioeither"
+)
+
+var (
+	// InjMain is the [InjectionToken] for the main application
+	InjMain = MakeToken[any]("APP")
+
+	// Main is the resolver for the main application
+	Main = Resolve(InjMain)
+)
+
+// RunMain runs the main application from a set of [DIE.Provider]s
+var RunMain = F.Flow3(
+	DIE.MakeInjector,
+	Main,
+	IOE.Fold(IO.Of[error], F.Constant1[any](IO.Of[error](nil))),
+)

di/doc.go

@@ -0,0 +1,43 @@
+// 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 di implements functions and data types supporting dependency injection patterns
+//
+// The fundamental building block is the concept of a [Dependency]. This describes the abstract concept of a function, service or value together with its type.
+// Examples for dependencies can be as simple as configuration values such as the API URL for a service, the current username, a [Dependency] could be the map
+// of the configuration environment, an http client or as complex as a service interface. Important is that a [Dependency] only defines the concept but
+// not the implementation.
+//
+// The implementation of a [Dependency] is called a [Provider], the dependency of an `API URL` could e.g. be realized by a provider that consults the environment to read the information
+// or a config file or simply hardcode it.
+// In many cases the implementation of a [Provider] depends in turn on other [Dependency] (but never directly on other [Provider]s), a provider for an `API URL` that reads
+// the information from the environment would e.g. depend on a [Dependency] that represents this environment.
+//
+// It is the resposibility of the [InjectableFactory] to create an instance of a [Dependency]. All instances are considered singletons. Create an [InjectableFactory] via the [MakeInjector] method. Use [Resolve] to create a strongly typed
+// factory for a particular [InjectionToken].
+//
+// In most cases it is not required to use [InjectableFactory] directly, instead you would create a [Provider] via the [MakeProvider2] method (suffix indicates the number of dependencies). In this call
+// you give a number of (strongly typed) [Dependency] identifiers and a (strongly typed) factory function for the implementation. The dependency injection framework makes
+// sure to resolve the dependencies before calling the factory method.
+//
+// For convenience purposes it can be helpful to attach a default implementation of a [Dependency]. In this case use the [MakeTokenWithDefault2] method (suffix indicates the number of dependencies)
+// to define the [InjectionToken].
+//
+// [Provider]: [github.com/IBM/fp-go/di/erasure.Provider]
+// [InjectableFactory]: [github.com/IBM/fp-go/di/erasure.InjectableFactory]
+// [MakeInjector]: [github.com/IBM/fp-go/di/erasure.MakeInjector]
+package di
+
+//go:generate go run .. di --count 10 --filename gen.go

di/erasure/injector.go

@@ -0,0 +1,170 @@
+// 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 erasure
+
+import (
+	A "github.com/IBM/fp-go/array"
+	"github.com/IBM/fp-go/errors"
+	F "github.com/IBM/fp-go/function"
+	I "github.com/IBM/fp-go/identity"
+	IG "github.com/IBM/fp-go/identity/generic"
+	IOE "github.com/IBM/fp-go/ioeither"
+	L "github.com/IBM/fp-go/lazy"
+	O "github.com/IBM/fp-go/option"
+	R "github.com/IBM/fp-go/record"
+	T "github.com/IBM/fp-go/tuple"
+
+	"sync"
+)
+
+func providerToEntry(p Provider) T.Tuple2[string, ProviderFactory] {
+	return T.MakeTuple2(p.Provides().Id(), p.Factory())
+}
+
+func itemProviderToMap(p Provider) map[string][]ProviderFactory {
+	return R.Singleton(p.Provides().Id(), A.Of(p.Factory()))
+}
+
+var (
+	// missingProviderError returns a [ProviderFactory] that fails due to a missing dependency
+	missingProviderError = F.Flow4(
+		Dependency.String,
+		errors.OnSome[string]("no provider for dependency [%s]"),
+		IOE.Left[any, error],
+		F.Constant1[InjectableFactory, IOE.IOEither[error, any]],
+	)
+
+	// missingProviderErrorOrDefault returns the default [ProviderFactory] or an error
+	missingProviderErrorOrDefault = F.Flow3(
+		T.Replicate2[Dependency],
+		T.Map2(Dependency.ProviderFactory, F.Flow2(missingProviderError, F.Constant[ProviderFactory])),
+		T.Tupled2(O.MonadGetOrElse[ProviderFactory]),
+	)
+
+	emptyMulti any = A.Empty[any]()
+
+	// emptyMultiDependency returns a [ProviderFactory] for an empty, multi dependency
+	emptyMultiDependency = F.Constant1[Dependency](F.Constant1[InjectableFactory](IOE.Of[error](emptyMulti)))
+
+	// handleMissingProvider covers the case of a missing provider. It either
+	// returns an error or an empty multi value provider
+	handleMissingProvider = F.Flow2(
+		F.Ternary(isMultiDependency, emptyMultiDependency, missingProviderErrorOrDefault),
+		F.Constant[ProviderFactory],
+	)
+
+	// mergeItemProviders is a monoid for item provider factories
+	mergeItemProviders = R.UnionMonoid[string](A.Semigroup[ProviderFactory]())
+
+	// mergeProviders is a monoid for provider factories
+	mergeProviders = R.UnionLastMonoid[string, ProviderFactory]()
+
+	// collectItemProviders create a provider map for item providers
+	collectItemProviders = F.Flow2(
+		A.FoldMap[Provider](mergeItemProviders)(itemProviderToMap),
+		R.Map[string](itemProviderFactory),
+	)
+
+	// collectProviders collects non-item providers
+	collectProviders = F.Flow2(
+		A.Map(providerToEntry),
+		R.FromEntries[string, ProviderFactory],
+	)
+
+	// assembleProviders constructs the provider map for item and non-item providers
+	assembleProviders = F.Flow3(
+		A.Partition(isItemProvider),
+		T.Map2(collectProviders, collectItemProviders),
+		T.Tupled2(mergeProviders.Concat),
+	)
+)
+
+// isMultiDependency tests if a dependency is a container dependency
+func isMultiDependency(dep Dependency) bool {
+	return dep.Flag()&Multi == Multi
+}
+
+// isItemProvider tests if a provivder provides a single item
+func isItemProvider(provider Provider) bool {
+	return provider.Provides().Flag()&Item == Item
+}
+
+// itemProviderFactory combines multiple factories into one, returning an array
+func itemProviderFactory(fcts []ProviderFactory) ProviderFactory {
+	return func(inj InjectableFactory) IOE.IOEither[error, any] {
+		return F.Pipe2(
+			fcts,
+			IOE.TraverseArray(I.Flap[IOE.IOEither[error, any]](inj)),
+			IOE.Map[error](F.ToAny[[]any]),
+		)
+	}
+}
+
+// MakeInjector creates an [InjectableFactory] based on a set of [Provider]s
+//
+// The resulting [InjectableFactory] can then be used to retrieve service instances given their [Dependency]. The implementation
+// makes sure to transitively resolve the required dependencies.
+func MakeInjector(providers []Provider) InjectableFactory {
+
+	type Result = IOE.IOEither[error, any]
+	type LazyResult = L.Lazy[Result]
+
+	// resolved stores the values resolved so far, key is the string ID
+	// of the token, value is a lazy result
+	var resolved sync.Map
+
+	// provide a mapping for all providers
+	factoryById := assembleProviders(providers)
+
+	// the actual factory, we need lazy initialization
+	var injFct InjectableFactory
+
+	// lazy initialization, so we can cross reference it
+	injFct = func(token Dependency) Result {
+
+		key := token.Id()
+
+		// according to https://github.com/golang/go/issues/44159 this
+		// is the best way to use the sync map
+		actual, loaded := resolved.Load(key)
+		if !loaded {
+
+			computeResult := L.MakeLazy(func() Result {
+				return F.Pipe5(
+					token,
+					T.Replicate2[Dependency],
+					T.Map2(F.Flow3(
+						Dependency.Id,
+						R.Lookup[ProviderFactory, string],
+						I.Ap[O.Option[ProviderFactory]](factoryById),
+					), handleMissingProvider),
+					T.Tupled2(O.MonadGetOrElse[ProviderFactory]),
+					IG.Ap[ProviderFactory](injFct),
+					IOE.Memoize[error, any],
+				)
+			})
+
+			actual, _ = resolved.LoadOrStore(key, F.Pipe1(
+				computeResult,
+				L.Memoize[Result],
+			))
+		}
+
+		return actual.(LazyResult)()
+	}
+
+	return injFct
+}

di/erasure/provider.go

@@ -0,0 +1,181 @@
+// 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 erasure
+
+import (
+	"fmt"
+
+	A "github.com/IBM/fp-go/array"
+	E "github.com/IBM/fp-go/either"
+	F "github.com/IBM/fp-go/function"
+	I "github.com/IBM/fp-go/identity"
+	IO "github.com/IBM/fp-go/io"
+	IOG "github.com/IBM/fp-go/io/generic"
+	IOE "github.com/IBM/fp-go/ioeither"
+	IOO "github.com/IBM/fp-go/iooption"
+	Int "github.com/IBM/fp-go/number/integer"
+	O "github.com/IBM/fp-go/option"
+	R "github.com/IBM/fp-go/record"
+)
+
+type (
+	// InjectableFactory is a factory function that can create an untyped instance of a service based on its [Dependency] identifier
+	InjectableFactory = func(Dependency) IOE.IOEither[error, any]
+	ProviderFactory   = func(InjectableFactory) IOE.IOEither[error, any]
+
+	paramIndex = map[int]int
+	paramValue = map[int]any
+	handler    = func(paramIndex) func([]IOE.IOEither[error, any]) IOE.IOEither[error, paramValue]
+	mapping    = map[int]paramIndex
+
+	Provider interface {
+		fmt.Stringer
+		// Provides returns the [Dependency] implemented by this provider
+		Provides() Dependency
+		// Factory returns s function that can create an instance of the dependency based on an [InjectableFactory]
+		Factory() ProviderFactory
+	}
+
+	provider struct {
+		provides Dependency
+		factory  ProviderFactory
+	}
+)
+
+func (p *provider) Provides() Dependency {
+	return p.provides
+}
+
+func (p *provider) Factory() ProviderFactory {
+	return p.factory
+}
+
+func (p *provider) String() string {
+	return fmt.Sprintf("Provider for [%s]", p.provides)
+}
+
+func MakeProvider(token Dependency, fct ProviderFactory) Provider {
+	return &provider{token, fct}
+}
+
+func mapFromToken(idx int, token Dependency) map[int]paramIndex {
+	return R.Singleton(token.Flag()&BehaviourMask, R.Singleton(idx, idx))
+}
+
+var (
+	// Empty is the empty array of providers
+	Empty = A.Empty[Provider]()
+
+	mergeTokenMaps = R.UnionMonoid[int](R.UnionLastSemigroup[int, int]())
+	foldDeps       = A.FoldMapWithIndex[Dependency](mergeTokenMaps)(mapFromToken)
+	mergeMaps      = R.UnionLastMonoid[int, any]()
+	collectParams  = R.CollectOrd[any, any](Int.Ord)(F.SK[int, any])
+
+	mapDeps = F.Curry2(A.MonadMap[Dependency, IOE.IOEither[error, any]])
+
+	handlers = map[int]handler{
+		Identity: func(mp paramIndex) func([]IOE.IOEither[error, any]) IOE.IOEither[error, paramValue] {
+			return func(res []IOE.IOEither[error, any]) IOE.IOEither[error, paramValue] {
+				return F.Pipe1(
+					mp,
+					IOE.TraverseRecord[int](getAt(res)),
+				)
+			}
+		},
+		Option: func(mp paramIndex) func([]IOE.IOEither[error, any]) IOE.IOEither[error, paramValue] {
+			return func(res []IOE.IOEither[error, any]) IOE.IOEither[error, paramValue] {
+				return F.Pipe3(
+					mp,
+					IOG.TraverseRecord[IO.IO[map[int]E.Either[error, any]], paramIndex](getAt(res)),
+					IO.Map(R.Map[int](F.Flow2(
+						E.ToOption[error, any],
+						F.ToAny[O.Option[any]],
+					))),
+					IOE.FromIO[error, paramValue],
+				)
+			}
+		},
+		IOEither: func(mp paramIndex) func([]IOE.IOEither[error, any]) IOE.IOEither[error, paramValue] {
+			return func(res []IOE.IOEither[error, any]) IOE.IOEither[error, paramValue] {
+				return F.Pipe2(
+					mp,
+					R.Map[int](F.Flow2(
+						getAt(res),
+						F.ToAny[IOE.IOEither[error, any]],
+					)),
+					IOE.Of[error, paramValue],
+				)
+			}
+		},
+		IOOption: func(mp paramIndex) func([]IOE.IOEither[error, any]) IOE.IOEither[error, paramValue] {
+			return func(res []IOE.IOEither[error, any]) IOE.IOEither[error, paramValue] {
+				return F.Pipe2(
+					mp,
+					R.Map[int](F.Flow3(
+						getAt(res),
+						IOE.ToIOOption[error, any],
+						F.ToAny[IOO.IOOption[any]],
+					)),
+					IOE.Of[error, paramValue],
+				)
+			}
+		},
+	}
+)
+
+func getAt[T any](ar []T) func(idx int) T {
+	return func(idx int) T {
+		return ar[idx]
+	}
+}
+
+func handleMapping(mp mapping) func(res []IOE.IOEither[error, any]) IOE.IOEither[error, []any] {
+	preFct := F.Pipe1(
+		mp,
+		R.Collect(func(idx int, p paramIndex) func([]IOE.IOEither[error, any]) IOE.IOEither[error, paramValue] {
+			return handlers[idx](p)
+		}),
+	)
+	doFct := F.Flow2(
+		I.Flap[IOE.IOEither[error, paramValue], []IOE.IOEither[error, any]],
+		IOE.TraverseArray[error, func([]IOE.IOEither[error, any]) IOE.IOEither[error, paramValue], paramValue],
+	)
+	postFct := IOE.Map[error](F.Flow2(
+		A.Fold(mergeMaps),
+		collectParams,
+	))
+
+	return func(res []IOE.IOEither[error, any]) IOE.IOEither[error, []any] {
+		return F.Pipe2(
+			preFct,
+			doFct(res),
+			postFct,
+		)
+	}
+}
+
+// MakeProviderFactory constructs a [ProviderFactory] based on a set of [Dependency]s and
+// a function that accepts the resolved dependencies to return a result
+func MakeProviderFactory(
+	deps []Dependency,
+	fct func(param ...any) IOE.IOEither[error, any]) ProviderFactory {
+
+	return F.Flow3(
+		mapDeps(deps),
+		handleMapping(foldDeps(deps)),
+		IOE.Chain(F.Unvariadic0(fct)),
+	)
+}

di/erasure/token.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 erasure
+
+import (
+	"fmt"
+
+	O "github.com/IBM/fp-go/option"
+)
+
+const (
+	BehaviourMask = 0x0f
+	Identity      = 0 // required dependency
+	Option        = 1 // optional dependency
+	IOEither      = 2 // lazy and required
+	IOOption      = 3 // lazy and optional
+
+	TypeMask = 0xf0
+	Multi    = 1 << 4 // array of implementations
+	Item     = 2 << 4 // item of a multi token
+)
+
+// Dependency describes the relationship to a service
+type Dependency interface {
+	fmt.Stringer
+	// Id returns a unique identifier for a token that can be used as a cache key
+	Id() string
+	// Flag returns a tag that identifies the behaviour of the dependency
+	Flag() int
+	// ProviderFactory optionally returns an attached [ProviderFactory] that represents the default for this dependency
+	ProviderFactory() O.Option[ProviderFactory]
+}

di/injector.go

@@ -0,0 +1,32 @@
+// 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 di
+
+import (
+	DIE "github.com/IBM/fp-go/di/erasure"
+	F "github.com/IBM/fp-go/function"
+	IG "github.com/IBM/fp-go/identity/generic"
+	IOE "github.com/IBM/fp-go/ioeither"
+	RIOE "github.com/IBM/fp-go/readerioeither"
+)
+
+// Resolve performs a type safe resolution of a dependency
+func Resolve[T any](token InjectionToken[T]) RIOE.ReaderIOEither[DIE.InjectableFactory, error, T] {
+	return F.Flow2(
+		IG.Ap[DIE.InjectableFactory](asDependency(token)),
+		IOE.ChainEitherK(token.Unerase),
+	)
+}

di/provider.go

@@ -0,0 +1,79 @@
+// 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 di
+
+import (
+	A "github.com/IBM/fp-go/array"
+	DIE "github.com/IBM/fp-go/di/erasure"
+	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"
+)
+
+func lookupAt[T any](idx int, token Dependency[T]) func(params []any) E.Either[error, T] {
+	return F.Flow3(
+		A.Lookup[any](idx),
+		E.FromOption[any](errors.OnNone("No parameter at position %d", idx)),
+		E.Chain(token.Unerase),
+	)
+}
+
+func eraseTuple[A, R any](f func(A) IOE.IOEither[error, R]) func(E.Either[error, A]) IOE.IOEither[error, any] {
+	return F.Flow3(
+		IOE.FromEither[error, A],
+		IOE.Chain(f),
+		IOE.Map[error](F.ToAny[R]),
+	)
+}
+
+func eraseProviderFactory0[R any](f IOE.IOEither[error, R]) func(params ...any) IOE.IOEither[error, any] {
+	return func(params ...any) IOE.IOEither[error, any] {
+		return F.Pipe1(
+			f,
+			IOE.Map[error](F.ToAny[R]),
+		)
+	}
+}
+
+func MakeProviderFactory0[R any](
+	fct IOE.IOEither[error, R],
+) DIE.ProviderFactory {
+	return DIE.MakeProviderFactory(
+		A.Empty[DIE.Dependency](),
+		eraseProviderFactory0(fct),
+	)
+}
+
+// MakeTokenWithDefault0 creates a unique [InjectionToken] for a specific type with an attached default [DIE.Provider]
+func MakeTokenWithDefault0[R any](name string, fct IOE.IOEither[error, R]) InjectionToken[R] {
+	return MakeTokenWithDefault[R](name, MakeProviderFactory0(fct))
+}
+
+func MakeProvider0[R any](
+	token InjectionToken[R],
+	fct IOE.IOEither[error, R],
+) DIE.Provider {
+	return DIE.MakeProvider(
+		token,
+		MakeProviderFactory0(fct),
+	)
+}
+
+// ConstProvider simple implementation for a provider with a constant value
+func ConstProvider[R any](token InjectionToken[R], value R) DIE.Provider {
+	return MakeProvider0[R](token, IOE.Of[error](value))
+}

di/provider_test.go

@@ -0,0 +1,346 @@
+// 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 di
+
+import (
+	"fmt"
+	"testing"
+	"time"
+
+	A "github.com/IBM/fp-go/array"
+	DIE "github.com/IBM/fp-go/di/erasure"
+	E "github.com/IBM/fp-go/either"
+	F "github.com/IBM/fp-go/function"
+	IOE "github.com/IBM/fp-go/ioeither"
+	O "github.com/IBM/fp-go/option"
+	"github.com/stretchr/testify/assert"
+)
+
+var (
+	INJ_KEY2 = MakeToken[string]("INJ_KEY2")
+	INJ_KEY1 = MakeToken[string]("INJ_KEY1")
+	INJ_KEY3 = MakeToken[string]("INJ_KEY3")
+)
+
+func TestSimpleProvider(t *testing.T) {
+
+	var staticCount int
+
+	staticValue := func(value string) IOE.IOEither[error, string] {
+		return func() E.Either[error, string] {
+			staticCount++
+			return E.Of[error](fmt.Sprintf("Static based on [%s], at [%s]", value, time.Now()))
+		}
+	}
+
+	var dynamicCount int
+
+	dynamicValue := func(value string) IOE.IOEither[error, string] {
+		return func() E.Either[error, string] {
+			dynamicCount++
+			return E.Of[error](fmt.Sprintf("Dynamic based on [%s] at [%s]", value, time.Now()))
+		}
+	}
+
+	p1 := MakeProvider0(INJ_KEY1, staticValue("Carsten"))
+	p2 := MakeProvider1(INJ_KEY2, INJ_KEY1.Identity(), dynamicValue)
+
+	inj := DIE.MakeInjector(A.From(p1, p2))
+
+	i1 := Resolve(INJ_KEY1)
+	i2 := Resolve(INJ_KEY2)
+
+	res := IOE.SequenceT4(
+		i2(inj),
+		i1(inj),
+		i2(inj),
+		i1(inj),
+	)
+
+	r := res()
+
+	assert.True(t, E.IsRight(r))
+	assert.Equal(t, 1, staticCount)
+	assert.Equal(t, 1, dynamicCount)
+}
+
+func TestOptionalProvider(t *testing.T) {
+
+	var staticCount int
+
+	staticValue := func(value string) IOE.IOEither[error, string] {
+		return func() E.Either[error, string] {
+			staticCount++
+			return E.Of[error](fmt.Sprintf("Static based on [%s], at [%s]", value, time.Now()))
+		}
+	}
+
+	var dynamicCount int
+
+	dynamicValue := func(value O.Option[string]) IOE.IOEither[error, string] {
+		return func() E.Either[error, string] {
+			dynamicCount++
+			return E.Of[error](fmt.Sprintf("Dynamic based on [%s] at [%s]", value, time.Now()))
+		}
+	}
+
+	p1 := MakeProvider0(INJ_KEY1, staticValue("Carsten"))
+	p2 := MakeProvider1(INJ_KEY2, INJ_KEY1.Option(), dynamicValue)
+
+	inj := DIE.MakeInjector(A.From(p1, p2))
+
+	i1 := Resolve(INJ_KEY1)
+	i2 := Resolve(INJ_KEY2)
+
+	res := IOE.SequenceT4(
+		i2(inj),
+		i1(inj),
+		i2(inj),
+		i1(inj),
+	)
+
+	r := res()
+
+	assert.True(t, E.IsRight(r))
+	assert.Equal(t, 1, staticCount)
+	assert.Equal(t, 1, dynamicCount)
+}
+
+func TestOptionalProviderMissingDependency(t *testing.T) {
+
+	var dynamicCount int
+
+	dynamicValue := func(value O.Option[string]) IOE.IOEither[error, string] {
+		return func() E.Either[error, string] {
+			dynamicCount++
+			return E.Of[error](fmt.Sprintf("Dynamic based on [%s] at [%s]", value, time.Now()))
+		}
+	}
+
+	p2 := MakeProvider1(INJ_KEY2, INJ_KEY1.Option(), dynamicValue)
+
+	inj := DIE.MakeInjector(A.From(p2))
+
+	i2 := Resolve(INJ_KEY2)
+
+	res := IOE.SequenceT2(
+		i2(inj),
+		i2(inj),
+	)
+
+	r := res()
+
+	assert.True(t, E.IsRight(r))
+	assert.Equal(t, 1, dynamicCount)
+}
+
+func TestProviderMissingDependency(t *testing.T) {
+
+	var dynamicCount int
+
+	dynamicValue := func(value string) IOE.IOEither[error, string] {
+		return func() E.Either[error, string] {
+			dynamicCount++
+			return E.Of[error](fmt.Sprintf("Dynamic based on [%s] at [%s]", value, time.Now()))
+		}
+	}
+
+	p2 := MakeProvider1(INJ_KEY2, INJ_KEY1.Identity(), dynamicValue)
+
+	inj := DIE.MakeInjector(A.From(p2))
+
+	i2 := Resolve(INJ_KEY2)
+
+	res := IOE.SequenceT2(
+		i2(inj),
+		i2(inj),
+	)
+
+	r := res()
+
+	assert.True(t, E.IsLeft(r))
+	assert.Equal(t, 0, dynamicCount)
+}
+
+func TestEagerAndLazyProvider(t *testing.T) {
+
+	var staticCount int
+
+	staticValue := func(value string) IOE.IOEither[error, string] {
+		return func() E.Either[error, string] {
+			staticCount++
+			return E.Of[error](fmt.Sprintf("Static based on [%s], at [%s]", value, time.Now()))
+		}
+	}
+
+	var dynamicCount int
+
+	dynamicValue := func(value string) IOE.IOEither[error, string] {
+		return func() E.Either[error, string] {
+			dynamicCount++
+			return E.Of[error](fmt.Sprintf("Dynamic based on [%s] at [%s]", value, time.Now()))
+		}
+	}
+
+	var lazyEagerCount int
+
+	lazyEager := func(laz IOE.IOEither[error, string], eager string) IOE.IOEither[error, string] {
+		return F.Pipe1(
+			laz,
+			IOE.Chain(func(lazValue string) IOE.IOEither[error, string] {
+				return func() E.Either[error, string] {
+					lazyEagerCount++
+					return E.Of[error](fmt.Sprintf("Dynamic based on [%s], [%s] at [%s]", lazValue, eager, time.Now()))
+				}
+			}),
+		)
+	}
+
+	p1 := MakeProvider0(INJ_KEY1, staticValue("Carsten"))
+	p2 := MakeProvider1(INJ_KEY2, INJ_KEY1.Identity(), dynamicValue)
+	p3 := MakeProvider2(INJ_KEY3, INJ_KEY2.IOEither(), INJ_KEY1.Identity(), lazyEager)
+
+	inj := DIE.MakeInjector(A.From(p1, p2, p3))
+
+	i3 := Resolve(INJ_KEY3)
+
+	r := i3(inj)()
+
+	fmt.Println(r)
+
+	assert.True(t, E.IsRight(r))
+	assert.Equal(t, 1, staticCount)
+	assert.Equal(t, 1, dynamicCount)
+	assert.Equal(t, 1, lazyEagerCount)
+}
+
+func TestItemProvider(t *testing.T) {
+	// define a multi token
+	injMulti := MakeMultiToken[string]("configs")
+
+	// provide some values
+	v1 := ConstProvider(injMulti.Item(), "Value1")
+	v2 := ConstProvider(injMulti.Item(), "Value2")
+	// mix in non-multi values
+	p1 := ConstProvider(INJ_KEY1, "Value3")
+	p2 := ConstProvider(INJ_KEY2, "Value4")
+
+	// populate the injector
+	inj := DIE.MakeInjector(A.From(p1, v1, p2, v2))
+
+	// access the multi value
+	multi := Resolve(injMulti.Container())
+
+	multiInj := multi(inj)
+
+	value := multiInj()
+
+	assert.Equal(t, E.Of[error](A.From("Value1", "Value2")), value)
+}
+
+func TestEmptyItemProvider(t *testing.T) {
+	// define a multi token
+	injMulti := MakeMultiToken[string]("configs")
+
+	// mix in non-multi values
+	p1 := ConstProvider(INJ_KEY1, "Value3")
+	p2 := ConstProvider(INJ_KEY2, "Value4")
+
+	// populate the injector
+	inj := DIE.MakeInjector(A.From(p1, p2))
+
+	// access the multi value
+	multi := Resolve(injMulti.Container())
+
+	multiInj := multi(inj)
+
+	value := multiInj()
+
+	assert.Equal(t, E.Of[error](A.Empty[string]()), value)
+}
+
+func TestDependencyOnMultiProvider(t *testing.T) {
+	// define a multi token
+	injMulti := MakeMultiToken[string]("configs")
+
+	// provide some values
+	v1 := ConstProvider(injMulti.Item(), "Value1")
+	v2 := ConstProvider(injMulti.Item(), "Value2")
+	// mix in non-multi values
+	p1 := ConstProvider(INJ_KEY1, "Value3")
+	p2 := ConstProvider(INJ_KEY2, "Value4")
+
+	fromMulti := func(val string, multi []string) IOE.IOEither[error, string] {
+		return IOE.Of[error](fmt.Sprintf("Val: %s, Multi: %s", val, multi))
+	}
+	p3 := MakeProvider2(INJ_KEY3, INJ_KEY1.Identity(), injMulti.Container().Identity(), fromMulti)
+
+	// populate the injector
+	inj := DIE.MakeInjector(A.From(p1, p2, v1, v2, p3))
+
+	r3 := Resolve(INJ_KEY3)
+
+	v := r3(inj)()
+
+	assert.Equal(t, E.Of[error]("Val: Value3, Multi: [Value1 Value2]"), v)
+}
+
+func TestTokenWithDefaultProvider(t *testing.T) {
+	// token without a default
+	injToken1 := MakeToken[string]("Token1")
+	// token with a default
+	injToken2 := MakeTokenWithDefault0("Token2", IOE.Of[error]("Carsten"))
+	// dependency
+	injToken3 := MakeToken[string]("Token3")
+
+	p3 := MakeProvider1(injToken3, injToken2.Identity(), func(data string) IOE.IOEither[error, string] {
+		return IOE.Of[error](fmt.Sprintf("Token: %s", data))
+	})
+
+	// populate the injector
+	inj := DIE.MakeInjector(A.From(p3))
+
+	// resolving injToken3 should work and use the default provider for injToken2
+	r1 := Resolve(injToken1)
+	r3 := Resolve(injToken3)
+
+	// inj1 should not be available
+	assert.True(t, E.IsLeft(r1(inj)()))
+	// r3 should work
+	assert.Equal(t, E.Of[error]("Token: Carsten"), r3(inj)())
+}
+
+func TestTokenWithDefaultProviderAndOverride(t *testing.T) {
+	// token with a default
+	injToken2 := MakeTokenWithDefault0("Token2", IOE.Of[error]("Carsten"))
+	// dependency
+	injToken3 := MakeToken[string]("Token3")
+
+	p2 := ConstProvider(injToken2, "Override")
+
+	p3 := MakeProvider1(injToken3, injToken2.Identity(), func(data string) IOE.IOEither[error, string] {
+		return IOE.Of[error](fmt.Sprintf("Token: %s", data))
+	})
+
+	// populate the injector
+	inj := DIE.MakeInjector(A.From(p2, p3))
+
+	// resolving injToken3 should work and use the default provider for injToken2
+	r3 := Resolve(injToken3)
+
+	// r3 should work
+	assert.Equal(t, E.Of[error]("Token: Override"), r3(inj)())
+}

di/token.go

@@ -0,0 +1,197 @@
+// 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 di
+
+import (
+	"fmt"
+	"strconv"
+	"sync/atomic"
+
+	DIE "github.com/IBM/fp-go/di/erasure"
+	E "github.com/IBM/fp-go/either"
+	IO "github.com/IBM/fp-go/io"
+	IOE "github.com/IBM/fp-go/ioeither"
+	IOO "github.com/IBM/fp-go/iooption"
+	O "github.com/IBM/fp-go/option"
+)
+
+// Dependency describes the relationship to a service, that has a type and
+// a behaviour such as required, option or lazy
+type Dependency[T any] interface {
+	DIE.Dependency
+	// Unerase converts a value with erased type signature into a strongly typed value
+	Unerase(val any) E.Either[error, T]
+}
+
+// InjectionToken uniquely identifies a dependency by giving it an Id, Type and name
+type InjectionToken[T any] interface {
+	Dependency[T]
+	// Identity idenifies this dependency as a mandatory, required dependency, it will be resolved eagerly and injected as `T`.
+	// If the dependency cannot be resolved, the resolution process fails
+	Identity() Dependency[T]
+	// Option identifies this dependency as optional, it will be resolved eagerly and injected as [O.Option[T]].
+	// If the dependency cannot be resolved, the resolution process continues and the dependency is represented as [O.None[T]]
+	Option() Dependency[O.Option[T]]
+	// IOEither identifies this dependency as mandatory but it will be resolved lazily as a [IOE.IOEither[error, T]]. This
+	// value is memoized to make sure the dependency is a singleton.
+	// If the dependency cannot be resolved, the resolution process fails
+	IOEither() Dependency[IOE.IOEither[error, T]]
+	// IOOption identifies this dependency as optional but it will be resolved lazily as a [IOO.IOOption[T]]. This
+	// value is memoized to make sure the dependency is a singleton.
+	// If the dependency cannot be resolved, the resolution process continues and the dependency is represented as the none value.
+	IOOption() Dependency[IOO.IOOption[T]]
+}
+
+// MultiInjectionToken uniquely identifies a dependency by giving it an Id, Type and name that can have multiple implementations.
+// Implementations are provided via the [MultiInjectionToken.Item] injection token.
+type MultiInjectionToken[T any] interface {
+	// Container returns the injection token used to request an array of all provided items
+	Container() InjectionToken[[]T]
+	// Item returns the injection token used to provide an item
+	Item() InjectionToken[T]
+}
+
+// makeID creates a generator of unique string IDs
+func makeId() IO.IO[string] {
+	var count atomic.Int64
+	return IO.MakeIO(func() string {
+		return strconv.FormatInt(count.Add(1), 16)
+	})
+}
+
+// genId is the common generator of unique string IDs
+var genId = makeId()
+
+type token[T any] struct {
+	name            string
+	id              string
+	flag            int
+	toType          func(val any) E.Either[error, T]
+	providerFactory O.Option[DIE.ProviderFactory]
+}
+
+func (t *token[T]) Id() string {
+	return t.id
+}
+
+func (t *token[T]) Flag() int {
+	return t.flag
+}
+
+func (t *token[T]) String() string {
+	return t.name
+}
+
+func (t *token[T]) Unerase(val any) E.Either[error, T] {
+	return t.toType(val)
+}
+
+func (t *token[T]) ProviderFactory() O.Option[DIE.ProviderFactory] {
+	return t.providerFactory
+}
+
+func makeToken[T any](name string, id string, typ int, unerase func(val any) E.Either[error, T], providerFactory O.Option[DIE.ProviderFactory]) Dependency[T] {
+	return &token[T]{name, id, typ, unerase, providerFactory}
+}
+
+type injectionToken[T any] struct {
+	token[T]
+	option   Dependency[O.Option[T]]
+	ioeither Dependency[IOE.IOEither[error, T]]
+	iooption Dependency[IOO.IOOption[T]]
+}
+
+type multiInjectionToken[T any] struct {
+	container *injectionToken[[]T]
+	item      *injectionToken[T]
+}
+
+func (i *injectionToken[T]) Identity() Dependency[T] {
+	return i
+}
+
+func (i *injectionToken[T]) Option() Dependency[O.Option[T]] {
+	return i.option
+}
+
+func (i *injectionToken[T]) IOEither() Dependency[IOE.IOEither[error, T]] {
+	return i.ioeither
+}
+
+func (i *injectionToken[T]) IOOption() Dependency[IOO.IOOption[T]] {
+	return i.iooption
+}
+
+func (i *injectionToken[T]) ProviderFactory() O.Option[DIE.ProviderFactory] {
+	return i.providerFactory
+}
+
+func (m *multiInjectionToken[T]) Container() InjectionToken[[]T] {
+	return m.container
+}
+
+func (m *multiInjectionToken[T]) Item() InjectionToken[T] {
+	return m.item
+}
+
+// makeToken create a unique [InjectionToken] for a specific type
+func makeInjectionToken[T any](name string, providerFactory O.Option[DIE.ProviderFactory]) InjectionToken[T] {
+	id := genId()
+	toIdentity := toType[T]()
+	return &injectionToken[T]{
+		token[T]{name, id, DIE.Identity, toIdentity, providerFactory},
+		makeToken[O.Option[T]](fmt.Sprintf("Option[%s]", name), id, DIE.Option, toOptionType(toIdentity), providerFactory),
+		makeToken[IOE.IOEither[error, T]](fmt.Sprintf("IOEither[%s]", name), id, DIE.IOEither, toIOEitherType(toIdentity), providerFactory),
+		makeToken[IOO.IOOption[T]](fmt.Sprintf("IOOption[%s]", name), id, DIE.IOOption, toIOOptionType(toIdentity), providerFactory),
+	}
+}
+
+// MakeToken create a unique [InjectionToken] for a specific type
+func MakeToken[T any](name string) InjectionToken[T] {
+	return makeInjectionToken[T](name, O.None[DIE.ProviderFactory]())
+}
+
+// MakeToken create a unique [InjectionToken] for a specific type
+func MakeTokenWithDefault[T any](name string, providerFactory DIE.ProviderFactory) InjectionToken[T] {
+	return makeInjectionToken[T](name, O.Of(providerFactory))
+}
+
+// MakeMultiToken creates a [MultiInjectionToken]
+func MakeMultiToken[T any](name string) MultiInjectionToken[T] {
+	id := genId()
+	toItem := toType[T]()
+	toContainer := toArrayType(toItem)
+	containerName := fmt.Sprintf("Container[%s]", name)
+	itemName := fmt.Sprintf("Item[%s]", name)
+	// empty factory
+	providerFactory := O.None[DIE.ProviderFactory]()
+	// container
+	container := &injectionToken[[]T]{
+		token[[]T]{containerName, id, DIE.Multi | DIE.Identity, toContainer, providerFactory},
+		makeToken[O.Option[[]T]](fmt.Sprintf("Option[%s]", containerName), id, DIE.Multi|DIE.Option, toOptionType(toContainer), providerFactory),
+		makeToken[IOE.IOEither[error, []T]](fmt.Sprintf("IOEither[%s]", containerName), id, DIE.Multi|DIE.IOEither, toIOEitherType(toContainer), providerFactory),
+		makeToken[IOO.IOOption[[]T]](fmt.Sprintf("IOOption[%s]", containerName), id, DIE.Multi|DIE.IOOption, toIOOptionType(toContainer), providerFactory),
+	}
+	// item
+	item := &injectionToken[T]{
+		token[T]{itemName, id, DIE.Item | DIE.Identity, toItem, providerFactory},
+		makeToken[O.Option[T]](fmt.Sprintf("Option[%s]", itemName), id, DIE.Item|DIE.Option, toOptionType(toItem), providerFactory),
+		makeToken[IOE.IOEither[error, T]](fmt.Sprintf("IOEither[%s]", itemName), id, DIE.Item|DIE.IOEither, toIOEitherType(toItem), providerFactory),
+		makeToken[IOO.IOOption[T]](fmt.Sprintf("IOOption[%s]", itemName), id, DIE.Item|DIE.IOOption, toIOOptionType(toItem), providerFactory),
+	}
+	// returns the token
+	return &multiInjectionToken[T]{container, item}
+}

di/utils.go

@@ -0,0 +1,77 @@
+// 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 di
+
+import (
+	DIE "github.com/IBM/fp-go/di/erasure"
+	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"
+	IOO "github.com/IBM/fp-go/iooption"
+	O "github.com/IBM/fp-go/option"
+)
+
+// asDependency converts a generic type to a [DIE.Dependency]
+func asDependency[T DIE.Dependency](t T) DIE.Dependency {
+	return t
+}
+
+// toType converts an any to a T
+func toType[T any]() func(t any) E.Either[error, T] {
+	return E.ToType[T](errors.OnSome[any]("Value of type [%T] cannot be converted."))
+}
+
+// toOptionType converts an any to an Option[any] and then to an Option[T]
+func toOptionType[T any](item func(any) E.Either[error, T]) func(t any) E.Either[error, O.Option[T]] {
+	return F.Flow2(
+		toType[O.Option[any]](),
+		E.Chain(O.Fold(
+			F.Nullary2(O.None[T], E.Of[error, O.Option[T]]),
+			F.Flow2(
+				item,
+				E.Map[error](O.Of[T]),
+			),
+		)),
+	)
+}
+
+// toIOEitherType converts an any to an IOEither[error, any] and then to an IOEither[error, T]
+func toIOEitherType[T any](item func(any) E.Either[error, T]) func(t any) E.Either[error, IOE.IOEither[error, T]] {
+	return F.Flow2(
+		toType[IOE.IOEither[error, any]](),
+		E.Map[error](IOE.ChainEitherK(item)),
+	)
+}
+
+// toIOOptionType converts an any to an IOOption[any] and then to an IOOption[T]
+func toIOOptionType[T any](item func(any) E.Either[error, T]) func(t any) E.Either[error, IOO.IOOption[T]] {
+	return F.Flow2(
+		toType[IOO.IOOption[any]](),
+		E.Map[error](IOO.ChainOptionK(F.Flow2(
+			item,
+			E.ToOption[error, T],
+		))),
+	)
+}
+
+// toArrayType converts an any to a []T
+func toArrayType[T any](item func(any) E.Either[error, T]) func(t any) E.Either[error, []T] {
+	return F.Flow2(
+		toType[[]any](),
+		E.Chain(E.TraverseArray(item)),
+	)
+}

di/utils_test.go

@@ -0,0 +1,84 @@
+// 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 di
+
+import (
+	"testing"
+
+	A "github.com/IBM/fp-go/array"
+	E "github.com/IBM/fp-go/either"
+	F "github.com/IBM/fp-go/function"
+	IOE "github.com/IBM/fp-go/ioeither"
+	O "github.com/IBM/fp-go/option"
+	"github.com/stretchr/testify/assert"
+)
+
+var (
+	toInt    = toType[int]()
+	toString = toType[string]()
+)
+
+func TestToType(t *testing.T) {
+	// good cases
+	assert.Equal(t, E.Of[error](10), toInt(any(10)))
+	assert.Equal(t, E.Of[error]("Carsten"), toString(any("Carsten")))
+	assert.Equal(t, E.Of[error](O.Of("Carsten")), toType[O.Option[string]]()(any(O.Of("Carsten"))))
+	assert.Equal(t, E.Of[error](O.Of(any("Carsten"))), toType[O.Option[any]]()(any(O.Of(any("Carsten")))))
+	// failure
+	assert.False(t, E.IsRight(toInt(any("Carsten"))))
+	assert.False(t, E.IsRight(toType[O.Option[string]]()(O.Of(any("Carsten")))))
+}
+
+func TestToOptionType(t *testing.T) {
+	// shortcuts
+	toOptInt := toOptionType(toInt)
+	toOptString := toOptionType(toString)
+	// good cases
+	assert.Equal(t, E.Of[error](O.Of(10)), toOptInt(any(O.Of(any(10)))))
+	assert.Equal(t, E.Of[error](O.Of("Carsten")), toOptString(any(O.Of(any("Carsten")))))
+	// bad cases
+	assert.False(t, E.IsRight(toOptInt(any(10))))
+	assert.False(t, E.IsRight(toOptInt(any(O.Of(10)))))
+}
+
+func invokeIOEither[T any](e E.Either[error, IOE.IOEither[error, T]]) E.Either[error, T] {
+	return F.Pipe1(
+		e,
+		E.Chain(func(ioe IOE.IOEither[error, T]) E.Either[error, T] {
+			return ioe()
+		}),
+	)
+}
+
+func TestToIOEitherType(t *testing.T) {
+	// shortcuts
+	toIOEitherInt := toIOEitherType(toInt)
+	toIOEitherString := toIOEitherType(toString)
+	// good cases
+	assert.Equal(t, E.Of[error](10), invokeIOEither(toIOEitherInt(any(IOE.Of[error](any(10))))))
+	assert.Equal(t, E.Of[error]("Carsten"), invokeIOEither(toIOEitherString(any(IOE.Of[error](any("Carsten"))))))
+	// bad cases
+	assert.False(t, E.IsRight(invokeIOEither(toIOEitherString(any(IOE.Of[error](any(10)))))))
+	assert.False(t, E.IsRight(invokeIOEither(toIOEitherString(any(IOE.Of[error]("Carsten"))))))
+	assert.False(t, E.IsRight(invokeIOEither(toIOEitherString(any("Carsten")))))
+}
+
+func TestToArrayType(t *testing.T) {
+	// shortcuts
+	toArrayString := toArrayType(toString)
+	// good cases
+	assert.Equal(t, E.Of[error](A.From("a", "b")), toArrayString(any(A.From(any("a"), any("b")))))
+}

either/array.go

@@ -61,14 +61,14 @@ 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
+// CompactArrayG discards the none values and keeps the right 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)))
+	}, make(A2, 0, len(fa)))
 }
 
-// CompactArray discards the none values and keeps the some values
+// CompactArray discards the none values and keeps the right values
 func CompactArray[E, A any](fa []Either[E, A]) []A {
 	return CompactArrayG[[]Either[E, A], []A](fa)
 }

either/array_test.go

@@ -0,0 +1,18 @@
+package either
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCompactArray(t *testing.T) {
+	ar := []Either[string, string]{
+		Of[string]("ok"),
+		Left[string]("err"),
+		Of[string]("ok"),
+	}
+
+	res := CompactArray(ar)
+	assert.Equal(t, 2, len(res))
+}

either/either.go

@@ -89,7 +89,7 @@ func MonadChainFirst[E, A, B any](ma Either[E, A], f func(a A) Either[E, B]) Eit
 	})
 }
 
-func MonadChainTo[E, A, B any](ma Either[E, A], mb Either[E, B]) Either[E, B] {
+func MonadChainTo[A, E, B any](ma Either[E, A], mb Either[E, B]) Either[E, B] {
 	return mb
 }
 
@@ -104,8 +104,8 @@ func ChainOptionK[A, B, E any](onNone func() E) func(func(A) O.Option[B]) func(E
 	}
 }
 
-func ChainTo[E, A, B any](mb Either[E, B]) func(Either[E, A]) Either[E, B] {
-	return F.Bind2nd(MonadChainTo[E, A, B], mb)
+func ChainTo[A, E, B any](mb Either[E, B]) func(Either[E, A]) Either[E, B] {
+	return F.Bind2nd(MonadChainTo[A, E, B], mb)
 }
 
 func Chain[E, A, B any](f func(a A) Either[E, B]) func(Either[E, A]) Either[E, B] {

either/logger.go

@@ -41,7 +41,7 @@ func Logger[E, A any](loggers ...*log.Logger) func(string) func(Either[E, A]) Ei
 		return func(ma Either[E, A]) Either[E, A] {
 			return F.Pipe1(
 				delegate(ma),
-				ChainTo[E, A](ma),
+				ChainTo[A](ma),
 			)
 		}
 	}

endomorphism/curry.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 endomorphism
+
+import (
+	G "github.com/IBM/fp-go/endomorphism/generic"
+)
+
+// Curry2 curries a binary function
+func Curry2[FCT ~func(T0, T1) T1, T0, T1 any](f FCT) func(T0) Endomorphism[T1] {
+	return G.Curry2[Endomorphism[T1]](f)
+}
+
+// Curry3 curries a ternary function
+func Curry3[FCT ~func(T0, T1, T2) T2, T0, T1, T2 any](f FCT) func(T0) func(T1) Endomorphism[T2] {
+	return G.Curry3[Endomorphism[T2]](f)
+}

endomorphism/endo.go

@@ -0,0 +1,36 @@
+// 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 endomorphism
+
+import (
+	G "github.com/IBM/fp-go/endomorphism/generic"
+)
+
+func MonadAp[A any](fab Endomorphism[A], fa A) A {
+	return G.MonadAp[Endomorphism[A]](fab, fa)
+}
+
+func Ap[A any](fa A) func(Endomorphism[A]) A {
+	return G.Ap[Endomorphism[A]](fa)
+}
+
+func MonadChain[A any](ma Endomorphism[A], f Endomorphism[A]) Endomorphism[A] {
+	return G.MonadChain[Endomorphism[A]](ma, f)
+}
+
+func Chain[A any](f Endomorphism[A]) Endomorphism[Endomorphism[A]] {
+	return G.Chain[Endomorphism[Endomorphism[A]], Endomorphism[A], A](f)
+}

endomorphism/generic/curry.go

@@ -0,0 +1,36 @@
+// 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
+
+// Curry2 is a duplicate of [F.Curry2] but because of the type system it's not compatible otherwise
+func Curry2[GT1 ~func(T1) T1, FCT ~func(T0, T1) T1, T0, T1 any](f FCT) func(T0) GT1 {
+	return func(t0 T0) GT1 {
+		return func(t1 T1) T1 {
+			return f(t0, t1)
+		}
+	}
+}
+
+// Curry2 is a duplicate of [F.Curry2] but because of the type system it's not compatible otherwise
+func Curry3[GT2 ~func(T2) T2, FCT ~func(T0, T1, T2) T2, T0, T1, T2 any](f FCT) func(T0) func(T1) GT2 {
+	return func(t0 T0) func(T1) GT2 {
+		return func(t1 T1) GT2 {
+			return func(t2 T2) T2 {
+				return f(t0, t1, t2)
+			}
+		}
+	}
+}

endomorphism/generic/endo.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 generic
+
+import (
+	F "github.com/IBM/fp-go/function"
+	I "github.com/IBM/fp-go/identity/generic"
+)
+
+func MonadAp[GA ~func(A) A, A any](fab GA, fa A) A {
+	return I.MonadAp[GA, A, A](fab, fa)
+}
+
+func Ap[GA ~func(A) A, A any](fa A) func(GA) A {
+	return I.Ap[GA, A, A](fa)
+}
+
+func MonadChain[GA ~func(A) A, A any](ma GA, f GA) GA {
+	return Compose(ma, f)
+}
+
+func Chain[ENDO ~func(GA) GA, GA ~func(A) A, A any](f GA) ENDO {
+	return Of[ENDO](F.Bind2nd(Compose[GA], f))
+}

endomorphism/generic/monoid.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 generic
+
+import (
+	F "github.com/IBM/fp-go/function"
+	M "github.com/IBM/fp-go/monoid"
+	S "github.com/IBM/fp-go/semigroup"
+)
+
+// Of converts any function to an [Endomorphism]
+func Of[ENDO ~func(A) A, F ~func(A) A, A any](f F) ENDO {
+	return func(a A) A {
+		return f(a)
+	}
+}
+
+func Identity[ENDO ~func(A) A, A any]() ENDO {
+	return Of[ENDO](F.Identity[A])
+}
+
+func Compose[ENDO ~func(A) A, A any](f1, f2 ENDO) ENDO {
+	return Of[ENDO](F.Flow2(f1, f2))
+}
+
+// Semigroup for the Endomorphism where the `concat` operation is the usual function composition.
+func Semigroup[ENDO ~func(A) A, A any]() S.Semigroup[ENDO] {
+	return S.MakeSemigroup(Compose[ENDO])
+}
+
+// Monoid for the Endomorphism where the `concat` operation is the usual function composition.
+func Monoid[ENDO ~func(A) A, A any]() M.Monoid[ENDO] {
+	return M.MakeMonoid(Compose[ENDO], Identity[ENDO]())
+}

endomorphism/monoid.go

@@ -16,17 +16,30 @@
 package endomorphism
 
 import (
-	F "github.com/IBM/fp-go/function"
+	G "github.com/IBM/fp-go/endomorphism/generic"
 	M "github.com/IBM/fp-go/monoid"
 	S "github.com/IBM/fp-go/semigroup"
 )
 
+// Endomorphism is a function  that
+type Endomorphism[A any] func(A) A
+
+// Of converts any function to an [Endomorphism]
+func Of[F ~func(A) A, A any](f F) Endomorphism[A] {
+	return G.Of[Endomorphism[A]](f)
+}
+
+// Identity returns the identity [Endomorphism]
+func Identity[A any]() Endomorphism[A] {
+	return G.Identity[Endomorphism[A]]()
+}
+
 // 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(F.Flow2[func(A) A, func(A) A])
+func Semigroup[A any]() S.Semigroup[Endomorphism[A]] {
+	return G.Semigroup[Endomorphism[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(F.Flow2[func(A) A, func(A) A], F.Identity[A])
+func Monoid[A any]() M.Monoid[Endomorphism[A]] {
+	return G.Monoid[Endomorphism[A]]()
 }

erasure/erasure.go

@@ -16,6 +16,8 @@
 package erasure
 
 import (
+	E "github.com/IBM/fp-go/either"
+	"github.com/IBM/fp-go/errors"
 	F "github.com/IBM/fp-go/function"
 )
 
@@ -29,6 +31,15 @@ func Unerase[T any](t any) T {
 	return *t.(*T)
 }
 
+// SafeUnerase converts an erased variable back to its original value
+func SafeUnerase[T any](t any) E.Either[error, T] {
+	return F.Pipe2(
+		t,
+		E.ToType[*T](errors.OnSome[any]("Value of type [%T] is not erased")),
+		E.Map[error](F.Deref[T]),
+	)
+}
+
 // Erase0 converts a type safe function into an erased function
 func Erase0[T1 any](f func() T1) func() any {
 	return F.Nullary2(f, Erase[T1])

file/getters.go

@@ -15,7 +15,10 @@
 
 package file
 
-import "path/filepath"
+import (
+	"io"
+	"path/filepath"
+)
 
 // Join appends a filename to a root path
 func Join(name string) func(root string) string {
@@ -23,3 +26,13 @@ func Join(name string) func(root string) string {
 		return filepath.Join(root, name)
 	}
 }
+
+// ToReader converts a [io.Reader]
+func ToReader[R io.Reader](r R) io.Reader {
+	return r
+}
+
+// ToCloser converts a [io.Closer]
+func ToCloser[C io.Closer](c C) io.Closer {
+	return c
+}

function/binds.go

@@ -1,6 +1,6 @@
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-10-23 08:30:44.6474482 +0200 CEST m=+0.150851901
+// 2023-12-18 09:38:59.1616876 +0100 CET m=+0.008641801
 
 package function
 

function/cache.go

@@ -28,3 +28,14 @@ func Memoize[K comparable, T any](f func(K) T) func(K) T {
 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)
 }
+
+// CacheCallback converts a unary function into a unary function that caches the value depending on the parameter
+func CacheCallback[
+	A any, K comparable, T any](kf func(A) K, getOrCreate func(K, func() func() T) func() T) func(func(A) T) func(A) T {
+	return G.CacheCallback[func(func(A) T) func(A) T](kf, getOrCreate)
+}
+
+// SingleElementCache creates a cache function for use with the [CacheCallback] method that has a maximum capacity of one single item
+func SingleElementCache[K comparable, T any]() func(K, func() func() T) func() T {
+	return G.SingleElementCache[func() func() T, K]()
+}

function/cache_test.go

@@ -16,6 +16,8 @@
 package function
 
 import (
+	"fmt"
+	"math/rand"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -48,3 +50,21 @@ func TestCache(t *testing.T) {
 	assert.Equal(t, 10, cached(10))
 	assert.Equal(t, 2, count)
 }
+
+func TestSingleElementCache(t *testing.T) {
+	f := func(key string) string {
+		return fmt.Sprintf("%s: %d", key, rand.Int())
+	}
+	cb := CacheCallback(func(s string) string { return s }, SingleElementCache[string, string]())
+	cf := cb(f)
+
+	v1 := cf("1")
+	v2 := cf("1")
+	v3 := cf("2")
+	v4 := cf("1")
+
+	assert.Equal(t, v1, v2)
+	assert.NotEqual(t, v2, v3)
+	assert.NotEqual(t, v3, v4)
+	assert.NotEqual(t, v1, v4)
+}

function/flip.go

@@ -0,0 +1,25 @@
+// 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
+
+// Flip reverses the order of parameters of a curried function
+func Flip[T1, T2, R any](f func(T1) func(T2) R) func(T2) func(T1) R {
+	return func(t2 T2) func(T1) R {
+		return func(t1 T1) R {
+			return f(t1)(t2)
+		}
+	}
+}

function/flip_test.go

@@ -0,0 +1,36 @@
+// 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"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFlip(t *testing.T) {
+
+	x := Curry2(func(a, b string) string {
+		return fmt.Sprintf("%s:%s", a, b)
+	})
+
+	assert.Equal(t, "a:b", x("a")("b"))
+
+	y := Flip(x)
+
+	assert.Equal(t, "b:a", y("a")("b"))
+}

function/gen.go

@@ -1,6 +1,6 @@
 // Code generated by go generate; DO NOT EDIT.
 // This file was generated by robots at
-// 2023-10-23 08:30:41.7972101 +0200 CEST m=+0.008029101
+// 2023-12-18 09:38:51.4946446 +0100 CET m=+0.008838401
 
 package function
 
@@ -55,7 +55,7 @@ func Nullary1[F1 ~func() T1, T1 any](f1 F1) func() T1 {
 
 // Curry1 takes a function with 1 parameters and returns a cascade of functions each taking only one parameter.
 // The inverse function is [Uncurry1]
-func Curry1[T0, T1 any](f func(T0) T1) func(T0) T1 {
+func Curry1[FCT ~func(T0) T1, T0, T1 any](f FCT) func(T0) T1 {
 	return func(t0 T0) T1 {
 		return f(t0)
 	}
@@ -63,7 +63,7 @@ func Curry1[T0, T1 any](f func(T0) T1) func(T0) T1 {
 
 // Uncurry1 takes a cascade of 1 functions each taking only one parameter and returns a function with 1 parameters .
 // The inverse function is [Curry1]
-func Uncurry1[T0, T1 any](f func(T0) T1) func(T0) T1 {
+func Uncurry1[FCT ~func(T0) T1, T0, T1 any](f FCT) func(T0) T1 {
 	return func(t0 T0) T1 {
 		return f(t0)
 	}
@@ -115,7 +115,7 @@ func Nullary2[F1 ~func() T1, F2 ~func(T1) T2, T1, T2 any](f1 F1, f2 F2) func() T
 
 // Curry2 takes a function with 2 parameters and returns a cascade of functions each taking only one parameter.
 // The inverse function is [Uncurry2]
-func Curry2[T0, T1, T2 any](f func(T0, T1) T2) func(T0) func(T1) T2 {
+func Curry2[FCT ~func(T0, T1) T2, T0, T1, T2 any](f FCT) func(T0) func(T1) T2 {
 	return func(t0 T0) func(t1 T1) T2 {
 		return func(t1 T1) T2 {
 			return f(t0, t1)
@@ -125,7 +125,7 @@ func Curry2[T0, T1, T2 any](f func(T0, T1) T2) func(T0) func(T1) T2 {
 
 // Uncurry2 takes a cascade of 2 functions each taking only one parameter and returns a function with 2 parameters .
 // The inverse function is [Curry2]
-func Uncurry2[T0, T1, T2 any](f func(T0) func(T1) T2) func(T0, T1) T2 {
+func Uncurry2[FCT ~func(T0) func(T1) T2, T0, T1, T2 any](f FCT) func(T0, T1) T2 {
 	return func(t0 T0, t1 T1) T2 {
 		return f(t0)(t1)
 	}
@@ -178,7 +178,7 @@ func Nullary3[F1 ~func() T1, F2 ~func(T1) T2, F3 ~func(T2) T3, T1, T2, T3 any](f
 
 // Curry3 takes a function with 3 parameters and returns a cascade of functions each taking only one parameter.
 // The inverse function is [Uncurry3]
-func Curry3[T0, T1, T2, T3 any](f func(T0, T1, T2) T3) func(T0) func(T1) func(T2) T3 {
+func Curry3[FCT ~func(T0, T1, T2) T3, T0, T1, T2, T3 any](f FCT) func(T0) func(T1) func(T2) T3 {
 	return func(t0 T0) func(t1 T1) func(t2 T2) T3 {
 		return func(t1 T1) func(t2 T2) T3 {
 			return func(t2 T2) T3 {
@@ -190,7 +190,7 @@ func Curry3[T0, T1, T2, T3 any](f func(T0, T1, T2) T3) func(T0) func(T1) func(T2
 
 // Uncurry3 takes a cascade of 3 functions each taking only one parameter and returns a function with 3 parameters .
 // The inverse function is [Curry3]
-func Uncurry3[T0, T1, T2, T3 any](f func(T0) func(T1) func(T2) T3) func(T0, T1, T2) T3 {
+func Uncurry3[FCT ~func(T0) func(T1) func(T2) T3, T0, T1, T2, T3 any](f FCT) func(T0, T1, T2) T3 {
 	return func(t0 T0, t1 T1, t2 T2) T3 {
 		return f(t0)(t1)(t2)
 	}
@@ -244,7 +244,7 @@ func Nullary4[F1 ~func() T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4,
 
 // Curry4 takes a function with 4 parameters and returns a cascade of functions each taking only one parameter.
 // The inverse function is [Uncurry4]
-func Curry4[T0, T1, T2, T3, T4 any](f func(T0, T1, T2, T3) T4) func(T0) func(T1) func(T2) func(T3) T4 {
+func Curry4[FCT ~func(T0, T1, T2, T3) T4, T0, T1, T2, T3, T4 any](f FCT) func(T0) func(T1) func(T2) func(T3) T4 {
 	return func(t0 T0) func(t1 T1) func(t2 T2) func(t3 T3) T4 {
 		return func(t1 T1) func(t2 T2) func(t3 T3) T4 {
 			return func(t2 T2) func(t3 T3) T4 {
@@ -258,7 +258,7 @@ func Curry4[T0, T1, T2, T3, T4 any](f func(T0, T1, T2, T3) T4) func(T0) func(T1)
 
 // Uncurry4 takes a cascade of 4 functions each taking only one parameter and returns a function with 4 parameters .
 // The inverse function is [Curry4]
-func Uncurry4[T0, T1, T2, T3, T4 any](f func(T0) func(T1) func(T2) func(T3) T4) func(T0, T1, T2, T3) T4 {
+func Uncurry4[FCT ~func(T0) func(T1) func(T2) func(T3) T4, T0, T1, T2, T3, T4 any](f FCT) func(T0, T1, T2, T3) T4 {
 	return func(t0 T0, t1 T1, t2 T2, t3 T3) T4 {
 		return f(t0)(t1)(t2)(t3)
 	}
@@ -313,7 +313,7 @@ func Nullary5[F1 ~func() T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4,
 
 // Curry5 takes a function with 5 parameters and returns a cascade of functions each taking only one parameter.
 // The inverse function is [Uncurry5]
-func Curry5[T0, T1, T2, T3, T4, T5 any](f func(T0, T1, T2, T3, T4) T5) func(T0) func(T1) func(T2) func(T3) func(T4) T5 {
+func Curry5[FCT ~func(T0, T1, T2, T3, T4) T5, T0, T1, T2, T3, T4, T5 any](f FCT) func(T0) func(T1) func(T2) func(T3) func(T4) T5 {
 	return func(t0 T0) func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) T5 {
 		return func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) T5 {
 			return func(t2 T2) func(t3 T3) func(t4 T4) T5 {
@@ -329,7 +329,7 @@ func Curry5[T0, T1, T2, T3, T4, T5 any](f func(T0, T1, T2, T3, T4) T5) func(T0)
 
 // Uncurry5 takes a cascade of 5 functions each taking only one parameter and returns a function with 5 parameters .
 // The inverse function is [Curry5]
-func Uncurry5[T0, T1, T2, T3, T4, T5 any](f func(T0) func(T1) func(T2) func(T3) func(T4) T5) func(T0, T1, T2, T3, T4) T5 {
+func Uncurry5[FCT ~func(T0) func(T1) func(T2) func(T3) func(T4) T5, T0, T1, T2, T3, T4, T5 any](f FCT) func(T0, T1, T2, T3, T4) T5 {
 	return func(t0 T0, t1 T1, t2 T2, t3 T3, t4 T4) T5 {
 		return f(t0)(t1)(t2)(t3)(t4)
 	}
@@ -385,7 +385,7 @@ func Nullary6[F1 ~func() T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4,
 
 // Curry6 takes a function with 6 parameters and returns a cascade of functions each taking only one parameter.
 // The inverse function is [Uncurry6]
-func Curry6[T0, T1, T2, T3, T4, T5, T6 any](f func(T0, T1, T2, T3, T4, T5) T6) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) T6 {
+func Curry6[FCT ~func(T0, T1, T2, T3, T4, T5) T6, T0, T1, T2, T3, T4, T5, T6 any](f FCT) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) T6 {
 	return func(t0 T0) func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) T6 {
 		return func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) T6 {
 			return func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) T6 {
@@ -403,7 +403,7 @@ func Curry6[T0, T1, T2, T3, T4, T5, T6 any](f func(T0, T1, T2, T3, T4, T5) T6) f
 
 // Uncurry6 takes a cascade of 6 functions each taking only one parameter and returns a function with 6 parameters .
 // The inverse function is [Curry6]
-func Uncurry6[T0, T1, T2, T3, T4, T5, T6 any](f func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) T6) func(T0, T1, T2, T3, T4, T5) T6 {
+func Uncurry6[FCT ~func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) T6, T0, T1, T2, T3, T4, T5, T6 any](f FCT) func(T0, T1, T2, T3, T4, T5) T6 {
 	return func(t0 T0, t1 T1, t2 T2, t3 T3, t4 T4, t5 T5) T6 {
 		return f(t0)(t1)(t2)(t3)(t4)(t5)
 	}
@@ -460,7 +460,7 @@ func Nullary7[F1 ~func() T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4,
 
 // Curry7 takes a function with 7 parameters and returns a cascade of functions each taking only one parameter.
 // The inverse function is [Uncurry7]
-func Curry7[T0, T1, T2, T3, T4, T5, T6, T7 any](f func(T0, T1, T2, T3, T4, T5, T6) T7) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) T7 {
+func Curry7[FCT ~func(T0, T1, T2, T3, T4, T5, T6) T7, T0, T1, T2, T3, T4, T5, T6, T7 any](f FCT) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) T7 {
 	return func(t0 T0) func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) T7 {
 		return func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) T7 {
 			return func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) T7 {
@@ -480,7 +480,7 @@ func Curry7[T0, T1, T2, T3, T4, T5, T6, T7 any](f func(T0, T1, T2, T3, T4, T5, T
 
 // Uncurry7 takes a cascade of 7 functions each taking only one parameter and returns a function with 7 parameters .
 // The inverse function is [Curry7]
-func Uncurry7[T0, T1, T2, T3, T4, T5, T6, T7 any](f func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) T7) func(T0, T1, T2, T3, T4, T5, T6) T7 {
+func Uncurry7[FCT ~func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) T7, T0, T1, T2, T3, T4, T5, T6, T7 any](f FCT) func(T0, T1, T2, T3, T4, T5, T6) T7 {
 	return func(t0 T0, t1 T1, t2 T2, t3 T3, t4 T4, t5 T5, t6 T6) T7 {
 		return f(t0)(t1)(t2)(t3)(t4)(t5)(t6)
 	}
@@ -538,7 +538,7 @@ func Nullary8[F1 ~func() T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4,
 
 // Curry8 takes a function with 8 parameters and returns a cascade of functions each taking only one parameter.
 // The inverse function is [Uncurry8]
-func Curry8[T0, T1, T2, T3, T4, T5, T6, T7, T8 any](f func(T0, T1, T2, T3, T4, T5, T6, T7) T8) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) T8 {
+func Curry8[FCT ~func(T0, T1, T2, T3, T4, T5, T6, T7) T8, T0, T1, T2, T3, T4, T5, T6, T7, T8 any](f FCT) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) T8 {
 	return func(t0 T0) func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) T8 {
 		return func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) T8 {
 			return func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) T8 {
@@ -560,7 +560,7 @@ func Curry8[T0, T1, T2, T3, T4, T5, T6, T7, T8 any](f func(T0, T1, T2, T3, T4, T
 
 // Uncurry8 takes a cascade of 8 functions each taking only one parameter and returns a function with 8 parameters .
 // The inverse function is [Curry8]
-func Uncurry8[T0, T1, T2, T3, T4, T5, T6, T7, T8 any](f func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) T8) func(T0, T1, T2, T3, T4, T5, T6, T7) T8 {
+func Uncurry8[FCT ~func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) T8, T0, T1, T2, T3, T4, T5, T6, T7, T8 any](f FCT) func(T0, T1, T2, T3, T4, T5, T6, T7) T8 {
 	return func(t0 T0, t1 T1, t2 T2, t3 T3, t4 T4, t5 T5, t6 T6, t7 T7) T8 {
 		return f(t0)(t1)(t2)(t3)(t4)(t5)(t6)(t7)
 	}
@@ -619,7 +619,7 @@ func Nullary9[F1 ~func() T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4,
 
 // Curry9 takes a function with 9 parameters and returns a cascade of functions each taking only one parameter.
 // The inverse function is [Uncurry9]
-func Curry9[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9 any](f func(T0, T1, T2, T3, T4, T5, T6, T7, T8) T9) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) T9 {
+func Curry9[FCT ~func(T0, T1, T2, T3, T4, T5, T6, T7, T8) T9, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9 any](f FCT) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) T9 {
 	return func(t0 T0) func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) T9 {
 		return func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) T9 {
 			return func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) T9 {
@@ -643,7 +643,7 @@ func Curry9[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9 any](f func(T0, T1, T2, T3, T
 
 // Uncurry9 takes a cascade of 9 functions each taking only one parameter and returns a function with 9 parameters .
 // The inverse function is [Curry9]
-func Uncurry9[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9 any](f func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) T9) func(T0, T1, T2, T3, T4, T5, T6, T7, T8) T9 {
+func Uncurry9[FCT ~func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) T9, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9 any](f FCT) func(T0, T1, T2, T3, T4, T5, T6, T7, T8) T9 {
 	return func(t0 T0, t1 T1, t2 T2, t3 T3, t4 T4, t5 T5, t6 T6, t7 T7, t8 T8) T9 {
 		return f(t0)(t1)(t2)(t3)(t4)(t5)(t6)(t7)(t8)
 	}
@@ -703,7 +703,7 @@ func Nullary10[F1 ~func() T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4,
 
 // Curry10 takes a function with 10 parameters and returns a cascade of functions each taking only one parameter.
 // The inverse function is [Uncurry10]
-func Curry10[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10 any](f func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9) T10) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) T10 {
+func Curry10[FCT ~func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9) T10, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10 any](f FCT) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) T10 {
 	return func(t0 T0) func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) T10 {
 		return func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) T10 {
 			return func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) T10 {
@@ -729,7 +729,7 @@ func Curry10[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10 any](f func(T0, T1, T2,
 
 // Uncurry10 takes a cascade of 10 functions each taking only one parameter and returns a function with 10 parameters .
 // The inverse function is [Curry10]
-func Uncurry10[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10 any](f func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) T10) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9) T10 {
+func Uncurry10[FCT ~func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) T10, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10 any](f FCT) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9) T10 {
 	return func(t0 T0, t1 T1, t2 T2, t3 T3, t4 T4, t5 T5, t6 T6, t7 T7, t8 T8, t9 T9) T10 {
 		return f(t0)(t1)(t2)(t3)(t4)(t5)(t6)(t7)(t8)(t9)
 	}
@@ -790,7 +790,7 @@ func Nullary11[F1 ~func() T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4,
 
 // Curry11 takes a function with 11 parameters and returns a cascade of functions each taking only one parameter.
 // The inverse function is [Uncurry11]
-func Curry11[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11 any](f func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10) T11) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) T11 {
+func Curry11[FCT ~func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10) T11, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11 any](f FCT) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) T11 {
 	return func(t0 T0) func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) T11 {
 		return func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) T11 {
 			return func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) T11 {
@@ -818,7 +818,7 @@ func Curry11[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11 any](f func(T0, T1
 
 // Uncurry11 takes a cascade of 11 functions each taking only one parameter and returns a function with 11 parameters .
 // The inverse function is [Curry11]
-func Uncurry11[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11 any](f func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) T11) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10) T11 {
+func Uncurry11[FCT ~func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) T11, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11 any](f FCT) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10) T11 {
 	return func(t0 T0, t1 T1, t2 T2, t3 T3, t4 T4, t5 T5, t6 T6, t7 T7, t8 T8, t9 T9, t10 T10) T11 {
 		return f(t0)(t1)(t2)(t3)(t4)(t5)(t6)(t7)(t8)(t9)(t10)
 	}
@@ -880,7 +880,7 @@ func Nullary12[F1 ~func() T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4,
 
 // Curry12 takes a function with 12 parameters and returns a cascade of functions each taking only one parameter.
 // The inverse function is [Uncurry12]
-func Curry12[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12 any](f func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11) T12) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) T12 {
+func Curry12[FCT ~func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11) T12, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12 any](f FCT) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) T12 {
 	return func(t0 T0) func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) T12 {
 		return func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) T12 {
 			return func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) T12 {
@@ -910,7 +910,7 @@ func Curry12[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12 any](f func(T
 
 // Uncurry12 takes a cascade of 12 functions each taking only one parameter and returns a function with 12 parameters .
 // The inverse function is [Curry12]
-func Uncurry12[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12 any](f func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) T12) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11) T12 {
+func Uncurry12[FCT ~func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) T12, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12 any](f FCT) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11) T12 {
 	return func(t0 T0, t1 T1, t2 T2, t3 T3, t4 T4, t5 T5, t6 T6, t7 T7, t8 T8, t9 T9, t10 T10, t11 T11) T12 {
 		return f(t0)(t1)(t2)(t3)(t4)(t5)(t6)(t7)(t8)(t9)(t10)(t11)
 	}
@@ -973,7 +973,7 @@ func Nullary13[F1 ~func() T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4,
 
 // Curry13 takes a function with 13 parameters and returns a cascade of functions each taking only one parameter.
 // The inverse function is [Uncurry13]
-func Curry13[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13 any](f func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12) T13) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) T13 {
+func Curry13[FCT ~func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12) T13, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13 any](f FCT) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) T13 {
 	return func(t0 T0) func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) T13 {
 		return func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) T13 {
 			return func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) T13 {
@@ -1005,7 +1005,7 @@ func Curry13[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13 any](f f
 
 // Uncurry13 takes a cascade of 13 functions each taking only one parameter and returns a function with 13 parameters .
 // The inverse function is [Curry13]
-func Uncurry13[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13 any](f func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) T13) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12) T13 {
+func Uncurry13[FCT ~func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) T13, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13 any](f FCT) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12) T13 {
 	return func(t0 T0, t1 T1, t2 T2, t3 T3, t4 T4, t5 T5, t6 T6, t7 T7, t8 T8, t9 T9, t10 T10, t11 T11, t12 T12) T13 {
 		return f(t0)(t1)(t2)(t3)(t4)(t5)(t6)(t7)(t8)(t9)(t10)(t11)(t12)
 	}
@@ -1069,7 +1069,7 @@ func Nullary14[F1 ~func() T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4,
 
 // Curry14 takes a function with 14 parameters and returns a cascade of functions each taking only one parameter.
 // The inverse function is [Uncurry14]
-func Curry14[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14 any](f func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13) T14) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) T14 {
+func Curry14[FCT ~func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13) T14, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14 any](f FCT) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) T14 {
 	return func(t0 T0) func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) T14 {
 		return func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) T14 {
 			return func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) T14 {
@@ -1103,7 +1103,7 @@ func Curry14[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14 any
 
 // Uncurry14 takes a cascade of 14 functions each taking only one parameter and returns a function with 14 parameters .
 // The inverse function is [Curry14]
-func Uncurry14[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14 any](f func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) T14) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13) T14 {
+func Uncurry14[FCT ~func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) T14, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14 any](f FCT) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13) T14 {
 	return func(t0 T0, t1 T1, t2 T2, t3 T3, t4 T4, t5 T5, t6 T6, t7 T7, t8 T8, t9 T9, t10 T10, t11 T11, t12 T12, t13 T13) T14 {
 		return f(t0)(t1)(t2)(t3)(t4)(t5)(t6)(t7)(t8)(t9)(t10)(t11)(t12)(t13)
 	}
@@ -1168,7 +1168,7 @@ func Nullary15[F1 ~func() T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4,
 
 // Curry15 takes a function with 15 parameters and returns a cascade of functions each taking only one parameter.
 // The inverse function is [Uncurry15]
-func Curry15[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15 any](f func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14) T15) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) T15 {
+func Curry15[FCT ~func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14) T15, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15 any](f FCT) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) T15 {
 	return func(t0 T0) func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) func(t14 T14) T15 {
 		return func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) func(t14 T14) T15 {
 			return func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) func(t14 T14) T15 {
@@ -1204,7 +1204,7 @@ func Curry15[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T1
 
 // Uncurry15 takes a cascade of 15 functions each taking only one parameter and returns a function with 15 parameters .
 // The inverse function is [Curry15]
-func Uncurry15[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15 any](f func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) T15) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14) T15 {
+func Uncurry15[FCT ~func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) T15, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15 any](f FCT) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14) T15 {
 	return func(t0 T0, t1 T1, t2 T2, t3 T3, t4 T4, t5 T5, t6 T6, t7 T7, t8 T8, t9 T9, t10 T10, t11 T11, t12 T12, t13 T13, t14 T14) T15 {
 		return f(t0)(t1)(t2)(t3)(t4)(t5)(t6)(t7)(t8)(t9)(t10)(t11)(t12)(t13)(t14)
 	}
@@ -1270,7 +1270,7 @@ func Nullary16[F1 ~func() T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4,
 
 // Curry16 takes a function with 16 parameters and returns a cascade of functions each taking only one parameter.
 // The inverse function is [Uncurry16]
-func Curry16[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16 any](f func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15) T16) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) func(T15) T16 {
+func Curry16[FCT ~func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15) T16, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16 any](f FCT) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) func(T15) T16 {
 	return func(t0 T0) func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) func(t14 T14) func(t15 T15) T16 {
 		return func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) func(t14 T14) func(t15 T15) T16 {
 			return func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) func(t14 T14) func(t15 T15) T16 {
@@ -1308,7 +1308,7 @@ func Curry16[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T1
 
 // Uncurry16 takes a cascade of 16 functions each taking only one parameter and returns a function with 16 parameters .
 // The inverse function is [Curry16]
-func Uncurry16[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16 any](f func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) func(T15) T16) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15) T16 {
+func Uncurry16[FCT ~func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) func(T15) T16, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16 any](f FCT) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15) T16 {
 	return func(t0 T0, t1 T1, t2 T2, t3 T3, t4 T4, t5 T5, t6 T6, t7 T7, t8 T8, t9 T9, t10 T10, t11 T11, t12 T12, t13 T13, t14 T14, t15 T15) T16 {
 		return f(t0)(t1)(t2)(t3)(t4)(t5)(t6)(t7)(t8)(t9)(t10)(t11)(t12)(t13)(t14)(t15)
 	}
@@ -1375,7 +1375,7 @@ func Nullary17[F1 ~func() T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4,
 
 // Curry17 takes a function with 17 parameters and returns a cascade of functions each taking only one parameter.
 // The inverse function is [Uncurry17]
-func Curry17[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17 any](f func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16) T17) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) func(T15) func(T16) T17 {
+func Curry17[FCT ~func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16) T17, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17 any](f FCT) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) func(T15) func(T16) T17 {
 	return func(t0 T0) func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) func(t14 T14) func(t15 T15) func(t16 T16) T17 {
 		return func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) func(t14 T14) func(t15 T15) func(t16 T16) T17 {
 			return func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) func(t14 T14) func(t15 T15) func(t16 T16) T17 {
@@ -1415,7 +1415,7 @@ func Curry17[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T1
 
 // Uncurry17 takes a cascade of 17 functions each taking only one parameter and returns a function with 17 parameters .
 // The inverse function is [Curry17]
-func Uncurry17[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17 any](f func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) func(T15) func(T16) T17) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16) T17 {
+func Uncurry17[FCT ~func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) func(T15) func(T16) T17, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17 any](f FCT) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16) T17 {
 	return func(t0 T0, t1 T1, t2 T2, t3 T3, t4 T4, t5 T5, t6 T6, t7 T7, t8 T8, t9 T9, t10 T10, t11 T11, t12 T12, t13 T13, t14 T14, t15 T15, t16 T16) T17 {
 		return f(t0)(t1)(t2)(t3)(t4)(t5)(t6)(t7)(t8)(t9)(t10)(t11)(t12)(t13)(t14)(t15)(t16)
 	}
@@ -1483,7 +1483,7 @@ func Nullary18[F1 ~func() T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4,
 
 // Curry18 takes a function with 18 parameters and returns a cascade of functions each taking only one parameter.
 // The inverse function is [Uncurry18]
-func Curry18[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18 any](f func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17) T18) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) func(T15) func(T16) func(T17) T18 {
+func Curry18[FCT ~func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17) T18, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18 any](f FCT) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) func(T15) func(T16) func(T17) T18 {
 	return func(t0 T0) func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) func(t14 T14) func(t15 T15) func(t16 T16) func(t17 T17) T18 {
 		return func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) func(t14 T14) func(t15 T15) func(t16 T16) func(t17 T17) T18 {
 			return func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) func(t14 T14) func(t15 T15) func(t16 T16) func(t17 T17) T18 {
@@ -1525,7 +1525,7 @@ func Curry18[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T1
 
 // Uncurry18 takes a cascade of 18 functions each taking only one parameter and returns a function with 18 parameters .
 // The inverse function is [Curry18]
-func Uncurry18[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18 any](f func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) func(T15) func(T16) func(T17) T18) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17) T18 {
+func Uncurry18[FCT ~func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) func(T15) func(T16) func(T17) T18, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18 any](f FCT) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17) T18 {
 	return func(t0 T0, t1 T1, t2 T2, t3 T3, t4 T4, t5 T5, t6 T6, t7 T7, t8 T8, t9 T9, t10 T10, t11 T11, t12 T12, t13 T13, t14 T14, t15 T15, t16 T16, t17 T17) T18 {
 		return f(t0)(t1)(t2)(t3)(t4)(t5)(t6)(t7)(t8)(t9)(t10)(t11)(t12)(t13)(t14)(t15)(t16)(t17)
 	}
@@ -1594,7 +1594,7 @@ func Nullary19[F1 ~func() T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4,
 
 // Curry19 takes a function with 19 parameters and returns a cascade of functions each taking only one parameter.
 // The inverse function is [Uncurry19]
-func Curry19[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19 any](f func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18) T19) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) func(T15) func(T16) func(T17) func(T18) T19 {
+func Curry19[FCT ~func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18) T19, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19 any](f FCT) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) func(T15) func(T16) func(T17) func(T18) T19 {
 	return func(t0 T0) func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) func(t14 T14) func(t15 T15) func(t16 T16) func(t17 T17) func(t18 T18) T19 {
 		return func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) func(t14 T14) func(t15 T15) func(t16 T16) func(t17 T17) func(t18 T18) T19 {
 			return func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) func(t14 T14) func(t15 T15) func(t16 T16) func(t17 T17) func(t18 T18) T19 {
@@ -1638,7 +1638,7 @@ func Curry19[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T1
 
 // Uncurry19 takes a cascade of 19 functions each taking only one parameter and returns a function with 19 parameters .
 // The inverse function is [Curry19]
-func Uncurry19[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19 any](f func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) func(T15) func(T16) func(T17) func(T18) T19) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18) T19 {
+func Uncurry19[FCT ~func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) func(T15) func(T16) func(T17) func(T18) T19, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19 any](f FCT) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18) T19 {
 	return func(t0 T0, t1 T1, t2 T2, t3 T3, t4 T4, t5 T5, t6 T6, t7 T7, t8 T8, t9 T9, t10 T10, t11 T11, t12 T12, t13 T13, t14 T14, t15 T15, t16 T16, t17 T17, t18 T18) T19 {
 		return f(t0)(t1)(t2)(t3)(t4)(t5)(t6)(t7)(t8)(t9)(t10)(t11)(t12)(t13)(t14)(t15)(t16)(t17)(t18)
 	}
@@ -1708,7 +1708,7 @@ func Nullary20[F1 ~func() T1, F2 ~func(T1) T2, F3 ~func(T2) T3, F4 ~func(T3) T4,
 
 // Curry20 takes a function with 20 parameters and returns a cascade of functions each taking only one parameter.
 // The inverse function is [Uncurry20]
-func Curry20[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20 any](f func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19) T20) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) func(T15) func(T16) func(T17) func(T18) func(T19) T20 {
+func Curry20[FCT ~func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19) T20, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20 any](f FCT) func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) func(T15) func(T16) func(T17) func(T18) func(T19) T20 {
 	return func(t0 T0) func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) func(t14 T14) func(t15 T15) func(t16 T16) func(t17 T17) func(t18 T18) func(t19 T19) T20 {
 		return func(t1 T1) func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) func(t14 T14) func(t15 T15) func(t16 T16) func(t17 T17) func(t18 T18) func(t19 T19) T20 {
 			return func(t2 T2) func(t3 T3) func(t4 T4) func(t5 T5) func(t6 T6) func(t7 T7) func(t8 T8) func(t9 T9) func(t10 T10) func(t11 T11) func(t12 T12) func(t13 T13) func(t14 T14) func(t15 T15) func(t16 T16) func(t17 T17) func(t18 T18) func(t19 T19) T20 {
@@ -1754,7 +1754,7 @@ func Curry20[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T1
 
 // Uncurry20 takes a cascade of 20 functions each taking only one parameter and returns a function with 20 parameters .
 // The inverse function is [Curry20]
-func Uncurry20[T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20 any](f func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) func(T15) func(T16) func(T17) func(T18) func(T19) T20) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19) T20 {
+func Uncurry20[FCT ~func(T0) func(T1) func(T2) func(T3) func(T4) func(T5) func(T6) func(T7) func(T8) func(T9) func(T10) func(T11) func(T12) func(T13) func(T14) func(T15) func(T16) func(T17) func(T18) 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](f FCT) func(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19) T20 {
 	return func(t0 T0, t1 T1, t2 T2, t3 T3, t4 T4, t5 T5, t6 T6, t7 T7, t8 T8, t9 T9, t10 T10, t11 T11, t12 T12, t13 T13, t14 T14, t15 T15, t16 T16, t17 T17, t18 T18, t19 T19) T20 {
 		return f(t0)(t1)(t2)(t3)(t4)(t5)(t6)(t7)(t8)(t9)(t10)(t11)(t12)(t13)(t14)(t15)(t16)(t17)(t18)(t19)
 	}

function/generic/cache.go

@@ -28,7 +28,7 @@ func Memoize[F ~func(K) T, K comparable, T any](f F) 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]())
+	return CacheCallback[func(F) F, func() func() T](kf, getOrCreate[K, T]())
 }
 
 // getOrCreate is a naive implementation of a cache, without bounds
@@ -50,13 +50,51 @@ func getOrCreate[K comparable, T any]() func(K, func() func() T) func() T {
 	}
 }
 
+// SingleElementCache is a cache with a capacity of a single element
+func SingleElementCache[
+	LLT ~func() LT, // generator of the generator
+	K comparable, // key into the cache
+	LT ~func() T, // generator of a value
+	T any, // the cached data type
+]() func(K, LLT) LT {
+	var l sync.Mutex
+
+	var key K
+	var value LT
+	hasKey := false
+
+	return func(k K, gen LLT) LT {
+		l.Lock()
+
+		existing := value
+		if !hasKey || key != k {
+			existing = gen()
+			// update state
+			key = k
+			value = existing
+			hasKey = true
+		}
+
+		l.Unlock()
+
+		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 {
+func CacheCallback[
+	EM ~func(F) F, // endomorphism of the function
+	LLT ~func() LT, // generator of the generator
+	LT ~func() T, // generator of a value
+	F ~func(A) T, // function to actually cache
+	KF func(A) K, // extracts the cache key from the input
+	C ~func(K, LLT) LT, // the cache callback function
+	A any, K comparable, T any](kf KF, getOrCreate C) EM {
 	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 getOrCreate(kf(a), func() LT {
+				return L.Memoize[LT](func() T {
 					return f(a)
 				})
 			})()

function/generic/switch.go

@@ -0,0 +1,28 @@
+// 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
+
+// Switch applies a handler to different cases. The handers are stored in a map. A key function
+// extracts the case from a value.
+func Switch[HF ~func(T) R, N ~map[K]HF, KF ~func(T) K, K comparable, T, R any](kf KF, n N, d HF) HF {
+	return func(t T) R {
+		f, ok := n[kf(t)]
+		if ok {
+			return f(t)
+		}
+		return d(t)
+	}
+}

function/switch.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 function
+
+import (
+	G "github.com/IBM/fp-go/function/generic"
+)
+
+// Switch applies a handler to different cases. The handers are stored in a map. A key function
+// extracts the case from a value.
+func Switch[K comparable, T, R any](kf func(T) K, n map[K]func(T) R, d func(T) R) func(T) R {
+	return G.Switch(kf, n, d)
+}

go.mod

@@ -4,7 +4,7 @@ go 1.20
 
 require (
 	github.com/stretchr/testify v1.8.4
-	github.com/urfave/cli/v2 v2.25.7
+	github.com/urfave/cli/v2 v2.27.1
 )
 
 require (
@@ -12,6 +12,6 @@ require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/russross/blackfriday/v2 v2.1.0 // indirect
-	github.com/xrash/smetrics v0.0.0-20201216005158-039620a65673 // indirect
+	github.com/xrash/smetrics v0.0.0-20231213231151-1d8dd44e695e // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -8,10 +8,10 @@ github.com/russross/blackfriday/v2 v2.1.0 h1:JIOH55/0cWyOuilr9/qlrm0BSXldqnqwMsf
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
 github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
-github.com/urfave/cli/v2 v2.25.7 h1:VAzn5oq403l5pHjc4OhD54+XGO9cdKVL/7lDjF+iKUs=
-github.com/urfave/cli/v2 v2.25.7/go.mod h1:8qnjx1vcq5s2/wpsqoZFndg2CE5tNFyrTvS6SinrnYQ=
-github.com/xrash/smetrics v0.0.0-20201216005158-039620a65673 h1:bAn7/zixMGCfxrRTfdpNzjtPYqr8smhKouy9mxVdGPU=
-github.com/xrash/smetrics v0.0.0-20201216005158-039620a65673/go.mod h1:N3UwUGtsrSj3ccvlPHLoLsHnpR27oXr4ZE984MbSER8=
+github.com/urfave/cli/v2 v2.27.1 h1:8xSQ6szndafKVRmfyeUMxkNUJQMjL1F2zmsZ+qHpfho=
+github.com/urfave/cli/v2 v2.27.1/go.mod h1:8qnjx1vcq5s2/wpsqoZFndg2CE5tNFyrTvS6SinrnYQ=
+github.com/xrash/smetrics v0.0.0-20231213231151-1d8dd44e695e h1:+SOyEddqYF09QP7vr7CgJ1eti3pY9Fn3LHO1M1r/0sI=
+github.com/xrash/smetrics v0.0.0-20231213231151-1d8dd44e695e/go.mod h1:N3UwUGtsrSj3ccvlPHLoLsHnpR27oXr4ZE984MbSER8=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

http/content/content.go

@@ -0,0 +1,22 @@
+// 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 content
+
+const (
+	TextPlain   = "text/plain"
+	Json        = "application/json"
+	FormEncoded = "application/x-www-form-urlencoded"
+)

http/form/form.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 form
+
+import (
+	"net/url"
+
+	A "github.com/IBM/fp-go/array"
+	ENDO "github.com/IBM/fp-go/endomorphism"
+	F "github.com/IBM/fp-go/function"
+	L "github.com/IBM/fp-go/optics/lens"
+	LA "github.com/IBM/fp-go/optics/lens/array"
+	LRG "github.com/IBM/fp-go/optics/lens/record/generic"
+	O "github.com/IBM/fp-go/option"
+	RG "github.com/IBM/fp-go/record/generic"
+)
+
+type (
+	// Endomorphism returns an [ENDO.Endomorphism] that transforms a form
+	Endomorphism = ENDO.Endomorphism[url.Values]
+)
+
+var (
+	// Default is the default form field
+	Default = make(url.Values)
+
+	noField = O.None[string]()
+
+	// FormMonoid is the [M.Monoid] for the [Endomorphism]
+	Monoid = ENDO.Monoid[url.Values]()
+
+	// ValuesMonoid is a [M.Monoid] to concatenate [url.Values] maps
+	ValuesMonoid = RG.UnionMonoid[url.Values](A.Semigroup[string]())
+
+	// AtValues is a [L.Lens] that focusses on the values of a form field
+	AtValues = LRG.AtRecord[url.Values, []string]
+
+	composeHead = F.Pipe1(
+		LA.AtHead[string](),
+		L.ComposeOptions[url.Values, string](A.Empty[string]()),
+	)
+
+	// AtValue is a [L.Lens] that focusses on first value in form fields
+	AtValue = F.Flow2(
+		AtValues,
+		composeHead,
+	)
+)
+
+// WithValue creates a [FormBuilder] for a certain field
+func WithValue(name string) func(value string) Endomorphism {
+	return F.Flow2(
+		O.Of[string],
+		AtValue(name).Set,
+	)
+}
+
+// WithoutValue creates a [FormBuilder] that removes a field
+func WithoutValue(name string) Endomorphism {
+	return AtValue(name).Set(noField)
+}

http/form/form_test.go

@@ -0,0 +1,93 @@
+// 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 form
+
+import (
+	"net/url"
+	"testing"
+
+	A "github.com/IBM/fp-go/array"
+	"github.com/IBM/fp-go/eq"
+	F "github.com/IBM/fp-go/function"
+	LT "github.com/IBM/fp-go/optics/lens/testing"
+	O "github.com/IBM/fp-go/option"
+	RG "github.com/IBM/fp-go/record/generic"
+	S "github.com/IBM/fp-go/string"
+	"github.com/stretchr/testify/assert"
+)
+
+var (
+	sEq      = eq.FromEquals(S.Eq)
+	valuesEq = RG.Eq[url.Values](A.Eq(sEq))
+)
+
+func TestLaws(t *testing.T) {
+	name := "Content-Type"
+	fieldLaws := LT.AssertLaws[url.Values, O.Option[string]](t, O.Eq(sEq), valuesEq)(AtValue(name))
+
+	n := O.None[string]()
+	s1 := O.Some("s1")
+
+	v1 := F.Pipe1(
+		Default,
+		WithValue(name)("v1"),
+	)
+
+	v2 := F.Pipe1(
+		Default,
+		WithValue("Other-Header")("v2"),
+	)
+
+	assert.True(t, fieldLaws(Default, n))
+	assert.True(t, fieldLaws(v1, n))
+	assert.True(t, fieldLaws(v2, n))
+
+	assert.True(t, fieldLaws(Default, s1))
+	assert.True(t, fieldLaws(v1, s1))
+	assert.True(t, fieldLaws(v2, s1))
+}
+
+func TestFormField(t *testing.T) {
+
+	v1 := F.Pipe1(
+		Default,
+		WithValue("h1")("v1"),
+	)
+
+	v2 := F.Pipe1(
+		v1,
+		WithValue("h2")("v2"),
+	)
+
+	// make sure the code does not change structures
+	assert.False(t, valuesEq.Equals(Default, v1))
+	assert.False(t, valuesEq.Equals(Default, v2))
+	assert.False(t, valuesEq.Equals(v1, v2))
+
+	// check for existence of values
+	assert.Equal(t, "v1", v1.Get("h1"))
+	assert.Equal(t, "v1", v2.Get("h1"))
+	assert.Equal(t, "v2", v2.Get("h2"))
+
+	// check getter on lens
+
+	l1 := AtValue("h1")
+	l2 := AtValue("h2")
+
+	assert.Equal(t, O.Of("v1"), l1.Get(v1))
+	assert.Equal(t, O.Of("v1"), l1.Get(v2))
+	assert.Equal(t, O.Of("v2"), l2.Get(v2))
+}

http/headers/headers.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 headers
+
+import (
+	"net/http"
+	"net/textproto"
+
+	A "github.com/IBM/fp-go/array"
+	F "github.com/IBM/fp-go/function"
+	L "github.com/IBM/fp-go/optics/lens"
+	LA "github.com/IBM/fp-go/optics/lens/array"
+	LRG "github.com/IBM/fp-go/optics/lens/record/generic"
+	RG "github.com/IBM/fp-go/record/generic"
+)
+
+// HTTP headers
+const (
+	Accept        = "Accept"
+	Authorization = "Authorization"
+	ContentType   = "Content-Type"
+	ContentLength = "Content-Length"
+)
+
+var (
+	// Monoid is a [M.Monoid] to concatenate [http.Header] maps
+	Monoid = RG.UnionMonoid[http.Header](A.Semigroup[string]())
+
+	// AtValues is a [L.Lens] that focusses on the values of a header
+	AtValues = F.Flow2(
+		textproto.CanonicalMIMEHeaderKey,
+		LRG.AtRecord[http.Header, []string],
+	)
+
+	composeHead = F.Pipe1(
+		LA.AtHead[string](),
+		L.ComposeOptions[http.Header, string](A.Empty[string]()),
+	)
+
+	// AtValue is a [L.Lens] that focusses on first value of a header
+	AtValue = F.Flow2(
+		AtValues,
+		composeHead,
+	)
+)

http/headers/headers_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 headers
+
+import (
+	"net/http"
+	"testing"
+
+	A "github.com/IBM/fp-go/array"
+	"github.com/IBM/fp-go/eq"
+	LT "github.com/IBM/fp-go/optics/lens/testing"
+	O "github.com/IBM/fp-go/option"
+	RG "github.com/IBM/fp-go/record/generic"
+	S "github.com/IBM/fp-go/string"
+	"github.com/stretchr/testify/assert"
+)
+
+var (
+	sEq      = eq.FromEquals(S.Eq)
+	valuesEq = RG.Eq[http.Header](A.Eq(sEq))
+)
+
+func TestLaws(t *testing.T) {
+	name := "Content-Type"
+	fieldLaws := LT.AssertLaws[http.Header, O.Option[string]](t, O.Eq(sEq), valuesEq)(AtValue(name))
+
+	n := O.None[string]()
+	s1 := O.Some("s1")
+
+	def := make(http.Header)
+
+	v1 := make(http.Header)
+	v1.Set(name, "v1")
+
+	v2 := make(http.Header)
+	v2.Set("Other-Header", "v2")
+
+	assert.True(t, fieldLaws(def, n))
+	assert.True(t, fieldLaws(v1, n))
+	assert.True(t, fieldLaws(v2, n))
+
+	assert.True(t, fieldLaws(def, s1))
+	assert.True(t, fieldLaws(v1, s1))
+	assert.True(t, fieldLaws(v2, s1))
+}

http/utils_test.go

@@ -20,6 +20,7 @@ import (
 
 	E "github.com/IBM/fp-go/either"
 	F "github.com/IBM/fp-go/function"
+	C "github.com/IBM/fp-go/http/content"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -38,7 +39,7 @@ func Error[A any](t *testing.T) func(E.Either[error, A]) bool {
 func TestValidateJsonContentTypeString(t *testing.T) {
 
 	res := F.Pipe1(
-		validateJsonContentTypeString("application/json"),
+		validateJsonContentTypeString(C.Json),
 		NoError[ParsedMediaType](t),
 	)
 

identity/generic/identity.go

@@ -57,6 +57,6 @@ 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 {
+func Flap[GAB ~func(A) B, B, A any](a A) func(GAB) B {
 	return F.Bind2nd(MonadFlap[GAB, A, B], a)
 }

internal/array/array.go

@@ -51,6 +51,24 @@ func ReduceWithIndex[GA ~[]A, A, B any](fa GA, f func(int, B, A) B, initial B) B
 	return current
 }
 
+func ReduceRight[GA ~[]A, A, B any](fa GA, f func(A, B) B, initial B) B {
+	current := initial
+	count := len(fa)
+	for i := count - 1; i >= 0; i-- {
+		current = f(fa[i], current)
+	}
+	return current
+}
+
+func ReduceRightWithIndex[GA ~[]A, A, B any](fa GA, f func(int, A, B) B, initial B) B {
+	current := initial
+	count := len(fa)
+	for i := count - 1; i >= 0; i-- {
+		current = f(i, fa[i], current)
+	}
+	return current
+}
+
 func Append[GA ~[]A, A any](as GA, a A) GA {
 	return append(as, a)
 }
@@ -88,6 +106,15 @@ func MonadMap[GA ~[]A, GB ~[]B, A, B any](as GA, f func(a A) B) GB {
 	return bs
 }
 
+func MonadMapWithIndex[GA ~[]A, GB ~[]B, A, B any](as GA, f func(idx int, a A) B) GB {
+	count := len(as)
+	bs := make(GB, count)
+	for i := count - 1; i >= 0; i-- {
+		bs[i] = f(i, as[i])
+	}
+	return bs
+}
+
 func ConstNil[GA ~[]A, A any]() GA {
 	return (GA)(nil)
 }

internal/array/prepend.go

@@ -0,0 +1,28 @@
+// 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
+
+// Prepend prepends a single value to an array
+func Prepend[ENDO ~func(AS) AS, AS ~[]A, A any](head A) ENDO {
+	return func(as AS) AS {
+		l := len(as)
+		cpy := make(AS, l+1)
+		copy(cpy[1:], as)
+		cpy[0] = head
+		return cpy
+
+	}
+}

internal/eithert/either.go

@@ -32,6 +32,17 @@ func MonadAlt[LAZY ~func() HKTFA, E, A, HKTFA any](
 	return fchain(first, ET.Fold(F.Ignore1of1[E](second), F.Flow2(ET.Of[E, A], fof)))
 }
 
+func Alt[LAZY ~func() HKTFA, E, A, HKTFA any](
+	fof func(ET.Either[E, A]) HKTFA,
+	fchain func(HKTFA, func(ET.Either[E, A]) HKTFA) HKTFA,
+
+	second LAZY) func(HKTFA) HKTFA {
+
+	return func(fa HKTFA) HKTFA {
+		return MonadAlt(fof, fchain, fa, second)
+	}
+}
+
 // 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/optiont/option.go

@@ -49,6 +49,16 @@ func MonadChain[A, B, HKTFA, HKTFB any](
 	return fchain(ma, O.Fold(F.Nullary2(O.None[B], fof), f))
 }
 
+func Chain[A, B, HKTFA, HKTFB any](
+	fchain func(HKTFA, func(O.Option[A]) HKTFB) HKTFB,
+	fof func(O.Option[B]) HKTFB,
+	f func(A) HKTFB) func(ma HKTFA) HKTFB {
+	// dispatch to the even more generic implementation
+	return func(ma HKTFA) HKTFB {
+		return MonadChain(fchain, fof, ma, f)
+	}
+}
+
 func MonadAp[A, B, HKTFAB, HKTFGAB, HKTFA, HKTFB any](
 	fap func(HKTFGAB, HKTFA) HKTFB,
 	fmap func(HKTFAB, func(O.Option[func(A) B]) func(O.Option[A]) O.Option[B]) HKTFGAB,
@@ -78,3 +88,24 @@ func MonadChainOptionK[A, B, HKTA, HKTB any](
 ) HKTB {
 	return MonadChain(fchain, fof, ma, FromOptionK(fof, f))
 }
+
+func MonadAlt[LAZY ~func() HKTFA, A, HKTFA any](
+	fof func(O.Option[A]) HKTFA,
+	fchain func(HKTFA, func(O.Option[A]) HKTFA) HKTFA,
+
+	first HKTFA,
+	second LAZY) HKTFA {
+
+	return fchain(first, O.Fold(second, F.Flow2(O.Of[A], fof)))
+}
+
+func Alt[LAZY ~func() HKTFA, A, HKTFA any](
+	fof func(O.Option[A]) HKTFA,
+	fchain func(HKTFA, func(O.Option[A]) HKTFA) HKTFA,
+
+	second LAZY) func(HKTFA) HKTFA {
+
+	return func(fa HKTFA) HKTFA {
+		return MonadAlt(fof, fchain, fa, second)
+	}
+}

io/generic/ap.go

@@ -16,6 +16,7 @@
 package generic
 
 import (
+	F "github.com/IBM/fp-go/function"
 	G "github.com/IBM/fp-go/internal/apply"
 )
 
@@ -27,7 +28,10 @@ const (
 // MonadApSeq implements the applicative on a single thread by first executing mab and the ma
 func MonadApSeq[GA ~func() A, GB ~func() B, GAB ~func() func(A) B, A, B any](mab GAB, ma GA) GB {
 	return MakeIO[GB](func() B {
-		return mab()(ma())
+		return F.Pipe1(
+			ma(),
+			mab(),
+		)
 	})
 }
 

io/generic/resource.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 generic
+
+import (
+	F "github.com/IBM/fp-go/function"
+)
+
+// WithResource constructs a function that creates a resource, then operates on it and then releases the resource
+func WithResource[
+	GA ~func() A,
+	GR ~func() R,
+	GANY ~func() ANY,
+	R, A, ANY any](onCreate GR, onRelease func(R) GANY) func(func(R) GA) GA {
+	// simply map to implementation of bracket
+	return F.Bind13of3(Bracket[GR, GA, GANY, R, A, ANY])(onCreate, F.Ignore2of2[A](onRelease))
+}

io/generic/traverse.go

@@ -57,7 +57,7 @@ func SequenceArray[GA ~func() A, GAS ~func() AAS, AAS ~[]A, GAAS ~[]GA, A any](t
 }
 
 // MonadTraverseRecord transforms a record using an IO transform an IO of a record
-func MonadTraverseRecord[GB ~func() B, GBS ~func() MB, MA ~map[K]A, MB ~map[K]B, K comparable, A, B any](ma MA, f func(A) GB) GBS {
+func MonadTraverseRecord[GBS ~func() MB, MA ~map[K]A, GB ~func() B, MB ~map[K]B, K comparable, A, B any](ma MA, f func(A) GB) GBS {
 	return RR.MonadTraverse[MA](
 		Of[GBS, MB],
 		Map[GBS, func() func(B) MB, MB, func(B) MB],
@@ -67,7 +67,7 @@ func MonadTraverseRecord[GB ~func() B, GBS ~func() MB, MA ~map[K]A, MB ~map[K]B,
 }
 
 // TraverseRecord transforms a record using an IO transform an IO of a record
-func TraverseRecord[GB ~func() B, GBS ~func() MB, MA ~map[K]A, MB ~map[K]B, K comparable, A, B any](f func(A) GB) func(MA) GBS {
+func TraverseRecord[GBS ~func() MB, MA ~map[K]A, GB ~func() B, MB ~map[K]B, K comparable, A, B any](f func(A) GB) func(MA) GBS {
 	return RR.Traverse[MA](
 		Of[GBS, MB],
 		Map[GBS, func() func(B) MB, MB, func(B) MB],
@@ -87,5 +87,5 @@ func TraverseRecordWithIndex[GB ~func() B, GBS ~func() MB, MA ~map[K]A, MB ~map[
 }
 
 func SequenceRecord[GA ~func() A, GAS ~func() AAS, AAS ~map[K]A, GAAS ~map[K]GA, K comparable, A any](tas GAAS) GAS {
-	return MonadTraverseRecord[GA, GAS](tas, F.Identity[GA])
+	return MonadTraverseRecord[GAS](tas, F.Identity[GA])
 }

io/resource.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 io
+
+import (
+	G "github.com/IBM/fp-go/io/generic"
+)
+
+// WithResource constructs a function that creates a resource, then operates on it and then releases the resource
+func WithResource[
+	R, A, ANY any](onCreate IO[R], onRelease func(R) IO[ANY]) func(func(R) IO[A]) IO[A] {
+	// just dispatch
+	return G.WithResource[IO[A], IO[R], IO[ANY]](onCreate, onRelease)
+}

io/traverse.go

@@ -41,13 +41,13 @@ func SequenceArray[A any](tas []IO[A]) IO[[]A] {
 }
 
 func MonadTraverseRecord[K comparable, A, B any](tas map[K]A, f func(A) IO[B]) IO[map[K]B] {
-	return G.MonadTraverseRecord[IO[B], IO[map[K]B]](tas, f)
+	return G.MonadTraverseRecord[IO[map[K]B]](tas, f)
 }
 
 // TraverseRecord applies a function returning an [IO] to all elements in a record and the
 // transforms this into an [IO] of that record
 func TraverseRecord[K comparable, A, B any](f func(A) IO[B]) func(map[K]A) IO[map[K]B] {
-	return G.TraverseRecord[IO[B], IO[map[K]B], map[K]A](f)
+	return G.TraverseRecord[IO[map[K]B], map[K]A, IO[B]](f)
 }
 
 // TraverseRecordWithIndex applies a function returning an [IO] to all elements in a record and the

ioeither/generic/ioeither.go

@@ -275,6 +275,27 @@ func ChainFirstIOK[GA ~func() ET.Either[E, A], GIOB ~func() B, E, A, B any](f fu
 	)
 }
 
+// MonadChainFirstEitherK runs the monad returned by the function but returns the result of the original monad
+func MonadChainFirstEitherK[GA ~func() ET.Either[E, A], E, A, B any](first GA, f func(A) ET.Either[E, B]) GA {
+	return FE.MonadChainFirstEitherK(
+		MonadChain[GA, GA, E, A, A],
+		MonadMap[func() ET.Either[E, B], GA, E, B, A],
+		FromEither[func() ET.Either[E, B], E, B],
+		first,
+		f,
+	)
+}
+
+// ChainFirstEitherK runs the monad returned by the function but returns the result of the original monad
+func ChainFirstEitherK[GA ~func() ET.Either[E, A], E, A, B any](f func(A) ET.Either[E, B]) func(GA) GA {
+	return FE.ChainFirstEitherK(
+		MonadChain[GA, GA, E, A, A],
+		MonadMap[func() ET.Either[E, B], GA, E, B, A],
+		FromEither[func() ET.Either[E, B], E, B],
+		f,
+	)
+}
+
 // Swap changes the order of type parameters
 func Swap[GEA ~func() ET.Either[E, A], GAE ~func() ET.Either[A, E], E, A any](val GEA) GAE {
 	return MonadFold(val, Right[GAE], Left[GAE])
@@ -315,3 +336,14 @@ func MonadFlap[GEAB ~func() ET.Either[E, func(A) B], GEB ~func() ET.Either[E, B]
 func Flap[GEAB ~func() ET.Either[E, func(A) B], GEB ~func() ET.Either[E, B], E, B, A any](a A) func(GEAB) GEB {
 	return FC.Flap(MonadMap[GEAB, GEB], a)
 }
+
+func ToIOOption[GA ~func() O.Option[A], GEA ~func() ET.Either[E, A], E, A any](ioe GEA) GA {
+	return F.Pipe1(
+		ioe,
+		IO.Map[GEA, GA](ET.ToOption[E, A]),
+	)
+}
+
+func FromIOOption[GEA ~func() ET.Either[E, A], GA ~func() O.Option[A], E, A any](onNone func() E) func(ioo GA) GEA {
+	return IO.Map[GA, GEA](ET.FromOption[A](onNone))
+}

ioeither/generic/traverse.go

@@ -111,3 +111,183 @@ func TraverseRecordWithIndex[GB ~func() ET.Either[E, B], GBS ~func() ET.Either[E
 func SequenceRecord[GA ~func() ET.Either[E, A], GAS ~func() ET.Either[E, AAS], AAS ~map[K]A, GAAS ~map[K]GA, K comparable, E, A any](tas GAAS) GAS {
 	return MonadTraverseRecord[GA, GAS](tas, F.Identity[GA])
 }
+
+// MonadTraverseArraySeq transforms an array
+func MonadTraverseArraySeq[GB ~func() ET.Either[E, B], GBS ~func() ET.Either[E, BBS], AAS ~[]A, BBS ~[]B, E, A, B any](tas AAS, f func(A) GB) GBS {
+	return RA.MonadTraverse[AAS](
+		Of[GBS, E, BBS],
+		Map[GBS, func() ET.Either[E, func(B) BBS], E, BBS, func(B) BBS],
+		ApSeq[GBS, func() ET.Either[E, func(B) BBS], GB],
+
+		tas,
+		f,
+	)
+}
+
+// TraverseArraySeq transforms an array
+func TraverseArraySeq[GB ~func() ET.Either[E, B], GBS ~func() ET.Either[E, BBS], AAS ~[]A, BBS ~[]B, E, A, B any](f func(A) GB) func(AAS) GBS {
+	return RA.Traverse[AAS](
+		Of[GBS, E, BBS],
+		Map[GBS, func() ET.Either[E, func(B) BBS], E, BBS, func(B) BBS],
+		ApSeq[GBS, func() ET.Either[E, func(B) BBS], GB],
+
+		f,
+	)
+}
+
+// MonadTraverseArrayWithIndexSeq transforms an array
+func MonadTraverseArrayWithIndexSeq[GB ~func() ET.Either[E, B], GBS ~func() ET.Either[E, BBS], AAS ~[]A, BBS ~[]B, E, A, B any](tas AAS, f func(int, A) GB) GBS {
+	return RA.MonadTraverseWithIndex[AAS](
+		Of[GBS, E, BBS],
+		Map[GBS, func() ET.Either[E, func(B) BBS], E, BBS, func(B) BBS],
+		ApSeq[GBS, func() ET.Either[E, func(B) BBS], GB],
+
+		tas,
+		f,
+	)
+}
+
+// TraverseArrayWithIndexSeq transforms an array
+func TraverseArrayWithIndexSeq[GB ~func() ET.Either[E, B], GBS ~func() ET.Either[E, BBS], AAS ~[]A, BBS ~[]B, E, A, B any](f func(int, A) GB) func(AAS) GBS {
+	return RA.TraverseWithIndex[AAS](
+		Of[GBS, E, BBS],
+		Map[GBS, func() ET.Either[E, func(B) BBS], E, BBS, func(B) BBS],
+		ApSeq[GBS, func() ET.Either[E, func(B) BBS], GB],
+
+		f,
+	)
+}
+
+// SequenceArraySeq converts a homogeneous sequence of either into an either of sequence
+func SequenceArraySeq[GA ~func() ET.Either[E, A], GAS ~func() ET.Either[E, AAS], AAS ~[]A, GAAS ~[]GA, E, A any](tas GAAS) GAS {
+	return MonadTraverseArraySeq[GA, GAS](tas, F.Identity[GA])
+}
+
+// MonadTraverseRecordSeq transforms an array
+func MonadTraverseRecordSeq[GB ~func() ET.Either[E, B], GBS ~func() ET.Either[E, BBS], AAS ~map[K]A, BBS ~map[K]B, K comparable, E, A, B any](tas AAS, f func(A) GB) GBS {
+	return RR.MonadTraverse[AAS](
+		Of[GBS, E, BBS],
+		Map[GBS, func() ET.Either[E, func(B) BBS], E, BBS, func(B) BBS],
+		ApSeq[GBS, func() ET.Either[E, func(B) BBS], GB],
+
+		tas,
+		f,
+	)
+}
+
+// TraverseRecordSeq transforms an array
+func TraverseRecordSeq[GB ~func() ET.Either[E, B], GBS ~func() ET.Either[E, BBS], AAS ~map[K]A, BBS ~map[K]B, K comparable, E, A, B any](f func(A) GB) func(AAS) GBS {
+	return RR.Traverse[AAS](
+		Of[GBS, E, BBS],
+		Map[GBS, func() ET.Either[E, func(B) BBS], E, BBS, func(B) BBS],
+		ApSeq[GBS, func() ET.Either[E, func(B) BBS], GB],
+
+		f,
+	)
+}
+
+// TraverseRecordWithIndexSeq transforms an array
+func TraverseRecordWithIndexSeq[GB ~func() ET.Either[E, B], GBS ~func() ET.Either[E, BBS], AAS ~map[K]A, BBS ~map[K]B, K comparable, E, A, B any](f func(K, A) GB) func(AAS) GBS {
+	return RR.TraverseWithIndex[AAS](
+		Of[GBS, E, BBS],
+		Map[GBS, func() ET.Either[E, func(B) BBS], E, BBS, func(B) BBS],
+		ApSeq[GBS, func() ET.Either[E, func(B) BBS], GB],
+
+		f,
+	)
+}
+
+// SequenceRecordSeq converts a homogeneous sequence of either into an either of sequence
+func SequenceRecordSeq[GA ~func() ET.Either[E, A], GAS ~func() ET.Either[E, AAS], AAS ~map[K]A, GAAS ~map[K]GA, K comparable, E, A any](tas GAAS) GAS {
+	return MonadTraverseRecordSeq[GA, GAS](tas, F.Identity[GA])
+}
+
+// MonadTraverseArrayPar transforms an array
+func MonadTraverseArrayPar[GB ~func() ET.Either[E, B], GBS ~func() ET.Either[E, BBS], AAS ~[]A, BBS ~[]B, E, A, B any](tas AAS, f func(A) GB) GBS {
+	return RA.MonadTraverse[AAS](
+		Of[GBS, E, BBS],
+		Map[GBS, func() ET.Either[E, func(B) BBS], E, BBS, func(B) BBS],
+		ApPar[GBS, func() ET.Either[E, func(B) BBS], GB],
+
+		tas,
+		f,
+	)
+}
+
+// TraverseArrayPar transforms an array
+func TraverseArrayPar[GB ~func() ET.Either[E, B], GBS ~func() ET.Either[E, BBS], AAS ~[]A, BBS ~[]B, E, A, B any](f func(A) GB) func(AAS) GBS {
+	return RA.Traverse[AAS](
+		Of[GBS, E, BBS],
+		Map[GBS, func() ET.Either[E, func(B) BBS], E, BBS, func(B) BBS],
+		ApPar[GBS, func() ET.Either[E, func(B) BBS], GB],
+
+		f,
+	)
+}
+
+// MonadTraverseArrayWithIndexPar transforms an array
+func MonadTraverseArrayWithIndexPar[GB ~func() ET.Either[E, B], GBS ~func() ET.Either[E, BBS], AAS ~[]A, BBS ~[]B, E, A, B any](tas AAS, f func(int, A) GB) GBS {
+	return RA.MonadTraverseWithIndex[AAS](
+		Of[GBS, E, BBS],
+		Map[GBS, func() ET.Either[E, func(B) BBS], E, BBS, func(B) BBS],
+		ApPar[GBS, func() ET.Either[E, func(B) BBS], GB],
+
+		tas,
+		f,
+	)
+}
+
+// TraverseArrayWithIndexPar transforms an array
+func TraverseArrayWithIndexPar[GB ~func() ET.Either[E, B], GBS ~func() ET.Either[E, BBS], AAS ~[]A, BBS ~[]B, E, A, B any](f func(int, A) GB) func(AAS) GBS {
+	return RA.TraverseWithIndex[AAS](
+		Of[GBS, E, BBS],
+		Map[GBS, func() ET.Either[E, func(B) BBS], E, BBS, func(B) BBS],
+		ApPar[GBS, func() ET.Either[E, func(B) BBS], GB],
+
+		f,
+	)
+}
+
+// SequenceArrayPar converts a homogeneous sequence of either into an either of sequence
+func SequenceArrayPar[GA ~func() ET.Either[E, A], GAS ~func() ET.Either[E, AAS], AAS ~[]A, GAAS ~[]GA, E, A any](tas GAAS) GAS {
+	return MonadTraverseArrayPar[GA, GAS](tas, F.Identity[GA])
+}
+
+// MonadTraverseRecordPar transforms an array
+func MonadTraverseRecordPar[GB ~func() ET.Either[E, B], GBS ~func() ET.Either[E, BBS], AAS ~map[K]A, BBS ~map[K]B, K comparable, E, A, B any](tas AAS, f func(A) GB) GBS {
+	return RR.MonadTraverse[AAS](
+		Of[GBS, E, BBS],
+		Map[GBS, func() ET.Either[E, func(B) BBS], E, BBS, func(B) BBS],
+		ApPar[GBS, func() ET.Either[E, func(B) BBS], GB],
+
+		tas,
+		f,
+	)
+}
+
+// TraverseRecordPar transforms an array
+func TraverseRecordPar[GB ~func() ET.Either[E, B], GBS ~func() ET.Either[E, BBS], AAS ~map[K]A, BBS ~map[K]B, K comparable, E, A, B any](f func(A) GB) func(AAS) GBS {
+	return RR.Traverse[AAS](
+		Of[GBS, E, BBS],
+		Map[GBS, func() ET.Either[E, func(B) BBS], E, BBS, func(B) BBS],
+		ApPar[GBS, func() ET.Either[E, func(B) BBS], GB],
+
+		f,
+	)
+}
+
+// TraverseRecordWithIndexPar transforms an array
+func TraverseRecordWithIndexPar[GB ~func() ET.Either[E, B], GBS ~func() ET.Either[E, BBS], AAS ~map[K]A, BBS ~map[K]B, K comparable, E, A, B any](f func(K, A) GB) func(AAS) GBS {
+	return RR.TraverseWithIndex[AAS](
+		Of[GBS, E, BBS],
+		Map[GBS, func() ET.Either[E, func(B) BBS], E, BBS, func(B) BBS],
+		ApPar[GBS, func() ET.Either[E, func(B) BBS], GB],
+
+		f,
+	)
+}
+
+// SequenceRecordPar converts a homogeneous sequence of either into an either of sequence
+func SequenceRecordPar[GA ~func() ET.Either[E, A], GAS ~func() ET.Either[E, AAS], AAS ~map[K]A, GAAS ~map[K]GA, K comparable, E, A any](tas GAAS) GAS {
+	return MonadTraverseRecordPar[GA, GAS](tas, F.Identity[GA])
+}

ioeither/http/builder/builder.go

@@ -0,0 +1,356 @@
+// 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 builder
+
+import (
+	"bytes"
+	"net/http"
+	"net/url"
+	"strconv"
+
+	E "github.com/IBM/fp-go/either"
+	ENDO "github.com/IBM/fp-go/endomorphism"
+	F "github.com/IBM/fp-go/function"
+	C "github.com/IBM/fp-go/http/content"
+	FM "github.com/IBM/fp-go/http/form"
+	H "github.com/IBM/fp-go/http/headers"
+	IOG "github.com/IBM/fp-go/io/generic"
+	IOE "github.com/IBM/fp-go/ioeither"
+	IOEH "github.com/IBM/fp-go/ioeither/http"
+	J "github.com/IBM/fp-go/json"
+	LZ "github.com/IBM/fp-go/lazy"
+	L "github.com/IBM/fp-go/optics/lens"
+	O "github.com/IBM/fp-go/option"
+	S "github.com/IBM/fp-go/string"
+	T "github.com/IBM/fp-go/tuple"
+)
+
+type (
+	Builder struct {
+		method  O.Option[string]
+		url     string
+		headers http.Header
+		body    O.Option[IOE.IOEither[error, []byte]]
+		query   url.Values
+	}
+
+	// Endomorphism returns an [ENDO.Endomorphism] that transforms a builder
+	Endomorphism = ENDO.Endomorphism[*Builder]
+)
+
+var (
+	// Default is the default builder
+	Default = &Builder{method: O.Some(defaultMethod()), headers: make(http.Header), body: noBody}
+
+	defaultMethod = F.Constant(http.MethodGet)
+
+	// Monoid is the [M.Monoid] for the [Endomorphism]
+	Monoid = ENDO.Monoid[*Builder]()
+
+	// Url is a [L.Lens] for the URL
+	Url = L.MakeLensRef((*Builder).GetUrl, (*Builder).SetUrl)
+	// Method is a [L.Lens] for the HTTP method
+	Method = L.MakeLensRef((*Builder).GetMethod, (*Builder).SetMethod)
+	// Body is a [L.Lens] for the request body
+	Body = L.MakeLensRef((*Builder).GetBody, (*Builder).SetBody)
+	// Headers is a [L.Lens] for the complete set of request headers
+	Headers = L.MakeLensRef((*Builder).GetHeaders, (*Builder).SetHeaders)
+	// Query is a [L.Lens] for the set of query parameters
+	Query = L.MakeLensRef((*Builder).GetQuery, (*Builder).SetQuery)
+
+	rawQuery = L.MakeLensRef(getRawQuery, setRawQuery)
+
+	getHeader = F.Bind2of2((*Builder).GetHeader)
+	delHeader = F.Bind2of2((*Builder).DelHeader)
+	setHeader = F.Bind2of3((*Builder).SetHeader)
+
+	noHeader   = O.None[string]()
+	noBody     = O.None[IOE.IOEither[error, []byte]]()
+	noQueryArg = O.None[string]()
+
+	parseUrl   = E.Eitherize1(url.Parse)
+	parseQuery = E.Eitherize1(url.ParseQuery)
+
+	// WithQuery creates a [Endomorphism] for a complete set of query parameters
+	WithQuery = Query.Set
+	// WithMethod creates a [Endomorphism] for a certain method
+	WithMethod = Method.Set
+	// WithUrl creates a [Endomorphism] for a certain method
+	WithUrl = Url.Set
+	// WithHeaders creates a [Endomorphism] for a set of headers
+	WithHeaders = Headers.Set
+	// WithBody creates a [Endomorphism] for a request body
+	WithBody = F.Flow2(
+		O.Of[IOE.IOEither[error, []byte]],
+		Body.Set,
+	)
+	// WithBytes creates a [Endomorphism] for a request body using bytes
+	WithBytes = F.Flow2(
+		IOE.Of[error, []byte],
+		WithBody,
+	)
+	// WithContentType adds the [H.ContentType] header
+	WithContentType = WithHeader(H.ContentType)
+	// WithAuthorization adds the [H.Authorization] header
+	WithAuthorization = WithHeader(H.Authorization)
+
+	// WithGet adds the [http.MethodGet] method
+	WithGet = WithMethod(http.MethodGet)
+	// WithPost adds the [http.MethodPost] method
+	WithPost = WithMethod(http.MethodPost)
+	// WithPut adds the [http.MethodPut] method
+	WithPut = WithMethod(http.MethodPut)
+	// WithDelete adds the [http.MethodDelete] method
+	WithDelete = WithMethod(http.MethodDelete)
+
+	// WithBearer creates a [Endomorphism] to add a Bearer [H.Authorization] header
+	WithBearer = F.Flow2(
+		S.Format[string]("Bearer %s"),
+		WithAuthorization,
+	)
+
+	// Requester creates a requester from a builder
+	Requester = (*Builder).Requester
+
+	// WithoutBody creates a [Endomorphism] to remove the body
+	WithoutBody = F.Pipe1(
+		noBody,
+		Body.Set,
+	)
+)
+
+func setRawQuery(u *url.URL, raw string) *url.URL {
+	u.RawQuery = raw
+	return u
+}
+
+func getRawQuery(u *url.URL) string {
+	return u.RawQuery
+}
+
+func (builder *Builder) clone() *Builder {
+	cpy := *builder
+	cpy.headers = cpy.headers.Clone()
+	return &cpy
+}
+
+func (builder *Builder) GetUrl() string {
+	return builder.url
+}
+
+func (builder *Builder) GetMethod() string {
+	return F.Pipe1(
+		builder.method,
+		O.GetOrElse(defaultMethod),
+	)
+}
+
+func (builder *Builder) GetHeaders() http.Header {
+	return builder.headers
+}
+
+func (builder *Builder) GetQuery() url.Values {
+	return builder.query
+}
+
+func (builder *Builder) SetQuery(query url.Values) *Builder {
+	builder.query = query
+	return builder
+}
+
+func (builder *Builder) GetBody() O.Option[IOE.IOEither[error, []byte]] {
+	return builder.body
+}
+
+func (builder *Builder) SetMethod(method string) *Builder {
+	builder.method = O.Some(method)
+	return builder
+}
+
+func (builder *Builder) SetUrl(url string) *Builder {
+	builder.url = url
+	return builder
+}
+
+func (builder *Builder) SetHeaders(headers http.Header) *Builder {
+	builder.headers = headers
+	return builder
+}
+
+func (builder *Builder) SetBody(body O.Option[IOE.IOEither[error, []byte]]) *Builder {
+	builder.body = body
+	return builder
+}
+
+func (builder *Builder) SetHeader(name, value string) *Builder {
+	builder.headers.Set(name, value)
+	return builder
+}
+
+func (builder *Builder) DelHeader(name string) *Builder {
+	builder.headers.Del(name)
+	return builder
+}
+
+func (builder *Builder) GetHeader(name string) O.Option[string] {
+	return F.Pipe2(
+		name,
+		builder.headers.Get,
+		O.FromPredicate(S.IsNonEmpty),
+	)
+}
+
+func (builder *Builder) GetHeaderValues(name string) []string {
+	return builder.headers.Values(name)
+}
+
+func (builder *Builder) Requester() IOEH.Requester {
+
+	withBody := F.Curry3(func(data []byte, url string, method string) IOE.IOEither[error, *http.Request] {
+		return IOE.TryCatchError(func() (*http.Request, error) {
+			req, err := http.NewRequest(method, url, bytes.NewReader(data))
+			if err == nil {
+				req.Header.Set(H.ContentLength, strconv.Itoa(len(data)))
+				H.Monoid.Concat(req.Header, builder.headers)
+			}
+			return req, err
+		})
+	})
+
+	withoutBody := F.Curry2(func(url string, method string) IOE.IOEither[error, *http.Request] {
+		return IOE.TryCatchError(func() (*http.Request, error) {
+			req, err := http.NewRequest(method, url, nil)
+			if err == nil {
+				H.Monoid.Concat(req.Header, builder.headers)
+			}
+			return req, err
+		})
+	})
+
+	// construct the final URL
+	targetUrl := F.Pipe3(
+		builder,
+		Url.Get,
+		parseUrl,
+		E.Chain(F.Flow4(
+			T.Replicate2[*url.URL],
+			T.Map2(
+				F.Flow2(
+					F.Curry2(setRawQuery),
+					E.Of[error, func(string) *url.URL],
+				),
+				F.Flow3(
+					rawQuery.Get,
+					parseQuery,
+					E.Map[error](F.Flow2(
+						F.Curry2(FM.ValuesMonoid.Concat)(builder.GetQuery()),
+						(url.Values).Encode,
+					)),
+				),
+			),
+			T.Tupled2(E.MonadAp[*url.URL, error, string]),
+			E.Map[error]((*url.URL).String),
+		)),
+	)
+
+	return F.Pipe5(
+		builder,
+		Body.Get,
+		O.Fold(LZ.Of(IOE.Of[error](withoutBody)), IOE.Map[error](withBody)),
+		IOG.Map[IOE.IOEither[error, func(string) func(string) IOE.IOEither[error, *http.Request]], IOE.IOEither[error, func(string) IOE.IOEither[error, *http.Request]]](E.Ap[func(string) IOE.IOEither[error, *http.Request]](targetUrl)),
+		IOE.Flap[error, IOE.IOEither[error, *http.Request]](builder.GetMethod()),
+		IOE.Flatten[error, *http.Request],
+	)
+}
+
+// Header returns a [L.Lens] for a single header
+func Header(name string) L.Lens[*Builder, O.Option[string]] {
+	get := getHeader(name)
+	set := F.Bind1of2(setHeader(name))
+	del := F.Flow2(
+		LZ.Of[*Builder],
+		LZ.Map(delHeader(name)),
+	)
+
+	return L.MakeLens(get, func(b *Builder, value O.Option[string]) *Builder {
+		cpy := b.clone()
+		return F.Pipe1(
+			value,
+			O.Fold(del(cpy), set(cpy)),
+		)
+	})
+}
+
+// WithHeader creates a [Endomorphism] for a certain header
+func WithHeader(name string) func(value string) Endomorphism {
+	return F.Flow2(
+		O.Of[string],
+		Header(name).Set,
+	)
+}
+
+// WithoutHeader creates a [Endomorphism] to remove a certain header
+func WithoutHeader(name string) Endomorphism {
+	return Header(name).Set(noHeader)
+}
+
+// WithFormData creates a [Endomorphism] to send form data payload
+func WithFormData(value url.Values) Endomorphism {
+	return F.Flow2(
+		F.Pipe4(
+			value,
+			url.Values.Encode,
+			S.ToBytes,
+			IOE.Of[error, []byte],
+			WithBody,
+		),
+		WithContentType(C.FormEncoded),
+	)
+}
+
+// WithJson creates a [Endomorphism] to send JSON payload
+func WithJson[T any](data T) Endomorphism {
+	return F.Flow2(
+		F.Pipe3(
+			data,
+			J.Marshal[T],
+			IOE.FromEither[error, []byte],
+			WithBody,
+		),
+		WithContentType(C.Json),
+	)
+}
+
+// QueryArg is a [L.Lens] for the first value of a query argument
+func QueryArg(name string) L.Lens[*Builder, O.Option[string]] {
+	return F.Pipe1(
+		Query,
+		L.Compose[*Builder](FM.AtValue(name)),
+	)
+}
+
+// WithQueryArg creates a [Endomorphism] for a certain query argument
+func WithQueryArg(name string) func(value string) Endomorphism {
+	return F.Flow2(
+		O.Of[string],
+		QueryArg(name).Set,
+	)
+}
+
+// WithoutQueryArg creates a [Endomorphism] that removes a query argument
+func WithoutQueryArg(name string) Endomorphism {
+	return QueryArg(name).Set(noQueryArg)
+}

ioeither/http/builder/builder_test.go

@@ -0,0 +1,86 @@
+// 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 builder
+
+import (
+	"net/http"
+	"net/url"
+	"testing"
+
+	E "github.com/IBM/fp-go/either"
+	F "github.com/IBM/fp-go/function"
+	C "github.com/IBM/fp-go/http/content"
+	H "github.com/IBM/fp-go/http/headers"
+	IO "github.com/IBM/fp-go/io"
+	IOE "github.com/IBM/fp-go/ioeither"
+	O "github.com/IBM/fp-go/option"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestBuilder(t *testing.T) {
+
+	name := H.ContentType
+	withContentType := WithHeader(name)
+	withoutContentType := WithoutHeader(name)
+
+	b1 := F.Pipe1(
+		Default,
+		withContentType(C.Json),
+	)
+
+	b2 := F.Pipe1(
+		b1,
+		withContentType(C.TextPlain),
+	)
+
+	b3 := F.Pipe1(
+		b2,
+		withoutContentType,
+	)
+
+	assert.Equal(t, O.None[string](), Default.GetHeader(name))
+	assert.Equal(t, O.Of(C.Json), b1.GetHeader(name))
+	assert.Equal(t, O.Of(C.TextPlain), b2.GetHeader(name))
+	assert.Equal(t, O.None[string](), b3.GetHeader(name))
+}
+
+func TestBuilderWithQuery(t *testing.T) {
+	// add some query
+	withLimit := WithQueryArg("limit")("10")
+	withUrl := WithUrl("http://www.example.org?a=b")
+
+	b := F.Pipe2(
+		Default,
+		withLimit,
+		withUrl,
+	)
+
+	req := F.Pipe2(
+		b.Requester(),
+		IOE.Map[error](func(r *http.Request) *url.URL {
+			return r.URL
+		}),
+		IOE.ChainFirstIOK[error](func(u *url.URL) IO.IO[any] {
+			return IO.FromImpure(func() {
+				q := u.Query()
+				assert.Equal(t, "10", q.Get("limit"))
+				assert.Equal(t, "b", q.Get("a"))
+			})
+		}),
+	)
+
+	assert.True(t, E.IsRight(req()))
+}

ioeither/http/di/di.go

@@ -0,0 +1,32 @@
+// 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 di
+
+import (
+	"net/http"
+
+	DI "github.com/IBM/fp-go/di"
+	IOE "github.com/IBM/fp-go/ioeither"
+	IOEH "github.com/IBM/fp-go/ioeither/http"
+)
+
+var (
+	// InjHttpClient is the [DI.InjectionToken] for the [http.DefaultClient]
+	InjHttpClient = DI.MakeTokenWithDefault0("HTTP_CLIENT", IOE.Of[error](http.DefaultClient))
+
+	// InjClient is the [DI.InjectionToken] for the default [IOEH.Client]
+	InjClient = DI.MakeTokenWithDefault1("CLIENT", InjHttpClient.IOEither(), IOE.Map[error](IOEH.MakeClient))
+)

ioeither/http/request.go

@@ -16,58 +16,118 @@
 package http
 
 import (
+	"bytes"
 	"io"
 	"net/http"
 
 	B "github.com/IBM/fp-go/bytes"
-	ER "github.com/IBM/fp-go/errors"
+	FL "github.com/IBM/fp-go/file"
 	F "github.com/IBM/fp-go/function"
+	H "github.com/IBM/fp-go/http"
 	IOE "github.com/IBM/fp-go/ioeither"
 	IOEF "github.com/IBM/fp-go/ioeither/file"
 	J "github.com/IBM/fp-go/json"
+	T "github.com/IBM/fp-go/tuple"
 )
 
-type Client interface {
-	Do(req *http.Request) IOE.IOEither[error, *http.Response]
+type (
+	// Requester is a reader that constructs a request
+	Requester = IOE.IOEither[error, *http.Request]
+
+	Client interface {
+		Do(Requester) IOE.IOEither[error, *http.Response]
+	}
+
+	client struct {
+		delegate *http.Client
+		doIOE    func(*http.Request) IOE.IOEither[error, *http.Response]
+	}
+)
+
+var (
+	// MakeRequest is an eitherized version of [http.NewRequest]
+	MakeRequest = IOE.Eitherize3(http.NewRequest)
+	makeRequest = F.Bind13of3(MakeRequest)
+
+	// specialize
+	MakeGetRequest = makeRequest("GET", nil)
+)
+
+// MakeBodyRequest creates a request that carries a body
+func MakeBodyRequest(method string, body IOE.IOEither[error, []byte]) func(url string) IOE.IOEither[error, *http.Request] {
+	onBody := F.Pipe1(
+		body,
+		IOE.Map[error](F.Flow2(
+			bytes.NewReader,
+			FL.ToReader[*bytes.Reader],
+		)),
+	)
+	onRelease := IOE.Of[error, io.Reader]
+	withMethod := F.Bind1of3(MakeRequest)(method)
+
+	return F.Flow2(
+		F.Bind1of2(withMethod),
+		IOE.WithResource[*http.Request](onBody, onRelease),
+	)
 }
 
-type client struct {
-	delegate *http.Client
-}
-
-func (client client) Do(req *http.Request) IOE.IOEither[error, *http.Response] {
-	return IOE.TryCatch(func() (*http.Response, error) {
-		return client.delegate.Do(req)
-	}, ER.IdentityError)
+func (client client) Do(req Requester) IOE.IOEither[error, *http.Response] {
+	return F.Pipe1(
+		req,
+		IOE.Chain(client.doIOE),
+	)
 }
 
 func MakeClient(httpClient *http.Client) Client {
-	return client{delegate: httpClient}
+	return client{delegate: httpClient, doIOE: IOE.Eitherize1(httpClient.Do)}
 }
 
-func ReadAll(client Client) func(*http.Request) IOE.IOEither[error, []byte] {
-	return func(req *http.Request) IOE.IOEither[error, []byte] {
-		return IOEF.ReadAll(F.Pipe2(
-			req,
-			client.Do,
-			IOE.Map[error](func(resp *http.Response) io.ReadCloser {
-				return resp.Body
-			}),
-		),
-		)
-	}
+// ReadFullResponse sends a request,  reads the response as a byte array and represents the result as a tuple
+func ReadFullResponse(client Client) func(Requester) IOE.IOEither[error, H.FullResponse] {
+	return F.Flow3(
+		client.Do,
+		IOE.ChainEitherK(H.ValidateResponse),
+		IOE.Chain(func(resp *http.Response) IOE.IOEither[error, H.FullResponse] {
+			return F.Pipe1(
+				F.Pipe3(
+					resp,
+					H.GetBody,
+					IOE.Of[error, io.ReadCloser],
+					IOEF.ReadAll[io.ReadCloser],
+				),
+				IOE.Map[error](F.Bind1st(T.MakeTuple2[*http.Response, []byte], resp)),
+			)
+		}),
+	)
 }
 
-func ReadText(client Client) func(*http.Request) IOE.IOEither[error, string] {
+// ReadAll sends a request and reads the response as bytes
+func ReadAll(client Client) func(Requester) IOE.IOEither[error, []byte] {
+	return F.Flow2(
+		ReadFullResponse(client),
+		IOE.Map[error](H.Body),
+	)
+}
+
+// ReadText sends a request, reads the response and represents the response as a text string
+func ReadText(client Client) func(Requester) IOE.IOEither[error, string] {
 	return F.Flow2(
 		ReadAll(client),
 		IOE.Map[error](B.ToString),
 	)
 }
 
-func ReadJson[A any](client Client) func(*http.Request) IOE.IOEither[error, A] {
-	return F.Flow2(
-		ReadAll(client),
-		IOE.ChainEitherK(J.Unmarshal[A]),
+// ReadJson sends a request, reads the response and parses the response as JSON
+func ReadJson[A any](client Client) func(Requester) IOE.IOEither[error, A] {
+	return F.Flow3(
+		ReadFullResponse(client),
+		IOE.ChainFirstEitherK(F.Flow2(
+			H.Response,
+			H.ValidateJsonResponse,
+		)),
+		IOE.ChainEitherK(F.Flow2(
+			H.Body,
+			J.Unmarshal[A],
+		)),
 	)
 }

ioeither/http/retry_test.go

@@ -23,7 +23,6 @@ import (
 
 	AR "github.com/IBM/fp-go/array"
 	E "github.com/IBM/fp-go/either"
-	HE "github.com/IBM/fp-go/either/http"
 	"github.com/IBM/fp-go/errors"
 	F "github.com/IBM/fp-go/function"
 	IOE "github.com/IBM/fp-go/ioeither"
@@ -53,17 +52,16 @@ func TestRetryHttp(t *testing.T) {
 	client := MakeClient(&http.Client{})
 
 	action := func(status R.RetryStatus) IOE.IOEither[error, *PostItem] {
-		return F.Pipe2(
-			HE.GetRequest(urls[status.IterNumber]),
-			IOE.FromEither[error, *http.Request],
-			IOE.Chain(ReadJson[*PostItem](client)),
+		return F.Pipe1(
+			MakeGetRequest(urls[status.IterNumber]),
+			ReadJson[*PostItem](client),
 		)
 	}
 
 	check := E.Fold(
 		F.Flow2(
 			errors.As[*net.DNSError](),
-			O.Fold(F.Constant(false), F.Constant1[*net.DNSError](true)),
+			O.IsSome[*net.DNSError],
 		),
 		F.Constant1[*PostItem](false),
 	)

ioeither/ioeither.go

@@ -19,6 +19,7 @@ import (
 	ET "github.com/IBM/fp-go/either"
 	I "github.com/IBM/fp-go/io"
 	G "github.com/IBM/fp-go/ioeither/generic"
+	IOO "github.com/IBM/fp-go/iooption"
 	L "github.com/IBM/fp-go/lazy"
 	O "github.com/IBM/fp-go/option"
 )
@@ -63,6 +64,10 @@ func FromOption[A, E any](onNone func() E) func(o O.Option[A]) IOEither[E, A] {
 	return G.FromOption[IOEither[E, A]](onNone)
 }
 
+func FromIOOption[A, E any](onNone func() E) func(o IOO.IOOption[A]) IOEither[E, A] {
+	return G.FromIOOption[IOEither[E, A], IOO.IOOption[A]](onNone)
+}
+
 func ChainOptionK[A, B, E any](onNone func() E) func(func(A) O.Option[B]) func(IOEither[E, A]) IOEither[E, B] {
 	return G.ChainOptionK[IOEither[E, A], IOEither[E, B]](onNone)
 }
@@ -192,12 +197,12 @@ func GetOrElse[E, A any](onLeft func(E) I.IO[A]) func(IOEither[E, A]) I.IO[A] {
 }
 
 // MonadChainTo composes to the second monad ignoring the return value of the first
-func MonadChainTo[E, A, B any](fa IOEither[E, A], fb IOEither[E, B]) IOEither[E, B] {
+func MonadChainTo[A, E, B any](fa IOEither[E, A], fb IOEither[E, B]) IOEither[E, B] {
 	return G.MonadChainTo(fa, fb)
 }
 
 // ChainTo composes to the second [IOEither] monad ignoring the return value of the first
-func ChainTo[E, A, B any](fb IOEither[E, B]) func(IOEither[E, A]) IOEither[E, B] {
+func ChainTo[A, E, B any](fb IOEither[E, B]) func(IOEither[E, A]) IOEither[E, B] {
 	return G.ChainTo[IOEither[E, A]](fb)
 }
 
@@ -211,6 +216,14 @@ func ChainFirst[E, A, B any](f func(A) IOEither[E, B]) func(IOEither[E, A]) IOEi
 	return G.ChainFirst[IOEither[E, A]](f)
 }
 
+func MonadChainFirstEitherK[A, E, B any](ma IOEither[E, A], f func(A) ET.Either[E, B]) IOEither[E, A] {
+	return G.MonadChainFirstEitherK[IOEither[E, A]](ma, f)
+}
+
+func ChainFirstEitherK[A, E, B any](f func(A) ET.Either[E, B]) func(ma IOEither[E, A]) IOEither[E, A] {
+	return G.ChainFirstEitherK[IOEither[E, A]](f)
+}
+
 // MonadChainFirstIOK runs [IO] the monad returned by the function but returns the result of the original monad
 func MonadChainFirstIOK[E, A, B any](ma IOEither[E, A], f func(A) I.IO[B]) IOEither[E, A] {
 	return G.MonadChainFirstIOK(ma, f)
@@ -258,3 +271,8 @@ func MonadFlap[E, B, A any](fab IOEither[E, func(A) B], a A) IOEither[E, B] {
 func Flap[E, B, A any](a A) func(IOEither[E, func(A) B]) IOEither[E, B] {
 	return G.Flap[IOEither[E, func(A) B], IOEither[E, B]](a)
 }
+
+// ToIOOption converts an [IOEither] to an [IOO.IOOption]
+func ToIOOption[E, A any](ioe IOEither[E, A]) IOO.IOOption[A] {
+	return G.ToIOOption[IOO.IOOption[A]](ioe)
+}

ioeither/traverse.go

@@ -48,3 +48,63 @@ func TraverseRecordWithIndex[K comparable, E, A, B any](f func(K, A) IOEither[E,
 func SequenceRecord[K comparable, E, A any](ma map[K]IOEither[E, A]) IOEither[E, map[K]A] {
 	return G.SequenceRecord[IOEither[E, A], IOEither[E, map[K]A]](ma)
 }
+
+// TraverseArraySeq transforms an array
+func TraverseArraySeq[E, A, B any](f func(A) IOEither[E, B]) func([]A) IOEither[E, []B] {
+	return G.TraverseArraySeq[IOEither[E, B], IOEither[E, []B], []A](f)
+}
+
+// TraverseArrayWithIndexSeq transforms an array
+func TraverseArrayWithIndexSeq[E, A, B any](f func(int, A) IOEither[E, B]) func([]A) IOEither[E, []B] {
+	return G.TraverseArrayWithIndexSeq[IOEither[E, B], IOEither[E, []B], []A](f)
+}
+
+// SequenceArraySeq converts a homogeneous sequence of either into an either of sequence
+func SequenceArraySeq[E, A any](ma []IOEither[E, A]) IOEither[E, []A] {
+	return G.SequenceArraySeq[IOEither[E, A], IOEither[E, []A]](ma)
+}
+
+// TraverseRecordSeq transforms a record
+func TraverseRecordSeq[K comparable, E, A, B any](f func(A) IOEither[E, B]) func(map[K]A) IOEither[E, map[K]B] {
+	return G.TraverseRecordSeq[IOEither[E, B], IOEither[E, map[K]B], map[K]A](f)
+}
+
+// TraverseRecordWithIndexSeq transforms a record
+func TraverseRecordWithIndexSeq[K comparable, E, A, B any](f func(K, A) IOEither[E, B]) func(map[K]A) IOEither[E, map[K]B] {
+	return G.TraverseRecordWithIndexSeq[IOEither[E, B], IOEither[E, map[K]B], map[K]A](f)
+}
+
+// SequenceRecordSeq converts a homogeneous sequence of either into an either of sequence
+func SequenceRecordSeq[K comparable, E, A any](ma map[K]IOEither[E, A]) IOEither[E, map[K]A] {
+	return G.SequenceRecordSeq[IOEither[E, A], IOEither[E, map[K]A]](ma)
+}
+
+// TraverseArrayPar transforms an array
+func TraverseArrayPar[E, A, B any](f func(A) IOEither[E, B]) func([]A) IOEither[E, []B] {
+	return G.TraverseArrayPar[IOEither[E, B], IOEither[E, []B], []A](f)
+}
+
+// TraverseArrayWithIndexPar transforms an array
+func TraverseArrayWithIndexPar[E, A, B any](f func(int, A) IOEither[E, B]) func([]A) IOEither[E, []B] {
+	return G.TraverseArrayWithIndexPar[IOEither[E, B], IOEither[E, []B], []A](f)
+}
+
+// SequenceArrayPar converts a homogeneous Paruence of either into an either of Paruence
+func SequenceArrayPar[E, A any](ma []IOEither[E, A]) IOEither[E, []A] {
+	return G.SequenceArrayPar[IOEither[E, A], IOEither[E, []A]](ma)
+}
+
+// TraverseRecordPar transforms a record
+func TraverseRecordPar[K comparable, E, A, B any](f func(A) IOEither[E, B]) func(map[K]A) IOEither[E, map[K]B] {
+	return G.TraverseRecordPar[IOEither[E, B], IOEither[E, map[K]B], map[K]A](f)
+}
+
+// TraverseRecordWithIndexPar transforms a record
+func TraverseRecordWithIndexPar[K comparable, E, A, B any](f func(K, A) IOEither[E, B]) func(map[K]A) IOEither[E, map[K]B] {
+	return G.TraverseRecordWithIndexPar[IOEither[E, B], IOEither[E, map[K]B], map[K]A](f)
+}
+
+// SequenceRecordPar converts a homogeneous Paruence of either into an either of Paruence
+func SequenceRecordPar[K comparable, E, A any](ma map[K]IOEither[E, A]) IOEither[E, map[K]A] {
+	return G.SequenceRecordPar[IOEither[E, A], IOEither[E, map[K]A]](ma)
+}

iooption/generic/iooption.go

@@ -20,6 +20,7 @@ import (
 
 	ET "github.com/IBM/fp-go/either"
 	F "github.com/IBM/fp-go/function"
+	C "github.com/IBM/fp-go/internal/chain"
 	FI "github.com/IBM/fp-go/internal/fromio"
 	"github.com/IBM/fp-go/internal/optiont"
 	IO "github.com/IBM/fp-go/io/generic"
@@ -64,13 +65,6 @@ func FromEither[GA ~func() O.Option[A], E, A any](e ET.Either[E, A]) GA {
 	)
 }
 
-func FromIOEither[GA ~func() O.Option[A], GEA ~func() ET.Either[E, A], E, A any](ioe GEA) GA {
-	return F.Pipe1(
-		ioe,
-		IO.Map[GEA, GA](ET.ToOption[E, A]),
-	)
-}
-
 func MonadMap[GA ~func() O.Option[A], GB ~func() O.Option[B], A, B any](fa GA, f func(A) B) GB {
 	return optiont.MonadMap(IO.MonadMap[GA, GB, O.Option[A], O.Option[B]], fa, f)
 }
@@ -83,8 +77,48 @@ func MonadChain[GA ~func() O.Option[A], GB ~func() O.Option[B], A, B any](fa GA,
 	return optiont.MonadChain(IO.MonadChain[GA, GB, O.Option[A], O.Option[B]], IO.MonadOf[GB, O.Option[B]], fa, f)
 }
 
+// MonadChainFirst runs the monad returned by the function but returns the result of the original monad
+func MonadChainFirst[GA ~func() O.Option[A], GB ~func() O.Option[B], A, B any](ma GA, f func(A) GB) GA {
+	return C.MonadChainFirst(
+		MonadChain[GA, GA, A, A],
+		MonadMap[GB, GA, B, A],
+		ma,
+		f,
+	)
+}
+
+// ChainFirst runs the monad returned by the function but returns the result of the original monad
+func ChainFirst[GA ~func() O.Option[A], GB ~func() O.Option[B], A, B any](f func(A) GB) func(GA) GA {
+	return C.ChainFirst(
+		MonadChain[GA, GA, A, A],
+		MonadMap[GB, GA, B, A],
+		f,
+	)
+}
+
+// MonadChainFirstIOK runs the monad returned by the function but returns the result of the original monad
+func MonadChainFirstIOK[GA ~func() O.Option[A], GIOB ~func() B, A, B any](first GA, f func(A) GIOB) GA {
+	return FI.MonadChainFirstIOK(
+		MonadChain[GA, GA, A, A],
+		MonadMap[func() O.Option[B], GA, B, A],
+		FromIO[func() O.Option[B], GIOB, B],
+		first,
+		f,
+	)
+}
+
+// ChainFirstIOK runs the monad returned by the function but returns the result of the original monad
+func ChainFirstIOK[GA ~func() O.Option[A], GIOB ~func() B, A, B any](f func(A) GIOB) func(GA) GA {
+	return FI.ChainFirstIOK(
+		MonadChain[GA, GA, A, A],
+		MonadMap[func() O.Option[B], GA, B, A],
+		FromIO[func() O.Option[B], GIOB, B],
+		f,
+	)
+}
+
 func Chain[GA ~func() O.Option[A], GB ~func() O.Option[B], A, B any](f func(A) GB) func(GA) GB {
-	return F.Bind2nd(MonadChain[GA, GB, A, B], f)
+	return optiont.Chain(IO.MonadChain[GA, GB, O.Option[A], O.Option[B]], IO.MonadOf[GB, O.Option[B]], f)
 }
 
 func MonadChainOptionK[GA ~func() O.Option[A], GB ~func() O.Option[B], A, B any](ma GA, f func(A) O.Option[B]) GB {
@@ -194,3 +228,17 @@ func Fold[GA ~func() O.Option[A], GB ~func() B, A, B any](onNone func() GB, onSo
 func Defer[GA ~func() O.Option[A], A any](gen func() GA) GA {
 	return IO.Defer[GA](gen)
 }
+
+func MonadAlt[LAZY ~func() GIOA, GIOA ~func() O.Option[A], A any](first GIOA, second LAZY) GIOA {
+	return optiont.MonadAlt(
+		IO.Of[GIOA],
+		IO.MonadChain[GIOA, GIOA],
+
+		first,
+		second,
+	)
+}
+
+func Alt[LAZY ~func() GIOA, GIOA ~func() O.Option[A], A any](second LAZY) func(GIOA) GIOA {
+	return F.Bind2nd(MonadAlt[LAZY], second)
+}

iooption/generic/resource.go

@@ -0,0 +1,31 @@
+// 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"
+	O "github.com/IBM/fp-go/option"
+)
+
+// WithResource constructs a function that creates a resource, then operates on it and then releases the resource
+func WithResource[
+	GA ~func() O.Option[A],
+	GR ~func() O.Option[R],
+	GANY ~func() O.Option[ANY],
+	R, A, ANY any](onCreate GR, onRelease func(R) GANY) func(func(R) GA) GA {
+	// simply map to implementation of bracket
+	return F.Bind13of3(Bracket[GR, GA, GANY, R, A, ANY])(onCreate, F.Ignore2of2[O.Option[A]](onRelease))
+}

iooption/iooption.go

@@ -18,8 +18,9 @@ package iooption
 import (
 	ET "github.com/IBM/fp-go/either"
 	I "github.com/IBM/fp-go/io"
-	IOE "github.com/IBM/fp-go/ioeither"
+	IO "github.com/IBM/fp-go/io"
 	G "github.com/IBM/fp-go/iooption/generic"
+	L "github.com/IBM/fp-go/lazy"
 	O "github.com/IBM/fp-go/option"
 )
 
@@ -129,12 +130,37 @@ func Defer[A any](gen func() IOOption[A]) IOOption[A] {
 	return G.Defer[IOOption[A]](gen)
 }
 
-// FromIOEither converts an [IOEither] into an [IOOption]
-func FromIOEither[E, A any](ioe IOE.IOEither[E, A]) IOOption[A] {
-	return G.FromIOEither[IOOption[A]](ioe)
-}
-
 // FromEither converts an [Either] into an [IOOption]
 func FromEither[E, A any](e ET.Either[E, A]) IOOption[A] {
 	return G.FromEither[IOOption[A]](e)
 }
+
+// MonadAlt identifies an associative operation on a type constructor
+func MonadAlt[A any](first IOOption[A], second L.Lazy[IOOption[A]]) IOOption[A] {
+	return G.MonadAlt(first, second)
+}
+
+// Alt identifies an associative operation on a type constructor
+func Alt[A any](second L.Lazy[IOOption[A]]) func(IOOption[A]) IOOption[A] {
+	return G.Alt(second)
+}
+
+// MonadChainFirst runs the monad returned by the function but returns the result of the original monad
+func MonadChainFirst[A, B any](ma IOOption[A], f func(A) IOOption[B]) IOOption[A] {
+	return G.MonadChainFirst[IOOption[A], IOOption[B]](ma, f)
+}
+
+// ChainFirst runs the monad returned by the function but returns the result of the original monad
+func ChainFirst[A, B any](f func(A) IOOption[B]) func(IOOption[A]) IOOption[A] {
+	return G.ChainFirst[IOOption[A], IOOption[B]](f)
+}
+
+// MonadChainFirstIOK runs the monad returned by the function but returns the result of the original monad
+func MonadChainFirstIOK[A, B any](first IOOption[A], f func(A) IO.IO[B]) IOOption[A] {
+	return G.MonadChainFirstIOK[IOOption[A], IO.IO[B]](first, f)
+}
+
+// ChainFirstIOK runs the monad returned by the function but returns the result of the original monad
+func ChainFirstIOK[A, B any](f func(A) IO.IO[B]) func(IOOption[A]) IOOption[A] {
+	return G.ChainFirstIOK[IOOption[A], IO.IO[B]](f)
+}

iooption/resource.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 iooption
+
+import (
+	G "github.com/IBM/fp-go/iooption/generic"
+)
+
+// WithResource constructs a function that creates a resource, then operates on it and then releases the resource
+func WithResource[
+	R, A, ANY any](onCreate IOOption[R], onRelease func(R) IOOption[ANY]) func(func(R) IOOption[A]) IOOption[A] {
+	// just dispatch
+	return G.WithResource[IOOption[A], IOOption[R], IOOption[ANY]](onCreate, onRelease)
+}

iterator/stateless/generic/any.go

@@ -26,6 +26,6 @@ func Any[GU ~func() O.Option[T.Tuple2[GU, U]], FCT ~func(U) bool, U any](pred FC
 	return F.Flow3(
 		Filter[GU](pred),
 		First[GU],
-		O.Fold(F.ConstFalse, F.Constant1[U](true)),
+		O.IsSome[U],
 	)
 }

iterator/stateless/generic/io.go

@@ -0,0 +1,34 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package generic
+
+import (
+	F "github.com/IBM/fp-go/function"
+	L "github.com/IBM/fp-go/io/generic"
+	O "github.com/IBM/fp-go/option"
+	T "github.com/IBM/fp-go/tuple"
+)
+
+// FromLazy returns an iterator on top of a lazy function
+func FromLazy[GU ~func() O.Option[T.Tuple2[GU, U]], LZ ~func() U, U any](l LZ) GU {
+	return F.Pipe1(
+		l,
+		L.Map[LZ, GU](F.Flow2(
+			F.Bind1st(T.MakeTuple2[GU, U], Empty[GU]()),
+			O.Of[T.Tuple2[GU, U]],
+		)),
+	)
+}

iterator/stateless/io.go

@@ -0,0 +1,32 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package stateless
+
+import (
+	IO "github.com/IBM/fp-go/io"
+	G "github.com/IBM/fp-go/iterator/stateless/generic"
+	L "github.com/IBM/fp-go/lazy"
+)
+
+// FromLazy returns an [Iterator] on top of a lazy function
+func FromLazy[U any](l L.Lazy[U]) Iterator[U] {
+	return G.FromLazy[Iterator[U], L.Lazy[U]](l)
+}
+
+// FromIO returns an [Iterator] on top of an IO function
+func FromIO[U any](io IO.IO[U]) Iterator[U] {
+	return G.FromLazy[Iterator[U], IO.IO[U]](io)
+}

iterator/stateless/io_test.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 stateless
+
+import (
+	"math/rand"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIteratorFromLazy(t *testing.T) {
+	num := rand.Int
+
+	cit := FromLazy(num)
+
+	// create arrays twice
+	c1 := ToArray(cit)
+	c2 := ToArray(cit)
+
+	assert.Equal(t, 1, len(c1))
+	assert.Equal(t, 1, len(c2))
+
+	assert.NotEqual(t, c1, c2)
+}

iterator/stateless/uniq.go

@@ -19,13 +19,13 @@ import (
 	G "github.com/IBM/fp-go/iterator/stateless/generic"
 )
 
-// StrictUniq converts an [Iterator] or arbitrary items into an [Iterator] or unique items
+// StrictUniq converts an [Iterator] of arbitrary items into an [Iterator] or unique items
 // where uniqueness is determined by the built-in uniqueness constraint
 func StrictUniq[A comparable](as Iterator[A]) Iterator[A] {
 	return G.StrictUniq[Iterator[A]](as)
 }
 
-// Uniq converts an [Iterator] or arbitrary items into an [Iterator] or unique items
+// Uniq converts an [Iterator] of arbitrary items into an [Iterator] or unique items
 // where uniqueness is determined based on a key extractor function
 func Uniq[A any, K comparable](f func(A) K) func(as Iterator[A]) Iterator[A] {
 	return G.Uniq[Iterator[A], K](f)

lambda/y.go

@@ -15,16 +15,12 @@
 
 package lambda
 
-type (
-	// RecFct is the function called recursively
-	RecFct[T, R any] func(T) R
-
-	internalCombinator[T, R any] func(internalCombinator[T, R]) RecFct[T, R]
-)
-
 // Y is the Y-combinator based on https://dreamsongs.com/Files/WhyOfY.pdf
-func Y[TRFRM ~func(RecFct[T, R]) RecFct[T, R], T, R any](f TRFRM) RecFct[T, R] {
-	g := func(h internalCombinator[T, R]) RecFct[T, R] {
+func Y[Endo ~func(RecFct) RecFct, RecFct ~func(T) R, T, R any](f Endo) RecFct {
+
+	type internal[RecFct ~func(T) R, T, R any] func(internal[RecFct, T, R]) RecFct
+
+	g := func(h internal[RecFct, T, R]) RecFct {
 		return func(t T) R {
 			return f(h(h))(t)
 		}

lambda/y_test.go

@@ -16,12 +16,13 @@
 package lambda
 
 import (
-	"fmt"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
 func TestFactorial(t *testing.T) {
-	fct := Y(func(r RecFct[int, int]) RecFct[int, int] {
+	fct := Y(func(r func(int) int) func(int) int {
 		return func(n int) int {
 			if n <= 0 {
 				return 1
@@ -29,6 +30,5 @@ func TestFactorial(t *testing.T) {
 			return n * r(n-1)
 		}
 	})
-
-	fmt.Println(fct(10))
+	assert.Equal(t, 3628800, fct(10))
 }

lazy/traverse.go

@@ -41,13 +41,13 @@ func SequenceArray[A any](tas []Lazy[A]) Lazy[[]A] {
 }
 
 func MonadTraverseRecord[K comparable, A, B any](tas map[K]A, f func(A) Lazy[B]) Lazy[map[K]B] {
-	return G.MonadTraverseRecord[Lazy[B], Lazy[map[K]B]](tas, f)
+	return G.MonadTraverseRecord[Lazy[map[K]B]](tas, f)
 }
 
 // TraverseRecord applies a function returning an [IO] to all elements in a record and the
 // transforms this into an [IO] of that record
 func TraverseRecord[K comparable, A, B any](f func(A) Lazy[B]) func(map[K]A) Lazy[map[K]B] {
-	return G.TraverseRecord[Lazy[B], Lazy[map[K]B], map[K]A](f)
+	return G.TraverseRecord[Lazy[map[K]B], map[K]A, Lazy[B]](f)
 }
 
 // TraverseRecord applies a function returning an [IO] to all elements in a record and the

optics/iso/iso.go

@@ -17,6 +17,7 @@
 package iso
 
 import (
+	EM "github.com/IBM/fp-go/endomorphism"
 	F "github.com/IBM/fp-go/function"
 )
 
@@ -52,7 +53,7 @@ func Reverse[S, A any](sa Iso[S, A]) Iso[A, S] {
 	)
 }
 
-func modify[S, A any](f func(A) A, sa Iso[S, A], s S) S {
+func modify[FCT ~func(A) A, S, A any](f FCT, sa Iso[S, A], s S) S {
 	return F.Pipe3(
 		s,
 		sa.Get,
@@ -62,8 +63,8 @@ func modify[S, A any](f func(A) A, sa Iso[S, A], s S) S {
 }
 
 // Modify applies a transformation
-func Modify[S, A any](f func(A) A) func(Iso[S, A]) func(S) S {
-	return F.Curry3(modify[S, A])(f)
+func Modify[S any, FCT ~func(A) A, A any](f FCT) func(Iso[S, A]) EM.Endomorphism[S] {
+	return EM.Curry3(modify[FCT, S, A])(f)
 }
 
 // Wrap wraps the value

optics/iso/lens/lens.go

@@ -16,6 +16,7 @@
 package lens
 
 import (
+	EM "github.com/IBM/fp-go/endomorphism"
 	F "github.com/IBM/fp-go/function"
 	I "github.com/IBM/fp-go/optics/iso"
 	L "github.com/IBM/fp-go/optics/lens"
@@ -23,10 +24,10 @@ import (
 
 // IsoAsLens converts an `Iso` to a `Lens`
 func IsoAsLens[S, A any](sa I.Iso[S, A]) L.Lens[S, A] {
-	return L.MakeLensCurried(sa.Get, F.Flow2(sa.ReverseGet, F.Constant1[S, S]))
+	return L.MakeLensCurried(sa.Get, F.Flow2(sa.ReverseGet, F.Flow2(F.Constant1[S, S], EM.Of[func(S) S])))
 }
 
 // IsoAsLensRef converts an `Iso` to a `Lens`
 func IsoAsLensRef[S, A any](sa I.Iso[*S, A]) L.Lens[*S, A] {
-	return L.MakeLensRefCurried(sa.Get, F.Flow2(sa.ReverseGet, F.Constant1[*S, *S]))
+	return L.MakeLensRefCurried(sa.Get, F.Flow2(sa.ReverseGet, F.Flow2(F.Constant1[*S, *S], EM.Of[func(*S) *S])))
 }

optics/lens/array/generic/head.go

@@ -0,0 +1,39 @@
+// 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 (
+	AA "github.com/IBM/fp-go/array/generic"
+	L "github.com/IBM/fp-go/optics/lens"
+	O "github.com/IBM/fp-go/option"
+)
+
+// AtHead focusses on the head of an array. The setter works as follows
+// - if the new value is none, the result will be an empty array
+// - if the new value is some and the array is empty, it creates a new array with one element
+// - if the new value is some and the array is not empty, it replaces the head
+func AtHead[AS []A, A any]() L.Lens[AS, O.Option[A]] {
+	return L.MakeLens(AA.Head[AS, A], func(as AS, a O.Option[A]) AS {
+		return O.MonadFold(a, AA.Empty[AS], func(v A) AS {
+			if AA.IsEmpty(as) {
+				return AA.Of[AS, A](v)
+			}
+			cpy := AA.Copy(as)
+			cpy[0] = v
+			return cpy
+		})
+	})
+}

optics/lens/array/head.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 array
+
+import (
+	L "github.com/IBM/fp-go/optics/lens"
+	G "github.com/IBM/fp-go/optics/lens/array/generic"
+	O "github.com/IBM/fp-go/option"
+)
+
+// AtHead focusses on the head of an array. The setter works as follows
+// - if the new value is none, the result will be an empty array
+// - if the new value is some and the array is empty, it creates a new array with one element
+// - if the new value is some and the array is not empty, it replaces the head
+func AtHead[A any]() L.Lens[[]A, O.Option[A]] {
+	return G.AtHead[[]A]()
+}

optics/lens/array/head_test.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 array
+
+import (
+	"testing"
+
+	A "github.com/IBM/fp-go/array"
+	"github.com/IBM/fp-go/eq"
+	LT "github.com/IBM/fp-go/optics/lens/testing"
+	O "github.com/IBM/fp-go/option"
+	S "github.com/IBM/fp-go/string"
+	"github.com/stretchr/testify/assert"
+)
+
+var (
+	sEq = eq.FromEquals(S.Eq)
+)
+
+func TestLaws(t *testing.T) {
+	headLaws := LT.AssertLaws(t, O.Eq(sEq), A.Eq(sEq))(AtHead[string]())
+
+	assert.True(t, headLaws(A.Empty[string](), O.None[string]()))
+	assert.True(t, headLaws(A.Empty[string](), O.Of("a")))
+	assert.True(t, headLaws(A.From("a", "b"), O.None[string]()))
+	assert.True(t, headLaws(A.From("a", "b"), O.Of("c")))
+}

optics/lens/lens.go

@@ -17,8 +17,8 @@
 package lens
 
 import (
+	EM "github.com/IBM/fp-go/endomorphism"
 	F "github.com/IBM/fp-go/function"
-	I "github.com/IBM/fp-go/identity"
 	O "github.com/IBM/fp-go/option"
 )
 
@@ -26,13 +26,13 @@ type (
 	// Lens is a reference to a subpart of a data type
 	Lens[S, A any] struct {
 		Get func(s S) A
-		Set func(a A) func(S) S
+		Set func(a A) EM.Endomorphism[S]
 	}
 )
 
 // setCopy wraps a setter for a pointer into a setter that first creates a copy before
 // modifying that copy
-func setCopy[S, A any](setter func(*S, A) *S) func(s *S, a A) *S {
+func setCopy[SET ~func(*S, A) *S, S, A any](setter SET) func(s *S, a A) *S {
 	return func(s *S, a A) *S {
 		copy := *s
 		return setter(&copy, a)
@@ -41,8 +41,8 @@ func setCopy[S, A any](setter func(*S, A) *S) func(s *S, a A) *S {
 
 // setCopyCurried wraps a setter for a pointer into a setter that first creates a copy before
 // modifying that copy
-func setCopyCurried[S, A any](setter func(A) func(*S) *S) func(a A) func(*S) *S {
-	return func(a A) func(*S) *S {
+func setCopyCurried[SET ~func(A) EM.Endomorphism[*S], S, A any](setter SET) func(a A) EM.Endomorphism[*S] {
+	return func(a A) EM.Endomorphism[*S] {
 		seta := setter(a)
 		return func(s *S) *S {
 			copy := *s
@@ -51,53 +51,53 @@ func setCopyCurried[S, A any](setter func(A) func(*S) *S) func(a A) func(*S) *S
 	}
 }
 
-// MakeLens creates a lens based on a getter and a setter function. Make sure that the setter creates a (shallow) copy of the
+// MakeLens creates a [Lens] based on a getter and a setter function. Make sure that the setter creates a (shallow) copy of the
 // data. This happens automatically if the data is passed by value. For pointers consider to use `MakeLensRef`
 // and for other kinds of data structures that are copied by reference make sure the setter creates the copy.
-func MakeLens[S, A any](get func(S) A, set func(S, A) S) Lens[S, A] {
-	return MakeLensCurried(get, F.Curry2(F.Swap(set)))
+func MakeLens[GET ~func(S) A, SET ~func(S, A) S, S, A any](get GET, set SET) Lens[S, A] {
+	return MakeLensCurried(get, EM.Curry2(F.Swap(set)))
 }
 
-// MakeLensCurried creates a lens based on a getter and a setter function. Make sure that the setter creates a (shallow) copy of the
+// MakeLensCurried creates a [Lens] based on a getter and a setter function. Make sure that the setter creates a (shallow) copy of the
 // data. This happens automatically if the data is passed by value. For pointers consider to use `MakeLensRef`
 // and for other kinds of data structures that are copied by reference make sure the setter creates the copy.
-func MakeLensCurried[S, A any](get func(S) A, set func(A) func(S) S) Lens[S, A] {
+func MakeLensCurried[GET ~func(S) A, SET ~func(A) EM.Endomorphism[S], S, A any](get GET, set SET) Lens[S, A] {
 	return Lens[S, A]{Get: get, Set: set}
 }
 
-// MakeLensRef creates a lens based on a getter and a setter function. The setter passed in does not have to create a shallow
+// MakeLensRef creates a [Lens] based on a getter and a setter function. The setter passed in does not have to create a shallow
 // copy, the implementation wraps the setter into one that copies the pointer before modifying it
 //
-// Such a lens assumes that property A of S always exists
-func MakeLensRef[S, A any](get func(*S) A, set func(*S, A) *S) Lens[*S, A] {
+// Such a [Lens] assumes that property A of S always exists
+func MakeLensRef[GET ~func(*S) A, SET func(*S, A) *S, S, A any](get GET, set SET) Lens[*S, A] {
 	return MakeLens(get, setCopy(set))
 }
 
-// MakeLensRefCurried creates a lens based on a getter and a setter function. The setter passed in does not have to create a shallow
+// MakeLensRefCurried creates a [Lens] based on a getter and a setter function. The setter passed in does not have to create a shallow
 // copy, the implementation wraps the setter into one that copies the pointer before modifying it
 //
-// Such a lens assumes that property A of S always exists
-func MakeLensRefCurried[S, A any](get func(*S) A, set func(A) func(*S) *S) Lens[*S, A] {
+// Such a [Lens] assumes that property A of S always exists
+func MakeLensRefCurried[S, A any](get func(*S) A, set func(A) EM.Endomorphism[*S]) Lens[*S, A] {
 	return MakeLensCurried(get, setCopyCurried(set))
 }
 
-// Id returns a lens implementing the identity operation
-func id[S any](creator func(get func(S) S, set func(S, S) S) Lens[S, S]) Lens[S, S] {
+// id returns a [Lens] implementing the identity operation
+func id[GET ~func(S) S, SET ~func(S, S) S, S any](creator func(get GET, set SET) Lens[S, S]) Lens[S, S] {
 	return creator(F.Identity[S], F.Second[S, S])
 }
 
-// Id returns a lens implementing the identity operation
+// Id returns a [Lens] implementing the identity operation
 func Id[S any]() Lens[S, S] {
-	return id(MakeLens[S, S])
+	return id(MakeLens[EM.Endomorphism[S], func(S, S) S])
 }
 
-// IdRef returns a lens implementing the identity operation
+// IdRef returns a [Lens] implementing the identity operation
 func IdRef[S any]() Lens[*S, *S] {
-	return id(MakeLensRef[S, *S])
+	return id(MakeLensRef[EM.Endomorphism[*S], func(*S, *S) *S])
 }
 
 // Compose combines two lenses and allows to narrow down the focus to a sub-lens
-func compose[S, A, B any](creator func(get func(S) B, set func(S, B) S) Lens[S, B], ab Lens[A, B]) func(Lens[S, A]) Lens[S, B] {
+func compose[GET ~func(S) B, SET ~func(S, B) S, S, A, B any](creator func(get GET, set SET) Lens[S, B], ab Lens[A, B]) func(Lens[S, A]) Lens[S, B] {
 	abget := ab.Get
 	abset := ab.Set
 	return func(sa Lens[S, A]) Lens[S, B] {
@@ -114,7 +114,7 @@ func compose[S, A, B any](creator func(get func(S) B, set func(S, B) S) Lens[S,
 
 // Compose combines two lenses and allows to narrow down the focus to a sub-lens
 func Compose[S, A, B any](ab Lens[A, B]) func(Lens[S, A]) Lens[S, B] {
-	return compose(MakeLens[S, B], ab)
+	return compose(MakeLens[func(S) B, func(S, B) S], ab)
 }
 
 // ComposeOption combines a `Lens` that returns an optional value with a `Lens` that returns a definite value
@@ -141,7 +141,7 @@ func ComposeOption[S, B, A any](defaultA A) func(ab Lens[A, B]) func(Lens[S, O.O
 				func(s S, ob O.Option[B]) S {
 					return F.Pipe2(
 						ob,
-						O.Fold(unseta, func(b B) func(S) S {
+						O.Fold(unseta, func(b B) EM.Endomorphism[S] {
 							setbona := F.Flow2(
 								ab.Set(b),
 								seta,
@@ -158,7 +158,7 @@ func ComposeOption[S, B, A any](defaultA A) func(ab Lens[A, B]) func(Lens[S, O.O
 								),
 							)
 						}),
-						I.Ap[S, S](s),
+						EM.Ap(s),
 					)
 				},
 			)
@@ -174,7 +174,7 @@ func ComposeOption[S, B, A any](defaultA A) func(ab Lens[A, B]) func(Lens[S, O.O
 // if the setter is called with `None[B]` and `A` does exist, 'B' is removed from 'A'
 func ComposeOptions[S, B, A any](defaultA A) func(ab Lens[A, O.Option[B]]) func(Lens[S, O.Option[A]]) Lens[S, O.Option[B]] {
 	defa := F.Constant(defaultA)
-	noops := F.Constant(F.Identity[S])
+	noops := EM.Identity[S]
 	noneb := O.None[B]()
 	return func(ab Lens[A, O.Option[B]]) func(Lens[S, O.Option[A]]) Lens[S, O.Option[B]] {
 		unsetb := ab.Set(noneb)
@@ -189,15 +189,15 @@ func ComposeOptions[S, B, A any](defaultA A) func(ab Lens[A, O.Option[B]]) func(
 					sa.Get,
 					O.Chain(ab.Get),
 				),
-				func(b O.Option[B]) func(S) S {
+				func(b O.Option[B]) EM.Endomorphism[S] {
 					return func(s S) S {
-						return O.MonadFold(b, func() func(S) S {
+						return O.MonadFold(b, func() EM.Endomorphism[S] {
 							return F.Pipe2(
 								s,
 								sa.Get,
 								O.Fold(noops, F.Flow2(unsetb, seta)),
 							)
-						}, func(b B) func(S) S {
+						}, func(b B) EM.Endomorphism[S] {
 							// sets a B onto an A
 							setb := F.Flow2(
 								ab.Set(O.Some(b)),
@@ -218,20 +218,20 @@ func ComposeOptions[S, B, A any](defaultA A) func(ab Lens[A, O.Option[B]]) func(
 
 // Compose combines two lenses and allows to narrow down the focus to a sub-lens
 func ComposeRef[S, A, B any](ab Lens[A, B]) func(Lens[*S, A]) Lens[*S, B] {
-	return compose(MakeLensRef[S, B], ab)
+	return compose(MakeLensRef[func(*S) B, func(*S, B) *S], ab)
 }
 
-func modify[S, A any](f func(A) A, sa Lens[S, A], s S) S {
+func modify[FCT ~func(A) A, S, A any](f FCT, sa Lens[S, A], s S) S {
 	return sa.Set(f(sa.Get(s)))(s)
 }
 
-// Modify changes a property of a lens by invoking a transformation function
+// Modify changes a property of a [Lens] by invoking a transformation function
 // if the transformed property has not changes, the method returns the original state
-func Modify[S, A any](f func(A) A) func(Lens[S, A]) func(S) S {
-	return F.Curry3(modify[S, A])(f)
+func Modify[S any, FCT ~func(A) A, A any](f FCT) func(Lens[S, A]) EM.Endomorphism[S] {
+	return EM.Curry3(modify[FCT, S, A])(f)
 }
 
-func IMap[E, A, B any](ab func(A) B, ba func(B) A) func(Lens[E, A]) Lens[E, B] {
+func IMap[E any, AB ~func(A) B, BA ~func(B) A, A, B any](ab AB, ba BA) func(Lens[E, A]) Lens[E, B] {
 	return func(ea Lens[E, A]) Lens[E, B] {
 		return Lens[E, B]{Get: F.Flow2(ea.Get, ab), Set: F.Flow2(ba, ea.Set)}
 	}
@@ -239,7 +239,7 @@ func IMap[E, A, B any](ab func(A) B, ba func(B) A) func(Lens[E, A]) Lens[E, B] {
 
 // fromPredicate returns a `Lens` for a property accessibly as a getter and setter that can be optional
 // if the optional value is set then the nil value will be set instead
-func fromPredicate[S, A any](creator func(get func(S) O.Option[A], set func(S, O.Option[A]) S) Lens[S, O.Option[A]], pred func(A) bool, nilValue A) func(sa Lens[S, A]) Lens[S, O.Option[A]] {
+func fromPredicate[GET ~func(S) O.Option[A], SET ~func(S, O.Option[A]) S, S, A any](creator func(get GET, set SET) Lens[S, O.Option[A]], pred func(A) bool, nilValue A) func(sa Lens[S, A]) Lens[S, O.Option[A]] {
 	fromPred := O.FromPredicate(pred)
 	return func(sa Lens[S, A]) Lens[S, O.Option[A]] {
 		fold := O.Fold(F.Bind1of1(sa.Set)(nilValue), sa.Set)
@@ -247,7 +247,7 @@ func fromPredicate[S, A any](creator func(get func(S) O.Option[A], set func(S, O
 			return F.Pipe2(
 				a,
 				fold,
-				I.Ap[S, S](s),
+				EM.Ap(s),
 			)
 		})
 	}
@@ -256,13 +256,13 @@ func fromPredicate[S, A any](creator func(get func(S) O.Option[A], set func(S, O
 // FromPredicate returns a `Lens` for a property accessibly as a getter and setter that can be optional
 // if the optional value is set then the nil value will be set instead
 func FromPredicate[S, A any](pred func(A) bool, nilValue A) func(sa Lens[S, A]) Lens[S, O.Option[A]] {
-	return fromPredicate(MakeLens[S, O.Option[A]], pred, nilValue)
+	return fromPredicate(MakeLens[func(S) O.Option[A], func(S, O.Option[A]) S], pred, nilValue)
 }
 
 // FromPredicateRef returns a `Lens` for a property accessibly as a getter and setter that can be optional
 // if the optional value is set then the nil value will be set instead
 func FromPredicateRef[S, A any](pred func(A) bool, nilValue A) func(sa Lens[*S, A]) Lens[*S, O.Option[A]] {
-	return fromPredicate(MakeLensRef[S, O.Option[A]], pred, nilValue)
+	return fromPredicate(MakeLensRef[func(*S) O.Option[A], func(*S, O.Option[A]) *S], pred, nilValue)
 }
 
 // FromPredicate returns a `Lens` for a property accessibly as a getter and setter that can be optional
@@ -278,7 +278,7 @@ func FromNillableRef[S, A any](sa Lens[*S, *A]) Lens[*S, O.Option[*A]] {
 }
 
 // fromNullableProp returns a `Lens` from a property that may be optional. The getter returns a default value for these items
-func fromNullableProp[S, A any](creator func(get func(S) A, set func(S, A) S) Lens[S, A], isNullable func(A) O.Option[A], defaultValue A) func(sa Lens[S, A]) Lens[S, A] {
+func fromNullableProp[GET ~func(S) A, SET ~func(S, A) S, S, A any](creator func(get GET, set SET) Lens[S, A], isNullable func(A) O.Option[A], defaultValue A) func(sa Lens[S, A]) Lens[S, A] {
 	return func(sa Lens[S, A]) Lens[S, A] {
 		return creator(F.Flow3(
 			sa.Get,
@@ -293,16 +293,16 @@ func fromNullableProp[S, A any](creator func(get func(S) A, set func(S, A) S) Le
 
 // FromNullableProp returns a `Lens` from a property that may be optional. The getter returns a default value for these items
 func FromNullableProp[S, A any](isNullable func(A) O.Option[A], defaultValue A) func(sa Lens[S, A]) Lens[S, A] {
-	return fromNullableProp(MakeLens[S, A], isNullable, defaultValue)
+	return fromNullableProp(MakeLens[func(S) A, func(S, A) S], isNullable, defaultValue)
 }
 
 // FromNullablePropRef returns a `Lens` from a property that may be optional. The getter returns a default value for these items
 func FromNullablePropRef[S, A any](isNullable func(A) O.Option[A], defaultValue A) func(sa Lens[*S, A]) Lens[*S, A] {
-	return fromNullableProp(MakeLensRef[S, A], isNullable, defaultValue)
+	return fromNullableProp(MakeLensRef[func(*S) A, func(*S, A) *S], isNullable, defaultValue)
 }
 
 // fromFromOption returns a `Lens` from an option property. The getter returns a default value the setter will always set the some option
-func fromOption[S, A any](creator func(get func(S) A, set func(S, A) S) Lens[S, A], defaultValue A) func(sa Lens[S, O.Option[A]]) Lens[S, A] {
+func fromOption[GET ~func(S) A, SET ~func(S, A) S, S, A any](creator func(get GET, set SET) Lens[S, A], defaultValue A) func(sa Lens[S, O.Option[A]]) Lens[S, A] {
 	return func(sa Lens[S, O.Option[A]]) Lens[S, A] {
 		return creator(F.Flow2(
 			sa.Get,
@@ -316,10 +316,10 @@ func fromOption[S, A any](creator func(get func(S) A, set func(S, A) S) Lens[S,
 
 // FromFromOption returns a `Lens` from an option property. The getter returns a default value the setter will always set the some option
 func FromOption[S, A any](defaultValue A) func(sa Lens[S, O.Option[A]]) Lens[S, A] {
-	return fromOption(MakeLens[S, A], defaultValue)
+	return fromOption(MakeLens[func(S) A, func(S, A) S], defaultValue)
 }
 
 // FromFromOptionRef returns a `Lens` from an option property. The getter returns a default value the setter will always set the some option
 func FromOptionRef[S, A any](defaultValue A) func(sa Lens[*S, O.Option[A]]) Lens[*S, A] {
-	return fromOption(MakeLensRef[S, A], defaultValue)
+	return fromOption(MakeLensRef[func(*S) A, func(*S, A) *S], defaultValue)
 }