fix: use endomorphism

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

array/array.go

@@ -308,10 +308,16 @@ func SliceRight[A any](start int) func([]A) []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)

array/generic/array.go

@@ -304,6 +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 {

endomorphism/generic/monoid.go

@@ -0,0 +1,51 @@
+// 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 func(a A) A {
+		return a
+	}
+}
+
+func Compose[ENDO ~func(A) A, A any](f1, f2 ENDO) ENDO {
+	return func(a A) A {
+		return F.Pipe2(a, 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] {
+func Semigroup[A any]() S.Semigroup[Endomorphism[A]] {
-	return S.MakeSemigroup(F.Flow2[func(A) A, func(A) 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] {
+func Monoid[A any]() M.Monoid[Endomorphism[A]] {
-	return M.MakeMonoid(F.Flow2[func(A) A, func(A) A], F.Identity[A])
+	return G.Monoid[Endomorphism[A]]()
 }

http/form/form.go

@@ -19,6 +19,7 @@ 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"
@@ -27,8 +28,8 @@ import (
 )
 
 type (
-	// FormBuilder returns a function that transforms a form
+	// FormEndomorphism returns an [ENDO.Endomorphism] that transforms a form
-	FormBuilder = func(url.Values) url.Values
+	FormEndomorphism = ENDO.Endomorphism[url.Values]
 )
 
 var (
@@ -53,14 +54,15 @@ var (
 )
 
 // WithValue creates a [FormBuilder] for a certain field
-func WithValue(name string) func(value string) FormBuilder {
+func WithValue(name string) func(value string) FormEndomorphism {
-	return F.Flow2(
+	return F.Flow3(
 		O.Of[string],
 		AtValue(name).Set,
+		ENDO.Of[func(url.Values) url.Values],
 	)
 }
 
 // WithoutValue creates a [FormBuilder] that removes a field
-func WithoutValue(name string) FormBuilder {
+func WithoutValue(name string) FormEndomorphism {
 	return AtValue(name).Set(noField)
 }

ioeither/http/builder/builder.go

@@ -21,6 +21,7 @@ import (
 	"net/url"
 	"strconv"
 
+	ENDO "github.com/IBM/fp-go/endomorphism"
 	F "github.com/IBM/fp-go/function"
 	IOE "github.com/IBM/fp-go/ioeither"
 	IOEH "github.com/IBM/fp-go/ioeither/http"
@@ -39,8 +40,8 @@ type (
 		body    O.Option[IOE.IOEither[error, []byte]]
 	}
 
-	// BuilderBuilder returns a function that transforms a builder
+	// BuilderEndomorphism returns an [ENDO.Endomorphism] that transforms a builder
-	BuilderBuilder = func(*Builder) *Builder
+	BuilderEndomorphism = ENDO.Endomorphism[*Builder]
 )
 
 var (
@@ -208,20 +209,21 @@ func Header(name string) L.Lens[*Builder, O.Option[string]] {
 }
 
 // WithHeader creates a [BuilderBuilder] for a certain header
-func WithHeader(name string) func(value string) BuilderBuilder {
+func WithHeader(name string) func(value string) BuilderEndomorphism {
-	return F.Flow2(
+	return F.Flow3(
 		O.Of[string],
 		Header(name).Set,
+		ENDO.Of[func(*Builder) *Builder],
 	)
 }
 
 // WithoutHeader creates a [BuilderBuilder] to remove a certain header
-func WithoutHeader(name string) BuilderBuilder {
+func WithoutHeader(name string) BuilderEndomorphism {
 	return Header(name).Set(noHeader)
 }
 
 // WithFormData creates a [BuilderBuilder] to send form data payload
-func WithFormData(value url.Values) BuilderBuilder {
+func WithFormData(value url.Values) BuilderEndomorphism {
 	return F.Flow2(
 		F.Pipe4(
 			value,
@@ -235,7 +237,7 @@ func WithFormData(value url.Values) BuilderBuilder {
 }
 
 // WithJson creates a [BuilderBuilder] to send JSON payload
-func WithJson[T any](data T) BuilderBuilder {
+func WithJson[T any](data T) BuilderEndomorphism {
 	return F.Flow2(
 		F.Pipe3(
 			data,

record/generic/record.go

@@ -531,3 +531,12 @@ func MonadFlap[GFAB ~map[K]func(A) B, GB ~map[K]B, K comparable, A, B any](fab G
 func Flap[GFAB ~map[K]func(A) B, GB ~map[K]B, K comparable, A, B any](a A) func(GFAB) GB {
 	return FC.Flap(MonadMap[GFAB, GB], a)
 }
+
+func Copy[M ~map[K]V, K comparable, V any](m M) M {
+	return duplicate(m)
+}
+
+func Clone[M ~map[K]V, K comparable, V any](f func(V) V) func(m M) M {
+	// impementation assumes that map does not optimize for the empty map
+	return Map[M, M](f)
+}

record/record.go

@@ -284,3 +284,13 @@ func MonadFlap[B any, K comparable, A any](fab map[K]func(A) B, a A) map[K]B {
 func Flap[B any, K comparable, A any](a A) func(map[K]func(A) B) map[K]B {
 	return G.Flap[map[K]func(A) B, map[K]B](a)
 }
+
+// Copy creates a shallow copy of the map
+func Copy[K comparable, V any](m map[K]V) map[K]V {
+	return G.Copy[map[K]V](m)
+}
+
+// Clone creates a deep copy of the map using the provided endomorphism to clone the values
+func Clone[K comparable, V any](f func(V) V) func(m map[K]V) map[K]V {
+	return G.Clone[map[K]V](f)
+}

record/record_test.go

@@ -21,6 +21,7 @@ import (
 	"strings"
 	"testing"
 
+	A "github.com/IBM/fp-go/array"
 	"github.com/IBM/fp-go/internal/utils"
 	O "github.com/IBM/fp-go/option"
 	S "github.com/IBM/fp-go/string"
@@ -131,3 +132,20 @@ func ExampleValuesOrd() {
 	// Output: [c b a]
 
 }
+
+func TestCopyVsClone(t *testing.T) {
+	slc := []string{"b", "c"}
+	src := map[string][]string{
+		"a": slc,
+	}
+	// make a shallow copy
+	cpy := Copy(src)
+	// make a deep copy
+	cln := Clone[string](A.Copy[string])(src)
+
+	assert.Equal(t, cpy, cln)
+	// make a modification to the original slice
+	slc[0] = "d"
+	assert.NotEqual(t, cpy, cln)
+	assert.Equal(t, src, cpy)
+}