Add Do notation support and Bind to Monads (#100)

* fix: implement bind, let, apS for serveral monads

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

* fix: implement bind for maps

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

* fix: implement do notation for more monads

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

* fix: add bind to more monads

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

* fix: add Do and Bind support to Monads

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

---------

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

array/bind.go

@@ -0,0 +1,66 @@
+// 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"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[S any](
+	empty S,
+) []S {
+	return G.Do[[]S, S](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) []T,
+) func([]S1) []S2 {
+	return G.Bind[[]S1, []S2, []T, S1, S2, T](setter, f)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) T,
+) func([]S1) []S2 {
+	return G.Let[[]S1, []S2, S1, S2, T](setter, f)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	b T,
+) func([]S1) []S2 {
+	return G.LetTo[[]S1, []S2, S1, S2, T](setter, b)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[S1, T any](
+	setter func(T) S1,
+) func([]T) []S1 {
+	return G.BindTo[[]S1, []T, S1, T](setter)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa []T,
+) func([]S1) []S2 {
+	return G.ApS[[]S1, []S2, []T, S1, S2, T](setter, fa)
+}

array/bind_test.go

@@ -0,0 +1,56 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package array
+
+import (
+	"testing"
+
+	F "github.com/IBM/fp-go/function"
+	"github.com/IBM/fp-go/internal/utils"
+	"github.com/stretchr/testify/assert"
+)
+
+func getLastName(s utils.Initial) []string {
+	return Of("Doe")
+}
+
+func getGivenName(s utils.WithLastName) []string {
+	return Of("John")
+}
+
+func TestBind(t *testing.T) {
+
+	res := F.Pipe3(
+		Do(utils.Empty),
+		Bind(utils.SetLastName, getLastName),
+		Bind(utils.SetGivenName, getGivenName),
+		Map(utils.GetFullName),
+	)
+
+	assert.Equal(t, res, Of("John Doe"))
+}
+
+func TestApS(t *testing.T) {
+
+	res := F.Pipe3(
+		Do(utils.Empty),
+		ApS(utils.SetLastName, Of("Doe")),
+		ApS(utils.SetGivenName, Of("John")),
+		Map(utils.GetFullName),
+	)
+
+	assert.Equal(t, res, Of("John Doe"))
+}

array/generic/bind.go

@@ -0,0 +1,89 @@
+// 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 (
+	A "github.com/IBM/fp-go/internal/apply"
+	C "github.com/IBM/fp-go/internal/chain"
+	F "github.com/IBM/fp-go/internal/functor"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[GS ~[]S, S any](
+	empty S,
+) GS {
+	return Of[GS](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[GS1 ~[]S1, GS2 ~[]S2, GT ~[]T, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) GT,
+) func(GS1) GS2 {
+	return C.Bind(
+		Chain[GS1, GS2, S1, S2],
+		Map[GT, GS2, T, S2],
+		setter,
+		f,
+	)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[GS1 ~[]S1, GS2 ~[]S2, S1, S2, T any](
+	key func(T) func(S1) S2,
+	f func(S1) T,
+) func(GS1) GS2 {
+	return F.Let(
+		Map[GS1, GS2, S1, S2],
+		key,
+		f,
+	)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[GS1 ~[]S1, GS2 ~[]S2, S1, S2, B any](
+	key func(B) func(S1) S2,
+	b B,
+) func(GS1) GS2 {
+	return F.LetTo(
+		Map[GS1, GS2, S1, S2],
+		key,
+		b,
+	)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[GS1 ~[]S1, GT ~[]T, S1, T any](
+	setter func(T) S1,
+) func(GT) GS1 {
+	return C.BindTo(
+		Map[GT, GS1, T, S1],
+		setter,
+	)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[GS1 ~[]S1, GS2 ~[]S2, GT ~[]T, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa GT,
+) func(GS1) GS2 {
+	return A.ApS(
+		Ap[GS2, []func(T) S2, GT, S2, T],
+		Map[GS1, []func(T) S2, S1, func(T) S2],
+		setter,
+		fa,
+	)
+}

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

array/testing/laws_test.go

@@ -0,0 +1,47 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package testing
+
+import (
+	"fmt"
+	"testing"
+
+	EQ "github.com/IBM/fp-go/eq"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMonadLaws(t *testing.T) {
+	// some comparison
+	eqa := EQ.FromStrictEquals[bool]()
+	eqb := EQ.FromStrictEquals[int]()
+	eqc := EQ.FromStrictEquals[string]()
+
+	ab := func(a bool) int {
+		if a {
+			return 1
+		}
+		return 0
+	}
+
+	bc := func(b int) string {
+		return fmt.Sprintf("value %d", b)
+	}
+
+	laws := AssertLaws(t, eqa, eqb, eqc, ab, bc)
+
+	assert.True(t, laws(true))
+	assert.True(t, laws(false))
+}

context/readereither/bind.go

@@ -0,0 +1,68 @@
+// 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 readereither
+
+import (
+	"context"
+
+	G "github.com/IBM/fp-go/readereither/generic"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[S any](
+	empty S,
+) ReaderEither[S] {
+	return G.Do[ReaderEither[S], context.Context, error, S](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) ReaderEither[T],
+) func(ReaderEither[S1]) ReaderEither[S2] {
+	return G.Bind[ReaderEither[S1], ReaderEither[S2], ReaderEither[T], context.Context, error, S1, S2, T](setter, f)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) T,
+) func(ReaderEither[S1]) ReaderEither[S2] {
+	return G.Let[ReaderEither[S1], ReaderEither[S2], context.Context, error, S1, S2, T](setter, f)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	b T,
+) func(ReaderEither[S1]) ReaderEither[S2] {
+	return G.LetTo[ReaderEither[S1], ReaderEither[S2], context.Context, error, S1, S2, T](setter, b)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[S1, T any](
+	setter func(T) S1,
+) func(ReaderEither[T]) ReaderEither[S1] {
+	return G.BindTo[ReaderEither[S1], ReaderEither[T], context.Context, error, S1, T](setter)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa ReaderEither[T],
+) func(ReaderEither[S1]) ReaderEither[S2] {
+	return G.ApS[ReaderEither[S1], ReaderEither[S2], ReaderEither[T], context.Context, error, S1, S2, T](setter, fa)
+}

context/readereither/bind_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 readereither
+
+import (
+	"context"
+	"testing"
+
+	E "github.com/IBM/fp-go/either"
+	F "github.com/IBM/fp-go/function"
+	"github.com/IBM/fp-go/internal/utils"
+	"github.com/stretchr/testify/assert"
+)
+
+func getLastName(s utils.Initial) ReaderEither[string] {
+	return Of("Doe")
+}
+
+func getGivenName(s utils.WithLastName) ReaderEither[string] {
+	return Of("John")
+}
+
+func TestBind(t *testing.T) {
+
+	res := F.Pipe3(
+		Do(utils.Empty),
+		Bind(utils.SetLastName, getLastName),
+		Bind(utils.SetGivenName, getGivenName),
+		Map(utils.GetFullName),
+	)
+
+	assert.Equal(t, res(context.Background()), E.Of[error]("John Doe"))
+}
+
+func TestApS(t *testing.T) {
+
+	res := F.Pipe3(
+		Do(utils.Empty),
+		ApS(utils.SetLastName, Of("Doe")),
+		ApS(utils.SetGivenName, Of("John")),
+		Map(utils.GetFullName),
+	)
+
+	assert.Equal(t, res(context.Background()), E.Of[error]("John Doe"))
+}

context/readerioeither/bind.go

@@ -0,0 +1,67 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package readerioeither
+
+import (
+	G "github.com/IBM/fp-go/context/readerioeither/generic"
+	IOE "github.com/IBM/fp-go/ioeither"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[S any](
+	empty S,
+) ReaderIOEither[S] {
+	return G.Do[ReaderIOEither[S], IOE.IOEither[error, S], S](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) ReaderIOEither[T],
+) func(ReaderIOEither[S1]) ReaderIOEither[S2] {
+	return G.Bind[ReaderIOEither[S1], ReaderIOEither[S2], ReaderIOEither[T], IOE.IOEither[error, S1], IOE.IOEither[error, S2], IOE.IOEither[error, T], S1, S2, T](setter, f)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) T,
+) func(ReaderIOEither[S1]) ReaderIOEither[S2] {
+	return G.Let[ReaderIOEither[S1], ReaderIOEither[S2], IOE.IOEither[error, S1], IOE.IOEither[error, S2], S1, S2, T](setter, f)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	b T,
+) func(ReaderIOEither[S1]) ReaderIOEither[S2] {
+	return G.LetTo[ReaderIOEither[S1], ReaderIOEither[S2], IOE.IOEither[error, S1], IOE.IOEither[error, S2], S1, S2, T](setter, b)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[S1, T any](
+	setter func(T) S1,
+) func(ReaderIOEither[T]) ReaderIOEither[S1] {
+	return G.BindTo[ReaderIOEither[S1], ReaderIOEither[T], IOE.IOEither[error, S1], IOE.IOEither[error, T], S1, T](setter)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa ReaderIOEither[T],
+) func(ReaderIOEither[S1]) ReaderIOEither[S2] {
+	return G.ApS[ReaderIOEither[func(T) S2], ReaderIOEither[S1], ReaderIOEither[S2], ReaderIOEither[T], IOE.IOEither[error, func(T) S2], IOE.IOEither[error, S1], IOE.IOEither[error, S2], IOE.IOEither[error, T], S1, S2, T](setter, fa)
+}

context/readerioeither/bind_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 readerioeither
+
+import (
+	"context"
+	"testing"
+
+	E "github.com/IBM/fp-go/either"
+	F "github.com/IBM/fp-go/function"
+	"github.com/IBM/fp-go/internal/utils"
+	"github.com/stretchr/testify/assert"
+)
+
+func getLastName(s utils.Initial) ReaderIOEither[string] {
+	return Of("Doe")
+}
+
+func getGivenName(s utils.WithLastName) ReaderIOEither[string] {
+	return Of("John")
+}
+
+func TestBind(t *testing.T) {
+
+	res := F.Pipe3(
+		Do(utils.Empty),
+		Bind(utils.SetLastName, getLastName),
+		Bind(utils.SetGivenName, getGivenName),
+		Map(utils.GetFullName),
+	)
+
+	assert.Equal(t, res(context.Background())(), E.Of[error]("John Doe"))
+}
+
+func TestApS(t *testing.T) {
+
+	res := F.Pipe3(
+		Do(utils.Empty),
+		ApS(utils.SetLastName, Of("Doe")),
+		ApS(utils.SetGivenName, Of("John")),
+		Map(utils.GetFullName),
+	)
+
+	assert.Equal(t, res(context.Background())(), E.Of[error]("John Doe"))
+}

context/readerioeither/generic/bind.go

@@ -0,0 +1,92 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package generic
+
+import (
+	"context"
+
+	ET "github.com/IBM/fp-go/either"
+	A "github.com/IBM/fp-go/internal/apply"
+	C "github.com/IBM/fp-go/internal/chain"
+	F "github.com/IBM/fp-go/internal/functor"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[GRS ~func(context.Context) GS, GS ~func() ET.Either[error, S], S any](
+	empty S,
+) GRS {
+	return Of[GRS, GS, S](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[GRS1 ~func(context.Context) GS1, GRS2 ~func(context.Context) GS2, GRT ~func(context.Context) GT, GS1 ~func() ET.Either[error, S1], GS2 ~func() ET.Either[error, S2], GT ~func() ET.Either[error, T], S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) GRT,
+) func(GRS1) GRS2 {
+	return C.Bind(
+		Chain[GRS1, GRS2, GS1, GS2, S1, S2],
+		Map[GRT, GRS2, GT, GS2, T, S2],
+		setter,
+		f,
+	)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[GRS1 ~func(context.Context) GS1, GRS2 ~func(context.Context) GS2, GS1 ~func() ET.Either[error, S1], GS2 ~func() ET.Either[error, S2], S1, S2, T any](
+	key func(T) func(S1) S2,
+	f func(S1) T,
+) func(GRS1) GRS2 {
+	return F.Let(
+		Map[GRS1, GRS2, GS1, GS2, S1, S2],
+		key,
+		f,
+	)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[GRS1 ~func(context.Context) GS1, GRS2 ~func(context.Context) GS2, GS1 ~func() ET.Either[error, S1], GS2 ~func() ET.Either[error, S2], S1, S2, B any](
+	key func(B) func(S1) S2,
+	b B,
+) func(GRS1) GRS2 {
+	return F.LetTo(
+		Map[GRS1, GRS2, GS1, GS2, S1, S2],
+		key,
+		b,
+	)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[GRS1 ~func(context.Context) GS1, GRT ~func(context.Context) GT, GS1 ~func() ET.Either[error, S1], GT ~func() ET.Either[error, T], S1, T any](
+	setter func(T) S1,
+) func(GRT) GRS1 {
+	return C.BindTo(
+		Map[GRT, GRS1, GT, GS1, T, S1],
+		setter,
+	)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[GRTS1 ~func(context.Context) GTS1, GRS1 ~func(context.Context) GS1, GRS2 ~func(context.Context) GS2, GRT ~func(context.Context) GT, GTS1 ~func() ET.Either[error, func(T) S2], GS1 ~func() ET.Either[error, S1], GS2 ~func() ET.Either[error, S2], GT ~func() ET.Either[error, T], S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa GRT,
+) func(GRS1) GRS2 {
+	return A.ApS(
+		Ap[GRS2, GRTS1, GRT, GS2, GTS1, GT],
+		Map[GRS1, GRTS1, GS1, GTS1, S1, func(T) S2],
+		setter,
+		fa,
+	)
+}

either/bind.go

@@ -0,0 +1,89 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package either
+
+import (
+	A "github.com/IBM/fp-go/internal/apply"
+	C "github.com/IBM/fp-go/internal/chain"
+	F "github.com/IBM/fp-go/internal/functor"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[E, S any](
+	empty S,
+) Either[E, S] {
+	return Of[E](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[E, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) Either[E, T],
+) func(Either[E, S1]) Either[E, S2] {
+	return C.Bind(
+		Chain[E, S1, S2],
+		Map[E, T, S2],
+		setter,
+		f,
+	)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[E, S1, S2, T any](
+	key func(T) func(S1) S2,
+	f func(S1) T,
+) func(Either[E, S1]) Either[E, S2] {
+	return F.Let(
+		Map[E, S1, S2],
+		key,
+		f,
+	)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[E, S1, S2, T any](
+	key func(T) func(S1) S2,
+	b T,
+) func(Either[E, S1]) Either[E, S2] {
+	return F.LetTo(
+		Map[E, S1, S2],
+		key,
+		b,
+	)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[E, S1, T any](
+	setter func(T) S1,
+) func(Either[E, T]) Either[E, S1] {
+	return C.BindTo(
+		Map[E, T, S1],
+		setter,
+	)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[E, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa Either[E, T],
+) func(Either[E, S1]) Either[E, S2] {
+	return A.ApS(
+		Ap[S2, E, T],
+		Map[E, S1, func(T) S2],
+		setter,
+		fa,
+	)
+}

either/bind_test.go

@@ -0,0 +1,56 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package either
+
+import (
+	"testing"
+
+	F "github.com/IBM/fp-go/function"
+	"github.com/IBM/fp-go/internal/utils"
+	"github.com/stretchr/testify/assert"
+)
+
+func getLastName(s utils.Initial) Either[error, string] {
+	return Of[error]("Doe")
+}
+
+func getGivenName(s utils.WithLastName) Either[error, string] {
+	return Of[error]("John")
+}
+
+func TestBind(t *testing.T) {
+
+	res := F.Pipe3(
+		Do[error](utils.Empty),
+		Bind(utils.SetLastName, getLastName),
+		Bind(utils.SetGivenName, getGivenName),
+		Map[error](utils.GetFullName),
+	)
+
+	assert.Equal(t, res, Of[error]("John Doe"))
+}
+
+func TestApS(t *testing.T) {
+
+	res := F.Pipe3(
+		Do[error](utils.Empty),
+		ApS(utils.SetLastName, Of[error]("Doe")),
+		ApS(utils.SetGivenName, Of[error]("John")),
+		Map[error](utils.GetFullName),
+	)
+
+	assert.Equal(t, res, Of[error]("John Doe"))
+}

either/eq.go

@@ -34,7 +34,7 @@ func Eq[E, A any](e EQ.Eq[E], a EQ.Eq[A]) EQ.Eq[Either[E, A]] {
 	return EQ.FromEquals(F.Uncurry2(fld))
 }
 
-// FromStrictEquals constructs an `Eq` from the canonical comparison function
+// FromStrictEquals constructs an [EQ.Eq] from the canonical comparison function
 func FromStrictEquals[E, A comparable]() EQ.Eq[Either[E, A]] {
 	return Eq(EQ.FromStrictEquals[E](), EQ.FromStrictEquals[A]())
 }

eq/eq.go

@@ -35,12 +35,12 @@ func strictEq[A comparable](a, b A) bool {
 	return a == b
 }
 
-// FromStrictEquals constructs an `Eq` from the canonical comparison function
+// FromStrictEquals constructs an [EQ.Eq] from the canonical comparison function
 func FromStrictEquals[T comparable]() Eq[T] {
 	return FromEquals(strictEq[T])
 }
 
-// FromEquals constructs an `Eq` from the comparison function
+// FromEquals constructs an [EQ.Eq] from the comparison function
 func FromEquals[T any](c func(x, y T) bool) Eq[T] {
 	return eq[T]{c: c}
 }

identity/bind.go

@@ -0,0 +1,89 @@
+// 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 identity
+
+import (
+	A "github.com/IBM/fp-go/internal/apply"
+	C "github.com/IBM/fp-go/internal/chain"
+	F "github.com/IBM/fp-go/internal/functor"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[S any](
+	empty S,
+) S {
+	return empty
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) T,
+) func(S1) S2 {
+	return C.Bind(
+		Chain[S1, S2],
+		Map[T, S2],
+		setter,
+		f,
+	)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[S1, S2, T any](
+	key func(T) func(S1) S2,
+	f func(S1) T,
+) func(S1) S2 {
+	return F.Let(
+		Map[S1, S2],
+		key,
+		f,
+	)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[S1, S2, B any](
+	key func(B) func(S1) S2,
+	b B,
+) func(S1) S2 {
+	return F.LetTo(
+		Map[S1, S2],
+		key,
+		b,
+	)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[S1, T any](
+	setter func(T) S1,
+) func(T) S1 {
+	return C.BindTo(
+		Map[T, S1],
+		setter,
+	)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa T,
+) func(S1) S2 {
+	return A.ApS(
+		Ap[S2, T],
+		Map[S1, func(T) S2],
+		setter,
+		fa,
+	)
+}

internal/apply/ap.go

@@ -37,6 +37,16 @@ func MonadAp[HKTGA, HKTGB, HKTGAB, HKTFGAB, HKTFGGAB, HKTFGA, HKTFGB any](
 	return fap(fmap(fab, F.Bind1st(F.Bind1st[HKTGAB, HKTGA, HKTGB], gap)), fa)
 }
 
+// func Ap[HKTGA, HKTGB, HKTGAB, HKTFGAB, HKTFGGAB, HKTFGA, HKTFGB any](
+// 	fap func(HKTFGA) func(HKTFGGAB) HKTFGB,
+// 	fmap func(func(HKTGAB) func(HKTGA) HKTGB) func(HKTFGAB) HKTFGGAB,
+// 	gap func(HKTGA) func(HKTGAB) HKTGB,
+
+// 	fa HKTFGA) func(HKTFGAB) HKTFGB {
+
+// 	return fap(fmap(F.Bind1st(F.Bind1st[HKTGAB, HKTGA, HKTGB], gap)), fa)
+// }
+
 // export function ap<F, G>(
 // 	F: Apply<F>,
 // 	G: Apply<G>
@@ -107,3 +117,25 @@ func ApSecond[HKTGA, HKTGB, HKTGBB, A, B any](
 		return MonadApSecond(fap, fmap, first, second)
 	}
 }
+
+func MonadApS[S1, S2, B, HKTBGBS2, HKTS1, HKTS2, HKTB any](
+	fap func(HKTBGBS2, HKTB) HKTS2,
+	fmap func(HKTS1, func(S1) func(B) S2) HKTBGBS2,
+	fa HKTS1,
+	key func(B) func(S1) S2,
+	fb HKTB,
+) HKTS2 {
+	return fap(fmap(fa, F.Flip(key)), fb)
+}
+
+func ApS[S1, S2, B, HKTBGBS2, HKTS1, HKTS2, HKTB any](
+	fap func(HKTB) func(HKTBGBS2) HKTS2,
+	fmap func(func(S1) func(B) S2) func(HKTS1) HKTBGBS2,
+	key func(B) func(S1) S2,
+	fb HKTB,
+) func(HKTS1) HKTS2 {
+	return F.Flow2(
+		fmap(F.Flip(key)),
+		fap(fb),
+	)
+}

internal/bindt/bind.go

@@ -1,75 +0,0 @@
-// Copyright (c) 2023 IBM Corp.
-// All rights reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package bindt
-
-import (
-	F "github.com/IBM/fp-go/function"
-	I "github.com/IBM/fp-go/identity"
-	T "github.com/IBM/fp-go/tuple"
-)
-
-func Bind[SET ~func(B) func(S1) S2, FCT ~func(S1) HKTB, S1, S2, B, HKTS1, HKTS2, HKTB any](
-	mchain func(func(S1) HKTS2) func(HKTS1) HKTS2,
-	mmap func(func(B) S2) func(HKTB) HKTS2,
-	s SET,
-	f FCT,
-) func(HKTS1) HKTS2 {
-	return mchain(F.Flow3(
-		T.Replicate2[S1],
-		T.Map2(F.Flow2(
-			I.Ap[S2, S1],
-			F.Flow2(
-				F.Bind1st(F.Flow2[SET, func(func(S1) S2) S2], s),
-				mmap,
-			)), f),
-		T.Tupled2(I.MonadAp[HKTS2, HKTB]),
-	))
-}
-
-func BindTo[SET ~func(B) S2, S2, B, HKTS2, HKTB any](
-	mmap func(func(B) S2) func(HKTB) HKTS2,
-	s SET,
-) func(HKTB) HKTS2 {
-	return mmap(s)
-}
-
-func ApS[
-	SET ~func(B) func(S1) S2,
-	S1, S2, B, HKTS1S2, HKTS1, HKTS2, HKTB any,
-](
-	ap func(HKTS1) func(HKTS1S2) HKTS2,
-	mmap func(func(B) func(S1) S2) func(HKTB) HKTS1S2,
-	s SET, fb HKTB) func(HKTS1) HKTS2 {
-
-	return F.Flow2(
-		ap,
-		I.Ap[HKTS2, HKTS1S2](mmap(s)(fb)),
-	)
-}
-
-func Let[SET ~func(B) func(S1) S2, FCT ~func(S1) B, S1, S2, B, HKTS1, HKTS2 any](
-	mmap func(func(S1) S2) func(HKTS1) HKTS2,
-	s SET,
-	f FCT,
-) func(HKTS1) HKTS2 {
-	return mmap(F.Flow3(
-		T.Replicate2[S1],
-		T.Map2(F.Flow2(
-			I.Ap[S2, S1],
-			F.Bind1st(F.Flow2[SET, func(func(S1) S2) S2], s)), f),
-		T.Tupled2(I.MonadAp[S2, B]),
-	))
-}

internal/chain/chain.go

@@ -52,10 +52,59 @@ func ChainFirst[A, B, HKTA, HKTB any](
 }
 
 func Chain[A, B, HKTA, HKTB any](
-	mchain func(HKTA, func(A) HKTB) HKTB,
+	mchain func(func(A) HKTB) func(HKTA) HKTB,
 	f func(A) HKTB,
 ) func(HKTA) HKTB {
-	return func(first HKTA) HKTB {
+	return mchain(f)
-		return MonadChain[A, B](mchain, first, f)
 }
+
+func MonadBind[S1, S2, B, HKTS1, HKTS2, HKTB any](
+	mchain func(HKTS1, func(S1) HKTS2) HKTS2,
+	mmap func(HKTB, func(B) S2) HKTS2,
+	first HKTS1,
+	key func(B) func(S1) S2,
+	f func(S1) HKTB,
+) HKTS2 {
+	return mchain(first, func(s1 S1) HKTS2 {
+		return mmap(f(s1), func(b B) S2 {
+			return key(b)(s1)
+		})
+	})
+}
+
+func Bind[S1, S2, B, HKTS1, HKTS2, HKTB any](
+	mchain func(func(S1) HKTS2) func(HKTS1) HKTS2,
+	mmap func(func(B) S2) func(HKTB) HKTS2,
+	key func(B) func(S1) S2,
+	f func(S1) HKTB,
+) func(HKTS1) HKTS2 {
+	mapb := F.Flow2(
+		F.Flip(key),
+		mmap,
+	)
+	return mchain(func(s1 S1) HKTS2 {
+		return F.Pipe2(
+			s1,
+			f,
+			F.Pipe1(
+				s1,
+				mapb,
+			),
+		)
+	})
+}
+
+func BindTo[S1, B, HKTS1, HKTB any](
+	mmap func(func(B) S1) func(HKTB) HKTS1,
+	key func(B) S1,
+) func(fa HKTB) HKTS1 {
+	return mmap(key)
+}
+
+func MonadBindTo[S1, B, HKTS1, HKTB any](
+	mmap func(HKTB, func(B) S1) HKTS1,
+	first HKTB,
+	key func(B) S1,
+) HKTS1 {
+	return mmap(first, key)
 }

internal/fromio/io.go

@@ -47,7 +47,7 @@ func MonadChainIOK[GR ~func() B, A, B, HKTA, HKTB any](
 }
 
 func ChainIOK[GR ~func() B, A, B, HKTA, HKTB any](
-	mchain func(HKTA, func(A) HKTB) HKTB,
+	mchain func(func(A) HKTB) func(HKTA) HKTB,
 	fromio func(GR) HKTB,
 	f func(A) GR) func(HKTA) HKTB {
 	// chain

internal/fromioeither/ioeither.go

@@ -48,7 +48,7 @@ func MonadChainIOEitherK[GIOB ~func() ET.Either[E, B], E, A, B, HKTA, HKTB any](
 }
 
 func ChainIOEitherK[GIOB ~func() ET.Either[E, B], E, A, B, HKTA, HKTB any](
-	mchain func(HKTA, func(A) HKTB) HKTB,
+	mchain func(func(A) HKTB) func(HKTA) HKTB,
 	fromio func(GIOB) HKTB,
 	f func(A) GIOB) func(HKTA) HKTB {
 	// chain

internal/functor/functor.go

@@ -21,6 +21,54 @@ import (
 
 // HKTFGA = HKT[F, HKT[G, A]]
 // HKTFGB = HKT[F, HKT[G, B]]
-func MonadMap[A, B, HKTGA, HKTGB, HKTFGA, HKTFGB any](fmap func(HKTFGA, func(HKTGA) HKTGB) HKTFGB, gmap func(HKTGA, func(A) B) HKTGB, fa HKTFGA, f func(A) B) HKTFGB {
+func MonadMap[A, B, HKTGA, HKTGB, HKTFGA, HKTFGB any](
+	fmap func(HKTFGA, func(HKTGA) HKTGB) HKTFGB,
+	gmap func(HKTGA, func(A) B) HKTGB,
+	fa HKTFGA,
+	f func(A) B) HKTFGB {
 	return fmap(fa, F.Bind2nd(gmap, f))
 }
+
+func Map[A, B, HKTGA, HKTGB, HKTFGA, HKTFGB any](
+	fmap func(func(HKTGA) HKTGB) func(HKTFGA) HKTFGB,
+	gmap func(func(A) B) func(HKTGA) HKTGB,
+	f func(A) B) func(HKTFGA) HKTFGB {
+	return F.Pipe2(
+		f,
+		gmap,
+		fmap,
+	)
+}
+
+func MonadLet[S1, S2, B, HKTS1, HKTS2 any](
+	mmap func(HKTS1, func(S1) S2) HKTS2,
+	first HKTS1,
+	key func(B) func(S1) S2,
+	f func(S1) B,
+) HKTS2 {
+	return mmap(first, func(s1 S1) S2 {
+		return key(f(s1))(s1)
+	})
+}
+
+func Let[S1, S2, B, HKTS1, HKTS2 any](
+	mmap func(func(S1) S2) func(HKTS1) HKTS2,
+	key func(B) func(S1) S2,
+	f func(S1) B,
+) func(HKTS1) HKTS2 {
+	return mmap(func(s1 S1) S2 {
+		return key(f(s1))(s1)
+	})
+}
+
+func LetTo[S1, S2, B, HKTS1, HKTS2 any](
+	mmap func(func(S1) S2) func(HKTS1) HKTS2,
+	key func(B) func(S1) S2,
+	b B,
+) func(HKTS1) HKTS2 {
+	return F.Pipe2(
+		b,
+		key,
+		mmap,
+	)
+}

internal/optiont/option.go

@@ -64,9 +64,6 @@ func MonadAp[A, B, HKTFAB, HKTFGAB, HKTFA, HKTFB any](
 	fmap func(HKTFAB, func(O.Option[func(A) B]) func(O.Option[A]) O.Option[B]) HKTFGAB,
 	fab HKTFAB,
 	fa HKTFA) HKTFB {
-	// HKTGA  = O.Option[A]
-	// HKTGB  = O.Option[B]
-	// HKTGAB = O.Option[func(a A) B]
 	return apply.MonadAp(fap, fmap, O.MonadAp[B, A], fab, fa)
 }
 

internal/readert/reader.go

@@ -23,10 +23,25 @@ import (
 // here we implement the monadic operations using callbacks from
 // higher kinded types, as good a golang allows use to do this
 
-func MonadMap[GEA ~func(E) HKTA, GEB ~func(E) HKTB, E, A, B, HKTA, HKTB any](fmap func(HKTA, func(A) B) HKTB, fa GEA, f func(A) B) GEB {
+func MonadMap[GEA ~func(E) HKTA, GEB ~func(E) HKTB, E, A, B, HKTA, HKTB any](
+	fmap func(HKTA, func(A) B) HKTB,
+	fa GEA,
+	f func(A) B,
+) GEB {
 	return R.MonadMap[GEA, GEB](fa, F.Bind2nd(fmap, f))
 }
 
+func Map[GEA ~func(E) HKTA, GEB ~func(E) HKTB, E, A, B, HKTA, HKTB any](
+	fmap func(func(A) B) func(HKTA) HKTB,
+	f func(A) B,
+) func(GEA) GEB {
+	return F.Pipe2(
+		f,
+		fmap,
+		R.Map[GEA, GEB, E, HKTA, HKTB],
+	)
+}
+
 func MonadChain[GEA ~func(E) HKTA, GEB ~func(E) HKTB, A, E, HKTA, HKTB any](fchain func(HKTA, func(A) HKTB) HKTB, ma GEA, f func(A) GEB) GEB {
 	return R.MakeReader(func(r E) HKTB {
 		return fchain(ma(r), func(a A) HKTB {

internal/utils/do.go

@@ -0,0 +1,59 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package utils
+
+import (
+	"fmt"
+
+	F "github.com/IBM/fp-go/function"
+)
+
+type (
+	Initial struct {
+	}
+
+	WithLastName struct {
+		Initial
+		LastName string
+	}
+
+	WithGivenName struct {
+		WithLastName
+		GivenName string
+	}
+)
+
+var (
+	Empty = Initial{}
+
+	SetLastName = F.Curry2(func(name string, s1 Initial) WithLastName {
+		return WithLastName{
+			Initial:  s1,
+			LastName: name,
+		}
+	})
+
+	SetGivenName = F.Curry2(func(name string, s1 WithLastName) WithGivenName {
+		return WithGivenName{
+			WithLastName: s1,
+			GivenName:    name,
+		}
+	})
+)
+
+func GetFullName(s WithGivenName) string {
+	return fmt.Sprintf("%s %s", s.GivenName, s.LastName)
+}

io/bind.go

@@ -0,0 +1,66 @@
+// 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"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[S any](
+	empty S,
+) IO[S] {
+	return G.Do[IO[S], S](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) IO[T],
+) func(IO[S1]) IO[S2] {
+	return G.Bind[IO[S1], IO[S2], IO[T], S1, S2, T](setter, f)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) T,
+) func(IO[S1]) IO[S2] {
+	return G.Let[IO[S1], IO[S2], S1, S2, T](setter, f)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	b T,
+) func(IO[S1]) IO[S2] {
+	return G.LetTo[IO[S1], IO[S2], S1, S2, T](setter, b)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[S1, T any](
+	setter func(T) S1,
+) func(IO[T]) IO[S1] {
+	return G.BindTo[IO[S1], IO[T], S1, T](setter)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa IO[T],
+) func(IO[S1]) IO[S2] {
+	return G.ApS[IO[S1], IO[S2], IO[T], S1, S2, T](setter, fa)
+}

io/bind_test.go

@@ -0,0 +1,56 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package io
+
+import (
+	"testing"
+
+	F "github.com/IBM/fp-go/function"
+	"github.com/IBM/fp-go/internal/utils"
+	"github.com/stretchr/testify/assert"
+)
+
+func getLastName(s utils.Initial) IO[string] {
+	return Of("Doe")
+}
+
+func getGivenName(s utils.WithLastName) IO[string] {
+	return Of("John")
+}
+
+func TestBind(t *testing.T) {
+
+	res := F.Pipe3(
+		Do(utils.Empty),
+		Bind(utils.SetLastName, getLastName),
+		Bind(utils.SetGivenName, getGivenName),
+		Map(utils.GetFullName),
+	)
+
+	assert.Equal(t, res(), "John Doe")
+}
+
+func TestApS(t *testing.T) {
+
+	res := F.Pipe3(
+		Do(utils.Empty),
+		ApS(utils.SetLastName, Of("Doe")),
+		ApS(utils.SetGivenName, Of("John")),
+		Map(utils.GetFullName),
+	)
+
+	assert.Equal(t, res(), "John Doe")
+}

io/generic/bind.go

@@ -0,0 +1,89 @@
+// 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 (
+	A "github.com/IBM/fp-go/internal/apply"
+	C "github.com/IBM/fp-go/internal/chain"
+	F "github.com/IBM/fp-go/internal/functor"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[GS ~func() S, S any](
+	empty S,
+) GS {
+	return Of[GS](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[GS1 ~func() S1, GS2 ~func() S2, GT ~func() T, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) GT,
+) func(GS1) GS2 {
+	return C.Bind(
+		Chain[GS1, GS2, S1, S2],
+		Map[GT, GS2, T, S2],
+		setter,
+		f,
+	)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[GS1 ~func() S1, GS2 ~func() S2, S1, S2, T any](
+	key func(T) func(S1) S2,
+	f func(S1) T,
+) func(GS1) GS2 {
+	return F.Let(
+		Map[GS1, GS2, S1, S2],
+		key,
+		f,
+	)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[GS1 ~func() S1, GS2 ~func() S2, S1, S2, B any](
+	key func(B) func(S1) S2,
+	b B,
+) func(GS1) GS2 {
+	return F.LetTo(
+		Map[GS1, GS2, S1, S2],
+		key,
+		b,
+	)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[GS1 ~func() S1, GT ~func() T, S1, T any](
+	setter func(T) S1,
+) func(GT) GS1 {
+	return C.BindTo(
+		Map[GT, GS1, T, S1],
+		setter,
+	)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[GS1 ~func() S1, GS2 ~func() S2, GT ~func() T, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa GT,
+) func(GS1) GS2 {
+	return A.ApS(
+		Ap[GS2, func() func(T) S2, GT, S2, T],
+		Map[GS1, func() func(T) S2, S1, func(T) S2],
+		setter,
+		fa,
+	)
+}

ioeither/bind.go

@@ -19,26 +19,48 @@ import (
 	G "github.com/IBM/fp-go/ioeither/generic"
 )
 
-// Bind applies a function to an input state and merges the result into that state
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
-func Bind[E, A, S1, S2 any](s func(A) func(S1) S2, f func(S1) IOEither[E, A]) func(IOEither[E, S1]) IOEither[E, S2] {
+func Do[E, S any](
-	return G.Bind[IOEither[E, S1], IOEither[E, S2], IOEither[E, A], func(S1) IOEither[E, A]](s, f)
+	empty S,
+) IOEither[E, S] {
+	return G.Do[IOEither[E, S], E, S](empty)
 }
 
-// BindTo initializes some state based on a value
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
-func BindTo[
+func Bind[E, S1, S2, T any](
-	E, A, S2 any](s func(A) S2) func(IOEither[E, A]) IOEither[E, S2] {
+	setter func(T) func(S1) S2,
-	return G.BindTo[IOEither[E, S2], IOEither[E, A]](s)
+	f func(S1) IOEither[E, T],
-}
-
-func ApS[
-	E, A, S1, S2 any,
-](s func(A) func(S1) S2, fa IOEither[E, A]) func(IOEither[E, S1]) IOEither[E, S2] {
-	return G.ApS[IOEither[E, S1], IOEither[E, S2], IOEither[E, A], IOEither[E, func(S1) S2]](s, fa)
-}
-
-func Let[E, A, S1, S2 any](
-	s func(A) func(S1) S2,
-	f func(S1) A,
 ) func(IOEither[E, S1]) IOEither[E, S2] {
-	return G.Let[IOEither[E, S1], IOEither[E, S2]](s, f)
+	return G.Bind[IOEither[E, S1], IOEither[E, S2], IOEither[E, T], E, S1, S2, T](setter, f)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[E, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) T,
+) func(IOEither[E, S1]) IOEither[E, S2] {
+	return G.Let[IOEither[E, S1], IOEither[E, S2], E, S1, S2, T](setter, f)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[E, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	b T,
+) func(IOEither[E, S1]) IOEither[E, S2] {
+	return G.LetTo[IOEither[E, S1], IOEither[E, S2], E, S1, S2, T](setter, b)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[E, S1, T any](
+	setter func(T) S1,
+) func(IOEither[E, T]) IOEither[E, S1] {
+	return G.BindTo[IOEither[E, S1], IOEither[E, T], E, S1, T](setter)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[E, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa IOEither[E, T],
+) func(IOEither[E, S1]) IOEither[E, S2] {
+	return G.ApS[IOEither[E, S1], IOEither[E, S2], IOEither[E, T], E, S1, S2, T](setter, fa)
 }

ioeither/bind_test.go

@@ -0,0 +1,57 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ioeither
+
+import (
+	"testing"
+
+	E "github.com/IBM/fp-go/either"
+	F "github.com/IBM/fp-go/function"
+	"github.com/IBM/fp-go/internal/utils"
+	"github.com/stretchr/testify/assert"
+)
+
+func getLastName(s utils.Initial) IOEither[error, string] {
+	return Of[error]("Doe")
+}
+
+func getGivenName(s utils.WithLastName) IOEither[error, string] {
+	return Of[error]("John")
+}
+
+func TestBind(t *testing.T) {
+
+	res := F.Pipe3(
+		Do[error](utils.Empty),
+		Bind(utils.SetLastName, getLastName),
+		Bind(utils.SetGivenName, getGivenName),
+		Map[error](utils.GetFullName),
+	)
+
+	assert.Equal(t, res(), E.Of[error]("John Doe"))
+}
+
+func TestApS(t *testing.T) {
+
+	res := F.Pipe3(
+		Do[error](utils.Empty),
+		ApS(utils.SetLastName, Of[error]("Doe")),
+		ApS(utils.SetGivenName, Of[error]("John")),
+		Map[error](utils.GetFullName),
+	)
+
+	assert.Equal(t, res(), E.Of[error]("John Doe"))
+}

ioeither/eq.go

@@ -26,7 +26,7 @@ func Eq[E, A any](eq EQ.Eq[ET.Either[E, A]]) EQ.Eq[IOEither[E, A]] {
 	return G.Eq[IOEither[E, A]](eq)
 }
 
-// FromStrictEquals constructs an `Eq` from the canonical comparison function
+// FromStrictEquals constructs an [EQ.Eq] from the canonical comparison function
 func FromStrictEquals[E, A comparable]() EQ.Eq[IOEither[E, A]] {
 	return G.FromStrictEquals[IOEither[E, A]]()
 }

ioeither/generic/bind.go

@@ -17,63 +17,74 @@ package generic
 
 import (
 	ET "github.com/IBM/fp-go/either"
-	G "github.com/IBM/fp-go/internal/bindt"
+	A "github.com/IBM/fp-go/internal/apply"
+	C "github.com/IBM/fp-go/internal/chain"
+	F "github.com/IBM/fp-go/internal/functor"
 )
 
-// Bind applies a function to an input state and merges the result into that state
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
-func Bind[
+func Do[GS ~func() ET.Either[E, S], E, S any](
-	GS1 ~func() ET.Either[E, S1],
+	empty S,
-	GS2 ~func() ET.Either[E, S2],
+) GS {
-	GA ~func() ET.Either[E, A],
+	return Of[GS, E, S](empty)
-	FCT ~func(S1) GA,
+}
-	E any,
+
-	SET ~func(A) func(S1) S2,
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
-	A, S1, S2 any](s SET, f FCT) func(GS1) GS2 {
+func Bind[GS1 ~func() ET.Either[E, S1], GS2 ~func() ET.Either[E, S2], GT ~func() ET.Either[E, T], E, S1, S2, T any](
-	return G.Bind(
+	setter func(T) func(S1) S2,
+	f func(S1) GT,
+) func(GS1) GS2 {
+	return C.Bind(
 		Chain[GS1, GS2, E, S1, S2],
-		Map[GA, GS2, E, A, S2],
+		Map[GT, GS2, E, T, S2],
-		s,
+		setter,
 		f,
 	)
 }
 
-// BindTo initializes some state based on a value
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
-func BindTo[
+func Let[GS1 ~func() ET.Either[E, S1], GS2 ~func() ET.Either[E, S2], E, S1, S2, T any](
-	GS2 ~func() ET.Either[E, S2],
+	key func(T) func(S1) S2,
-	GA ~func() ET.Either[E, A],
+	f func(S1) T,
-	E any,
-	SET ~func(A) S2,
-	A, S2 any](s SET) func(GA) GS2 {
-	return G.BindTo(
-		Map[GA, GS2, E, A, S2],
-		s,
-	)
-}
-
-func ApS[
-	GS1 ~func() ET.Either[E, S1],
-	GS2 ~func() ET.Either[E, S2],
-	GB ~func() ET.Either[E, B],
-	GS1S2 ~func() ET.Either[E, func(S1) S2],
-	SET ~func(B) func(S1) S2,
-	E, S1, S2, B any,
-](s SET, fb GB) func(GS1) GS2 {
-	return G.ApS[SET, S1, S2, B, GS1S2, GS1, GS2, GB](
-		Ap[GS2, GS1S2, GS1, E, S1, S2],
-		Map[GB, GS1S2, E, B, func(S1) S2],
-		s,
-		fb,
-	)
-}
-
-func Let[
-	GS1 ~func() ET.Either[E, S1],
-	GS2 ~func() ET.Either[E, S2],
-	SET ~func(B) func(S1) S2,
-	FCT ~func(S1) B,
-	E, S1, S2, B any](
-	s SET,
-	f FCT,
 ) func(GS1) GS2 {
-	return G.Let[SET, FCT, S1, S2, B, GS1, GS2](Map[GS1, GS2, E, S1, S2], s, f)
+	return F.Let(
+		Map[GS1, GS2, E, S1, S2],
+		key,
+		f,
+	)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[GS1 ~func() ET.Either[E, S1], GS2 ~func() ET.Either[E, S2], E, S1, S2, B any](
+	key func(B) func(S1) S2,
+	b B,
+) func(GS1) GS2 {
+	return F.LetTo(
+		Map[GS1, GS2, E, S1, S2],
+		key,
+		b,
+	)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[GS1 ~func() ET.Either[E, S1], GT ~func() ET.Either[E, T], E, S1, S2, T any](
+	setter func(T) S1,
+) func(GT) GS1 {
+	return C.BindTo(
+		Map[GT, GS1, E, T, S1],
+		setter,
+	)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[GS1 ~func() ET.Either[E, S1], GS2 ~func() ET.Either[E, S2], GT ~func() ET.Either[E, T], E, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa GT,
+) func(GS1) GS2 {
+	return A.ApS(
+		Ap[GS2, func() ET.Either[E, func(T) S2], GT, E, T, S2],
+		Map[GS1, func() ET.Either[E, func(T) S2], E, S1, func(T) S2],
+		setter,
+		fa,
+	)
 }

ioeither/generic/eq.go

@@ -26,7 +26,7 @@ func Eq[GA ~func() ET.Either[E, A], E, A any](eq EQ.Eq[ET.Either[E, A]]) EQ.Eq[G
 	return G.Eq[GA](eq)
 }
 
-// FromStrictEquals constructs an `Eq` from the canonical comparison function
+// FromStrictEquals constructs an [EQ.Eq] from the canonical comparison function
 func FromStrictEquals[GA ~func() ET.Either[E, A], E, A comparable]() EQ.Eq[GA] {
 	return Eq[GA](ET.FromStrictEquals[E, A]())
 }

ioeither/generic/ioeither.go

@@ -134,7 +134,7 @@ func MonadChainIOK[GA ~func() ET.Either[E, A], GB ~func() ET.Either[E, B], GR ~f
 
 func ChainIOK[GA ~func() ET.Either[E, A], GB ~func() ET.Either[E, B], GR ~func() B, E, A, B any](f func(A) GR) func(GA) GB {
 	return FI.ChainIOK(
-		MonadChain[GA, GB, E, A, B],
+		Chain[GA, GB, E, A, B],
 		FromIO[GB, GR, E, B],
 		f,
 	)

iooption/bind.go

@@ -0,0 +1,66 @@
+// 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"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[S any](
+	empty S,
+) IOOption[S] {
+	return G.Do[IOOption[S], S](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) IOOption[T],
+) func(IOOption[S1]) IOOption[S2] {
+	return G.Bind[IOOption[S1], IOOption[S2], IOOption[T], S1, S2, T](setter, f)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) T,
+) func(IOOption[S1]) IOOption[S2] {
+	return G.Let[IOOption[S1], IOOption[S2], S1, S2, T](setter, f)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	b T,
+) func(IOOption[S1]) IOOption[S2] {
+	return G.LetTo[IOOption[S1], IOOption[S2], S1, S2, T](setter, b)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[S1, T any](
+	setter func(T) S1,
+) func(IOOption[T]) IOOption[S1] {
+	return G.BindTo[IOOption[S1], IOOption[T], S1, T](setter)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa IOOption[T],
+) func(IOOption[S1]) IOOption[S2] {
+	return G.ApS[IOOption[S1], IOOption[S2], IOOption[T], S1, S2, T](setter, fa)
+}

iooption/bind_test.go

@@ -0,0 +1,57 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package iooption
+
+import (
+	"testing"
+
+	F "github.com/IBM/fp-go/function"
+	"github.com/IBM/fp-go/internal/utils"
+	O "github.com/IBM/fp-go/option"
+	"github.com/stretchr/testify/assert"
+)
+
+func getLastName(s utils.Initial) IOOption[string] {
+	return Of("Doe")
+}
+
+func getGivenName(s utils.WithLastName) IOOption[string] {
+	return Of("John")
+}
+
+func TestBind(t *testing.T) {
+
+	res := F.Pipe3(
+		Do(utils.Empty),
+		Bind(utils.SetLastName, getLastName),
+		Bind(utils.SetGivenName, getGivenName),
+		Map(utils.GetFullName),
+	)
+
+	assert.Equal(t, res(), O.Of("John Doe"))
+}
+
+func TestApS(t *testing.T) {
+
+	res := F.Pipe3(
+		Do(utils.Empty),
+		ApS(utils.SetLastName, Of("Doe")),
+		ApS(utils.SetGivenName, Of("John")),
+		Map(utils.GetFullName),
+	)
+
+	assert.Equal(t, res(), O.Of("John Doe"))
+}

iooption/eq.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 iooption
+
+import (
+	EQ "github.com/IBM/fp-go/eq"
+	G "github.com/IBM/fp-go/iooption/generic"
+)
+
+// Eq implements the equals predicate for values contained in the IO monad
+func Eq[A any](e EQ.Eq[A]) EQ.Eq[IOOption[A]] {
+	return G.Eq[IOOption[A]](e)
+}
+
+// FromStrictEquals constructs an [EQ.Eq] from the canonical comparison function
+func FromStrictEquals[A comparable]() EQ.Eq[IOOption[A]] {
+	return G.FromStrictEquals[IOOption[A]]()
+}

iooption/generic/bind.go

@@ -0,0 +1,90 @@
+// 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 (
+	A "github.com/IBM/fp-go/internal/apply"
+	C "github.com/IBM/fp-go/internal/chain"
+	F "github.com/IBM/fp-go/internal/functor"
+	O "github.com/IBM/fp-go/option"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[GS ~func() O.Option[S], S any](
+	empty S,
+) GS {
+	return Of[GS](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[GS1 ~func() O.Option[S1], GS2 ~func() O.Option[S2], GT ~func() O.Option[T], S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) GT,
+) func(GS1) GS2 {
+	return C.Bind(
+		Chain[GS1, GS2, S1, S2],
+		Map[GT, GS2, T, S2],
+		setter,
+		f,
+	)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[GS1 ~func() O.Option[S1], GS2 ~func() O.Option[S2], S1, S2, T any](
+	key func(T) func(S1) S2,
+	f func(S1) T,
+) func(GS1) GS2 {
+	return F.Let(
+		Map[GS1, GS2, S1, S2],
+		key,
+		f,
+	)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[GS1 ~func() O.Option[S1], GS2 ~func() O.Option[S2], S1, S2, B any](
+	key func(B) func(S1) S2,
+	b B,
+) func(GS1) GS2 {
+	return F.LetTo(
+		Map[GS1, GS2, S1, S2],
+		key,
+		b,
+	)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[GS1 ~func() O.Option[S1], GT ~func() O.Option[T], S1, T any](
+	setter func(T) S1,
+) func(GT) GS1 {
+	return C.BindTo(
+		Map[GT, GS1, T, S1],
+		setter,
+	)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[GS1 ~func() O.Option[S1], GS2 ~func() O.Option[S2], GT ~func() O.Option[T], S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa GT,
+) func(GS1) GS2 {
+	return A.ApS(
+		Ap[GS2, func() O.Option[func(T) S2], GT, T, S2],
+		Map[GS1, func() O.Option[func(T) S2], S1, func(T) S2],
+		setter,
+		fa,
+	)
+}

iooption/generic/eq.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 generic
+
+import (
+	EQ "github.com/IBM/fp-go/eq"
+	G "github.com/IBM/fp-go/io/generic"
+	O "github.com/IBM/fp-go/option"
+)
+
+// Eq implements the equals predicate for values contained in the IO monad
+func Eq[GA ~func() O.Option[A], A any](e EQ.Eq[A]) EQ.Eq[GA] {
+	return G.Eq[GA](O.Eq(e))
+}
+
+// FromStrictEquals constructs an [EQ.Eq] from the canonical comparison function
+func FromStrictEquals[GA ~func() O.Option[A], A comparable]() EQ.Eq[GA] {
+	return Eq[GA](EQ.FromStrictEquals[A]())
+}

iooption/generic/iooption.go

@@ -145,7 +145,7 @@ func MonadChainIOK[GA ~func() O.Option[A], GB ~func() O.Option[B], GR ~func() B,
 
 func ChainIOK[GA ~func() O.Option[A], GB ~func() O.Option[B], GR ~func() B, A, B any](f func(A) GR) func(GA) GB {
 	return FI.ChainIOK(
-		MonadChain[GA, GB, A, B],
+		Chain[GA, GB, A, B],
 		FromIO[GB, GR, B],
 		f,
 	)

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

iooption/testing/laws_test.go

@@ -0,0 +1,47 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package testing
+
+import (
+	"fmt"
+	"testing"
+
+	EQ "github.com/IBM/fp-go/eq"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMonadLaws(t *testing.T) {
+	// some comparison
+	eqa := EQ.FromStrictEquals[bool]()
+	eqb := EQ.FromStrictEquals[int]()
+	eqc := EQ.FromStrictEquals[string]()
+
+	ab := func(a bool) int {
+		if a {
+			return 1
+		}
+		return 0
+	}
+
+	bc := func(b int) string {
+		return fmt.Sprintf("value %d", b)
+	}
+
+	laws := AssertLaws(t, eqa, eqb, eqc, ab, bc)
+
+	assert.True(t, laws(true))
+	assert.True(t, laws(false))
+}

iterator/stateless/bind.go

@@ -0,0 +1,66 @@
+// 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 (
+	G "github.com/IBM/fp-go/iterator/stateless/generic"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[S any](
+	empty S,
+) Iterator[S] {
+	return G.Do[Iterator[S], S](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) Iterator[T],
+) func(Iterator[S1]) Iterator[S2] {
+	return G.Bind[Iterator[S1], Iterator[S2], Iterator[T], S1, S2, T](setter, f)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) T,
+) func(Iterator[S1]) Iterator[S2] {
+	return G.Let[Iterator[S1], Iterator[S2], S1, S2, T](setter, f)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	b T,
+) func(Iterator[S1]) Iterator[S2] {
+	return G.LetTo[Iterator[S1], Iterator[S2], S1, S2, T](setter, b)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[S1, T any](
+	setter func(T) S1,
+) func(Iterator[T]) Iterator[S1] {
+	return G.BindTo[Iterator[S1], Iterator[T], S1, T](setter)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa Iterator[T],
+) func(Iterator[S1]) Iterator[S2] {
+	return G.ApS[Iterator[func(T) S2], Iterator[S1], Iterator[S2], Iterator[T], S1, S2, T](setter, fa)
+}

iterator/stateless/bind_test.go

@@ -0,0 +1,57 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package stateless
+
+import (
+	"testing"
+
+	A "github.com/IBM/fp-go/array"
+	F "github.com/IBM/fp-go/function"
+	"github.com/IBM/fp-go/internal/utils"
+	"github.com/stretchr/testify/assert"
+)
+
+func getLastName(s utils.Initial) Iterator[string] {
+	return Of("Doe")
+}
+
+func getGivenName(s utils.WithLastName) Iterator[string] {
+	return Of("John")
+}
+
+func TestBind(t *testing.T) {
+
+	res := F.Pipe3(
+		Do(utils.Empty),
+		Bind(utils.SetLastName, getLastName),
+		Bind(utils.SetGivenName, getGivenName),
+		Map(utils.GetFullName),
+	)
+
+	assert.Equal(t, ToArray(res), A.Of("John Doe"))
+}
+
+func TestApS(t *testing.T) {
+
+	res := F.Pipe3(
+		Do(utils.Empty),
+		ApS(utils.SetLastName, Of("Doe")),
+		ApS(utils.SetGivenName, Of("John")),
+		Map(utils.GetFullName),
+	)
+
+	assert.Equal(t, ToArray(res), A.Of("John Doe"))
+}

iterator/stateless/generic/bind.go

@@ -0,0 +1,92 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package generic
+
+import (
+	"github.com/IBM/fp-go/internal/apply"
+	C "github.com/IBM/fp-go/internal/chain"
+	F "github.com/IBM/fp-go/internal/functor"
+	O "github.com/IBM/fp-go/option"
+	T "github.com/IBM/fp-go/tuple"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[GS ~func() O.Option[T.Tuple2[GS, S]], S any](
+	empty S,
+) GS {
+	return Of[GS](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[GS1 ~func() O.Option[T.Tuple2[GS1, S1]], GS2 ~func() O.Option[T.Tuple2[GS2, S2]], GA ~func() O.Option[T.Tuple2[GA, A]], S1, S2, A any](
+	setter func(A) func(S1) S2,
+	f func(S1) GA,
+) func(GS1) GS2 {
+
+	return C.Bind(
+		Chain[GS2, GS1, S1, S2],
+		Map[GS2, GA, func(A) S2, A, S2],
+		setter,
+		f,
+	)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[GS1 ~func() O.Option[T.Tuple2[GS1, S1]], GS2 ~func() O.Option[T.Tuple2[GS2, S2]], S1, S2, A any](
+	key func(A) func(S1) S2,
+	f func(S1) A,
+) func(GS1) GS2 {
+	return F.Let(
+		Map[GS2, GS1, func(S1) S2, S1, S2],
+		key,
+		f,
+	)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[GS1 ~func() O.Option[T.Tuple2[GS1, S1]], GS2 ~func() O.Option[T.Tuple2[GS2, S2]], S1, S2, B any](
+	key func(B) func(S1) S2,
+	b B,
+) func(GS1) GS2 {
+	return F.LetTo(
+		Map[GS2, GS1, func(S1) S2, S1, S2],
+		key,
+		b,
+	)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[GS1 ~func() O.Option[T.Tuple2[GS1, S1]], GA ~func() O.Option[T.Tuple2[GA, A]], S1, A any](
+	setter func(A) S1,
+) func(GA) GS1 {
+	return C.BindTo(
+		Map[GS1, GA, func(A) S1, A, S1],
+		setter,
+	)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[GAS2 ~func() O.Option[T.Tuple2[GAS2, func(A) S2]], GS1 ~func() O.Option[T.Tuple2[GS1, S1]], GS2 ~func() O.Option[T.Tuple2[GS2, S2]], GA ~func() O.Option[T.Tuple2[GA, A]], S1, S2, A any](
+	setter func(A) func(S1) S2,
+	fa GA,
+) func(GS1) GS2 {
+	return apply.ApS(
+		Ap[GAS2, GS2, GA, A, S2],
+		Map[GAS2, GS1, func(S1) func(A) S2, S1, func(A) S2],
+		setter,
+		fa,
+	)
+}

lazy/bind.go

@@ -0,0 +1,66 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package lazy
+
+import (
+	G "github.com/IBM/fp-go/io/generic"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[S any](
+	empty S,
+) Lazy[S] {
+	return G.Do[Lazy[S], S](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) Lazy[T],
+) func(Lazy[S1]) Lazy[S2] {
+	return G.Bind[Lazy[S1], Lazy[S2], Lazy[T], S1, S2, T](setter, f)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) T,
+) func(Lazy[S1]) Lazy[S2] {
+	return G.Let[Lazy[S1], Lazy[S2], S1, S2, T](setter, f)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	b T,
+) func(Lazy[S1]) Lazy[S2] {
+	return G.LetTo[Lazy[S1], Lazy[S2], S1, S2, T](setter, b)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[S1, T any](
+	setter func(T) S1,
+) func(Lazy[T]) Lazy[S1] {
+	return G.BindTo[Lazy[S1], Lazy[T], S1, T](setter)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa Lazy[T],
+) func(Lazy[S1]) Lazy[S2] {
+	return G.ApS[Lazy[S1], Lazy[S2], Lazy[T], S1, S2, T](setter, fa)
+}

lazy/bind_test.go

@@ -0,0 +1,56 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package lazy
+
+import (
+	"testing"
+
+	F "github.com/IBM/fp-go/function"
+	"github.com/IBM/fp-go/internal/utils"
+	"github.com/stretchr/testify/assert"
+)
+
+func getLastName(s utils.Initial) Lazy[string] {
+	return Of("Doe")
+}
+
+func getGivenName(s utils.WithLastName) Lazy[string] {
+	return Of("John")
+}
+
+func TestBind(t *testing.T) {
+
+	res := F.Pipe3(
+		Do(utils.Empty),
+		Bind(utils.SetLastName, getLastName),
+		Bind(utils.SetGivenName, getGivenName),
+		Map(utils.GetFullName),
+	)
+
+	assert.Equal(t, res(), "John Doe")
+}
+
+func TestApS(t *testing.T) {
+
+	res := F.Pipe3(
+		Do(utils.Empty),
+		ApS(utils.SetLastName, Of("Doe")),
+		ApS(utils.SetGivenName, Of("John")),
+		Map(utils.GetFullName),
+	)
+
+	assert.Equal(t, res(), "John Doe")
+}

option/bind.go

@@ -0,0 +1,89 @@
+// 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 option
+
+import (
+	A "github.com/IBM/fp-go/internal/apply"
+	C "github.com/IBM/fp-go/internal/chain"
+	F "github.com/IBM/fp-go/internal/functor"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[S any](
+	empty S,
+) Option[S] {
+	return Of(empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[S1, S2, A any](
+	setter func(A) func(S1) S2,
+	f func(S1) Option[A],
+) func(Option[S1]) Option[S2] {
+	return C.Bind(
+		Chain[S1, S2],
+		Map[A, S2],
+		setter,
+		f,
+	)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[S1, S2, B any](
+	key func(B) func(S1) S2,
+	f func(S1) B,
+) func(Option[S1]) Option[S2] {
+	return F.Let(
+		Map[S1, S2],
+		key,
+		f,
+	)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[S1, S2, B any](
+	key func(B) func(S1) S2,
+	b B,
+) func(Option[S1]) Option[S2] {
+	return F.LetTo(
+		Map[S1, S2],
+		key,
+		b,
+	)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[S1, T any](
+	setter func(T) S1,
+) func(Option[T]) Option[S1] {
+	return C.BindTo(
+		Map[T, S1],
+		setter,
+	)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa Option[T],
+) func(Option[S1]) Option[S2] {
+	return A.ApS(
+		Ap[S2, T],
+		Map[S1, func(T) S2],
+		setter,
+		fa,
+	)
+}

option/bind_test.go

@@ -0,0 +1,56 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package option
+
+import (
+	"testing"
+
+	F "github.com/IBM/fp-go/function"
+	"github.com/IBM/fp-go/internal/utils"
+	"github.com/stretchr/testify/assert"
+)
+
+func getLastName(s utils.Initial) Option[string] {
+	return Of("Doe")
+}
+
+func getGivenName(s utils.WithLastName) Option[string] {
+	return Of("John")
+}
+
+func TestBind(t *testing.T) {
+
+	res := F.Pipe3(
+		Do(utils.Empty),
+		Bind(utils.SetLastName, getLastName),
+		Bind(utils.SetGivenName, getGivenName),
+		Map(utils.GetFullName),
+	)
+
+	assert.Equal(t, res, Of("John Doe"))
+}
+
+func TestApS(t *testing.T) {
+
+	res := F.Pipe3(
+		Do(utils.Empty),
+		ApS(utils.SetLastName, Of("Doe")),
+		ApS(utils.SetGivenName, Of("John")),
+		Map(utils.GetFullName),
+	)
+
+	assert.Equal(t, res, Of("John Doe"))
+}

option/eq.go

@@ -31,7 +31,7 @@ func Eq[A any](a EQ.Eq[A]) EQ.Eq[Option[A]] {
 	return EQ.FromEquals(F.Uncurry2(fld))
 }
 
-// FromStrictEquals constructs an `Eq` from the canonical comparison function
+// FromStrictEquals constructs an [EQ.Eq] from the canonical comparison function
 func FromStrictEquals[A comparable]() EQ.Eq[Option[A]] {
 	return Eq(EQ.FromStrictEquals[A]())
 }

reader/bind.go

@@ -0,0 +1,66 @@
+// 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 reader
+
+import (
+	G "github.com/IBM/fp-go/reader/generic"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[R, S any](
+	empty S,
+) Reader[R, S] {
+	return G.Do[Reader[R, S], R, S](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[R, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) Reader[R, T],
+) func(Reader[R, S1]) Reader[R, S2] {
+	return G.Bind[Reader[R, S1], Reader[R, S2], Reader[R, T], R, S1, S2, T](setter, f)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[R, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) T,
+) func(Reader[R, S1]) Reader[R, S2] {
+	return G.Let[Reader[R, S1], Reader[R, S2], R, S1, S2, T](setter, f)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[R, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	b T,
+) func(Reader[R, S1]) Reader[R, S2] {
+	return G.LetTo[Reader[R, S1], Reader[R, S2], R, S1, S2, T](setter, b)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[R, S1, T any](
+	setter func(T) S1,
+) func(Reader[R, T]) Reader[R, S1] {
+	return G.BindTo[Reader[R, S1], Reader[R, T], R, S1, T](setter)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[R, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa Reader[R, T],
+) func(Reader[R, S1]) Reader[R, S2] {
+	return G.ApS[Reader[R, S1], Reader[R, S2], Reader[R, T], R, S1, S2, T](setter, fa)
+}

reader/bind_test.go

@@ -0,0 +1,57 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package reader
+
+import (
+	"context"
+	"testing"
+
+	F "github.com/IBM/fp-go/function"
+	"github.com/IBM/fp-go/internal/utils"
+	"github.com/stretchr/testify/assert"
+)
+
+func getLastName(s utils.Initial) Reader[context.Context, string] {
+	return Of[context.Context]("Doe")
+}
+
+func getGivenName(s utils.WithLastName) Reader[context.Context, string] {
+	return Of[context.Context]("John")
+}
+
+func TestBind(t *testing.T) {
+
+	res := F.Pipe3(
+		Do[context.Context](utils.Empty),
+		Bind(utils.SetLastName, getLastName),
+		Bind(utils.SetGivenName, getGivenName),
+		Map[context.Context](utils.GetFullName),
+	)
+
+	assert.Equal(t, res(context.Background()), "John Doe")
+}
+
+func TestApS(t *testing.T) {
+
+	res := F.Pipe3(
+		Do[context.Context](utils.Empty),
+		ApS(utils.SetLastName, Of[context.Context]("Doe")),
+		ApS(utils.SetGivenName, Of[context.Context]("John")),
+		Map[context.Context](utils.GetFullName),
+	)
+
+	assert.Equal(t, res(context.Background()), "John Doe")
+}

reader/generic/bind.go

@@ -0,0 +1,89 @@
+// 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 (
+	A "github.com/IBM/fp-go/internal/apply"
+	C "github.com/IBM/fp-go/internal/chain"
+	F "github.com/IBM/fp-go/internal/functor"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[GS ~func(R) S, R, S any](
+	empty S,
+) GS {
+	return Of[GS, R, S](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[GS1 ~func(R) S1, GS2 ~func(R) S2, GT ~func(R) T, R, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) GT,
+) func(GS1) GS2 {
+	return C.Bind(
+		Chain[GS1, GS2, R, S1, S2],
+		Map[GT, GS2, R, T, S2],
+		setter,
+		f,
+	)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[GS1 ~func(R) S1, GS2 ~func(R) S2, R, S1, S2, T any](
+	key func(T) func(S1) S2,
+	f func(S1) T,
+) func(GS1) GS2 {
+	return F.Let(
+		Map[GS1, GS2, R, S1, S2],
+		key,
+		f,
+	)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[GS1 ~func(R) S1, GS2 ~func(R) S2, R, S1, S2, B any](
+	key func(B) func(S1) S2,
+	b B,
+) func(GS1) GS2 {
+	return F.LetTo(
+		Map[GS1, GS2, R, S1, S2],
+		key,
+		b,
+	)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[GS1 ~func(R) S1, GT ~func(R) T, R, S1, T any](
+	setter func(T) S1,
+) func(GT) GS1 {
+	return C.BindTo(
+		Map[GT, GS1, R, T, S1],
+		setter,
+	)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[GS1 ~func(R) S1, GS2 ~func(R) S2, GT ~func(R) T, R, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa GT,
+) func(GS1) GS2 {
+	return A.ApS(
+		Ap[GT, GS2, func(R) func(T) S2, R, T, S2],
+		Map[GS1, func(R) func(T) S2, R, S1, func(T) S2],
+		setter,
+		fa,
+	)
+}

readereither/bind.go

@@ -0,0 +1,66 @@
+// 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 readereither
+
+import (
+	G "github.com/IBM/fp-go/readereither/generic"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[R, E, S any](
+	empty S,
+) ReaderEither[R, E, S] {
+	return G.Do[ReaderEither[R, E, S], R, E, S](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[R, E, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) ReaderEither[R, E, T],
+) func(ReaderEither[R, E, S1]) ReaderEither[R, E, S2] {
+	return G.Bind[ReaderEither[R, E, S1], ReaderEither[R, E, S2], ReaderEither[R, E, T], R, E, S1, S2, T](setter, f)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[R, E, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) T,
+) func(ReaderEither[R, E, S1]) ReaderEither[R, E, S2] {
+	return G.Let[ReaderEither[R, E, S1], ReaderEither[R, E, S2], R, E, S1, S2, T](setter, f)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[R, E, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	b T,
+) func(ReaderEither[R, E, S1]) ReaderEither[R, E, S2] {
+	return G.LetTo[ReaderEither[R, E, S1], ReaderEither[R, E, S2], R, E, S1, S2, T](setter, b)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[R, E, S1, T any](
+	setter func(T) S1,
+) func(ReaderEither[R, E, T]) ReaderEither[R, E, S1] {
+	return G.BindTo[ReaderEither[R, E, S1], ReaderEither[R, E, T], R, E, S1, T](setter)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[R, E, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa ReaderEither[R, E, T],
+) func(ReaderEither[R, E, S1]) ReaderEither[R, E, S2] {
+	return G.ApS[ReaderEither[R, E, S1], ReaderEither[R, E, S2], ReaderEither[R, E, T], R, E, S1, S2, T](setter, fa)
+}

readereither/bind_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 readereither
+
+import (
+	"context"
+	"testing"
+
+	E "github.com/IBM/fp-go/either"
+	F "github.com/IBM/fp-go/function"
+	"github.com/IBM/fp-go/internal/utils"
+	"github.com/stretchr/testify/assert"
+)
+
+func getLastName(s utils.Initial) ReaderEither[context.Context, error, string] {
+	return Of[context.Context, error]("Doe")
+}
+
+func getGivenName(s utils.WithLastName) ReaderEither[context.Context, error, string] {
+	return Of[context.Context, error]("John")
+}
+
+func TestBind(t *testing.T) {
+
+	res := F.Pipe3(
+		Do[context.Context, error](utils.Empty),
+		Bind(utils.SetLastName, getLastName),
+		Bind(utils.SetGivenName, getGivenName),
+		Map[context.Context, error](utils.GetFullName),
+	)
+
+	assert.Equal(t, res(context.Background()), E.Of[error]("John Doe"))
+}
+
+func TestApS(t *testing.T) {
+
+	res := F.Pipe3(
+		Do[context.Context, error](utils.Empty),
+		ApS(utils.SetLastName, Of[context.Context, error]("Doe")),
+		ApS(utils.SetGivenName, Of[context.Context, error]("John")),
+		Map[context.Context, error](utils.GetFullName),
+	)
+
+	assert.Equal(t, res(context.Background()), E.Of[error]("John Doe"))
+}

readereither/generic/bind.go

@@ -0,0 +1,90 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package generic
+
+import (
+	ET "github.com/IBM/fp-go/either"
+	A "github.com/IBM/fp-go/internal/apply"
+	C "github.com/IBM/fp-go/internal/chain"
+	F "github.com/IBM/fp-go/internal/functor"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[GS ~func(R) ET.Either[E, S], R, E, S any](
+	empty S,
+) GS {
+	return Of[GS, E, R, S](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[GS1 ~func(R) ET.Either[E, S1], GS2 ~func(R) ET.Either[E, S2], GT ~func(R) ET.Either[E, T], R, E, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) GT,
+) func(GS1) GS2 {
+	return C.Bind(
+		Chain[GS1, GS2, E, R, S1, S2],
+		Map[GT, GS2, E, R, T, S2],
+		setter,
+		f,
+	)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[GS1 ~func(R) ET.Either[E, S1], GS2 ~func(R) ET.Either[E, S2], R, E, S1, S2, T any](
+	key func(T) func(S1) S2,
+	f func(S1) T,
+) func(GS1) GS2 {
+	return F.Let(
+		Map[GS1, GS2, E, R, S1, S2],
+		key,
+		f,
+	)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[GS1 ~func(R) ET.Either[E, S1], GS2 ~func(R) ET.Either[E, S2], R, E, S1, S2, B any](
+	key func(B) func(S1) S2,
+	b B,
+) func(GS1) GS2 {
+	return F.LetTo(
+		Map[GS1, GS2, E, R, S1, S2],
+		key,
+		b,
+	)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[GS1 ~func(R) ET.Either[E, S1], GT ~func(R) ET.Either[E, T], R, E, S1, T any](
+	setter func(T) S1,
+) func(GT) GS1 {
+	return C.BindTo(
+		Map[GT, GS1, E, R, T, S1],
+		setter,
+	)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[GS1 ~func(R) ET.Either[E, S1], GS2 ~func(R) ET.Either[E, S2], GT ~func(R) ET.Either[E, T], R, E, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa GT,
+) func(GS1) GS2 {
+	return A.ApS(
+		Ap[GT, GS2, func(R) ET.Either[E, func(T) S2], E, R, T, S2],
+		Map[GS1, func(R) ET.Either[E, func(T) S2], E, R, S1, func(T) S2],
+		setter,
+		fa,
+	)
+}

readereither/generic/reader.go

@@ -60,7 +60,7 @@ func MonadMap[GEA ~func(E) ET.Either[L, A], GEB ~func(E) ET.Either[L, B], L, E,
 }
 
 func Map[GEA ~func(E) ET.Either[L, A], GEB ~func(E) ET.Either[L, B], L, E, A, B any](f func(A) B) func(GEA) GEB {
-	return F.Bind2nd(MonadMap[GEA, GEB, L, E, A, B], f)
+	return readert.Map[GEA, GEB](ET.Map[L, A, B], f)
 }
 
 func MonadChain[GEA ~func(E) ET.Either[L, A], GEB ~func(E) ET.Either[L, B], L, E, A, B any](ma GEA, f func(A) GEB) GEB {

readerio/bind.go

@@ -0,0 +1,67 @@
+// 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 readerio
+
+import (
+	IO "github.com/IBM/fp-go/io"
+	G "github.com/IBM/fp-go/readerio/generic"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[R, S any](
+	empty S,
+) ReaderIO[R, S] {
+	return G.Do[ReaderIO[R, S], IO.IO[S], R, S](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[R, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) ReaderIO[R, T],
+) func(ReaderIO[R, S1]) ReaderIO[R, S2] {
+	return G.Bind[ReaderIO[R, S1], ReaderIO[R, S2], ReaderIO[R, T], IO.IO[S1], IO.IO[S2], IO.IO[T], R, S1, S2, T](setter, f)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[R, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) T,
+) func(ReaderIO[R, S1]) ReaderIO[R, S2] {
+	return G.Let[ReaderIO[R, S1], ReaderIO[R, S2], IO.IO[S1], IO.IO[S2], R, S1, S2, T](setter, f)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[R, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	b T,
+) func(ReaderIO[R, S1]) ReaderIO[R, S2] {
+	return G.LetTo[ReaderIO[R, S1], ReaderIO[R, S2], IO.IO[S1], IO.IO[S2], R, S1, S2, T](setter, b)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[R, S1, T any](
+	setter func(T) S1,
+) func(ReaderIO[R, T]) ReaderIO[R, S1] {
+	return G.BindTo[ReaderIO[R, S1], ReaderIO[R, T], IO.IO[S1], IO.IO[T], R, S1, T](setter)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[R, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa ReaderIO[R, T],
+) func(ReaderIO[R, S1]) ReaderIO[R, S2] {
+	return G.ApS[ReaderIO[R, func(T) S2], ReaderIO[R, S1], ReaderIO[R, S2], ReaderIO[R, T], IO.IO[func(T) S2], IO.IO[S1], IO.IO[S2], IO.IO[T], R, S1, S2, T](setter, fa)
+}

readerio/bind_test.go

@@ -0,0 +1,57 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package readerio
+
+import (
+	"context"
+	"testing"
+
+	F "github.com/IBM/fp-go/function"
+	"github.com/IBM/fp-go/internal/utils"
+	"github.com/stretchr/testify/assert"
+)
+
+func getLastName(s utils.Initial) ReaderIO[context.Context, string] {
+	return Of[context.Context]("Doe")
+}
+
+func getGivenName(s utils.WithLastName) ReaderIO[context.Context, string] {
+	return Of[context.Context]("John")
+}
+
+func TestBind(t *testing.T) {
+
+	res := F.Pipe3(
+		Do[context.Context](utils.Empty),
+		Bind(utils.SetLastName, getLastName),
+		Bind(utils.SetGivenName, getGivenName),
+		Map[context.Context](utils.GetFullName),
+	)
+
+	assert.Equal(t, res(context.Background())(), "John Doe")
+}
+
+func TestApS(t *testing.T) {
+
+	res := F.Pipe3(
+		Do[context.Context](utils.Empty),
+		ApS(utils.SetLastName, Of[context.Context]("Doe")),
+		ApS(utils.SetGivenName, Of[context.Context]("John")),
+		Map[context.Context](utils.GetFullName),
+	)
+
+	assert.Equal(t, res(context.Background())(), "John Doe")
+}

readerio/generic/bind.go

@@ -0,0 +1,89 @@
+// 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 (
+	A "github.com/IBM/fp-go/internal/apply"
+	C "github.com/IBM/fp-go/internal/chain"
+	F "github.com/IBM/fp-go/internal/functor"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[GRS ~func(R) GS, GS ~func() S, R, S any](
+	empty S,
+) GRS {
+	return Of[GRS, GS, R, S](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[GRS1 ~func(R) GS1, GRS2 ~func(R) GS2, GRT ~func(R) GT, GS1 ~func() S1, GS2 ~func() S2, GT ~func() T, R, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) GRT,
+) func(GRS1) GRS2 {
+	return C.Bind(
+		Chain[GRS1, GRS2, GS1, GS2, R, S1, S2],
+		Map[GRT, GRS2, GT, GS2, R, T, S2],
+		setter,
+		f,
+	)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[GRS1 ~func(R) GS1, GRS2 ~func(R) GS2, GS1 ~func() S1, GS2 ~func() S2, R, S1, S2, T any](
+	key func(T) func(S1) S2,
+	f func(S1) T,
+) func(GRS1) GRS2 {
+	return F.Let(
+		Map[GRS1, GRS2, GS1, GS2, R, S1, S2],
+		key,
+		f,
+	)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[GRS1 ~func(R) GS1, GRS2 ~func(R) GS2, GS1 ~func() S1, GS2 ~func() S2, R, S1, S2, B any](
+	key func(B) func(S1) S2,
+	b B,
+) func(GRS1) GRS2 {
+	return F.LetTo(
+		Map[GRS1, GRS2, GS1, GS2, R, S1, S2],
+		key,
+		b,
+	)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[GRS1 ~func(R) GS1, GRT ~func(R) GT, GS1 ~func() S1, GT ~func() T, R, S1, T any](
+	setter func(T) S1,
+) func(GRT) GRS1 {
+	return C.BindTo(
+		Map[GRT, GRS1, GT, GS1, R, T, S1],
+		setter,
+	)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[GRTS1 ~func(R) GTS1, GRS1 ~func(R) GS1, GRS2 ~func(R) GS2, GRT ~func(R) GT, GTS1 ~func() func(T) S2, GS1 ~func() S1, GS2 ~func() S2, GT ~func() T, R, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa GRT,
+) func(GRS1) GRS2 {
+	return A.ApS(
+		Ap[GRT, GRS2, GRTS1, GT, GS2, GTS1, R, T, S2],
+		Map[GRS1, GRTS1, GS1, GTS1, R, S1, func(T) S2],
+		setter,
+		fa,
+	)
+}

readerio/generic/reader.go

@@ -40,7 +40,7 @@ func MonadMap[GEA ~func(E) GIOA, GEB ~func(E) GIOB, GIOA ~func() A, GIOB ~func()
 }
 
 func Map[GEA ~func(E) GIOA, GEB ~func(E) GIOB, GIOA ~func() A, GIOB ~func() B, E, A, B any](f func(A) B) func(GEA) GEB {
-	return F.Bind2nd(MonadMap[GEA, GEB, GIOA, GIOB, E, A, B], f)
+	return readert.Map[GEA, GEB](IO.Map[GIOA, GIOB, A, B], f)
 }
 
 func MonadChain[GEA ~func(E) GIOA, GEB ~func(E) GIOB, GIOA ~func() A, GIOB ~func() B, E, A, B any](ma GEA, f func(A) GEB) GEB {
@@ -97,7 +97,7 @@ func MonadChainIOK[GEA ~func(E) GIOA, GEB ~func(E) GIOB, GIOA ~func() A, GIOB ~f
 
 func ChainIOK[GEA ~func(E) GIOA, GEB ~func(E) GIOB, GIOA ~func() A, GIOB ~func() B, E, A, B any](f func(A) GIOB) func(GEA) GEB {
 	return FIO.ChainIOK(
-		MonadChain[GEA, GEB],
+		Chain[GEA, GEB],
 		FromIO[GEB],
 		f,
 	)

readerioeither/bind.go

@@ -0,0 +1,67 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package readerioeither
+
+import (
+	IOE "github.com/IBM/fp-go/ioeither"
+	G "github.com/IBM/fp-go/readerioeither/generic"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[R, E, S any](
+	empty S,
+) ReaderIOEither[R, E, S] {
+	return G.Do[ReaderIOEither[R, E, S], IOE.IOEither[E, S], R, E, S](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[R, E, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) ReaderIOEither[R, E, T],
+) func(ReaderIOEither[R, E, S1]) ReaderIOEither[R, E, S2] {
+	return G.Bind[ReaderIOEither[R, E, S1], ReaderIOEither[R, E, S2], ReaderIOEither[R, E, T], IOE.IOEither[E, S1], IOE.IOEither[E, S2], IOE.IOEither[E, T], R, E, S1, S2, T](setter, f)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[R, E, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) T,
+) func(ReaderIOEither[R, E, S1]) ReaderIOEither[R, E, S2] {
+	return G.Let[ReaderIOEither[R, E, S1], ReaderIOEither[R, E, S2], IOE.IOEither[E, S1], IOE.IOEither[E, S2], R, E, S1, S2, T](setter, f)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[R, E, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	b T,
+) func(ReaderIOEither[R, E, S1]) ReaderIOEither[R, E, S2] {
+	return G.LetTo[ReaderIOEither[R, E, S1], ReaderIOEither[R, E, S2], IOE.IOEither[E, S1], IOE.IOEither[E, S2], R, E, S1, S2, T](setter, b)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[R, E, S1, T any](
+	setter func(T) S1,
+) func(ReaderIOEither[R, E, T]) ReaderIOEither[R, E, S1] {
+	return G.BindTo[ReaderIOEither[R, E, S1], ReaderIOEither[R, E, T], IOE.IOEither[E, S1], IOE.IOEither[E, T], R, E, S1, T](setter)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[R, E, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa ReaderIOEither[R, E, T],
+) func(ReaderIOEither[R, E, S1]) ReaderIOEither[R, E, S2] {
+	return G.ApS[ReaderIOEither[R, E, func(T) S2], ReaderIOEither[R, E, S1], ReaderIOEither[R, E, S2], ReaderIOEither[R, E, T], IOE.IOEither[E, func(T) S2], IOE.IOEither[E, S1], IOE.IOEither[E, S2], IOE.IOEither[E, T], R, E, S1, S2, T](setter, fa)
+}

readerioeither/bind_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 readerioeither
+
+import (
+	"context"
+	"testing"
+
+	E "github.com/IBM/fp-go/either"
+	F "github.com/IBM/fp-go/function"
+	"github.com/IBM/fp-go/internal/utils"
+	"github.com/stretchr/testify/assert"
+)
+
+func getLastName(s utils.Initial) ReaderIOEither[context.Context, error, string] {
+	return Of[context.Context, error]("Doe")
+}
+
+func getGivenName(s utils.WithLastName) ReaderIOEither[context.Context, error, string] {
+	return Of[context.Context, error]("John")
+}
+
+func TestBind(t *testing.T) {
+
+	res := F.Pipe3(
+		Do[context.Context, error](utils.Empty),
+		Bind(utils.SetLastName, getLastName),
+		Bind(utils.SetGivenName, getGivenName),
+		Map[context.Context, error](utils.GetFullName),
+	)
+
+	assert.Equal(t, res(context.Background())(), E.Of[error]("John Doe"))
+}
+
+func TestApS(t *testing.T) {
+
+	res := F.Pipe3(
+		Do[context.Context, error](utils.Empty),
+		ApS(utils.SetLastName, Of[context.Context, error]("Doe")),
+		ApS(utils.SetGivenName, Of[context.Context, error]("John")),
+		Map[context.Context, error](utils.GetFullName),
+	)
+
+	assert.Equal(t, res(context.Background())(), E.Of[error]("John Doe"))
+}

readerioeither/eq.go

@@ -26,7 +26,7 @@ func Eq[R, E, A any](eq EQ.Eq[ET.Either[E, A]]) func(R) EQ.Eq[ReaderIOEither[R,
 	return G.Eq[ReaderIOEither[R, E, A]](eq)
 }
 
-// FromStrictEquals constructs an `Eq` from the canonical comparison function
+// FromStrictEquals constructs an [EQ.Eq] from the canonical comparison function
 func FromStrictEquals[R, E, A comparable]() func(R) EQ.Eq[ReaderIOEither[R, E, A]] {
 	return G.FromStrictEquals[ReaderIOEither[R, E, A]]()
 }

readerioeither/generic/bind.go

@@ -0,0 +1,90 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package generic
+
+import (
+	ET "github.com/IBM/fp-go/either"
+	A "github.com/IBM/fp-go/internal/apply"
+	C "github.com/IBM/fp-go/internal/chain"
+	F "github.com/IBM/fp-go/internal/functor"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[GRS ~func(R) GS, GS ~func() ET.Either[E, S], R, E, S any](
+	empty S,
+) GRS {
+	return Of[GRS, GS, R, E, S](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[GRS1 ~func(R) GS1, GRS2 ~func(R) GS2, GRT ~func(R) GT, GS1 ~func() ET.Either[E, S1], GS2 ~func() ET.Either[E, S2], GT ~func() ET.Either[E, T], R, E, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) GRT,
+) func(GRS1) GRS2 {
+	return C.Bind(
+		Chain[GRS1, GRS2, GS1, GS2, R, E, S1, S2],
+		Map[GRT, GRS2, GT, GS2, R, E, T, S2],
+		setter,
+		f,
+	)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[GRS1 ~func(R) GS1, GRS2 ~func(R) GS2, GS1 ~func() ET.Either[E, S1], GS2 ~func() ET.Either[E, S2], R, E, S1, S2, T any](
+	key func(T) func(S1) S2,
+	f func(S1) T,
+) func(GRS1) GRS2 {
+	return F.Let(
+		Map[GRS1, GRS2, GS1, GS2, R, E, S1, S2],
+		key,
+		f,
+	)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[GRS1 ~func(R) GS1, GRS2 ~func(R) GS2, GS1 ~func() ET.Either[E, S1], GS2 ~func() ET.Either[E, S2], R, E, S1, S2, B any](
+	key func(B) func(S1) S2,
+	b B,
+) func(GRS1) GRS2 {
+	return F.LetTo(
+		Map[GRS1, GRS2, GS1, GS2, R, E, S1, S2],
+		key,
+		b,
+	)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[GRS1 ~func(R) GS1, GRT ~func(R) GT, GS1 ~func() ET.Either[E, S1], GT ~func() ET.Either[E, T], R, E, S1, T any](
+	setter func(T) S1,
+) func(GRT) GRS1 {
+	return C.BindTo(
+		Map[GRT, GRS1, GT, GS1, R, E, T, S1],
+		setter,
+	)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[GRTS1 ~func(R) GTS1, GRS1 ~func(R) GS1, GRS2 ~func(R) GS2, GRT ~func(R) GT, GTS1 ~func() ET.Either[E, func(T) S2], GS1 ~func() ET.Either[E, S1], GS2 ~func() ET.Either[E, S2], GT ~func() ET.Either[E, T], R, E, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa GRT,
+) func(GRS1) GRS2 {
+	return A.ApS(
+		Ap[GRT, GRS2, GRTS1, GT, GS2, GTS1, R, E, T, S2],
+		Map[GRS1, GRTS1, GS1, GTS1, R, E, S1, func(T) S2],
+		setter,
+		fa,
+	)
+}

readerioeither/generic/eq.go

@@ -26,7 +26,7 @@ func Eq[GEA ~func(R) GIOA, GIOA ~func() ET.Either[E, A], R, E, A any](eq EQ.Eq[E
 	return G.Eq[GEA](eq)
 }
 
-// FromStrictEquals constructs an `Eq` from the canonical comparison function
+// FromStrictEquals constructs an [EQ.Eq] from the canonical comparison function
 func FromStrictEquals[GEA ~func(R) GIOA, GIOA ~func() ET.Either[E, A], R any, E, A comparable]() func(R) EQ.Eq[GEA] {
 	return Eq[GEA](ET.FromStrictEquals[E, A]())
 }

record/bind.go

@@ -0,0 +1,57 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package record
+
+import (
+	Mo "github.com/IBM/fp-go/monoid"
+	G "github.com/IBM/fp-go/record/generic"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[K comparable, S any]() map[K]S {
+	return G.Do[map[K]S, K, S]()
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[S1, T any, K comparable, S2 any](m Mo.Monoid[map[K]S2]) func(setter func(T) func(S1) S2, f func(S1) map[K]T) func(map[K]S1) map[K]S2 {
+	return G.Bind[map[K]S1, map[K]S2, map[K]T, K, S1, S2, T](m)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[S1, T any, K comparable, S2 any](
+	setter func(T) func(S1) S2,
+	f func(S1) T,
+) func(map[K]S1) map[K]S2 {
+	return G.Let[map[K]S1, map[K]S2, K, S1, S2, T](setter, f)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[S1, T any, K comparable, S2 any](
+	setter func(T) func(S1) S2,
+	b T,
+) func(map[K]S1) map[K]S2 {
+	return G.LetTo[map[K]S1, map[K]S2, K, S1, S2, T](setter, b)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[S1, T any, K comparable](setter func(T) S1) func(map[K]T) map[K]S1 {
+	return G.BindTo[map[K]S1, map[K]T, K, S1, T](setter)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[S1, T any, K comparable, S2 any](m Mo.Monoid[map[K]S2]) func(setter func(T) func(S1) S2, fa map[K]T) func(map[K]S1) map[K]S2 {
+	return G.ApS[map[K]S1, map[K]S2, map[K]T, K, S1, S2, T](m)
+}

record/generic/bind.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 generic
+
+import (
+	A "github.com/IBM/fp-go/internal/apply"
+	C "github.com/IBM/fp-go/internal/chain"
+	F "github.com/IBM/fp-go/internal/functor"
+	Mo "github.com/IBM/fp-go/monoid"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[GS ~map[K]S, K comparable, S any]() GS {
+	return Empty[GS, K, S]()
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[GS1 ~map[K]S1, GS2 ~map[K]S2, GT ~map[K]T, K comparable, S1, S2, T any](m Mo.Monoid[GS2]) func(setter func(T) func(S1) S2, f func(S1) GT) func(GS1) GS2 {
+	c := Chain[GS1, GS2, K, S1, S2](m)
+	return func(setter func(T) func(S1) S2, f func(S1) GT) func(GS1) GS2 {
+		return C.Bind(
+			c,
+			Map[GT, GS2, K, T, S2],
+			setter,
+			f,
+		)
+	}
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[GS1 ~map[K]S1, GS2 ~map[K]S2, K comparable, S1, S2, T any](
+	key func(T) func(S1) S2,
+	f func(S1) T,
+) func(GS1) GS2 {
+	return F.Let(
+		Map[GS1, GS2, K, S1, S2],
+		key,
+		f,
+	)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[GS1 ~map[K]S1, GS2 ~map[K]S2, K comparable, S1, S2, B any](
+	key func(B) func(S1) S2,
+	b B,
+) func(GS1) GS2 {
+	return F.LetTo(
+		Map[GS1, GS2, K, S1, S2],
+		key,
+		b,
+	)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[GS1 ~map[K]S1, GT ~map[K]T, K comparable, S1, T any](setter func(T) S1) func(GT) GS1 {
+	return C.BindTo(
+		Map[GT, GS1, K, T, S1],
+		setter,
+	)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[GS1 ~map[K]S1, GS2 ~map[K]S2, GT ~map[K]T, K comparable, S1, S2, T any](m Mo.Monoid[GS2]) func(setter func(T) func(S1) S2, fa GT) func(GS1) GS2 {
+	a := Ap[GS2, map[K]func(T) S2, GT, K, S2, T](m)
+	return func(setter func(T) func(S1) S2, fa GT) func(GS1) GS2 {
+		return A.ApS(
+			a,
+			Map[GS1, map[K]func(T) S2, K, S1, func(T) S2],
+			setter,
+			fa,
+		)
+	}
+}

record/generic/record.go

@@ -132,6 +132,18 @@ func ReduceRefWithIndex[M ~map[K]V, K comparable, V, R any](f func(K, R, *V) R,
 	}
 }
 
+func MonadAp[BS ~map[K]B, ABS ~map[K]func(A) B, AS ~map[K]A, K comparable, B, A any](m Mo.Monoid[BS], fab ABS, fa AS) BS {
+	return MonadChain(m, fab, F.Bind1st(MonadMap[AS, BS, K, A, B], fa))
+}
+
+func Ap[BS ~map[K]B, ABS ~map[K]func(A) B, AS ~map[K]A, K comparable, B, A any](m Mo.Monoid[BS]) func(fa AS) func(ABS) BS {
+	return func(ma AS) func(ABS) BS {
+		return func(abs ABS) BS {
+			return MonadAp(m, abs, ma)
+		}
+	}
+}
+
 func MonadMap[M ~map[K]V, N ~map[K]R, K comparable, V, R any](r M, f func(V) R) N {
 	return MonadMapWithIndex[M, N](r, F.Ignore1of2[K](f))
 }

record/record.go

@@ -333,3 +333,11 @@ func FromArray[
 	V any](m Mg.Magma[V]) func(fa []T.Tuple2[K, V]) map[K]V {
 	return G.FromArray[[]T.Tuple2[K, V], map[K]V](m)
 }
+
+func MonadAp[A any, K comparable, B any](m Mo.Monoid[map[K]B], fab map[K]func(A) B, fa map[K]A) map[K]B {
+	return G.MonadAp[map[K]B, map[K]func(A) B, map[K]A](m, fab, fa)
+}
+
+func Ap[A any, K comparable, B any](m Mo.Monoid[map[K]B]) func(fa map[K]A) func(map[K]func(A) B) map[K]B {
+	return G.Ap[map[K]B, map[K]func(A) B, map[K]A](m)
+}

writer/bind.go

@@ -0,0 +1,66 @@
+// 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 writer
+
+import (
+	M "github.com/IBM/fp-go/monoid"
+	S "github.com/IBM/fp-go/semigroup"
+	G "github.com/IBM/fp-go/writer/generic"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[S, W any](m M.Monoid[W]) func(S) Writer[W, S] {
+	return G.Do[Writer[W, S], W, S](m)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[S1, S2, T, W any](s S.Semigroup[W]) func(
+	setter func(T) func(S1) S2,
+	f func(S1) Writer[W, T],
+) func(Writer[W, S1]) Writer[W, S2] {
+	return G.Bind[Writer[W, S1], Writer[W, S2], Writer[W, T], W, S1, S2, T](s)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[W, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) T,
+) func(Writer[W, S1]) Writer[W, S2] {
+	return G.Let[Writer[W, S1], Writer[W, S2], W, S1, S2, T](setter, f)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[W, S1, S2, T any](
+	setter func(T) func(S1) S2,
+	b T,
+) func(Writer[W, S1]) Writer[W, S2] {
+	return G.LetTo[Writer[W, S1], Writer[W, S2], W, S1, S2, T](setter, b)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[W, S1, T any](
+	setter func(T) S1,
+) func(Writer[W, T]) Writer[W, S1] {
+	return G.BindTo[Writer[W, S1], Writer[W, T], W, S1, T](setter)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[S1, S2, T, W any](s S.Semigroup[W]) func(
+	setter func(T) func(S1) S2,
+	fa Writer[W, T],
+) func(Writer[W, S1]) Writer[W, S2] {
+	return G.ApS[Writer[W, S1], Writer[W, S2], Writer[W, T], W, S1, S2, T](s)
+}

writer/bind_test.go

@@ -0,0 +1,63 @@
+// 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 writer
+
+import (
+	"testing"
+
+	A "github.com/IBM/fp-go/array"
+	F "github.com/IBM/fp-go/function"
+	"github.com/IBM/fp-go/internal/utils"
+	M "github.com/IBM/fp-go/monoid"
+	"github.com/stretchr/testify/assert"
+)
+
+var (
+	monoid = A.Monoid[string]()
+	sg     = M.ToSemigroup(monoid)
+)
+
+func getLastName(s utils.Initial) Writer[[]string, string] {
+	return Of[string](monoid)("Doe")
+}
+
+func getGivenName(s utils.WithLastName) Writer[[]string, string] {
+	return Of[string](monoid)("John")
+}
+
+func TestBind(t *testing.T) {
+
+	res := F.Pipe3(
+		Do[utils.Initial](monoid)(utils.Empty),
+		Bind[utils.Initial, utils.WithLastName, string](sg)(utils.SetLastName, getLastName),
+		Bind[utils.WithLastName, utils.WithGivenName, string](sg)(utils.SetGivenName, getGivenName),
+		Map[[]string](utils.GetFullName),
+	)
+
+	assert.Equal(t, res(), Of[string](monoid)("John Doe")())
+}
+
+func TestApS(t *testing.T) {
+
+	res := F.Pipe3(
+		Do[utils.Initial](monoid)(utils.Empty),
+		ApS[utils.Initial, utils.WithLastName, string](sg)(utils.SetLastName, Of[string](monoid)("Doe")),
+		ApS[utils.WithLastName, utils.WithGivenName, string](sg)(utils.SetGivenName, Of[string](monoid)("John")),
+		Map[[]string](utils.GetFullName),
+	)
+
+	assert.Equal(t, res(), Of[string](monoid)("John Doe")())
+}

writer/eq.go

@@ -25,7 +25,7 @@ func Eq[W, A any](w EQ.Eq[W], a EQ.Eq[A]) EQ.Eq[Writer[W, A]] {
 	return G.Eq[Writer[W, A]](w, a)
 }
 
-// FromStrictEquals constructs an `Eq` from the canonical comparison function
+// FromStrictEquals constructs an [EQ.Eq] from the canonical comparison function
 func FromStrictEquals[W, A comparable]() EQ.Eq[Writer[W, A]] {
 	return G.FromStrictEquals[Writer[W, A]]()
 }

writer/generic/bind.go

@@ -0,0 +1,102 @@
+// 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 (
+	"github.com/IBM/fp-go/internal/apply"
+	C "github.com/IBM/fp-go/internal/chain"
+	F "github.com/IBM/fp-go/internal/functor"
+	M "github.com/IBM/fp-go/monoid"
+	S "github.com/IBM/fp-go/semigroup"
+	T "github.com/IBM/fp-go/tuple"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[GS ~func() T.Tuple2[S, W], W, S any](m M.Monoid[W]) func(S) GS {
+	return Of[GS, W, S](m)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[GS1 ~func() T.Tuple2[S1, W], GS2 ~func() T.Tuple2[S2, W], GT ~func() T.Tuple2[A, W], W, S1, S2, A any](s S.Semigroup[W]) func(
+	setter func(A) func(S1) S2,
+	f func(S1) GT,
+) func(GS1) GS2 {
+	ch := Chain[GS2, GS1, func(S1) GS2, W, S1, S2](s)
+	return func(
+		setter func(A) func(S1) S2,
+		f func(S1) GT,
+	) func(GS1) GS2 {
+		return C.Bind(
+			ch,
+			Map[GS2, GT, func(A) S2, W, A, S2],
+			setter,
+			f,
+		)
+	}
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[GS1 ~func() T.Tuple2[S1, W], GS2 ~func() T.Tuple2[S2, W], W, S1, S2, A any](
+	key func(A) func(S1) S2,
+	f func(S1) A,
+) func(GS1) GS2 {
+	return F.Let(
+		Map[GS2, GS1, func(S1) S2, W, S1, S2],
+		key,
+		f,
+	)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[GS1 ~func() T.Tuple2[S1, W], GS2 ~func() T.Tuple2[S2, W], W, S1, S2, B any](
+	key func(B) func(S1) S2,
+	b B,
+) func(GS1) GS2 {
+	return F.LetTo(
+		Map[GS2, GS1, func(S1) S2, W, S1, S2],
+		key,
+		b,
+	)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[GS1 ~func() T.Tuple2[S1, W], GT ~func() T.Tuple2[A, W], W, S1, A any](
+	setter func(A) S1,
+) func(GT) GS1 {
+	return C.BindTo(
+		Map[GS1, GT, func(A) S1, W, A, S1],
+		setter,
+	)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[GS1 ~func() T.Tuple2[S1, W], GS2 ~func() T.Tuple2[S2, W], GT ~func() T.Tuple2[A, W], W, S1, S2, A any](s S.Semigroup[W]) func(
+	setter func(A) func(S1) S2,
+	fa GT,
+) func(GS1) GS2 {
+	ap := Ap[GS2, func() T.Tuple2[func(A) S2, W], GT, W, A, S2](s)
+	return func(
+		setter func(A) func(S1) S2,
+		fa GT,
+	) func(GS1) GS2 {
+		return apply.ApS(
+			ap,
+			Map[func() T.Tuple2[func(A) S2, W], GS1, func(S1) func(A) S2],
+			setter,
+			fa,
+		)
+	}
+}

writer/generic/eq.go

@@ -30,7 +30,7 @@ func Eq[GA ~func() T.Tuple2[A, W], W, A any](w EQ.Eq[W], a EQ.Eq[A]) EQ.Eq[GA] {
 	})
 }
 
-// FromStrictEquals constructs an `Eq` from the canonical comparison function
+// FromStrictEquals constructs an [EQ.Eq] from the canonical comparison function
 func FromStrictEquals[GA ~func() T.Tuple2[A, W], W, A comparable]() EQ.Eq[GA] {
 	return Eq[GA](EQ.FromStrictEquals[W](), EQ.FromStrictEquals[A]())
 }

writer/generic/writer.go

@@ -30,6 +30,22 @@ func Of[GA ~func() T.Tuple2[A, W], W, A any](m M.Monoid[W]) func(A) GA {
 	)
 }
 
+// Listen modifies the result to include the changes to the accumulator
+func Listen[GA ~func() T.Tuple2[A, W], GTA ~func() T.Tuple2[T.Tuple2[A, W], W], W, A any](fa GA) GTA {
+	return func() T.Tuple2[T.Tuple2[A, W], W] {
+		t := fa()
+		return T.MakeTuple2(T.MakeTuple2(t.F1, t.F2), t.F2)
+	}
+}
+
+// Pass applies the returned function to the accumulator
+func Pass[GFA ~func() T.Tuple2[T.Tuple2[A, FCT], W], GA ~func() T.Tuple2[A, W], FCT ~func(W) W, W, A any](fa GFA) GA {
+	return func() T.Tuple2[A, W] {
+		t := fa()
+		return T.MakeTuple2(t.F1.F1, t.F1.F2(t.F2))
+	}
+}
+
 func MonadMap[GB ~func() T.Tuple2[B, W], GA ~func() T.Tuple2[A, W], FCT ~func(A) B, W, A, B any](fa GA, f FCT) GB {
 	return IO.MonadMap[GA, GB](fa, T.Map2(f, F.Identity[W]))
 }

writer/writer.go

@@ -16,23 +16,35 @@
 package writer
 
 import (
+	EM "github.com/IBM/fp-go/endomorphism"
+	IO "github.com/IBM/fp-go/io"
 	M "github.com/IBM/fp-go/monoid"
 	S "github.com/IBM/fp-go/semigroup"
 	T "github.com/IBM/fp-go/tuple"
 	G "github.com/IBM/fp-go/writer/generic"
 )
 
-type Writer[W, A any] func() T.Tuple2[A, W]
+type Writer[W, A any] IO.IO[T.Tuple2[A, W]]
 
 func Of[A, W any](m M.Monoid[W]) func(A) Writer[W, A] {
 	return G.Of[Writer[W, A]](m)
 }
 
+// Listen modifies the result to include the changes to the accumulator
+func Listen[W, A any](fa Writer[W, A]) Writer[W, T.Tuple2[A, W]] {
+	return G.Listen[Writer[W, A], Writer[W, T.Tuple2[A, W]], W, A](fa)
+}
+
+// Pass applies the returned function to the accumulator
+func Pass[W, A any](fa Writer[W, T.Tuple2[A, EM.Endomorphism[W]]]) Writer[W, A] {
+	return G.Pass[Writer[W, T.Tuple2[A, EM.Endomorphism[W]]], Writer[W, A]](fa)
+}
+
 func MonadMap[FCT ~func(A) B, W, A, B any](fa Writer[W, A], f FCT) Writer[W, B] {
 	return G.MonadMap[Writer[W, B], Writer[W, A]](fa, f)
 }
 
-func Map[FCT ~func(A) B, W, A, B any](f FCT) func(Writer[W, A]) Writer[W, B] {
+func Map[W any, FCT ~func(A) B, A, B any](f FCT) func(Writer[W, A]) Writer[W, B] {
 	return G.Map[Writer[W, B], Writer[W, A]](f)
 }
 
@@ -64,10 +76,12 @@ func Flatten[W, A any](s S.Semigroup[W]) func(Writer[W, Writer[W, A]]) Writer[W,
 	return G.Flatten[Writer[W, Writer[W, A]], Writer[W, A]](s)
 }
 
+// Execute extracts the accumulator
 func Execute[W, A any](fa Writer[W, A]) W {
 	return G.Execute(fa)
 }
 
+// Evaluate extracts the value
 func Evaluate[W, A any](fa Writer[W, A]) A {
 	return G.Evaluate(fa)
 }

writer/writer_test.go

@@ -46,5 +46,4 @@ func ExampleWriter_logging() {
 	fmt.Println(res())
 
 	// Output: Tuple2[int, []string](40, [Doubled 10 -> 20 Doubled 20 -> 40])
-
 }