fix: add conversions for StateReaderIOEither

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

context/readerioeither/http/request.go

@@ -26,7 +26,7 @@ import (
 	IOE "github.com/IBM/fp-go/ioeither"
 	IOEF "github.com/IBM/fp-go/ioeither/file"
 	J "github.com/IBM/fp-go/json"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
 type (
@@ -79,7 +79,7 @@ func ReadFullResponse(client Client) func(Requester) RIOE.ReaderIOEither[H.FullR
 						IOE.Of[error, io.ReadCloser],
 						IOEF.ReadAll[io.ReadCloser],
 					),
-					IOE.Map[error](F.Bind1st(T.MakeTuple2[*http.Response, []byte], resp)),
+					IOE.Map[error](F.Bind1st(P.MakePair[*http.Response, []byte], resp)),
 				)
 			}),
 		)

exec/exec.go

@@ -16,18 +16,18 @@
 package exec
 
 import (
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
 type (
 	// CommandOutput represents the output of executing a command. The first field in the [Tuple2] is
 	// stdout, the second one is stderr. Use [StdOut] and [StdErr] to access these fields
-	CommandOutput = T.Tuple2[[]byte, []byte]
+	CommandOutput = P.Pair[[]byte, []byte]
 )
 
 var (
 	// StdOut returns the field of a [CommandOutput] representing `stdout`
-	StdOut = T.First[[]byte, []byte]
+	StdOut = P.Head[[]byte, []byte]
 	// StdErr returns the field of a [CommandOutput] representing `stderr`
-	StdErr = T.Second[[]byte, []byte]
+	StdErr = P.Tail[[]byte, []byte]
 )

http/types.go

@@ -18,15 +18,15 @@ package http
 import (
 	H "net/http"
 
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
 type (
 	// FullResponse represents a full http response, including headers and body
-	FullResponse = T.Tuple2[*H.Response, []byte]
+	FullResponse = P.Pair[*H.Response, []byte]
 )
 
 var (
-	Response = T.First[*H.Response, []byte]
-	Body     = T.Second[*H.Response, []byte]
+	Response = P.Head[*H.Response, []byte]
+	Body     = P.Tail[*H.Response, []byte]
 )

http/utils.go

@@ -28,12 +28,12 @@ import (
 	"github.com/IBM/fp-go/errors"
 	F "github.com/IBM/fp-go/function"
 	O "github.com/IBM/fp-go/option"
+	P "github.com/IBM/fp-go/pair"
 	R "github.com/IBM/fp-go/record/generic"
-	T "github.com/IBM/fp-go/tuple"
 )
 
 type (
-	ParsedMediaType = T.Tuple2[string, map[string]string]
+	ParsedMediaType = P.Pair[string, map[string]string]
 
 	HttpError struct {
 		statusCode int
@@ -45,17 +45,15 @@ type (
 
 var (
 	// mime type to check if a media type matches
-	reJSONMimeType = regexp.MustCompile(`application/(?:\w+\+)?json`)
+	isJSONMimeType = regexp.MustCompile(`application/(?:\w+\+)?json`).MatchString
 	// ValidateResponse validates an HTTP response and returns an [E.Either] if the response is not a success
 	ValidateResponse = E.FromPredicate(isValidStatus, StatusCodeError)
 	// alidateJsonContentTypeString parses a content type a validates that it is valid JSON
 	validateJSONContentTypeString = F.Flow2(
 		ParseMediaType,
 		E.ChainFirst(F.Flow2(
-			T.First[string, map[string]string],
-			E.FromPredicate(reJSONMimeType.MatchString, func(mimeType string) error {
-				return fmt.Errorf("mimetype [%s] is not a valid JSON content type", mimeType)
-			}),
+			P.Head[string, map[string]string],
+			E.FromPredicate(isJSONMimeType, errors.OnSome[string]("mimetype [%s] is not a valid JSON content type")),
 		)),
 	)
 	// ValidateJSONResponse checks if an HTTP response is a valid JSON response
@@ -81,7 +79,7 @@ const (
 // ParseMediaType parses a media type into a tuple
 func ParseMediaType(mediaType string) E.Either[error, ParsedMediaType] {
 	m, p, err := mime.ParseMediaType(mediaType)
-	return E.TryCatchError(T.MakeTuple2(m, p), err)
+	return E.TryCatchError(P.MakePair(m, p), err)
 }
 
 // Error fulfills the error interface

internal/exec/exec.go

@@ -23,7 +23,7 @@ import (
 
 	EX "github.com/IBM/fp-go/exec"
 
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
 func Exec(ctx context.Context, name string, args []string, in []byte) (EX.CommandOutput, error) {
@@ -42,5 +42,5 @@ func Exec(ctx context.Context, name string, args []string, in []byte) (EX.Comman
 		err = fmt.Errorf("command execution of [%s][%s] failed, stdout [%s], stderr [%s], cause [%w]", name, args, stdOut.String(), stdErr.String(), err)
 	}
 	// return the outputs
-	return T.MakeTuple2(stdOut.Bytes(), stdErr.Bytes()), err
+	return P.MakePair(stdOut.Bytes(), stdErr.Bytes()), err
 }

internal/statet/state.go

@@ -0,0 +1,198 @@
+// Copyright (c) 2024 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 state
+
+import (
+	F "github.com/IBM/fp-go/function"
+	P "github.com/IBM/fp-go/pair"
+)
+
+func Of[
+	HKTSA ~func(S) HKTA,
+	HKTA,
+	S, A any,
+](
+	fof func(P.Pair[A, S]) HKTA,
+
+	a A) HKTSA {
+
+	return F.Flow2(
+		F.Bind1st(P.MakePair[A, S], a),
+		fof,
+	)
+}
+
+func MonadMap[
+	HKTSA ~func(S) HKTA,
+	HKTSB ~func(S) HKTB,
+	HKTA,
+	HKTB,
+	S, A, B any,
+](
+	fmap func(HKTA, func(P.Pair[A, S]) P.Pair[B, S]) HKTB,
+
+	fa HKTSA,
+	f func(A) B,
+) HKTSB {
+
+	return F.Flow2(
+		fa,
+		F.Bind2nd(fmap, P.Map[S](f)),
+	)
+}
+
+func Map[
+	HKTSA ~func(S) HKTA,
+	HKTSB ~func(S) HKTB,
+	HKTA,
+	HKTB,
+	S, A, B any,
+](
+	fmap func(func(P.Pair[A, S]) P.Pair[B, S]) func(HKTA) HKTB,
+
+	f func(A) B,
+) func(HKTSA) HKTSB {
+	mp := fmap(P.Map[S](f))
+
+	return func(fa HKTSA) HKTSB {
+		return F.Flow2(
+			fa,
+			mp,
+		)
+	}
+}
+
+func MonadChain[
+	HKTSA ~func(S) HKTA,
+	HKTSB ~func(S) HKTB,
+	HKTA,
+	HKTB,
+	S, A any,
+](
+	fchain func(HKTA, func(P.Pair[A, S]) HKTB) HKTB,
+
+	fa HKTSA,
+	f func(A) HKTSB,
+) HKTSB {
+	return F.Flow2(
+		fa,
+		F.Bind2nd(fchain, func(a P.Pair[A, S]) HKTB {
+			return f(P.Head(a))(P.Tail(a))
+		}),
+	)
+}
+
+func Chain[
+	HKTSA ~func(S) HKTA,
+	HKTSB ~func(S) HKTB,
+	HKTA,
+	HKTB,
+	S, A any,
+](
+	fchain func(func(P.Pair[A, S]) HKTB) func(HKTA) HKTB,
+
+	f func(A) HKTSB,
+) func(HKTSA) HKTSB {
+	mp := fchain(func(a P.Pair[A, S]) HKTB {
+		return f(P.Head(a))(P.Tail(a))
+	})
+
+	return func(fa HKTSA) HKTSB {
+		return F.Flow2(
+			fa,
+			mp,
+		)
+	}
+}
+
+func MonadAp[
+	HKTSA ~func(S) HKTA,
+	HKTSB ~func(S) HKTB,
+	HKTSAB ~func(S) HKTAB,
+	HKTA,
+	HKTB,
+	HKTAB,
+
+	S, A, B any,
+](
+	fmap func(HKTA, func(P.Pair[A, S]) P.Pair[B, S]) HKTB,
+	fchain func(HKTAB, func(P.Pair[func(A) B, S]) HKTB) HKTB,
+
+	fab HKTSAB,
+	fa HKTSA,
+) HKTSB {
+	return func(s S) HKTB {
+		return fchain(fab(s), func(ab P.Pair[func(A) B, S]) HKTB {
+			return fmap(fa(P.Tail(ab)), P.Map[S](P.Head(ab)))
+		})
+	}
+}
+
+func Ap[
+	HKTSA ~func(S) HKTA,
+	HKTSB ~func(S) HKTB,
+	HKTSAB ~func(S) HKTAB,
+	HKTA,
+	HKTB,
+	HKTAB,
+
+	S, A, B any,
+](
+	fmap func(func(P.Pair[A, S]) P.Pair[B, S]) func(HKTA) HKTB,
+	fchain func(func(P.Pair[func(A) B, S]) HKTB) func(HKTAB) HKTB,
+
+	fa HKTSA,
+) func(HKTSAB) HKTSB {
+	return func(fab HKTSAB) HKTSB {
+		return F.Flow2(
+			fab,
+			fchain(func(ab P.Pair[func(A) B, S]) HKTB {
+				return fmap(P.Map[S](P.Head(ab)))(fa(P.Tail(ab)))
+			}),
+		)
+	}
+}
+
+func FromF[
+	HKTSA ~func(S) HKTA,
+	HKTA,
+
+	HKTFA,
+
+	S, A any,
+](
+	fmap func(HKTFA, func(A) P.Pair[A, S]) HKTA,
+	ma HKTFA) HKTSA {
+
+	f1 := F.Bind1st(fmap, ma)
+
+	return func(s S) HKTA {
+		return f1(F.Bind2nd(P.MakePair[A, S], s))
+	}
+}
+
+func FromState[
+	HKTSA ~func(S) HKTA,
+	ST ~func(S) P.Pair[A, S],
+	HKTA,
+
+	S, A any,
+](
+	fof func(P.Pair[A, S]) HKTA,
+	sa ST,
+) HKTSA {
+	return F.Flow2(sa, fof)
+}

io/generic/ap.go

@@ -27,16 +27,11 @@ const (
 
 // MonadApSeq implements the applicative on a single thread by first executing mab and the ma
 func MonadApSeq[GA ~func() A, GB ~func() B, GAB ~func() func(A) B, A, B any](mab GAB, ma GA) GB {
-	return MakeIO[GB](func() B {
-		return F.Pipe1(
-			ma(),
-			mab(),
-		)
-	})
+	return MonadChain(mab, F.Bind1st(MonadMap[GA, GB], ma))
 }
 
 // MonadApPar implements the applicative on two threads, the main thread executes mab and the actuall
-// apply operation and the second thred computes ma. Communication between the threads happens via a channel
+// apply operation and the second thread computes ma. Communication between the threads happens via a channel
 func MonadApPar[GA ~func() A, GB ~func() B, GAB ~func() func(A) B, A, B any](mab GAB, ma GA) GB {
 	return MakeIO[GB](func() B {
 		c := make(chan A)

io/generic/traverse.go

@@ -32,6 +32,28 @@ func MonadTraverseArray[GB ~func() B, GBS ~func() BBS, AAS ~[]A, BBS ~[]B, A, B
 	)
 }
 
+func MonadTraverseArraySeq[GB ~func() B, GBS ~func() BBS, AAS ~[]A, BBS ~[]B, A, B any](tas AAS, f func(A) GB) GBS {
+	return RA.MonadTraverse(
+		Of[GBS, BBS],
+		Map[GBS, func() func(B) BBS, BBS, func(B) BBS],
+		ApSeq[GBS, func() func(B) BBS, GB],
+
+		tas,
+		f,
+	)
+}
+
+func MonadTraverseArrayPar[GB ~func() B, GBS ~func() BBS, AAS ~[]A, BBS ~[]B, A, B any](tas AAS, f func(A) GB) GBS {
+	return RA.MonadTraverse(
+		Of[GBS, BBS],
+		Map[GBS, func() func(B) BBS, BBS, func(B) BBS],
+		ApPar[GBS, func() func(B) BBS, GB],
+
+		tas,
+		f,
+	)
+}
+
 func TraverseArray[GB ~func() B, GBS ~func() BBS, AAS ~[]A, BBS ~[]B, A, B any](f func(A) GB) func(AAS) GBS {
 	return RA.Traverse[AAS](
 		Of[GBS, BBS],
@@ -42,6 +64,26 @@ func TraverseArray[GB ~func() B, GBS ~func() BBS, AAS ~[]A, BBS ~[]B, A, B any](
 	)
 }
 
+func TraverseArraySeq[GB ~func() B, GBS ~func() BBS, AAS ~[]A, BBS ~[]B, A, B any](f func(A) GB) func(AAS) GBS {
+	return RA.Traverse[AAS](
+		Of[GBS, BBS],
+		Map[GBS, func() func(B) BBS, BBS, func(B) BBS],
+		ApSeq[GBS, func() func(B) BBS, GB],
+
+		f,
+	)
+}
+
+func TraverseArrayPar[GB ~func() B, GBS ~func() BBS, AAS ~[]A, BBS ~[]B, A, B any](f func(A) GB) func(AAS) GBS {
+	return RA.Traverse[AAS](
+		Of[GBS, BBS],
+		Map[GBS, func() func(B) BBS, BBS, func(B) BBS],
+		ApPar[GBS, func() func(B) BBS, GB],
+
+		f,
+	)
+}
+
 func TraverseArrayWithIndex[GB ~func() B, GBS ~func() BBS, AAS ~[]A, BBS ~[]B, A, B any](f func(int, A) GB) func(AAS) GBS {
 	return RA.TraverseWithIndex[AAS](
 		Of[GBS, BBS],
@@ -52,10 +94,38 @@ func TraverseArrayWithIndex[GB ~func() B, GBS ~func() BBS, AAS ~[]A, BBS ~[]B, A
 	)
 }
 
+func TraverseArrayWithIndexSeq[GB ~func() B, GBS ~func() BBS, AAS ~[]A, BBS ~[]B, A, B any](f func(int, A) GB) func(AAS) GBS {
+	return RA.TraverseWithIndex[AAS](
+		Of[GBS, BBS],
+		Map[GBS, func() func(B) BBS, BBS, func(B) BBS],
+		ApSeq[GBS, func() func(B) BBS, GB],
+
+		f,
+	)
+}
+
+func TraverseArrayWithIndexPar[GB ~func() B, GBS ~func() BBS, AAS ~[]A, BBS ~[]B, A, B any](f func(int, A) GB) func(AAS) GBS {
+	return RA.TraverseWithIndex[AAS](
+		Of[GBS, BBS],
+		Map[GBS, func() func(B) BBS, BBS, func(B) BBS],
+		ApPar[GBS, func() func(B) BBS, GB],
+
+		f,
+	)
+}
+
 func SequenceArray[GA ~func() A, GAS ~func() AAS, AAS ~[]A, GAAS ~[]GA, A any](tas GAAS) GAS {
 	return MonadTraverseArray[GA, GAS](tas, F.Identity[GA])
 }
 
+func SequenceArraySeq[GA ~func() A, GAS ~func() AAS, AAS ~[]A, GAAS ~[]GA, A any](tas GAAS) GAS {
+	return MonadTraverseArraySeq[GA, GAS](tas, F.Identity[GA])
+}
+
+func SequenceArrayPar[GA ~func() A, GAS ~func() AAS, AAS ~[]A, GAAS ~[]GA, A any](tas GAAS) GAS {
+	return MonadTraverseArrayPar[GA, GAS](tas, F.Identity[GA])
+}
+
 // MonadTraverseRecord transforms a record using an IO transform an IO of a record
 func MonadTraverseRecord[GBS ~func() MB, MA ~map[K]A, GB ~func() B, MB ~map[K]B, K comparable, A, B any](ma MA, f func(A) GB) GBS {
 	return RR.MonadTraverse[MA](
@@ -89,3 +159,71 @@ func TraverseRecordWithIndex[GB ~func() B, GBS ~func() MB, MA ~map[K]A, MB ~map[
 func SequenceRecord[GA ~func() A, GAS ~func() AAS, AAS ~map[K]A, GAAS ~map[K]GA, K comparable, A any](tas GAAS) GAS {
 	return MonadTraverseRecord[GAS](tas, F.Identity[GA])
 }
+
+// MonadTraverseRecordSeq transforms a record using an IO transform an IO of a record
+func MonadTraverseRecordSeq[GBS ~func() MB, MA ~map[K]A, GB ~func() B, MB ~map[K]B, K comparable, A, B any](ma MA, f func(A) GB) GBS {
+	return RR.MonadTraverse[MA](
+		Of[GBS, MB],
+		Map[GBS, func() func(B) MB, MB, func(B) MB],
+		ApSeq[GBS, func() func(B) MB, GB],
+		ma, f,
+	)
+}
+
+// TraverseRecordSeq transforms a record using an IO transform an IO of a record
+func TraverseRecordSeq[GBS ~func() MB, MA ~map[K]A, GB ~func() B, MB ~map[K]B, K comparable, A, B any](f func(A) GB) func(MA) GBS {
+	return RR.Traverse[MA](
+		Of[GBS, MB],
+		Map[GBS, func() func(B) MB, MB, func(B) MB],
+		ApSeq[GBS, func() func(B) MB, GB],
+		f,
+	)
+}
+
+// TraverseRecordWithIndexSeq transforms a record using an IO transform an IO of a record
+func TraverseRecordWithIndexSeq[GB ~func() B, GBS ~func() MB, MA ~map[K]A, MB ~map[K]B, K comparable, A, B any](f func(K, A) GB) func(MA) GBS {
+	return RR.TraverseWithIndex[MA](
+		Of[GBS, MB],
+		Map[GBS, func() func(B) MB, MB, func(B) MB],
+		ApSeq[GBS, func() func(B) MB, GB],
+		f,
+	)
+}
+
+func SequenceRecordSeq[GA ~func() A, GAS ~func() AAS, AAS ~map[K]A, GAAS ~map[K]GA, K comparable, A any](tas GAAS) GAS {
+	return MonadTraverseRecordSeq[GAS](tas, F.Identity[GA])
+}
+
+// MonadTraverseRecordPar transforms a record using an IO transform an IO of a record
+func MonadTraverseRecordPar[GBS ~func() MB, MA ~map[K]A, GB ~func() B, MB ~map[K]B, K comparable, A, B any](ma MA, f func(A) GB) GBS {
+	return RR.MonadTraverse[MA](
+		Of[GBS, MB],
+		Map[GBS, func() func(B) MB, MB, func(B) MB],
+		ApPar[GBS, func() func(B) MB, GB],
+		ma, f,
+	)
+}
+
+// TraverseRecordPar transforms a record using an IO transform an IO of a record
+func TraverseRecordPar[GBS ~func() MB, MA ~map[K]A, GB ~func() B, MB ~map[K]B, K comparable, A, B any](f func(A) GB) func(MA) GBS {
+	return RR.Traverse[MA](
+		Of[GBS, MB],
+		Map[GBS, func() func(B) MB, MB, func(B) MB],
+		ApPar[GBS, func() func(B) MB, GB],
+		f,
+	)
+}
+
+// TraverseRecordWithIndexPar transforms a record using an IO transform an IO of a record
+func TraverseRecordWithIndexPar[GB ~func() B, GBS ~func() MB, MA ~map[K]A, MB ~map[K]B, K comparable, A, B any](f func(K, A) GB) func(MA) GBS {
+	return RR.TraverseWithIndex[MA](
+		Of[GBS, MB],
+		Map[GBS, func() func(B) MB, MB, func(B) MB],
+		ApPar[GBS, func() func(B) MB, GB],
+		f,
+	)
+}
+
+func SequenceRecordPar[GA ~func() A, GAS ~func() AAS, AAS ~map[K]A, GAAS ~map[K]GA, K comparable, A any](tas GAAS) GAS {
+	return MonadTraverseRecordPar[GAS](tas, F.Identity[GA])
+}

io/sequence_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 io
+
+import (
+	A "github.com/IBM/fp-go/array"
+	F "github.com/IBM/fp-go/function"
+	"github.com/stretchr/testify/assert"
+
+	"testing"
+)
+
+func TestMapSeq(t *testing.T) {
+	var results []string
+
+	handler := func(value string) IO[string] {
+		return func() string {
+			results = append(results, value)
+			return value
+		}
+	}
+
+	src := A.From("a", "b", "c")
+
+	res := F.Pipe2(
+		src,
+		TraverseArraySeq(handler),
+		Map(func(data []string) bool {
+			return assert.Equal(t, data, results)
+		}),
+	)
+
+	assert.True(t, res())
+}

io/traverse.go

@@ -60,3 +60,45 @@ func TraverseRecordWithIndex[K comparable, A, B any](f func(K, A) IO[B]) func(ma
 func SequenceRecord[K comparable, A any](tas map[K]IO[A]) IO[map[K]A] {
 	return G.SequenceRecord[IO[A], IO[map[K]A]](tas)
 }
+
+func MonadTraverseArraySeq[A, B any](tas []A, f func(A) IO[B]) IO[[]B] {
+	return G.MonadTraverseArraySeq[IO[B], IO[[]B]](tas, f)
+}
+
+// TraverseArraySeq applies a function returning an [IO] to all elements in an array and the
+// transforms this into an [IO] of that array
+func TraverseArraySeq[A, B any](f func(A) IO[B]) func([]A) IO[[]B] {
+	return G.TraverseArraySeq[IO[B], IO[[]B], []A](f)
+}
+
+// TraverseArrayWithIndexSeq applies a function returning an [IO] to all elements in an array and the
+// transforms this into an [IO] of that array
+func TraverseArrayWithIndexSeq[A, B any](f func(int, A) IO[B]) func([]A) IO[[]B] {
+	return G.TraverseArrayWithIndexSeq[IO[B], IO[[]B], []A](f)
+}
+
+// SequenceArraySeq converts an array of [IO] to an [IO] of an array
+func SequenceArraySeq[A any](tas []IO[A]) IO[[]A] {
+	return G.SequenceArraySeq[IO[A], IO[[]A]](tas)
+}
+
+func MonadTraverseRecordSeq[K comparable, A, B any](tas map[K]A, f func(A) IO[B]) IO[map[K]B] {
+	return G.MonadTraverseRecordSeq[IO[map[K]B]](tas, f)
+}
+
+// TraverseRecord applies a function returning an [IO] to all elements in a record and the
+// transforms this into an [IO] of that record
+func TraverseRecordSeq[K comparable, A, B any](f func(A) IO[B]) func(map[K]A) IO[map[K]B] {
+	return G.TraverseRecordSeq[IO[map[K]B], map[K]A, IO[B]](f)
+}
+
+// TraverseRecordWithIndexSeq applies a function returning an [IO] to all elements in a record and the
+// transforms this into an [IO] of that record
+func TraverseRecordWithIndeSeq[K comparable, A, B any](f func(K, A) IO[B]) func(map[K]A) IO[map[K]B] {
+	return G.TraverseRecordWithIndexSeq[IO[B], IO[map[K]B], map[K]A](f)
+}
+
+// SequenceRecordSeq converts a record of [IO] to an [IO] of a record
+func SequenceRecordSeq[K comparable, A any](tas map[K]IO[A]) IO[map[K]A] {
+	return G.SequenceRecordSeq[IO[A], IO[map[K]A]](tas)
+}

ioeither/generic/monad.go

@@ -0,0 +1,56 @@
+// Copyright (c) 2024 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"
+	"github.com/IBM/fp-go/internal/monad"
+	"github.com/IBM/fp-go/internal/pointed"
+)
+
+type ioEitherPointed[E, A any, GA ~func() ET.Either[E, A]] struct{}
+
+type ioEitherMonad[E, A, B any, GA ~func() ET.Either[E, A], GB ~func() ET.Either[E, B], GAB ~func() ET.Either[E, func(A) B]] struct{}
+
+func (o *ioEitherPointed[E, A, GA]) Of(a A) GA {
+	return Of[GA, E, A](a)
+}
+
+func (o *ioEitherMonad[E, A, B, GA, GB, GAB]) Of(a A) GA {
+	return Of[GA, E, A](a)
+}
+
+func (o *ioEitherMonad[E, A, B, GA, GB, GAB]) Map(f func(A) B) func(GA) GB {
+	return Map[GA, GB, E, A, B](f)
+}
+
+func (o *ioEitherMonad[E, A, B, GA, GB, GAB]) Chain(f func(A) GB) func(GA) GB {
+	return Chain[GA, GB, E, A, B](f)
+}
+
+func (o *ioEitherMonad[E, A, B, GA, GB, GAB]) Ap(fa GA) func(GAB) GB {
+	return Ap[GB, GAB, GA, E, A, B](fa)
+}
+
+// Pointed implements the pointed operations for [IOEither]
+func Pointed[E, A any, GA ~func() ET.Either[E, A]]() pointed.Pointed[A, GA] {
+	return &ioEitherPointed[E, A, GA]{}
+}
+
+// Monad implements the monadic operations for [IOEither]
+func Monad[E, A, B any, GA ~func() ET.Either[E, A], GB ~func() ET.Either[E, B], GAB ~func() ET.Either[E, func(A) B]]() monad.Monad[A, B, GA, GB, GAB] {
+	return &ioEitherMonad[E, A, B, GA, GB, GAB]{}
+}

ioeither/http/request.go

@@ -27,7 +27,7 @@ import (
 	IOE "github.com/IBM/fp-go/ioeither"
 	IOEF "github.com/IBM/fp-go/ioeither/file"
 	J "github.com/IBM/fp-go/json"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
 type (
@@ -95,7 +95,7 @@ func ReadFullResponse(client Client) func(Requester) IOE.IOEither[error, H.FullR
 					IOE.Of[error, io.ReadCloser],
 					IOEF.ReadAll[io.ReadCloser],
 				),
-				IOE.Map[error](F.Bind1st(T.MakeTuple2[*http.Response, []byte], resp)),
+				IOE.Map[error](F.Bind1st(P.MakePair[*http.Response, []byte], resp)),
 			)
 		}),
 	)

ioeither/monad.go

@@ -0,0 +1,32 @@
+// Copyright (c) 2024 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 (
+	"github.com/IBM/fp-go/internal/monad"
+	"github.com/IBM/fp-go/internal/pointed"
+	G "github.com/IBM/fp-go/ioeither/generic"
+)
+
+// Pointed returns the pointed operations for [IOEither]
+func Pointed[E, A any]() pointed.Pointed[A, IOEither[E, A]] {
+	return G.Pointed[E, A, IOEither[E, A]]()
+}
+
+// Monad returns the monadic operations for [IOEither]
+func Monad[E, A, B any]() monad.Monad[A, B, IOEither[E, A], IOEither[E, B], IOEither[E, func(A) B]] {
+	return G.Monad[E, A, B, IOEither[E, A], IOEither[E, B], IOEither[E, func(A) B]]()
+}

ioeither/sequence_test.go

@@ -0,0 +1,48 @@
+// 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 (
+	A "github.com/IBM/fp-go/array"
+	E "github.com/IBM/fp-go/either"
+	F "github.com/IBM/fp-go/function"
+	"github.com/stretchr/testify/assert"
+
+	"testing"
+)
+
+func TestMapSeq(t *testing.T) {
+	var results []string
+
+	handler := func(value string) IOEither[error, string] {
+		return func() E.Either[error, string] {
+			results = append(results, value)
+			return E.Of[error](value)
+		}
+	}
+
+	src := A.From("a", "b", "c")
+
+	res := F.Pipe2(
+		src,
+		TraverseArraySeq(handler),
+		Map[error](func(data []string) bool {
+			return assert.Equal(t, data, results)
+		}),
+	)
+
+	assert.Equal(t, E.Of[error](true), res())
+}

iterator/stateless/compress.go

@@ -17,11 +17,11 @@ package stateless
 
 import (
 	G "github.com/IBM/fp-go/iterator/stateless/generic"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
 // Compress returns an [Iterator] that filters elements from a data [Iterator] returning only those that have a corresponding element in selector [Iterator] that evaluates to `true`.
 // Stops when either the data or selectors iterator has been exhausted.
 func Compress[U any](sel Iterator[bool]) func(Iterator[U]) Iterator[U] {
-	return G.Compress[Iterator[U], Iterator[bool], Iterator[T.Tuple2[U, bool]]](sel)
+	return G.Compress[Iterator[U], Iterator[bool], Iterator[P.Pair[U, bool]]](sel)
 }

iterator/stateless/generic/any.go

@@ -18,11 +18,11 @@ package generic
 import (
 	F "github.com/IBM/fp-go/function"
 	O "github.com/IBM/fp-go/option"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
 // Any returns `true` if any element of the iterable is `true`. If the iterable is empty, return `false`
-func Any[GU ~func() O.Option[T.Tuple2[GU, U]], FCT ~func(U) bool, U any](pred FCT) func(ma GU) bool {
+func Any[GU ~func() O.Option[P.Pair[GU, U]], FCT ~func(U) bool, U any](pred FCT) func(ma GU) bool {
 	return F.Flow3(
 		Filter[GU](pred),
 		First[GU],

iterator/stateless/generic/bind.go

@@ -20,18 +20,18 @@ import (
 	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"
+	P "github.com/IBM/fp-go/pair"
 )
 
 // 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](
+func Do[GS ~func() O.Option[P.Pair[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](
+func Bind[GS1 ~func() O.Option[P.Pair[GS1, S1]], GS2 ~func() O.Option[P.Pair[GS2, S2]], GA ~func() O.Option[P.Pair[GA, A]], S1, S2, A any](
 	setter func(A) func(S1) S2,
 	f func(S1) GA,
 ) func(GS1) GS2 {
@@ -45,7 +45,7 @@ func Bind[GS1 ~func() O.Option[T.Tuple2[GS1, S1]], GS2 ~func() O.Option[T.Tuple2
 }
 
 // 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](
+func Let[GS1 ~func() O.Option[P.Pair[GS1, S1]], GS2 ~func() O.Option[P.Pair[GS2, S2]], S1, S2, A any](
 	key func(A) func(S1) S2,
 	f func(S1) A,
 ) func(GS1) GS2 {
@@ -57,7 +57,7 @@ func Let[GS1 ~func() O.Option[T.Tuple2[GS1, S1]], GS2 ~func() O.Option[T.Tuple2[
 }
 
 // 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](
+func LetTo[GS1 ~func() O.Option[P.Pair[GS1, S1]], GS2 ~func() O.Option[P.Pair[GS2, S2]], S1, S2, B any](
 	key func(B) func(S1) S2,
 	b B,
 ) func(GS1) GS2 {
@@ -69,7 +69,7 @@ func LetTo[GS1 ~func() O.Option[T.Tuple2[GS1, S1]], GS2 ~func() O.Option[T.Tuple
 }
 
 // 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](
+func BindTo[GS1 ~func() O.Option[P.Pair[GS1, S1]], GA ~func() O.Option[P.Pair[GA, A]], S1, A any](
 	setter func(A) S1,
 ) func(GA) GS1 {
 	return C.BindTo(
@@ -79,7 +79,7 @@ func BindTo[GS1 ~func() O.Option[T.Tuple2[GS1, S1]], GA ~func() O.Option[T.Tuple
 }
 
 // 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](
+func ApS[GAS2 ~func() O.Option[P.Pair[GAS2, func(A) S2]], GS1 ~func() O.Option[P.Pair[GS1, S1]], GS2 ~func() O.Option[P.Pair[GS2, S2]], GA ~func() O.Option[P.Pair[GA, A]], S1, S2, A any](
 	setter func(A) func(S1) S2,
 	fa GA,
 ) func(GS1) GS2 {

iterator/stateless/generic/compress.go

@@ -18,17 +18,17 @@ package generic
 import (
 	F "github.com/IBM/fp-go/function"
 	O "github.com/IBM/fp-go/option"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
 // Compress returns an [Iterator] that filters elements from a data [Iterator] returning only those that have a corresponding element in selector [Iterator] that evaluates to `true`.
 // Stops when either the data or selectors iterator has been exhausted.
-func Compress[GU ~func() O.Option[T.Tuple2[GU, U]], GB ~func() O.Option[T.Tuple2[GB, bool]], CS ~func() O.Option[T.Tuple2[CS, T.Tuple2[U, bool]]], U any](sel GB) func(GU) GU {
+func Compress[GU ~func() O.Option[P.Pair[GU, U]], GB ~func() O.Option[P.Pair[GB, bool]], CS ~func() O.Option[P.Pair[CS, P.Pair[U, bool]]], U any](sel GB) func(GU) GU {
 	return F.Flow2(
 		Zip[GU, GB, CS](sel),
 		FilterMap[GU, CS](F.Flow2(
-			O.FromPredicate(T.Second[U, bool]),
-			O.Map(T.First[U, bool]),
+			O.FromPredicate(P.Tail[U, bool]),
+			O.Map(P.Head[U, bool]),
 		)),
 	)
 }

iterator/stateless/generic/cycle.go

@@ -18,12 +18,12 @@ package generic
 import (
 	F "github.com/IBM/fp-go/function"
 	O "github.com/IBM/fp-go/option"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
-func Cycle[GU ~func() O.Option[T.Tuple2[GU, U]], U any](ma GU) GU {
+func Cycle[GU ~func() O.Option[P.Pair[GU, U]], U any](ma GU) GU {
 	// avoid cyclic references
-	var m func(O.Option[T.Tuple2[GU, U]]) O.Option[T.Tuple2[GU, U]]
+	var m func(O.Option[P.Pair[GU, U]]) O.Option[P.Pair[GU, U]]
 
 	recurse := func(mu GU) GU {
 		return F.Nullary2(
@@ -32,11 +32,11 @@ func Cycle[GU ~func() O.Option[T.Tuple2[GU, U]], U any](ma GU) GU {
 		)
 	}
 
-	m = O.Fold(func() O.Option[T.Tuple2[GU, U]] {
+	m = O.Fold(func() O.Option[P.Pair[GU, U]] {
 		return recurse(ma)()
 	}, F.Flow2(
-		T.Map2(recurse, F.Identity[U]),
-		O.Of[T.Tuple2[GU, U]],
+		P.BiMap(recurse, F.Identity[U]),
+		O.Of[P.Pair[GU, U]],
 	))
 
 	return recurse(ma)

iterator/stateless/generic/dropwhile.go

@@ -18,17 +18,17 @@ package generic
 import (
 	F "github.com/IBM/fp-go/function"
 	O "github.com/IBM/fp-go/option"
-	P "github.com/IBM/fp-go/predicate"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
+	PR "github.com/IBM/fp-go/predicate"
 )
 
 // DropWhile creates an [Iterator] that drops elements from the [Iterator] as long as the predicate is true; afterwards, returns every element.
 // Note, the [Iterator] does not produce any output until the predicate first becomes false
-func DropWhile[GU ~func() O.Option[T.Tuple2[GU, U]], U any](pred func(U) bool) func(GU) GU {
+func DropWhile[GU ~func() O.Option[P.Pair[GU, U]], U any](pred func(U) bool) func(GU) GU {
 	// avoid cyclic references
-	var m func(O.Option[T.Tuple2[GU, U]]) O.Option[T.Tuple2[GU, U]]
+	var m func(O.Option[P.Pair[GU, U]]) O.Option[P.Pair[GU, U]]
 
-	fromPred := O.FromPredicate(P.Not(P.ContraMap(T.Second[GU, U])(pred)))
+	fromPred := O.FromPredicate(PR.Not(PR.ContraMap(P.Tail[GU, U])(pred)))
 
 	recurse := func(mu GU) GU {
 		return F.Nullary2(
@@ -37,11 +37,11 @@ func DropWhile[GU ~func() O.Option[T.Tuple2[GU, U]], U any](pred func(U) bool) f
 		)
 	}
 
-	m = O.Chain(func(t T.Tuple2[GU, U]) O.Option[T.Tuple2[GU, U]] {
+	m = O.Chain(func(t P.Pair[GU, U]) O.Option[P.Pair[GU, U]] {
 		return F.Pipe2(
 			t,
 			fromPred,
-			O.Fold(recurse(Next(t)), O.Of[T.Tuple2[GU, U]]),
+			O.Fold(recurse(Next(t)), O.Of[P.Pair[GU, U]]),
 		)
 	})
 

iterator/stateless/generic/first.go

@@ -18,13 +18,13 @@ package generic
 import (
 	F "github.com/IBM/fp-go/function"
 	O "github.com/IBM/fp-go/option"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
 // First returns the first item in an iterator if such an item exists
-func First[GU ~func() O.Option[T.Tuple2[GU, U]], U any](mu GU) O.Option[U] {
+func First[GU ~func() O.Option[P.Pair[GU, U]], U any](mu GU) O.Option[U] {
 	return F.Pipe1(
 		mu(),
-		O.Map(T.Second[GU, U]),
+		O.Map(P.Tail[GU, U]),
 	)
 }

iterator/stateless/generic/io.go

@@ -19,16 +19,16 @@ import (
 	F "github.com/IBM/fp-go/function"
 	L "github.com/IBM/fp-go/io/generic"
 	O "github.com/IBM/fp-go/option"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
 // FromLazy returns an iterator on top of a lazy function
-func FromLazy[GU ~func() O.Option[T.Tuple2[GU, U]], LZ ~func() U, U any](l LZ) GU {
+func FromLazy[GU ~func() O.Option[P.Pair[GU, U]], LZ ~func() U, U any](l LZ) GU {
 	return F.Pipe1(
 		l,
 		L.Map[LZ, GU](F.Flow2(
-			F.Bind1st(T.MakeTuple2[GU, U], Empty[GU]()),
-			O.Of[T.Tuple2[GU, U]],
+			F.Bind1st(P.MakePair[GU, U], Empty[GU]()),
+			O.Of[P.Pair[GU, U]],
 		)),
 	)
 }

iterator/stateless/generic/iterator.go

@@ -24,45 +24,45 @@ import (
 	M "github.com/IBM/fp-go/monoid"
 	N "github.com/IBM/fp-go/number"
 	O "github.com/IBM/fp-go/option"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
-// Next returns the iterator for the next element in an iterator `T.Tuple2`
-func Next[GU ~func() O.Option[T.Tuple2[GU, U]], U any](m T.Tuple2[GU, U]) GU {
-	return T.First(m)
+// Next returns the iterator for the next element in an iterator `P.Pair`
+func Next[GU ~func() O.Option[P.Pair[GU, U]], U any](m P.Pair[GU, U]) GU {
+	return P.Head(m)
 }
 
-// Current returns the current element in an iterator `T.Tuple2`
-func Current[GU ~func() O.Option[T.Tuple2[GU, U]], U any](m T.Tuple2[GU, U]) U {
-	return T.Second(m)
+// Current returns the current element in an iterator `P.Pair`
+func Current[GU ~func() O.Option[P.Pair[GU, U]], U any](m P.Pair[GU, U]) U {
+	return P.Tail(m)
 }
 
 // From constructs an array from a set of variadic arguments
-func From[GU ~func() O.Option[T.Tuple2[GU, U]], U any](data ...U) GU {
+func From[GU ~func() O.Option[P.Pair[GU, U]], U any](data ...U) GU {
 	return FromArray[GU](data)
 }
 
 // Empty returns the empty iterator
-func Empty[GU ~func() O.Option[T.Tuple2[GU, U]], U any]() GU {
+func Empty[GU ~func() O.Option[P.Pair[GU, U]], U any]() GU {
 	return IO.None[GU]()
 }
 
 // Of returns an iterator with one single element
-func Of[GU ~func() O.Option[T.Tuple2[GU, U]], U any](a U) GU {
-	return IO.Of[GU](T.MakeTuple2(Empty[GU](), a))
+func Of[GU ~func() O.Option[P.Pair[GU, U]], U any](a U) GU {
+	return IO.Of[GU](P.MakePair(Empty[GU](), a))
 }
 
 // FromArray returns an iterator from multiple elements
-func FromArray[GU ~func() O.Option[T.Tuple2[GU, U]], US ~[]U, U any](as US) GU {
+func FromArray[GU ~func() O.Option[P.Pair[GU, U]], US ~[]U, U any](as US) GU {
 	return A.MatchLeft(Empty[GU], func(head U, tail US) GU {
-		return func() O.Option[T.Tuple2[GU, U]] {
-			return O.Of(T.MakeTuple2(FromArray[GU](tail), head))
+		return func() O.Option[P.Pair[GU, U]] {
+			return O.Of(P.MakePair(FromArray[GU](tail), head))
 		}
 	})(as)
 }
 
 // reduce applies a function for each value of the iterator with a floating result
-func reduce[GU ~func() O.Option[T.Tuple2[GU, U]], U, V any](as GU, f func(V, U) V, initial V) V {
+func reduce[GU ~func() O.Option[P.Pair[GU, U]], U, V any](as GU, f func(V, U) V, initial V) V {
 	next, ok := O.Unwrap(as())
 	current := initial
 	for ok {
@@ -74,18 +74,18 @@ func reduce[GU ~func() O.Option[T.Tuple2[GU, U]], U, V any](as GU, f func(V, U)
 }
 
 // Reduce applies a function for each value of the iterator with a floating result
-func Reduce[GU ~func() O.Option[T.Tuple2[GU, U]], U, V any](f func(V, U) V, initial V) func(GU) V {
+func Reduce[GU ~func() O.Option[P.Pair[GU, U]], U, V any](f func(V, U) V, initial V) func(GU) V {
 	return F.Bind23of3(reduce[GU, U, V])(f, initial)
 }
 
 // ToArray converts the iterator to an array
-func ToArray[GU ~func() O.Option[T.Tuple2[GU, U]], US ~[]U, U any](u GU) US {
+func ToArray[GU ~func() O.Option[P.Pair[GU, U]], US ~[]U, U any](u GU) US {
 	return Reduce[GU](A.Append[US], A.Empty[US]())(u)
 }
 
-func Map[GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tuple2[GU, U]], FCT ~func(U) V, U, V any](f FCT) func(ma GU) GV {
+func Map[GV ~func() O.Option[P.Pair[GV, V]], GU ~func() O.Option[P.Pair[GU, U]], FCT ~func(U) V, U, V any](f FCT) func(ma GU) GV {
 	// pre-declare to avoid cyclic reference
-	var m func(O.Option[T.Tuple2[GU, U]]) O.Option[T.Tuple2[GV, V]]
+	var m func(O.Option[P.Pair[GU, U]]) O.Option[P.Pair[GV, V]]
 
 	recurse := func(ma GU) GV {
 		return F.Nullary2(
@@ -94,17 +94,17 @@ func Map[GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tuple2[GU,
 		)
 	}
 
-	m = O.Map(T.Map2(recurse, f))
+	m = O.Map(P.BiMap(recurse, f))
 
 	return recurse
 }
 
-func MonadMap[GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tuple2[GU, U]], U, V any](ma GU, f func(U) V) GV {
+func MonadMap[GV ~func() O.Option[P.Pair[GV, V]], GU ~func() O.Option[P.Pair[GU, U]], U, V any](ma GU, f func(U) V) GV {
 	return Map[GV, GU](f)(ma)
 }
 
-func concat[GU ~func() O.Option[T.Tuple2[GU, U]], U any](right, left GU) GU {
-	var m func(ma O.Option[T.Tuple2[GU, U]]) O.Option[T.Tuple2[GU, U]]
+func concat[GU ~func() O.Option[P.Pair[GU, U]], U any](right, left GU) GU {
+	var m func(ma O.Option[P.Pair[GU, U]]) O.Option[P.Pair[GU, U]]
 
 	recurse := func(left GU) GU {
 		return F.Nullary2(left, m)
@@ -113,16 +113,16 @@ func concat[GU ~func() O.Option[T.Tuple2[GU, U]], U any](right, left GU) GU {
 	m = O.Fold(
 		right,
 		F.Flow2(
-			T.Map2(recurse, F.Identity[U]),
-			O.Some[T.Tuple2[GU, U]],
+			P.BiMap(recurse, F.Identity[U]),
+			O.Some[P.Pair[GU, U]],
 		))
 
 	return recurse(left)
 }
 
-func Chain[GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tuple2[GU, U]], U, V any](f func(U) GV) func(GU) GV {
+func Chain[GV ~func() O.Option[P.Pair[GV, V]], GU ~func() O.Option[P.Pair[GU, U]], U, V any](f func(U) GV) func(GU) GV {
 	// pre-declare to avoid cyclic reference
-	var m func(O.Option[T.Tuple2[GU, U]]) O.Option[T.Tuple2[GV, V]]
+	var m func(O.Option[P.Pair[GU, U]]) O.Option[P.Pair[GV, V]]
 
 	recurse := func(ma GU) GV {
 		return F.Nullary2(
@@ -132,9 +132,9 @@ func Chain[GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tuple2[GU
 	}
 	m = O.Chain(
 		F.Flow3(
-			T.Map2(recurse, f),
-			T.Tupled2(concat[GV]),
-			func(v GV) O.Option[T.Tuple2[GV, V]] {
+			P.BiMap(recurse, f),
+			P.Paired(concat[GV]),
+			func(v GV) O.Option[P.Pair[GV, V]] {
 				return v()
 			},
 		),
@@ -143,11 +143,11 @@ func Chain[GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tuple2[GU
 	return recurse
 }
 
-func MonadChain[GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tuple2[GU, U]], U, V any](ma GU, f func(U) GV) GV {
+func MonadChain[GV ~func() O.Option[P.Pair[GV, V]], GU ~func() O.Option[P.Pair[GU, U]], U, V any](ma GU, f func(U) GV) GV {
 	return Chain[GV, GU](f)(ma)
 }
 
-func MonadChainFirst[GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tuple2[GU, U]], U, V any](ma GU, f func(U) GV) GU {
+func MonadChainFirst[GV ~func() O.Option[P.Pair[GV, V]], GU ~func() O.Option[P.Pair[GU, U]], U, V any](ma GU, f func(U) GV) GU {
 	return C.MonadChainFirst(
 		MonadChain[GU, GU, U, U],
 		MonadMap[GU, GV, V, U],
@@ -156,7 +156,7 @@ func MonadChainFirst[GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T
 	)
 }
 
-func ChainFirst[GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tuple2[GU, U]], U, V any](f func(U) GV) func(GU) GU {
+func ChainFirst[GV ~func() O.Option[P.Pair[GV, V]], GU ~func() O.Option[P.Pair[GU, U]], U, V any](f func(U) GV) func(GU) GU {
 	return C.ChainFirst(
 		Chain[GU, GU, U, U],
 		Map[GU, GV, func(V) U, V, U],
@@ -164,14 +164,14 @@ func ChainFirst[GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tupl
 	)
 }
 
-func Flatten[GV ~func() O.Option[T.Tuple2[GV, GU]], GU ~func() O.Option[T.Tuple2[GU, U]], U any](ma GV) GU {
+func Flatten[GV ~func() O.Option[P.Pair[GV, GU]], GU ~func() O.Option[P.Pair[GU, U]], U any](ma GV) GU {
 	return MonadChain(ma, F.Identity[GU])
 }
 
 // MakeBy returns an [Iterator] with an infinite number of elements initialized with `f(i)`
-func MakeBy[GU ~func() O.Option[T.Tuple2[GU, U]], FCT ~func(int) U, U any](f FCT) GU {
+func MakeBy[GU ~func() O.Option[P.Pair[GU, U]], FCT ~func(int) U, U any](f FCT) GU {
 
-	var m func(int) O.Option[T.Tuple2[GU, U]]
+	var m func(int) O.Option[P.Pair[GU, U]]
 
 	recurse := func(i int) GU {
 		return F.Nullary2(
@@ -181,12 +181,12 @@ func MakeBy[GU ~func() O.Option[T.Tuple2[GU, U]], FCT ~func(int) U, U any](f FCT
 	}
 
 	m = F.Flow3(
-		T.Replicate2[int],
-		T.Map2(F.Flow2(
+		P.Of[int],
+		P.BiMap(F.Flow2(
 			utils.Inc,
 			recurse),
 			f),
-		O.Of[T.Tuple2[GU, U]],
+		O.Of[P.Pair[GU, U]],
 	)
 
 	// bootstrap
@@ -194,13 +194,13 @@ func MakeBy[GU ~func() O.Option[T.Tuple2[GU, U]], FCT ~func(int) U, U any](f FCT
 }
 
 // Replicate creates an infinite [Iterator] containing a value.
-func Replicate[GU ~func() O.Option[T.Tuple2[GU, U]], U any](a U) GU {
+func Replicate[GU ~func() O.Option[P.Pair[GU, U]], U any](a U) GU {
 	return MakeBy[GU](F.Constant1[int](a))
 }
 
 // Repeat creates an [Iterator] containing a value repeated the specified number of times.
 // Alias of [Replicate] combined with [Take]
-func Repeat[GU ~func() O.Option[T.Tuple2[GU, U]], U any](n int, a U) GU {
+func Repeat[GU ~func() O.Option[P.Pair[GU, U]], U any](n int, a U) GU {
 	return F.Pipe2(
 		a,
 		Replicate[GU],
@@ -209,13 +209,13 @@ func Repeat[GU ~func() O.Option[T.Tuple2[GU, U]], U any](n int, a U) GU {
 }
 
 // Count creates an [Iterator] containing a consecutive sequence of integers starting with the provided start value
-func Count[GU ~func() O.Option[T.Tuple2[GU, int]]](start int) GU {
+func Count[GU ~func() O.Option[P.Pair[GU, int]]](start int) GU {
 	return MakeBy[GU](N.Add(start))
 }
 
-func FilterMap[GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tuple2[GU, U]], FCT ~func(U) O.Option[V], U, V any](f FCT) func(ma GU) GV {
+func FilterMap[GV ~func() O.Option[P.Pair[GV, V]], GU ~func() O.Option[P.Pair[GU, U]], FCT ~func(U) O.Option[V], U, V any](f FCT) func(ma GU) GV {
 	// pre-declare to avoid cyclic reference
-	var m func(O.Option[T.Tuple2[GU, U]]) O.Option[T.Tuple2[GV, V]]
+	var m func(O.Option[P.Pair[GU, U]]) O.Option[P.Pair[GV, V]]
 
 	recurse := func(ma GU) GV {
 		return F.Nullary2(
@@ -226,11 +226,11 @@ func FilterMap[GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tuple
 
 	m = O.Fold(
 		Empty[GV](),
-		func(t T.Tuple2[GU, U]) O.Option[T.Tuple2[GV, V]] {
+		func(t P.Pair[GU, U]) O.Option[P.Pair[GV, V]] {
 			r := recurse(Next(t))
 			return O.MonadFold(f(Current(t)), r, F.Flow2(
-				F.Bind1st(T.MakeTuple2[GV, V], r),
-				O.Some[T.Tuple2[GV, V]],
+				F.Bind1st(P.MakePair[GV, V], r),
+				O.Some[P.Pair[GV, V]],
 			))
 		},
 	)
@@ -238,26 +238,26 @@ func FilterMap[GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tuple
 	return recurse
 }
 
-func Filter[GU ~func() O.Option[T.Tuple2[GU, U]], FCT ~func(U) bool, U any](f FCT) func(ma GU) GU {
+func Filter[GU ~func() O.Option[P.Pair[GU, U]], FCT ~func(U) bool, U any](f FCT) func(ma GU) GU {
 	return FilterMap[GU, GU](O.FromPredicate(f))
 }
 
-func Ap[GUV ~func() O.Option[T.Tuple2[GUV, func(U) V]], GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tuple2[GU, U]], U, V any](ma GU) func(fab GUV) GV {
+func Ap[GUV ~func() O.Option[P.Pair[GUV, func(U) V]], GV ~func() O.Option[P.Pair[GV, V]], GU ~func() O.Option[P.Pair[GU, U]], U, V any](ma GU) func(fab GUV) GV {
 	return Chain[GV, GUV](F.Bind1st(MonadMap[GV, GU], ma))
 }
 
-func MonadAp[GUV ~func() O.Option[T.Tuple2[GUV, func(U) V]], GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tuple2[GU, U]], U, V any](fab GUV, ma GU) GV {
+func MonadAp[GUV ~func() O.Option[P.Pair[GUV, func(U) V]], GV ~func() O.Option[P.Pair[GV, V]], GU ~func() O.Option[P.Pair[GU, U]], U, V any](fab GUV, ma GU) GV {
 	return Ap[GUV, GV, GU](ma)(fab)
 }
 
-func FilterChain[GVV ~func() O.Option[T.Tuple2[GVV, GV]], GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tuple2[GU, U]], FCT ~func(U) O.Option[GV], U, V any](f FCT) func(ma GU) GV {
+func FilterChain[GVV ~func() O.Option[P.Pair[GVV, GV]], GV ~func() O.Option[P.Pair[GV, V]], GU ~func() O.Option[P.Pair[GU, U]], FCT ~func(U) O.Option[GV], U, V any](f FCT) func(ma GU) GV {
 	return F.Flow2(
 		FilterMap[GVV, GU](f),
 		Flatten[GVV],
 	)
 }
 
-func FoldMap[GU ~func() O.Option[T.Tuple2[GU, U]], FCT ~func(U) V, U, V any](m M.Monoid[V]) func(FCT) func(ma GU) V {
+func FoldMap[GU ~func() O.Option[P.Pair[GU, U]], FCT ~func(U) V, U, V any](m M.Monoid[V]) func(FCT) func(ma GU) V {
 	return func(f FCT) func(ma GU) V {
 		return Reduce[GU](func(cur V, a U) V {
 			return m.Concat(cur, f(a))
@@ -265,6 +265,6 @@ func FoldMap[GU ~func() O.Option[T.Tuple2[GU, U]], FCT ~func(U) V, U, V any](m M
 	}
 }
 
-func Fold[GU ~func() O.Option[T.Tuple2[GU, U]], U any](m M.Monoid[U]) func(ma GU) U {
+func Fold[GU ~func() O.Option[P.Pair[GU, U]], U any](m M.Monoid[U]) func(ma GU) U {
 	return Reduce[GU](m.Concat, m.Empty())
 }

iterator/stateless/generic/last.go

@@ -18,10 +18,10 @@ package generic
 import (
 	F "github.com/IBM/fp-go/function"
 	O "github.com/IBM/fp-go/option"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
 // Last returns the last item in an iterator if such an item exists
-func Last[GU ~func() O.Option[T.Tuple2[GU, U]], U any](mu GU) O.Option[U] {
+func Last[GU ~func() O.Option[P.Pair[GU, U]], U any](mu GU) O.Option[U] {
 	return reduce(mu, F.Ignore1of2[O.Option[U]](O.Of[U]), O.None[U]())
 }

iterator/stateless/generic/monad.go

@@ -18,10 +18,10 @@ package generic
 import (
 	"github.com/IBM/fp-go/internal/monad"
 	O "github.com/IBM/fp-go/option"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
-type iteratorMonad[A, B any, GA ~func() O.Option[T.Tuple2[GA, A]], GB ~func() O.Option[T.Tuple2[GB, B]], GAB ~func() O.Option[T.Tuple2[GAB, func(A) B]]] struct{}
+type iteratorMonad[A, B any, GA ~func() O.Option[P.Pair[GA, A]], GB ~func() O.Option[P.Pair[GB, B]], GAB ~func() O.Option[P.Pair[GAB, func(A) B]]] struct{}
 
 func (o *iteratorMonad[A, B, GA, GB, GAB]) Of(a A) GA {
 	return Of[GA, A](a)
@@ -40,6 +40,6 @@ func (o *iteratorMonad[A, B, GA, GB, GAB]) Ap(fa GA) func(GAB) GB {
 }
 
 // Monad implements the monadic operations for iterators
-func Monad[A, B any, GA ~func() O.Option[T.Tuple2[GA, A]], GB ~func() O.Option[T.Tuple2[GB, B]], GAB ~func() O.Option[T.Tuple2[GAB, func(A) B]]]() monad.Monad[A, B, GA, GB, GAB] {
+func Monad[A, B any, GA ~func() O.Option[P.Pair[GA, A]], GB ~func() O.Option[P.Pair[GB, B]], GAB ~func() O.Option[P.Pair[GAB, func(A) B]]]() monad.Monad[A, B, GA, GB, GAB] {
 	return &iteratorMonad[A, B, GA, GB, GAB]{}
 }

iterator/stateless/generic/monoid.go

@@ -19,10 +19,10 @@ import (
 	F "github.com/IBM/fp-go/function"
 	M "github.com/IBM/fp-go/monoid"
 	O "github.com/IBM/fp-go/option"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
-func Monoid[GU ~func() O.Option[T.Tuple2[GU, U]], U any]() M.Monoid[GU] {
+func Monoid[GU ~func() O.Option[P.Pair[GU, U]], U any]() M.Monoid[GU] {
 	return M.MakeMonoid(
 		F.Swap(concat[GU]),
 		Empty[GU](),

iterator/stateless/generic/reflect.go

@@ -24,10 +24,10 @@ import (
 	N "github.com/IBM/fp-go/number"
 	I "github.com/IBM/fp-go/number/integer"
 	O "github.com/IBM/fp-go/option"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
-func FromReflect[GR ~func() O.Option[T.Tuple2[GR, R.Value]]](val R.Value) GR {
+func FromReflect[GR ~func() O.Option[P.Pair[GR, R.Value]]](val R.Value) GR {
 	// recursive callback
 	var recurse func(idx int) GR
 
@@ -41,8 +41,8 @@ func FromReflect[GR ~func() O.Option[T.Tuple2[GR, R.Value]]](val R.Value) GR {
 			L.Map(fromPred),
 			LG.Map[L.Lazy[O.Option[int]], GR](O.Map(
 				F.Flow2(
-					T.Replicate2[int],
-					T.Map2(F.Flow2(N.Add(1), recurse), val.Index),
+					P.Of[int],
+					P.BiMap(F.Flow2(N.Add(1), recurse), val.Index),
 				),
 			)),
 		)

iterator/stateless/generic/scan.go

@@ -18,14 +18,14 @@ package generic
 import (
 	F "github.com/IBM/fp-go/function"
 	O "github.com/IBM/fp-go/option"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
-func apTuple[A, B any](t T.Tuple2[func(A) B, A]) T.Tuple2[B, A] {
-	return T.MakeTuple2(t.F1(t.F2), t.F2)
+func apTuple[A, B any](t P.Pair[func(A) B, A]) P.Pair[B, A] {
+	return P.MakePair(P.Head(t)(P.Tail(t)), P.Tail(t))
 }
 
-func Scan[GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tuple2[GU, U]], FCT ~func(V, U) V, U, V any](f FCT, initial V) func(ma GU) GV {
+func Scan[GV ~func() O.Option[P.Pair[GV, V]], GU ~func() O.Option[P.Pair[GU, U]], FCT ~func(V, U) V, U, V any](f FCT, initial V) func(ma GU) GV {
 	// pre-declare to avoid cyclic reference
 	var m func(GU) func(V) GV
 
@@ -33,7 +33,7 @@ func Scan[GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tuple2[GU,
 		return F.Nullary2(
 			ma,
 			O.Map(F.Flow2(
-				T.Map2(m, F.Bind1st(f, current)),
+				P.BiMap(m, F.Bind1st(f, current)),
 				apTuple[V, GV],
 			)),
 		)

iterator/stateless/generic/take.go

@@ -19,10 +19,10 @@ import (
 	F "github.com/IBM/fp-go/function"
 	N "github.com/IBM/fp-go/number/integer"
 	O "github.com/IBM/fp-go/option"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
-func Take[GU ~func() O.Option[T.Tuple2[GU, U]], U any](n int) func(ma GU) GU {
+func Take[GU ~func() O.Option[P.Pair[GU, U]], U any](n int) func(ma GU) GU {
 	// pre-declare to avoid cyclic reference
 	var recurse func(ma GU, idx int) GU
 
@@ -34,7 +34,7 @@ func Take[GU ~func() O.Option[T.Tuple2[GU, U]], U any](n int) func(ma GU) GU {
 			fromPred,
 			O.Chain(F.Ignore1of1[int](F.Nullary2(
 				ma,
-				O.Map(T.Map2(F.Bind2nd(recurse, idx+1), F.Identity[U])),
+				O.Map(P.BiMap(F.Bind2nd(recurse, idx+1), F.Identity[U])),
 			))),
 		)
 	}

iterator/stateless/generic/uniq.go

@@ -18,7 +18,7 @@ package generic
 import (
 	F "github.com/IBM/fp-go/function"
 	O "github.com/IBM/fp-go/option"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
 // addToMap makes a deep copy of a map and adds a value
@@ -31,23 +31,23 @@ func addToMap[A comparable](a A, m map[A]bool) map[A]bool {
 	return cpy
 }
 
-func Uniq[AS ~func() O.Option[T.Tuple2[AS, A]], K comparable, A any](f func(A) K) func(as AS) AS {
+func Uniq[AS ~func() O.Option[P.Pair[AS, A]], K comparable, A any](f func(A) K) func(as AS) AS {
 
 	var recurse func(as AS, mp map[K]bool) AS
 
 	recurse = func(as AS, mp map[K]bool) AS {
 		return F.Nullary2(
 			as,
-			O.Chain(func(a T.Tuple2[AS, A]) O.Option[T.Tuple2[AS, A]] {
+			O.Chain(func(a P.Pair[AS, A]) O.Option[P.Pair[AS, A]] {
 				return F.Pipe3(
-					a.F2,
+					P.Tail(a),
 					f,
 					O.FromPredicate(func(k K) bool {
 						_, ok := mp[k]
 						return !ok
 					}),
-					O.Fold(recurse(a.F1, mp), func(k K) O.Option[T.Tuple2[AS, A]] {
-						return O.Of(T.MakeTuple2(recurse(a.F1, addToMap(k, mp)), a.F2))
+					O.Fold(recurse(P.Head(a), mp), func(k K) O.Option[P.Pair[AS, A]] {
+						return O.Of(P.MakePair(recurse(P.Head(a), addToMap(k, mp)), P.Tail(a)))
 					}),
 				)
 			}),
@@ -57,6 +57,6 @@ func Uniq[AS ~func() O.Option[T.Tuple2[AS, A]], K comparable, A any](f func(A) K
 	return F.Bind2nd(recurse, make(map[K]bool, 0))
 }
 
-func StrictUniq[AS ~func() O.Option[T.Tuple2[AS, A]], A comparable](as AS) AS {
+func StrictUniq[AS ~func() O.Option[P.Pair[AS, A]], A comparable](as AS) AS {
 	return Uniq[AS](F.Identity[A])(as)
 }

iterator/stateless/generic/zip.go

@@ -18,29 +18,29 @@ package generic
 import (
 	F "github.com/IBM/fp-go/function"
 	O "github.com/IBM/fp-go/option"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
 // ZipWith applies a function to pairs of elements at the same index in two iterators, collecting the results in a new iterator. If one
 // input iterator is short, excess elements of the longer iterator are discarded.
-func ZipWith[AS ~func() O.Option[T.Tuple2[AS, A]], BS ~func() O.Option[T.Tuple2[BS, B]], CS ~func() O.Option[T.Tuple2[CS, C]], FCT ~func(A, B) C, A, B, C any](fa AS, fb BS, f FCT) CS {
+func ZipWith[AS ~func() O.Option[P.Pair[AS, A]], BS ~func() O.Option[P.Pair[BS, B]], CS ~func() O.Option[P.Pair[CS, C]], FCT ~func(A, B) C, A, B, C any](fa AS, fb BS, f FCT) CS {
 	// pre-declare to avoid cyclic reference
-	var m func(T.Tuple2[O.Option[T.Tuple2[AS, A]], O.Option[T.Tuple2[BS, B]]]) O.Option[T.Tuple2[CS, C]]
+	var m func(P.Pair[O.Option[P.Pair[AS, A]], O.Option[P.Pair[BS, B]]]) O.Option[P.Pair[CS, C]]
 
 	recurse := func(as AS, bs BS) CS {
-		return func() O.Option[T.Tuple2[CS, C]] {
+		return func() O.Option[P.Pair[CS, C]] {
 			// combine
 			return F.Pipe1(
-				T.MakeTuple2(as(), bs()),
+				P.MakePair(as(), bs()),
 				m,
 			)
 		}
 	}
 
 	m = F.Flow2(
-		O.SequenceTuple2[T.Tuple2[AS, A], T.Tuple2[BS, B]],
-		O.Map(func(t T.Tuple2[T.Tuple2[AS, A], T.Tuple2[BS, B]]) T.Tuple2[CS, C] {
-			return T.MakeTuple2(recurse(t.F1.F1, t.F2.F1), f(t.F1.F2, t.F2.F2))
+		O.SequencePair[P.Pair[AS, A], P.Pair[BS, B]],
+		O.Map(func(t P.Pair[P.Pair[AS, A], P.Pair[BS, B]]) P.Pair[CS, C] {
+			return P.MakePair(recurse(P.Head(P.Head(t)), P.Head(P.Tail(t))), f(P.Tail(P.Head(t)), P.Tail(P.Tail(t))))
 		}))
 
 	// trigger the recursion
@@ -49,6 +49,6 @@ func ZipWith[AS ~func() O.Option[T.Tuple2[AS, A]], BS ~func() O.Option[T.Tuple2[
 
 // Zip takes two iterators and returns an iterators of corresponding pairs. If one input iterators is short, excess elements of the
 // longer iterator are discarded
-func Zip[AS ~func() O.Option[T.Tuple2[AS, A]], BS ~func() O.Option[T.Tuple2[BS, B]], CS ~func() O.Option[T.Tuple2[CS, T.Tuple2[A, B]]], A, B any](fb BS) func(AS) CS {
-	return F.Bind23of3(ZipWith[AS, BS, CS, func(A, B) T.Tuple2[A, B]])(fb, T.MakeTuple2[A, B])
+func Zip[AS ~func() O.Option[P.Pair[AS, A]], BS ~func() O.Option[P.Pair[BS, B]], CS ~func() O.Option[P.Pair[CS, P.Pair[A, B]]], A, B any](fb BS) func(AS) CS {
+	return F.Bind23of3(ZipWith[AS, BS, CS, func(A, B) P.Pair[A, B]])(fb, P.MakePair[A, B])
 }

iterator/stateless/iterator.go

@@ -20,19 +20,19 @@ import (
 	L "github.com/IBM/fp-go/lazy"
 	M "github.com/IBM/fp-go/monoid"
 	O "github.com/IBM/fp-go/option"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
 // Iterator represents a stateless, pure way to iterate over a sequence
-type Iterator[U any] L.Lazy[O.Option[T.Tuple2[Iterator[U], U]]]
+type Iterator[U any] L.Lazy[O.Option[P.Pair[Iterator[U], U]]]
 
-// Next returns the [Iterator] for the next element in an iterator `T.Tuple2`
-func Next[U any](m T.Tuple2[Iterator[U], U]) Iterator[U] {
+// Next returns the [Iterator] for the next element in an iterator `P.Pair`
+func Next[U any](m P.Pair[Iterator[U], U]) Iterator[U] {
 	return G.Next(m)
 }
 
-// Current returns the current element in an [Iterator] `T.Tuple2`
-func Current[U any](m T.Tuple2[Iterator[U], U]) U {
+// Current returns the current element in an [Iterator] `P.Pair`
+func Current[U any](m P.Pair[Iterator[U], U]) U {
 	return G.Current(m)
 }
 

iterator/stateless/scan_test.go

@@ -19,7 +19,7 @@ import (
 	"testing"
 
 	F "github.com/IBM/fp-go/function"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -29,14 +29,14 @@ func TestScan(t *testing.T) {
 
 	dst := F.Pipe1(
 		src,
-		Scan(func(cur T.Tuple2[int, string], val string) T.Tuple2[int, string] {
-			return T.MakeTuple2(cur.F1+1, val)
-		}, T.MakeTuple2(0, "")),
+		Scan(func(cur P.Pair[int, string], val string) P.Pair[int, string] {
+			return P.MakePair(P.Head(cur)+1, val)
+		}, P.MakePair(0, "")),
 	)
 
 	assert.Equal(t, ToArray(From(
-		T.MakeTuple2(1, "a"),
-		T.MakeTuple2(2, "b"),
-		T.MakeTuple2(3, "c"),
+		P.MakePair(1, "a"),
+		P.MakePair(2, "b"),
+		P.MakePair(3, "c"),
 	)), ToArray(dst))
 }

iterator/stateless/zip.go

@@ -17,7 +17,7 @@ package stateless
 
 import (
 	G "github.com/IBM/fp-go/iterator/stateless/generic"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
 // ZipWith applies a function to pairs of elements at the same index in two iterators, collecting the results in a new iterator. If one
@@ -28,6 +28,6 @@ func ZipWith[FCT ~func(A, B) C, A, B, C any](fa Iterator[A], fb Iterator[B], f F
 
 // Zip takes two iterators and returns an iterators of corresponding pairs. If one input iterators is short, excess elements of the
 // longer iterator are discarded
-func Zip[A, B any](fb Iterator[B]) func(Iterator[A]) Iterator[T.Tuple2[A, B]] {
-	return G.Zip[Iterator[A], Iterator[B], Iterator[T.Tuple2[A, B]]](fb)
+func Zip[A, B any](fb Iterator[B]) func(Iterator[A]) Iterator[P.Pair[A, B]] {
+	return G.Zip[Iterator[A], Iterator[B], Iterator[P.Pair[A, B]]](fb)
 }

iterator/stateless/zip_test.go

@@ -19,7 +19,7 @@ import (
 	"fmt"
 	"testing"
 
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -40,5 +40,5 @@ func TestZip(t *testing.T) {
 
 	res := Zip[string](left)(right)
 
-	assert.Equal(t, ToArray(From(T.MakeTuple2("a", 1), T.MakeTuple2("b", 2), T.MakeTuple2("c", 3))), ToArray(res))
+	assert.Equal(t, ToArray(From(P.MakePair("a", 1), P.MakePair("b", 2), P.MakePair("c", 3))), ToArray(res))
 }

option/pair.go

@@ -0,0 +1,30 @@
+// Copyright (c) 2024 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 (
+	P "github.com/IBM/fp-go/pair"
+	PG "github.com/IBM/fp-go/pair/generic"
+)
+
+// SequencePair converts a [Pair] of [Option[T]] into an [Option[Pair]].
+func SequencePair[T1, T2 any](t P.Pair[Option[T1], Option[T2]]) Option[P.Pair[T1, T2]] {
+	return PG.SequencePair(
+		Map[T1, func(T2) P.Pair[T1, T2]],
+		Ap[P.Pair[T1, T2], T2],
+		t,
+	)
+}

pair/generic/sequence.go

@@ -0,0 +1,71 @@
+// Copyright (c) 2024 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package generic
+
+import (
+	F "github.com/IBM/fp-go/function"
+	P "github.com/IBM/fp-go/pair"
+)
+
+// SequencePair is a utility function used to implement the sequence operation for higher kinded types based only on map and ap.
+// The function takes a [Pair] of higher higher kinded types and returns a higher kinded type of a [Pair] with the resolved values.
+func SequencePair[
+	MAP ~func(func(T1) func(T2) P.Pair[T1, T2]) func(HKT_T1) HKT_F_T2,
+	AP1 ~func(HKT_T2) func(HKT_F_T2) HKT_PAIR,
+	T1,
+	T2,
+	HKT_T1, // HKT[T1]
+	HKT_T2, // HKT[T2]
+	HKT_F_T2, // HKT[func(T2) P.Pair[T1, T2]]
+	HKT_PAIR any, // HKT[Pair[T1, T2]]
+](
+	fmap MAP,
+	fap1 AP1,
+	t P.Pair[HKT_T1, HKT_T2],
+) HKT_PAIR {
+	return F.Pipe2(
+		P.Head(t),
+		fmap(F.Curry2(P.MakePair[T1, T2])),
+		fap1(P.Tail(t)),
+	)
+}
+
+// TraversePair is a utility function used to implement the sequence operation for higher kinded types based only on map and ap.
+// The function takes a [Pair] of base types and 2 functions that transform these based types into higher higher kinded types. It returns a higher kinded type of a [Pair] with the resolved values.
+func TraversePair[
+	MAP ~func(func(T1) func(T2) P.Pair[T1, T2]) func(HKT_T1) HKT_F_T2,
+	AP1 ~func(HKT_T2) func(HKT_F_T2) HKT_PAIR,
+	F1 ~func(A1) HKT_T1,
+	F2 ~func(A2) HKT_T2,
+	A1, T1,
+	A2, T2,
+	HKT_T1, // HKT[T1]
+	HKT_T2, // HKT[T2]
+	HKT_F_T2, // HKT[func(T2) P.Pair[T1, T2]]
+	HKT_PAIR any, // HKT[Pair[T1, T2]]
+](
+	fmap MAP,
+	fap1 AP1,
+	f1 F1,
+	f2 F2,
+	t P.Pair[A1, A2],
+) HKT_PAIR {
+	return F.Pipe2(
+		f1(P.Head(t)),
+		fmap(F.Curry2(P.MakePair[T1, T2])),
+		fap1(f2(P.Tail(t))),
+	)
+}

pair/pair.go

@@ -25,7 +25,7 @@ import (
 
 type (
 	pair struct {
-		head, Tail any
+		h, t any
 	}
 
 	// Pair defines a data structure that holds two strongly typed values
@@ -36,7 +36,7 @@ type (
 //
 // go:noinline
 func pairString(s *pair) string {
-	return fmt.Sprintf("Pair[%T, %t](%v, %v)", s.head, s.Tail, s.head, s.Tail)
+	return fmt.Sprintf("Pair[%T, %t](%v, %v)", s.h, s.t, s.h, s.t)
 }
 
 // Format prints some debug info for the object
@@ -63,12 +63,12 @@ func (s Pair[A, B]) Format(f fmt.State, c rune) {
 
 // Of creates a [Pair] with the same value to to both fields
 func Of[A any](value A) Pair[A, A] {
-	return Pair[A, A]{head: value, Tail: value}
+	return Pair[A, A]{h: value, t: value}
 }
 
 // FromTuple creates a [Pair] from a [T.Tuple2]
 func FromTuple[A, B any](t T.Tuple2[A, B]) Pair[A, B] {
-	return Pair[A, B]{head: t.F1, Tail: t.F2}
+	return Pair[A, B]{h: t.F1, t: t.F2}
 }
 
 // ToTuple creates a [T.Tuple2] from a [Pair]
@@ -78,22 +78,22 @@ func ToTuple[A, B any](t Pair[A, B]) T.Tuple2[A, B] {
 
 // MakePair creates a [Pair] from two values
 func MakePair[A, B any](a A, b B) Pair[A, B] {
-	return Pair[A, B]{head: a, Tail: b}
+	return Pair[A, B]{h: a, t: b}
 }
 
 // Head returns the head value of the pair
 func Head[A, B any](fa Pair[A, B]) A {
-	return fa.head.(A)
+	return fa.h.(A)
 }
 
 // Tail returns the head value of the pair
 func Tail[A, B any](fa Pair[A, B]) B {
-	return fa.Tail.(B)
+	return fa.t.(B)
 }
 
 // MonadMapHead maps the head value
 func MonadMapHead[B, A, A1 any](fa Pair[A, B], f func(A) A1) Pair[A1, B] {
-	return Pair[A1, B]{f(Head(fa)), fa.Tail}
+	return Pair[A1, B]{f(Head(fa)), fa.t}
 }
 
 // MonadMap maps the head value
@@ -103,7 +103,7 @@ func MonadMap[B, A, A1 any](fa Pair[A, B], f func(A) A1) Pair[A1, B] {
 
 // MonadMapTail maps the Tail value
 func MonadMapTail[A, B, B1 any](fa Pair[A, B], f func(B) B1) Pair[A, B1] {
-	return Pair[A, B1]{fa.head, f(Tail(fa))}
+	return Pair[A, B1]{fa.h, f(Tail(fa))}
 }
 
 // MonadBiMap maps both values
@@ -136,13 +136,13 @@ func BiMap[A, B, A1, B1 any](f func(A) A1, g func(B) B1) func(Pair[A, B]) Pair[A
 // MonadChainHead chains on the head value
 func MonadChainHead[B, A, A1 any](sg Sg.Semigroup[B], fa Pair[A, B], f func(A) Pair[A1, B]) Pair[A1, B] {
 	fb := f(Head(fa))
-	return Pair[A1, B]{fb.head, sg.Concat(Tail(fa), Tail(fb))}
+	return Pair[A1, B]{fb.h, sg.Concat(Tail(fa), Tail(fb))}
 }
 
 // MonadChainTail chains on the Tail value
 func MonadChainTail[A, B, B1 any](sg Sg.Semigroup[A], fb Pair[A, B], f func(B) Pair[A, B1]) Pair[A, B1] {
 	fa := f(Tail(fb))
-	return Pair[A, B1]{sg.Concat(Head(fb), Head(fa)), fa.Tail}
+	return Pair[A, B1]{sg.Concat(Head(fb), Head(fa)), fa.t}
 }
 
 // MonadChain chains on the head value
@@ -202,3 +202,30 @@ func ApTail[A, B, B1 any](sg Sg.Semigroup[A], fb Pair[A, B]) func(Pair[A, func(B
 func Ap[B, A, A1 any](sg Sg.Semigroup[B], fa Pair[A, B]) func(Pair[func(A) A1, B]) Pair[A1, B] {
 	return ApHead[B, A, A1](sg, fa)
 }
+
+// Swap swaps the two channels
+func Swap[A, B any](fa Pair[A, B]) Pair[B, A] {
+	return MakePair(Tail(fa), Head(fa))
+}
+
+// Paired converts a function with 2 parameters into a function taking a [Pair]
+// The inverse function is [Unpaired]
+func Paired[F ~func(T1, T2) R, T1, T2, R any](f F) func(Pair[T1, T2]) R {
+	return func(t Pair[T1, T2]) R {
+		return f(Head(t), Tail(t))
+	}
+}
+
+// Unpaired converts a function with a [Pair] parameter into a function with 2 parameters
+// The inverse function is [Paired]
+func Unpaired[F ~func(Pair[T1, T2]) R, T1, T2, R any](f F) func(T1, T2) R {
+	return func(t1 T1, t2 T2) R {
+		return f(MakePair(t1, t2))
+	}
+}
+
+func Merge[F ~func(B) func(A) R, A, B, R any](f F) func(Pair[A, B]) R {
+	return func(p Pair[A, B]) R {
+		return f(Tail(p))(Head(p))
+	}
+}

scan.bat

@@ -0,0 +1,3 @@
+@echo off
+
+busybox find . -type f -name "*\.go" | busybox xargs gopls check

state/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 state
+
+import (
+	EQ "github.com/IBM/fp-go/eq"
+	G "github.com/IBM/fp-go/state/generic"
+)
+
+// Constructs an equal predicate for a [State]
+func Eq[S, A any](w EQ.Eq[S], a EQ.Eq[A]) func(S) EQ.Eq[State[S, A]] {
+	return G.Eq[State[S, A]](w, a)
+}
+
+// FromStrictEquals constructs an [EQ.Eq] from the canonical comparison function
+func FromStrictEquals[S, A comparable]() func(S) EQ.Eq[State[S, A]] {
+	return G.FromStrictEquals[State[S, A]]()
+}

state/generic/eq.go

@@ -0,0 +1,36 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package generic
+
+import (
+	EQ "github.com/IBM/fp-go/eq"
+	P "github.com/IBM/fp-go/pair"
+)
+
+// Constructs an equal predicate for a [State]
+func Eq[GA ~func(S) P.Pair[A, S], S, A any](w EQ.Eq[S], a EQ.Eq[A]) func(S) EQ.Eq[GA] {
+	eqp := P.Eq(a, w)
+	return func(s S) EQ.Eq[GA] {
+		return EQ.FromEquals(func(l, r GA) bool {
+			return eqp.Equals(l(s), r(s))
+		})
+	}
+}
+
+// FromStrictEquals constructs an [EQ.Eq] from the canonical comparison function
+func FromStrictEquals[GA ~func(S) P.Pair[A, S], S, A comparable]() func(S) EQ.Eq[GA] {
+	return Eq[GA](EQ.FromStrictEquals[S](), EQ.FromStrictEquals[A]())
+}

state/generic/monad.go

@@ -0,0 +1,88 @@
+// Copyright (c) 2024 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/applicative"
+	"github.com/IBM/fp-go/internal/functor"
+	"github.com/IBM/fp-go/internal/monad"
+	"github.com/IBM/fp-go/internal/pointed"
+	P "github.com/IBM/fp-go/pair"
+)
+
+type statePointed[GA ~func(S) P.Pair[A, S], S, A any] struct{}
+
+type stateFunctor[GB ~func(S) P.Pair[B, S], GA ~func(S) P.Pair[A, S], S, A, B any] struct{}
+
+type stateApplicative[GB ~func(S) P.Pair[B, S], GAB ~func(S) P.Pair[func(A) B, S], GA ~func(S) P.Pair[A, S], S, A, B any] struct{}
+
+type stateMonad[GB ~func(S) P.Pair[B, S], GAB ~func(S) P.Pair[func(A) B, S], GA ~func(S) P.Pair[A, S], S, A, B any] struct{}
+
+func (o *statePointed[GA, S, A]) Of(a A) GA {
+	return Of[GA](a)
+}
+
+func (o *stateApplicative[GB, GAB, GA, S, A, B]) Of(a A) GA {
+	return Of[GA](a)
+}
+
+func (o *stateMonad[GB, GAB, GA, S, A, B]) Of(a A) GA {
+	return Of[GA](a)
+}
+
+func (o *stateFunctor[GB, GA, S, A, B]) Map(f func(A) B) func(GA) GB {
+	return Map[GB, GA](f)
+}
+
+func (o *stateApplicative[GB, GAB, GA, S, A, B]) Map(f func(A) B) func(GA) GB {
+	return Map[GB, GA](f)
+}
+
+func (o *stateMonad[GB, GAB, GA, S, A, B]) Map(f func(A) B) func(GA) GB {
+	return Map[GB, GA](f)
+}
+
+func (o *stateMonad[GB, GAB, GA, S, A, B]) Chain(f func(A) GB) func(GA) GB {
+	return Chain[GB, GA](f)
+}
+
+func (o *stateApplicative[GB, GAB, GA, S, A, B]) Ap(fa GA) func(GAB) GB {
+	return Ap[GB, GAB, GA](fa)
+}
+
+func (o *stateMonad[GB, GAB, GA, S, A, B]) Ap(fa GA) func(GAB) GB {
+	return Ap[GB, GAB, GA](fa)
+}
+
+// Pointed implements the pointed operations for [Writer]
+func Pointed[GA ~func(S) P.Pair[A, S], S, A any]() pointed.Pointed[A, GA] {
+	return &statePointed[GA, S, A]{}
+}
+
+// Functor implements the functor operations for [Writer]
+func Functor[GB ~func(S) P.Pair[B, S], GA ~func(S) P.Pair[A, S], S, A, B any]() functor.Functor[A, B, GA, GB] {
+	return &stateFunctor[GB, GA, S, A, B]{}
+}
+
+// Applicative implements the applicative operations for [Writer]
+func Applicative[GB ~func(S) P.Pair[B, S], GAB ~func(S) P.Pair[func(A) B, S], GA ~func(S) P.Pair[A, S], S, A, B any]() applicative.Applicative[A, B, GA, GB, GAB] {
+	return &stateApplicative[GB, GAB, GA, S, A, B]{}
+}
+
+// Monad implements the monadic operations for [Writer]
+func Monad[GB ~func(S) P.Pair[B, S], GAB ~func(S) P.Pair[func(A) B, S], GA ~func(S) P.Pair[A, S], S, A, B any]() monad.Monad[A, B, GA, GB, GAB] {
+	return &stateMonad[GB, GAB, GA, S, A, B]{}
+}

state/generic/state.go

@@ -0,0 +1,131 @@
+// Copyright (c) 2024 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package generic
+
+import (
+	F "github.com/IBM/fp-go/function"
+	C "github.com/IBM/fp-go/internal/chain"
+	FC "github.com/IBM/fp-go/internal/functor"
+	P "github.com/IBM/fp-go/pair"
+)
+
+var (
+	undefined any = struct{}{}
+)
+
+func Get[GA ~func(S) P.Pair[S, S], S any]() GA {
+	return P.Of[S]
+}
+
+func Gets[GA ~func(S) P.Pair[A, S], FCT ~func(S) A, A, S any](f FCT) GA {
+	return func(s S) P.Pair[A, S] {
+		return P.MakePair(f(s), s)
+	}
+}
+
+func Put[GA ~func(S) P.Pair[any, S], S any]() GA {
+	return F.Bind1st(P.MakePair[any, S], undefined)
+}
+
+func Modify[GA ~func(S) P.Pair[any, S], FCT ~func(S) S, S any](f FCT) GA {
+	return F.Flow2(
+		f,
+		F.Bind1st(P.MakePair[any, S], undefined),
+	)
+}
+
+func Of[GA ~func(S) P.Pair[A, S], S, A any](a A) GA {
+	return F.Bind1st(P.MakePair[A, S], a)
+}
+
+func MonadMap[GB ~func(S) P.Pair[B, S], GA ~func(S) P.Pair[A, S], FCT ~func(A) B, S, A, B any](fa GA, f FCT) GB {
+	return func(s S) P.Pair[B, S] {
+		p2 := fa(s)
+		return P.MakePair(f(P.Head(p2)), P.Tail(p2))
+	}
+}
+
+func Map[GB ~func(S) P.Pair[B, S], GA ~func(S) P.Pair[A, S], FCT ~func(A) B, S, A, B any](f FCT) func(GA) GB {
+	return F.Bind2nd(MonadMap[GB, GA, FCT, S, A, B], f)
+}
+
+func MonadChain[GB ~func(S) P.Pair[B, S], GA ~func(S) P.Pair[A, S], FCT ~func(A) GB, S, A, B any](fa GA, f FCT) GB {
+	return func(s S) P.Pair[B, S] {
+		a := fa(s)
+		return f(P.Head(a))(P.Tail(a))
+	}
+}
+
+func Chain[GB ~func(S) P.Pair[B, S], GA ~func(S) P.Pair[A, S], FCT ~func(A) GB, S, A, B any](f FCT) func(GA) GB {
+	return F.Bind2nd(MonadChain[GB, GA, FCT, S, A, B], f)
+}
+
+func MonadAp[GB ~func(S) P.Pair[B, S], GAB ~func(S) P.Pair[func(A) B, S], GA ~func(S) P.Pair[A, S], S, A, B any](fab GAB, fa GA) GB {
+	return func(s S) P.Pair[B, S] {
+		f := fab(s)
+		a := fa(P.Tail(f))
+
+		return P.MakePair(P.Head(f)(P.Head(a)), P.Tail(a))
+	}
+}
+
+func Ap[GB ~func(S) P.Pair[B, S], GAB ~func(S) P.Pair[func(A) B, S], GA ~func(S) P.Pair[A, S], S, A, B any](ga GA) func(GAB) GB {
+	return F.Bind2nd(MonadAp[GB, GAB, GA, S, A, B], ga)
+}
+
+func MonadChainFirst[GB ~func(S) P.Pair[B, S], GA ~func(S) P.Pair[A, S], FCT ~func(A) GB, S, A, B any](ma GA, f FCT) GA {
+	return C.MonadChainFirst(
+		MonadChain[GA, GA, func(A) GA],
+		MonadMap[GA, GB, func(B) A],
+		ma,
+		f,
+	)
+}
+
+func ChainFirst[GB ~func(S) P.Pair[B, S], GA ~func(S) P.Pair[A, S], FCT ~func(A) GB, S, A, B any](f FCT) func(GA) GA {
+	return C.ChainFirst(
+		Chain[GA, GA, func(A) GA],
+		Map[GA, GB, func(B) A],
+		f,
+	)
+}
+
+func Flatten[GAA ~func(S) P.Pair[GA, S], GA ~func(S) P.Pair[A, S], S, A any](mma GAA) GA {
+	return MonadChain[GA, GAA, func(GA) GA](mma, F.Identity[GA])
+}
+
+func Execute[GA ~func(S) P.Pair[A, S], S, A any](s S) func(GA) S {
+	return func(fa GA) S {
+		return P.Tail(fa(s))
+	}
+}
+
+func Evaluate[GA ~func(S) P.Pair[A, S], S, A any](s S) func(GA) A {
+	return func(fa GA) A {
+		return P.Head(fa(s))
+	}
+}
+
+func MonadFlap[FAB ~func(A) B, GFAB ~func(S) P.Pair[FAB, S], GB ~func(S) P.Pair[B, S], S, A, B any](fab GFAB, a A) GB {
+	return FC.MonadFlap(
+		MonadMap[GB, GFAB, func(FAB) B],
+		fab,
+		a)
+}
+
+func Flap[FAB ~func(A) B, GFAB ~func(S) P.Pair[FAB, S], GB ~func(S) P.Pair[B, S], S, A, B any](a A) func(GFAB) GB {
+	return FC.Flap(Map[GB, GFAB, func(FAB) B], a)
+}

state/monad.go

@@ -0,0 +1,44 @@
+// Copyright (c) 2024 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 state
+
+import (
+	"github.com/IBM/fp-go/internal/applicative"
+	"github.com/IBM/fp-go/internal/functor"
+	"github.com/IBM/fp-go/internal/monad"
+	"github.com/IBM/fp-go/internal/pointed"
+	G "github.com/IBM/fp-go/state/generic"
+)
+
+// Pointed implements the pointed operations for [State]
+func Pointed[S, A any]() pointed.Pointed[A, State[S, A]] {
+	return G.Pointed[State[S, A], S, A]()
+}
+
+// Functor implements the pointed operations for [State]
+func Functor[S, A, B any]() functor.Functor[A, B, State[S, A], State[S, B]] {
+	return G.Functor[State[S, B], State[S, A], S, A, B]()
+}
+
+// Applicative implements the applicative operations for [State]
+func Applicative[S, A, B any]() applicative.Applicative[A, B, State[S, A], State[S, B], State[S, func(A) B]] {
+	return G.Applicative[State[S, B], State[S, func(A) B], State[S, A]]()
+}
+
+// Monad implements the monadic operations for [State]
+func Monad[S, A, B any]() monad.Monad[A, B, State[S, A], State[S, B], State[S, func(A) B]] {
+	return G.Monad[State[S, B], State[S, func(A) B], State[S, A]]()
+}

state/state.go

@@ -0,0 +1,97 @@
+// Copyright (c) 2024 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 state
+
+import (
+	P "github.com/IBM/fp-go/pair"
+	R "github.com/IBM/fp-go/reader"
+	G "github.com/IBM/fp-go/state/generic"
+)
+
+// State represents an operation on top of a current [State] that produces a value and a new [State]
+type State[S, A any] R.Reader[S, P.Pair[A, S]]
+
+func Get[S any]() State[S, S] {
+	return G.Get[State[S, S]]()
+}
+
+func Gets[FCT ~func(S) A, A, S any](f FCT) State[S, A] {
+	return G.Gets[State[S, A]](f)
+}
+
+func Put[S any]() State[S, any] {
+	return G.Put[State[S, any]]()
+}
+
+func Modify[FCT ~func(S) S, S any](f FCT) State[S, any] {
+	return G.Modify[State[S, any]](f)
+}
+
+func Of[S, A any](a A) State[S, A] {
+	return G.Of[State[S, A]](a)
+}
+
+func MonadMap[S any, FCT ~func(A) B, A, B any](fa State[S, A], f FCT) State[S, B] {
+	return G.MonadMap[State[S, B], State[S, A]](fa, f)
+}
+
+func Map[S any, FCT ~func(A) B, A, B any](f FCT) func(State[S, A]) State[S, B] {
+	return G.Map[State[S, B], State[S, A]](f)
+}
+
+func MonadChain[S any, FCT ~func(A) State[S, B], A, B any](fa State[S, A], f FCT) State[S, B] {
+	return G.MonadChain[State[S, B], State[S, A]](fa, f)
+}
+
+func Chain[S any, FCT ~func(A) State[S, B], A, B any](f FCT) func(State[S, A]) State[S, B] {
+	return G.Chain[State[S, B], State[S, A]](f)
+}
+
+func MonadAp[S, A, B any](fab State[S, func(A) B], fa State[S, A]) State[S, B] {
+	return G.MonadAp[State[S, B], State[S, func(A) B], State[S, A]](fab, fa)
+}
+
+func Ap[S, A, B any](ga State[S, A]) func(State[S, func(A) B]) State[S, B] {
+	return G.Ap[State[S, B], State[S, func(A) B], State[S, A]](ga)
+}
+
+func MonadChainFirst[S any, FCT ~func(A) State[S, B], A, B any](ma State[S, A], f FCT) State[S, A] {
+	return G.MonadChainFirst[State[S, B], State[S, A]](ma, f)
+}
+
+func ChainFirst[S any, FCT ~func(A) State[S, B], A, B any](f FCT) func(State[S, A]) State[S, A] {
+	return G.ChainFirst[State[S, B], State[S, A]](f)
+}
+
+func Flatten[S, A any](mma State[S, State[S, A]]) State[S, A] {
+	return G.Flatten[State[S, State[S, A]], State[S, A]](mma)
+}
+
+func Execute[A, S any](s S) func(State[S, A]) S {
+	return G.Execute[State[S, A]](s)
+}
+
+func Evaluate[A, S any](s S) func(State[S, A]) A {
+	return G.Evaluate[State[S, A]](s)
+}
+
+func MonadFlap[FAB ~func(A) B, S, A, B any](fab State[S, FAB], a A) State[S, B] {
+	return G.MonadFlap[FAB, State[S, FAB], State[S, B], S, A, B](fab, a)
+}
+
+func Flap[S, A, B any](a A) func(State[S, func(A) B]) State[S, B] {
+	return G.Flap[func(A) B, State[S, func(A) B], State[S, B]](a)
+}

state/testing/laws.go

@@ -0,0 +1,78 @@
+// 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"
+	ST "github.com/IBM/fp-go/state"
+)
+
+// AssertLaws asserts the apply monad laws for the `Either` monad
+func AssertLaws[S, A, B, C any](t *testing.T,
+	eqw EQ.Eq[S],
+	eqa EQ.Eq[A],
+	eqb EQ.Eq[B],
+	eqc EQ.Eq[C],
+
+	ab func(A) B,
+	bc func(B) C,
+
+	s S,
+) func(a A) bool {
+
+	fofc := ST.Pointed[S, C]()
+	fofaa := ST.Pointed[S, func(A) A]()
+	fofbc := ST.Pointed[S, func(B) C]()
+	fofabb := ST.Pointed[S, func(func(A) B) B]()
+
+	fmap := ST.Functor[S, func(B) C, func(func(A) B) func(A) C]()
+
+	fapabb := ST.Applicative[S, func(A) B, B]()
+	fapabac := ST.Applicative[S, func(A) B, func(A) C]()
+
+	maa := ST.Monad[S, A, A]()
+	mab := ST.Monad[S, A, B]()
+	mac := ST.Monad[S, A, C]()
+	mbc := ST.Monad[S, B, C]()
+
+	return L.MonadAssertLaws(t,
+		ST.Eq(eqw, eqa)(s),
+		ST.Eq(eqw, eqb)(s),
+		ST.Eq(eqw, eqc)(s),
+
+		fofc,
+		fofaa,
+		fofbc,
+		fofabb,
+
+		fmap,
+
+		fapabb,
+		fapabac,
+
+		maa,
+		mab,
+		mac,
+		mbc,
+
+		ab,
+		bc,
+	)
+
+}

state/testing/laws_test.go

@@ -0,0 +1,49 @@
+// 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"
+
+	A "github.com/IBM/fp-go/array"
+	EQ "github.com/IBM/fp-go/eq"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMonadLaws(t *testing.T) {
+	// some comparison
+	eqs := A.Eq[string](EQ.FromStrictEquals[string]())
+	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, eqs, eqa, eqb, eqc, ab, bc, A.Empty[string]())
+
+	assert.True(t, laws(true))
+	assert.True(t, laws(false))
+}

statereaderioeither/eq.go

@@ -0,0 +1,35 @@
+// Copyright (c) 2024 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 statereaderioeither
+
+import (
+	EQ "github.com/IBM/fp-go/eq"
+	P "github.com/IBM/fp-go/pair"
+	RIOE "github.com/IBM/fp-go/readerioeither"
+	G "github.com/IBM/fp-go/statereaderioeither/generic"
+)
+
+// Eq implements the equals predicate for values contained in the [StateReaderIOEither] monad
+func Eq[
+	S, R, E, A any](eqr EQ.Eq[RIOE.ReaderIOEither[R, E, P.Pair[A, S]]]) func(S) EQ.Eq[StateReaderIOEither[S, R, E, A]] {
+	return G.Eq[StateReaderIOEither[S, R, E, A]](eqr)
+}
+
+// FromStrictEquals constructs an [EQ.Eq] from the canonical comparison function
+func FromStrictEquals[
+	S, R any, E, A comparable]() func(R) func(S) EQ.Eq[StateReaderIOEither[S, R, E, A]] {
+	return G.FromStrictEquals[StateReaderIOEither[S, R, E, A]]()
+}

statereaderioeither/generic/eq.go

@@ -0,0 +1,49 @@
+// Copyright (c) 2024 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"
+	EQ "github.com/IBM/fp-go/eq"
+	F "github.com/IBM/fp-go/function"
+	P "github.com/IBM/fp-go/pair"
+	G "github.com/IBM/fp-go/readerioeither/generic"
+)
+
+// Eq implements the equals predicate for values contained in the [StateReaderIOEither] monad
+func Eq[
+	SRIOEA ~func(S) RIOEA,
+	RIOEA ~func(R) IOEA,
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	S, R, E, A any](eqr EQ.Eq[RIOEA]) func(S) EQ.Eq[SRIOEA] {
+	return func(s S) EQ.Eq[SRIOEA] {
+		return EQ.FromEquals(func(l, r SRIOEA) bool {
+			return eqr.Equals(l(s), r(s))
+		})
+	}
+}
+
+// FromStrictEquals constructs an [EQ.Eq] from the canonical comparison function
+func FromStrictEquals[
+	SRIOEA ~func(S) RIOEA,
+	RIOEA ~func(R) IOEA,
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	S, R any, E, A comparable]() func(R) func(S) EQ.Eq[SRIOEA] {
+	return F.Flow2(
+		G.FromStrictEquals[RIOEA](),
+		Eq[SRIOEA, RIOEA, IOEA, S, R, E, A],
+	)
+}

statereaderioeither/generic/monad.go

@@ -0,0 +1,159 @@
+// Copyright (c) 2024 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"
+	"github.com/IBM/fp-go/internal/applicative"
+	"github.com/IBM/fp-go/internal/functor"
+	"github.com/IBM/fp-go/internal/monad"
+	"github.com/IBM/fp-go/internal/pointed"
+	P "github.com/IBM/fp-go/pair"
+)
+
+type stateReaderIOEitherPointed[
+	SRIOEA ~func(S) RIOEA,
+	RIOEA ~func(R) IOEA,
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	S, R, E, A any,
+] struct{}
+
+type stateReaderIOEitherFunctor[
+	SRIOEA ~func(S) RIOEA,
+	SRIOEB ~func(S) RIOEB,
+	RIOEA ~func(R) IOEA,
+	RIOEB ~func(R) IOEB,
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	IOEB ~func() ET.Either[E, P.Pair[B, S]],
+	S, R, E, A, B any,
+] struct{}
+
+type stateReaderIOEitherApplicative[
+	SRIOEA ~func(S) RIOEA,
+	SRIOEB ~func(S) RIOEB,
+	SRIOEAB ~func(S) RIOEAB,
+	RIOEA ~func(R) IOEA,
+	RIOEB ~func(R) IOEB,
+	RIOEAB ~func(R) IOEAB,
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	IOEB ~func() ET.Either[E, P.Pair[B, S]],
+	IOEAB ~func() ET.Either[E, P.Pair[func(A) B, S]],
+	S, R, E, A, B any,
+] struct{}
+
+type stateReaderIOEitherMonad[
+	SRIOEA ~func(S) RIOEA,
+	SRIOEB ~func(S) RIOEB,
+	SRIOEAB ~func(S) RIOEAB,
+	RIOEA ~func(R) IOEA,
+	RIOEB ~func(R) IOEB,
+	RIOEAB ~func(R) IOEAB,
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	IOEB ~func() ET.Either[E, P.Pair[B, S]],
+	IOEAB ~func() ET.Either[E, P.Pair[func(A) B, S]],
+	S, R, E, A, B any,
+] struct{}
+
+func (o *stateReaderIOEitherPointed[SRIOEA, RIOEA, IOEA, S, R, E, A]) Of(a A) SRIOEA {
+	return Of[SRIOEA](a)
+}
+
+func (o *stateReaderIOEitherMonad[SRIOEA, SRIOEB, SRIOEAB, RIOEA, RIOEB, RIOEAB, IOEA, IOEB, IOEAB, S, R, E, A, B]) Of(a A) SRIOEA {
+	return Of[SRIOEA](a)
+}
+
+func (o *stateReaderIOEitherApplicative[SRIOEA, SRIOEB, SRIOEAB, RIOEA, RIOEB, RIOEAB, IOEA, IOEB, IOEAB, S, R, E, A, B]) Of(a A) SRIOEA {
+	return Of[SRIOEA](a)
+}
+
+func (o *stateReaderIOEitherMonad[SRIOEA, SRIOEB, SRIOEAB, RIOEA, RIOEB, RIOEAB, IOEA, IOEB, IOEAB, S, R, E, A, B]) Map(f func(A) B) func(SRIOEA) SRIOEB {
+	return Map[SRIOEA, SRIOEB](f)
+}
+
+func (o *stateReaderIOEitherApplicative[SRIOEA, SRIOEB, SRIOEAB, RIOEA, RIOEB, RIOEAB, IOEA, IOEB, IOEAB, S, R, E, A, B]) Map(f func(A) B) func(SRIOEA) SRIOEB {
+	return Map[SRIOEA, SRIOEB](f)
+}
+
+func (o *stateReaderIOEitherFunctor[SRIOEA, SRIOEB, RIOEA, RIOEB, IOEA, IOEB, S, R, E, A, B]) Map(f func(A) B) func(SRIOEA) SRIOEB {
+	return Map[SRIOEA, SRIOEB](f)
+}
+
+func (o *stateReaderIOEitherMonad[SRIOEA, SRIOEB, SRIOEAB, RIOEA, RIOEB, RIOEAB, IOEA, IOEB, IOEAB, S, R, E, A, B]) Chain(f func(A) SRIOEB) func(SRIOEA) SRIOEB {
+	return Chain[SRIOEA, SRIOEB](f)
+}
+
+func (o *stateReaderIOEitherMonad[SRIOEA, SRIOEB, SRIOEAB, RIOEA, RIOEB, RIOEAB, IOEA, IOEB, IOEAB, S, R, E, A, B]) Ap(fa SRIOEA) func(SRIOEAB) SRIOEB {
+	return Ap[SRIOEA, SRIOEB, SRIOEAB, RIOEA, RIOEB, RIOEAB, IOEA, IOEB, IOEAB, S, R, E, A, B](fa)
+}
+
+func (o *stateReaderIOEitherApplicative[SRIOEA, SRIOEB, SRIOEAB, RIOEA, RIOEB, RIOEAB, IOEA, IOEB, IOEAB, S, R, E, A, B]) Ap(fa SRIOEA) func(SRIOEAB) SRIOEB {
+	return Ap[SRIOEA, SRIOEB, SRIOEAB, RIOEA, RIOEB, RIOEAB, IOEA, IOEB, IOEAB, S, R, E, A, B](fa)
+}
+
+// Pointed implements the pointed operations for [StateReaderIOEither]
+func Pointed[
+	SRIOEA ~func(S) RIOEA,
+	RIOEA ~func(R) IOEA,
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	S, R, E, A any,
+]() pointed.Pointed[A, SRIOEA] {
+	return &stateReaderIOEitherPointed[SRIOEA, RIOEA, IOEA, S, R, E, A]{}
+}
+
+// Functor implements the functor operations for [StateReaderIOEither]
+func Functor[
+	SRIOEA ~func(S) RIOEA,
+	SRIOEB ~func(S) RIOEB,
+	RIOEA ~func(R) IOEA,
+	RIOEB ~func(R) IOEB,
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	IOEB ~func() ET.Either[E, P.Pair[B, S]],
+	S, R, E, A, B any,
+]() functor.Functor[A, B, SRIOEA, SRIOEB] {
+	return &stateReaderIOEitherFunctor[SRIOEA, SRIOEB, RIOEA, RIOEB, IOEA, IOEB, S, R, E, A, B]{}
+}
+
+// Applicative implements the applicative operations for [StateReaderIOEither]
+func Applicative[
+	SRIOEA ~func(S) RIOEA,
+	SRIOEB ~func(S) RIOEB,
+	SRIOEAB ~func(S) RIOEAB,
+	RIOEA ~func(R) IOEA,
+	RIOEB ~func(R) IOEB,
+	RIOEAB ~func(R) IOEAB,
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	IOEB ~func() ET.Either[E, P.Pair[B, S]],
+	IOEAB ~func() ET.Either[E, P.Pair[func(A) B, S]],
+	S, R, E, A, B any,
+]() applicative.Applicative[A, B, SRIOEA, SRIOEB, SRIOEAB] {
+	return &stateReaderIOEitherApplicative[SRIOEA, SRIOEB, SRIOEAB, RIOEA, RIOEB, RIOEAB, IOEA, IOEB, IOEAB, S, R, E, A, B]{}
+}
+
+// Monad implements the monadic operations for [StateReaderIOEither]
+func Monad[
+	SRIOEA ~func(S) RIOEA,
+	SRIOEB ~func(S) RIOEB,
+	SRIOEAB ~func(S) RIOEAB,
+	RIOEA ~func(R) IOEA,
+	RIOEB ~func(R) IOEB,
+	RIOEAB ~func(R) IOEAB,
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	IOEB ~func() ET.Either[E, P.Pair[B, S]],
+	IOEAB ~func() ET.Either[E, P.Pair[func(A) B, S]],
+	S, R, E, A, B any,
+]() monad.Monad[A, B, SRIOEA, SRIOEB, SRIOEAB] {
+	return &stateReaderIOEitherMonad[SRIOEA, SRIOEB, SRIOEAB, RIOEA, RIOEB, RIOEAB, IOEA, IOEB, IOEAB, S, R, E, A, B]{}
+}

statereaderioeither/generic/state.go

@@ -0,0 +1,256 @@
+// Copyright (c) 2024 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"
+	F "github.com/IBM/fp-go/function"
+	ST "github.com/IBM/fp-go/internal/statet"
+	P "github.com/IBM/fp-go/pair"
+	G "github.com/IBM/fp-go/readerioeither/generic"
+)
+
+func Left[
+	SRIOEA ~func(S) RIOEA,
+	RIOEA ~func(R) IOEA,
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	S, R, E, A any,
+](e E) SRIOEA {
+	return F.Constant1[S](G.Left[RIOEA](e))
+}
+
+func Right[
+	SRIOEA ~func(S) RIOEA,
+	RIOEA ~func(R) IOEA,
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	S, R, E, A any,
+](a A) SRIOEA {
+	return ST.Of[SRIOEA](
+		G.Of[RIOEA],
+		a,
+	)
+}
+
+func Of[
+	SRIOEA ~func(S) RIOEA,
+	RIOEA ~func(R) IOEA,
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	S, R, E, A any,
+](a A) SRIOEA {
+	return Right[SRIOEA](a)
+}
+
+func MonadMap[
+	SRIOEA ~func(S) RIOEA,
+	SRIOEB ~func(S) RIOEB,
+	RIOEA ~func(R) IOEA,
+	RIOEB ~func(R) IOEB,
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	IOEB ~func() ET.Either[E, P.Pair[B, S]],
+	S, R, E, A, B any,
+](fa SRIOEA, f func(A) B) SRIOEB {
+	return ST.MonadMap[SRIOEA, SRIOEB](
+		G.MonadMap[RIOEA, RIOEB],
+		fa,
+		f,
+	)
+}
+
+func Map[
+	SRIOEA ~func(S) RIOEA,
+	SRIOEB ~func(S) RIOEB,
+	RIOEA ~func(R) IOEA,
+	RIOEB ~func(R) IOEB,
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	IOEB ~func() ET.Either[E, P.Pair[B, S]],
+	S, R, E, A, B any,
+](f func(A) B) func(SRIOEA) SRIOEB {
+	return ST.Map[SRIOEA, SRIOEB](
+		G.Map[RIOEA, RIOEB],
+		f,
+	)
+}
+
+func MonadChain[
+	SRIOEA ~func(S) RIOEA,
+	SRIOEB ~func(S) RIOEB,
+	RIOEA ~func(R) IOEA,
+	RIOEB ~func(R) IOEB,
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	IOEB ~func() ET.Either[E, P.Pair[B, S]],
+	S, R, E, A, B any,
+](fa SRIOEA, f func(A) SRIOEB) SRIOEB {
+	return ST.MonadChain[SRIOEA, SRIOEB](
+		G.MonadChain[RIOEA, RIOEB],
+		fa,
+		f,
+	)
+}
+
+func Chain[
+	SRIOEA ~func(S) RIOEA,
+	SRIOEB ~func(S) RIOEB,
+	RIOEA ~func(R) IOEA,
+	RIOEB ~func(R) IOEB,
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	IOEB ~func() ET.Either[E, P.Pair[B, S]],
+	S, R, E, A, B any,
+](f func(A) SRIOEB) func(SRIOEA) SRIOEB {
+	return ST.Chain[SRIOEA, SRIOEB](
+		G.Chain[RIOEA, RIOEB],
+		f,
+	)
+}
+
+func MonadAp[
+	SRIOEA ~func(S) RIOEA,
+	SRIOEB ~func(S) RIOEB,
+	SRIOEAB ~func(S) RIOEAB,
+	RIOEA ~func(R) IOEA,
+	RIOEB ~func(R) IOEB,
+	RIOEAB ~func(R) IOEAB,
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	IOEB ~func() ET.Either[E, P.Pair[B, S]],
+	IOEAB ~func() ET.Either[E, P.Pair[func(A) B, S]],
+	S, R, E, A, B any,
+](fab SRIOEAB, fa SRIOEA) SRIOEB {
+	return ST.MonadAp[SRIOEA, SRIOEB, SRIOEAB](
+		G.MonadMap[RIOEA, RIOEB],
+		G.MonadChain[RIOEAB, RIOEB],
+		fab,
+		fa,
+	)
+}
+
+func Ap[
+	SRIOEA ~func(S) RIOEA,
+	SRIOEB ~func(S) RIOEB,
+	SRIOEAB ~func(S) RIOEAB,
+	RIOEA ~func(R) IOEA,
+	RIOEB ~func(R) IOEB,
+	RIOEAB ~func(R) IOEAB,
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	IOEB ~func() ET.Either[E, P.Pair[B, S]],
+	IOEAB ~func() ET.Either[E, P.Pair[func(A) B, S]],
+	S, R, E, A, B any,
+](fa SRIOEA) func(SRIOEAB) SRIOEB {
+	return ST.Ap[SRIOEA, SRIOEB, SRIOEAB](
+		G.Map[RIOEA, RIOEB],
+		G.Chain[RIOEAB, RIOEB],
+		fa,
+	)
+}
+
+func FromReaderIOEither[
+	SRIOEA ~func(S) RIOEA,
+	RIOEA ~func(R) IOEA,
+
+	RIOEA_IN ~func(R) IOEA_IN,
+
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	IOEA_IN ~func() ET.Either[E, A],
+
+	S, R, E, A any,
+](fa RIOEA_IN) SRIOEA {
+	return ST.FromF[SRIOEA](
+		G.MonadMap[RIOEA_IN, RIOEA],
+		fa,
+	)
+}
+
+func FromReaderEither[
+	SRIOEA ~func(S) RIOEA,
+	RIOEA_IN ~func(R) IOEA_IN,
+	RIOEA ~func(R) IOEA,
+
+	REA_IN ~func(R) ET.Either[E, A],
+
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	IOEA_IN ~func() ET.Either[E, A],
+
+	S, R, E, A any,
+](fa REA_IN) SRIOEA {
+	return FromReaderIOEither[SRIOEA](G.FromReaderEither[REA_IN, RIOEA_IN](fa))
+}
+
+func FromIOEither[
+	SRIOEA ~func(S) RIOEA,
+	RIOEA_IN ~func(R) IOEA_IN,
+	RIOEA ~func(R) IOEA,
+
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	IOEA_IN ~func() ET.Either[E, A],
+
+	S, R, E, A any,
+](fa IOEA_IN) SRIOEA {
+	return FromReaderIOEither[SRIOEA](G.FromIOEither[RIOEA_IN](fa))
+}
+
+func FromIO[
+	SRIOEA ~func(S) RIOEA,
+	RIOEA_IN ~func(R) IOEA_IN,
+
+	IO_IN ~func() A,
+
+	RIOEA ~func(R) IOEA,
+
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	IOEA_IN ~func() ET.Either[E, A],
+
+	S, R, E, A any,
+](fa IO_IN) SRIOEA {
+	return FromReaderIOEither[SRIOEA](G.FromIO[RIOEA_IN](fa))
+}
+
+func FromReader[
+	SRIOEA ~func(S) RIOEA,
+	RIOEA_IN ~func(R) IOEA_IN,
+
+	R_IN ~func(R) A,
+
+	RIOEA ~func(R) IOEA,
+
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+	IOEA_IN ~func() ET.Either[E, A],
+
+	S, R, E, A any,
+](fa R_IN) SRIOEA {
+	return FromReaderIOEither[SRIOEA](G.FromReader[R_IN, RIOEA_IN](fa))
+}
+
+func FromEither[
+	SRIOEA ~func(S) RIOEA,
+
+	RIOEA ~func(R) IOEA,
+
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+
+	S, R, E, A any,
+](ma ET.Either[E, A]) SRIOEA {
+	return ET.MonadFold(ma, Left[SRIOEA], Right[SRIOEA])
+}
+
+func FromState[
+	SRIOEA ~func(S) RIOEA,
+	STATE ~func(S) P.Pair[A, S],
+	RIOEA ~func(R) IOEA,
+
+	IOEA ~func() ET.Either[E, P.Pair[A, S]],
+
+	S, R, E, A any,
+](fa STATE) SRIOEA {
+	return ST.FromState[SRIOEA](G.Of[RIOEA], fa)
+}

statereaderioeither/monad.go

@@ -0,0 +1,44 @@
+// Copyright (c) 2024 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 statereaderioeither
+
+import (
+	"github.com/IBM/fp-go/internal/applicative"
+	"github.com/IBM/fp-go/internal/functor"
+	"github.com/IBM/fp-go/internal/monad"
+	"github.com/IBM/fp-go/internal/pointed"
+	G "github.com/IBM/fp-go/statereaderioeither/generic"
+)
+
+// Pointed returns the pointed operations for [StateReaderIOEither]
+func Pointed[S, R, E, A any]() pointed.Pointed[A, StateReaderIOEither[S, R, E, A]] {
+	return G.Pointed[StateReaderIOEither[S, R, E, A]]()
+}
+
+// Functor returns the functor operations for [StateReaderIOEither]
+func Functor[S, R, E, A, B any]() functor.Functor[A, B, StateReaderIOEither[S, R, E, A], StateReaderIOEither[S, R, E, B]] {
+	return G.Functor[StateReaderIOEither[S, R, E, A], StateReaderIOEither[S, R, E, B]]()
+}
+
+// Applicative returns the applicative operations for [StateReaderIOEither]
+func Applicative[S, R, E, A, B any]() applicative.Applicative[A, B, StateReaderIOEither[S, R, E, A], StateReaderIOEither[S, R, E, B], StateReaderIOEither[S, R, E, func(A) B]] {
+	return G.Applicative[StateReaderIOEither[S, R, E, A], StateReaderIOEither[S, R, E, B], StateReaderIOEither[S, R, E, func(A) B]]()
+}
+
+// Monad returns the monadic operations for [StateReaderIOEither]
+func Monad[S, R, E, A, B any]() monad.Monad[A, B, StateReaderIOEither[S, R, E, A], StateReaderIOEither[S, R, E, B], StateReaderIOEither[S, R, E, func(A) B]] {
+	return G.Monad[StateReaderIOEither[S, R, E, A], StateReaderIOEither[S, R, E, B], StateReaderIOEither[S, R, E, func(A) B]]()
+}

statereaderioeither/state.go

@@ -0,0 +1,91 @@
+// Copyright (c) 2024 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 statereaderioeither
+
+import (
+	ET "github.com/IBM/fp-go/either"
+	IO "github.com/IBM/fp-go/io"
+	IOE "github.com/IBM/fp-go/ioeither"
+	RD "github.com/IBM/fp-go/reader"
+	RE "github.com/IBM/fp-go/readereither"
+	RIOE "github.com/IBM/fp-go/readerioeither"
+	ST "github.com/IBM/fp-go/state"
+	G "github.com/IBM/fp-go/statereaderioeither/generic"
+)
+
+func Left[S, R, A, E any](e E) StateReaderIOEither[S, R, E, A] {
+	return G.Left[StateReaderIOEither[S, R, E, A]](e)
+}
+
+func Right[S, R, E, A any](a A) StateReaderIOEither[S, R, E, A] {
+	return G.Right[StateReaderIOEither[S, R, E, A]](a)
+}
+
+func Of[S, R, E, A any](a A) StateReaderIOEither[S, R, E, A] {
+	return G.Of[StateReaderIOEither[S, R, E, A]](a)
+}
+
+func MonadMap[S, R, E, A, B any](fa StateReaderIOEither[S, R, E, A], f func(A) B) StateReaderIOEither[S, R, E, B] {
+	return G.MonadMap[StateReaderIOEither[S, R, E, A], StateReaderIOEither[S, R, E, B]](fa, f)
+}
+
+func Map[S, R, E, A, B any](f func(A) B) func(StateReaderIOEither[S, R, E, A]) StateReaderIOEither[S, R, E, B] {
+	return G.Map[StateReaderIOEither[S, R, E, A], StateReaderIOEither[S, R, E, B]](f)
+}
+
+func MonadChain[S, R, E, A, B any](fa StateReaderIOEither[S, R, E, A], f func(A) StateReaderIOEither[S, R, E, B]) StateReaderIOEither[S, R, E, B] {
+	return G.MonadChain[StateReaderIOEither[S, R, E, A], StateReaderIOEither[S, R, E, B]](fa, f)
+}
+
+func Chain[S, R, E, A, B any](f func(A) StateReaderIOEither[S, R, E, B]) func(StateReaderIOEither[S, R, E, A]) StateReaderIOEither[S, R, E, B] {
+	return G.Chain[StateReaderIOEither[S, R, E, A], StateReaderIOEither[S, R, E, B]](f)
+}
+
+func MonadAp[S, R, E, A, B any](fab StateReaderIOEither[S, R, E, func(A) B], fa StateReaderIOEither[S, R, E, A]) StateReaderIOEither[S, R, E, B] {
+	return G.MonadAp[StateReaderIOEither[S, R, E, A], StateReaderIOEither[S, R, E, B], StateReaderIOEither[S, R, E, func(A) B]](fab, fa)
+}
+
+func Ap[S, R, E, A, B any](fa StateReaderIOEither[S, R, E, A]) func(StateReaderIOEither[S, R, E, func(A) B]) StateReaderIOEither[S, R, E, B] {
+	return G.Ap[StateReaderIOEither[S, R, E, A], StateReaderIOEither[S, R, E, B], StateReaderIOEither[S, R, E, func(A) B]](fa)
+}
+
+func FromReaderIOEither[S, R, E, A any](fa RIOE.ReaderIOEither[R, E, A]) StateReaderIOEither[S, R, E, A] {
+	return G.FromReaderIOEither[StateReaderIOEither[S, R, E, A]](fa)
+}
+
+func FromReaderEither[S, R, E, A any](fa RE.ReaderEither[R, E, A]) StateReaderIOEither[S, R, E, A] {
+	return G.FromReaderEither[StateReaderIOEither[S, R, E, A], RIOE.ReaderIOEither[R, E, A]](fa)
+}
+
+func FromIOEither[S, R, E, A any](fa IOE.IOEither[E, A]) StateReaderIOEither[S, R, E, A] {
+	return G.FromIOEither[StateReaderIOEither[S, R, E, A], RIOE.ReaderIOEither[R, E, A]](fa)
+}
+
+func FromState[S, R, E, A any](sa ST.State[S, A]) StateReaderIOEither[S, R, E, A] {
+	return G.FromState[StateReaderIOEither[S, R, E, A]](sa)
+}
+
+func FromIO[S, R, E, A any](fa IO.IO[A]) StateReaderIOEither[S, R, E, A] {
+	return G.FromIO[StateReaderIOEither[S, R, E, A], RIOE.ReaderIOEither[R, E, A]](fa)
+}
+
+func FromReader[S, R, E, A any](fa RD.Reader[R, A]) StateReaderIOEither[S, R, E, A] {
+	return G.FromReader[StateReaderIOEither[S, R, E, A], RIOE.ReaderIOEither[R, E, A]](fa)
+}
+
+func FromEither[S, R, E, A any](ma ET.Either[E, A]) StateReaderIOEither[S, R, E, A] {
+	return G.FromEither[StateReaderIOEither[S, R, E, A]](ma)
+}

statereaderioeither/testing/laws.go

@@ -0,0 +1,87 @@
+// Copyright (c) 2024 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"
+
+	ET "github.com/IBM/fp-go/either"
+	EQ "github.com/IBM/fp-go/eq"
+	L "github.com/IBM/fp-go/internal/monad/testing"
+	P "github.com/IBM/fp-go/pair"
+	RIOE "github.com/IBM/fp-go/readerioeither"
+	ST "github.com/IBM/fp-go/statereaderioeither"
+)
+
+// AssertLaws asserts the apply monad laws for the `Either` monad
+func AssertLaws[S, E, R, A, B, C any](t *testing.T,
+	eqs EQ.Eq[S],
+	eqe EQ.Eq[E],
+	eqa EQ.Eq[A],
+	eqb EQ.Eq[B],
+	eqc EQ.Eq[C],
+
+	ab func(A) B,
+	bc func(B) C,
+
+	s S,
+	r R,
+) func(a A) bool {
+
+	eqra := RIOE.Eq[R](ET.Eq(eqe, P.Eq(eqa, eqs)))(r)
+	eqrb := RIOE.Eq[R](ET.Eq(eqe, P.Eq(eqb, eqs)))(r)
+	eqrc := RIOE.Eq[R](ET.Eq(eqe, P.Eq(eqc, eqs)))(r)
+
+	fofc := ST.Pointed[S, R, E, C]()
+	fofaa := ST.Pointed[S, R, E, func(A) A]()
+	fofbc := ST.Pointed[S, R, E, func(B) C]()
+	fofabb := ST.Pointed[S, R, E, func(func(A) B) B]()
+
+	fmap := ST.Functor[S, R, E, func(B) C, func(func(A) B) func(A) C]()
+
+	fapabb := ST.Applicative[S, R, E, func(A) B, B]()
+	fapabac := ST.Applicative[S, R, E, func(A) B, func(A) C]()
+
+	maa := ST.Monad[S, R, E, A, A]()
+	mab := ST.Monad[S, R, E, A, B]()
+	mac := ST.Monad[S, R, E, A, C]()
+	mbc := ST.Monad[S, R, E, B, C]()
+
+	return L.MonadAssertLaws(t,
+		ST.Eq(eqra)(s),
+		ST.Eq(eqrb)(s),
+		ST.Eq(eqrc)(s),
+
+		fofc,
+		fofaa,
+		fofbc,
+		fofabb,
+
+		fmap,
+
+		fapabb,
+		fapabac,
+
+		maa,
+		mab,
+		mac,
+		mbc,
+
+		ab,
+		bc,
+	)
+
+}

statereaderioeither/testing/laws_test.go

@@ -0,0 +1,51 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package testing
+
+import (
+	"context"
+	"fmt"
+	"testing"
+
+	A "github.com/IBM/fp-go/array"
+	EQ "github.com/IBM/fp-go/eq"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMonadLaws(t *testing.T) {
+	// some comparison
+	eqs := A.Eq[string](EQ.FromStrictEquals[string]())
+	eqe := EQ.FromStrictEquals[error]()
+	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, eqs, eqe, eqa, eqb, eqc, ab, bc, A.Empty[string](), context.Background())
+
+	assert.True(t, laws(true))
+	assert.True(t, laws(false))
+}

statereaderioeither/type.go

@@ -0,0 +1,24 @@
+// Copyright (c) 2024 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 statereaderioeither
+
+import (
+	P "github.com/IBM/fp-go/pair"
+	RD "github.com/IBM/fp-go/reader"
+	RIOE "github.com/IBM/fp-go/readerioeither"
+)
+
+type StateReaderIOEither[S, R, E, A any] RD.Reader[S, RIOE.ReaderIOEither[R, E, P.Pair[A, S]]]

writer/bind.go

@@ -17,20 +17,22 @@ package writer
 
 import (
 	M "github.com/IBM/fp-go/monoid"
+	SG "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)
+func Do[S, W any](m M.Monoid[W], s S) Writer[W, S] {
+	return G.Do[Writer[W, S], W, S](m, s)
 }
 
 // Bind attaches the result of a computation to a context [S1] to produce a context [S2]
 func Bind[S1, S2, T, W any](
+	s SG.Semigroup[W],
 	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](setter, f)
+	return G.Bind[Writer[W, S1], Writer[W, S2], Writer[W, T], W, S1, S2, T](s, setter, f)
 }
 
 // Let attaches the result of a computation to a context [S1] to produce a context [S2]
@@ -58,8 +60,9 @@ func BindTo[W, S1, T any](
 
 // 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 SG.Semigroup[W],
 	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](setter, fa)
+	return G.ApS[Writer[W, S1], Writer[W, S2], Writer[W, T], W, S1, S2, T](s, setter, fa)
 }

writer/bind_test.go

@@ -34,33 +34,33 @@ var (
 )
 
 func getLastName(s utils.Initial) Writer[[]string, string] {
-	return Of[string](monoid)("Doe")
+	return Of[string](monoid, "Doe")
 }
 
 func getGivenName(s utils.WithLastName) Writer[[]string, string] {
-	return Of[string](monoid)("John")
+	return Of[string](monoid, "John")
 }
 
 func TestBind(t *testing.T) {
 
 	res := F.Pipe3(
-		Do[utils.Initial](monoid)(utils.Empty),
-		Bind(utils.SetLastName, getLastName),
-		Bind(utils.SetGivenName, getGivenName),
+		Do[utils.Initial](monoid, utils.Empty),
+		Bind(sg, utils.SetLastName, getLastName),
+		Bind(sg, utils.SetGivenName, getGivenName),
 		Map[[]string](utils.GetFullName),
 	)
 
-	assert.True(t, eq.Equals(res, Of[string](monoid)("John Doe")))
+	assert.True(t, eq.Equals(res, Of[string](monoid, "John Doe")))
 }
 
 func TestApS(t *testing.T) {
 
 	res := F.Pipe3(
-		Do[utils.Initial](monoid)(utils.Empty),
-		ApS(utils.SetLastName, Of[string](monoid)("Doe")),
-		ApS(utils.SetGivenName, Of[string](monoid)("John")),
+		Do[utils.Initial](monoid, utils.Empty),
+		ApS(sg, utils.SetLastName, Of[string](monoid, "Doe")),
+		ApS(sg, utils.SetGivenName, Of[string](monoid, "John")),
 		Map[[]string](utils.GetFullName),
 	)
 
-	assert.True(t, eq.Equals(res, Of[string](monoid)("John Doe")))
+	assert.True(t, eq.Equals(res, Of[string](monoid, "John Doe")))
 }

writer/generic/bind.go

@@ -16,26 +16,28 @@
 package generic
 
 import (
+	FCT "github.com/IBM/fp-go/function"
 	"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"
+	P "github.com/IBM/fp-go/pair"
 	SG "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.Tuple3[S, W, SG.Semigroup[W]], W, S any](m M.Monoid[W]) func(S) GS {
-	return Of[GS, W, S](m)
+func Do[GS ~func() P.Pair[S, W], W, S any](m M.Monoid[W], s S) GS {
+	return Of[GS, W, S](m, s)
 }
 
 // Bind attaches the result of a computation to a context [S1] to produce a context [S2]
-func Bind[GS1 ~func() T.Tuple3[S1, W, SG.Semigroup[W]], GS2 ~func() T.Tuple3[S2, W, SG.Semigroup[W]], GT ~func() T.Tuple3[A, W, SG.Semigroup[W]], W, S1, S2, A any](
+func Bind[GS1 ~func() P.Pair[S1, W], GS2 ~func() P.Pair[S2, W], GT ~func() P.Pair[A, W], W, S1, S2, A any](
+	s SG.Semigroup[W],
 	setter func(A) func(S1) S2,
 	f func(S1) GT,
 ) func(GS1) GS2 {
 	return C.Bind(
-		Chain[GS2, GS1, func(S1) GS2, W, S1, S2],
+		FCT.Bind1st(Chain[GS2, GS1, func(S1) GS2, W, S1, S2], s),
 		Map[GS2, GT, func(A) S2, W, A, S2],
 		setter,
 		f,
@@ -43,7 +45,7 @@ func Bind[GS1 ~func() T.Tuple3[S1, W, SG.Semigroup[W]], GS2 ~func() T.Tuple3[S2,
 }
 
 // Let attaches the result of a computation to a context [S1] to produce a context [S2]
-func Let[GS1 ~func() T.Tuple3[S1, W, SG.Semigroup[W]], GS2 ~func() T.Tuple3[S2, W, SG.Semigroup[W]], W, S1, S2, A any](
+func Let[GS1 ~func() P.Pair[S1, W], GS2 ~func() P.Pair[S2, W], W, S1, S2, A any](
 	key func(A) func(S1) S2,
 	f func(S1) A,
 ) func(GS1) GS2 {
@@ -55,7 +57,7 @@ func Let[GS1 ~func() T.Tuple3[S1, W, SG.Semigroup[W]], GS2 ~func() T.Tuple3[S2,
 }
 
 // LetTo attaches the a value to a context [S1] to produce a context [S2]
-func LetTo[GS1 ~func() T.Tuple3[S1, W, SG.Semigroup[W]], GS2 ~func() T.Tuple3[S2, W, SG.Semigroup[W]], W, S1, S2, B any](
+func LetTo[GS1 ~func() P.Pair[S1, W], GS2 ~func() P.Pair[S2, W], W, S1, S2, B any](
 	key func(B) func(S1) S2,
 	b B,
 ) func(GS1) GS2 {
@@ -67,7 +69,7 @@ func LetTo[GS1 ~func() T.Tuple3[S1, W, SG.Semigroup[W]], GS2 ~func() T.Tuple3[S2
 }
 
 // BindTo initializes a new state [S1] from a value [T]
-func BindTo[GS1 ~func() T.Tuple3[S1, W, SG.Semigroup[W]], GT ~func() T.Tuple3[A, W, SG.Semigroup[W]], W, S1, A any](
+func BindTo[GS1 ~func() P.Pair[S1, W], GT ~func() P.Pair[A, W], W, S1, A any](
 	setter func(A) S1,
 ) func(GT) GS1 {
 	return C.BindTo(
@@ -77,13 +79,14 @@ func BindTo[GS1 ~func() T.Tuple3[S1, W, SG.Semigroup[W]], GT ~func() T.Tuple3[A,
 }
 
 // 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.Tuple3[S1, W, SG.Semigroup[W]], GS2 ~func() T.Tuple3[S2, W, SG.Semigroup[W]], GT ~func() T.Tuple3[A, W, SG.Semigroup[W]], W, S1, S2, A any](
+func ApS[GS1 ~func() P.Pair[S1, W], GS2 ~func() P.Pair[S2, W], GT ~func() P.Pair[A, W], W, S1, S2, A any](
+	s SG.Semigroup[W],
 	setter func(A) func(S1) S2,
 	fa GT,
 ) func(GS1) GS2 {
 	return apply.ApS(
-		Ap[GS2, func() T.Tuple3[func(A) S2, W, SG.Semigroup[W]], GT, W, A, S2],
-		Map[func() T.Tuple3[func(A) S2, W, SG.Semigroup[W]], GS1, func(S1) func(A) S2],
+		FCT.Bind1st(Ap[GS2, func() P.Pair[func(A) S2, W], GT, W, A, S2], s),
+		Map[func() P.Pair[func(A) S2, W], GS1, func(S1) func(A) S2],
 		setter,
 		fa,
 	)

writer/generic/eq.go

@@ -17,21 +17,18 @@ package generic
 
 import (
 	EQ "github.com/IBM/fp-go/eq"
-	SG "github.com/IBM/fp-go/semigroup"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
 // Constructs an equal predicate for a [Writer]
-func Eq[GA ~func() T.Tuple3[A, W, SG.Semigroup[W]], W, A any](w EQ.Eq[W], a EQ.Eq[A]) EQ.Eq[GA] {
+func Eq[GA ~func() P.Pair[A, W], W, A any](w EQ.Eq[W], a EQ.Eq[A]) EQ.Eq[GA] {
+	eqp := P.Eq(a, w)
 	return EQ.FromEquals(func(l, r GA) bool {
-		ll := l()
-		rr := r()
-
-		return a.Equals(ll.F1, rr.F1) && w.Equals(ll.F2, rr.F2)
+		return eqp.Equals(l(), r())
 	})
 }
 
 // FromStrictEquals constructs an [EQ.Eq] from the canonical comparison function
-func FromStrictEquals[GA ~func() T.Tuple3[A, W, SG.Semigroup[W]], W, A comparable]() EQ.Eq[GA] {
+func FromStrictEquals[GA ~func() P.Pair[A, W], W, A comparable]() EQ.Eq[GA] {
 	return Eq[GA](EQ.FromStrictEquals[W](), EQ.FromStrictEquals[A]())
 }

writer/generic/monad.go

@@ -0,0 +1,106 @@
+// Copyright (c) 2024 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/applicative"
+	"github.com/IBM/fp-go/internal/functor"
+	"github.com/IBM/fp-go/internal/monad"
+	"github.com/IBM/fp-go/internal/pointed"
+	M "github.com/IBM/fp-go/monoid"
+	P "github.com/IBM/fp-go/pair"
+	SG "github.com/IBM/fp-go/semigroup"
+)
+
+type writerPointed[GA ~func() P.Pair[A, W], W, A any] struct {
+	m M.Monoid[W]
+}
+
+type writerFunctor[GB ~func() P.Pair[B, W], GA ~func() P.Pair[A, W], W, A, B any] struct{}
+
+type writerApplicative[GB ~func() P.Pair[B, W], GAB ~func() P.Pair[func(A) B, W], GA ~func() P.Pair[A, W], W, A, B any] struct {
+	s SG.Semigroup[W]
+	m M.Monoid[W]
+}
+
+type writerMonad[GB ~func() P.Pair[B, W], GAB ~func() P.Pair[func(A) B, W], GA ~func() P.Pair[A, W], W, A, B any] struct {
+	s SG.Semigroup[W]
+	m M.Monoid[W]
+}
+
+func (o *writerPointed[GA, W, A]) Of(a A) GA {
+	return Of[GA](o.m, a)
+}
+
+func (o *writerApplicative[GB, GAB, GA, W, A, B]) Of(a A) GA {
+	return Of[GA](o.m, a)
+}
+
+func (o *writerMonad[GB, GAB, GA, W, A, B]) Of(a A) GA {
+	return Of[GA](o.m, a)
+}
+
+func (o *writerFunctor[GB, GA, W, A, B]) Map(f func(A) B) func(GA) GB {
+	return Map[GB, GA](f)
+}
+
+func (o *writerApplicative[GB, GAB, GA, W, A, B]) Map(f func(A) B) func(GA) GB {
+	return Map[GB, GA](f)
+}
+
+func (o *writerMonad[GB, GAB, GA, W, A, B]) Map(f func(A) B) func(GA) GB {
+	return Map[GB, GA](f)
+}
+
+func (o *writerMonad[GB, GAB, GA, W, A, B]) Chain(f func(A) GB) func(GA) GB {
+	return Chain[GB, GA](o.s, f)
+}
+
+func (o *writerApplicative[GB, GAB, GA, W, A, B]) Ap(fa GA) func(GAB) GB {
+	return Ap[GB, GAB, GA](o.s, fa)
+}
+
+func (o *writerMonad[GB, GAB, GA, W, A, B]) Ap(fa GA) func(GAB) GB {
+	return Ap[GB, GAB, GA](o.s, fa)
+}
+
+// Pointed implements the pointed operations for [Writer]
+func Pointed[GA ~func() P.Pair[A, W], W, A any](m M.Monoid[W]) pointed.Pointed[A, GA] {
+	return &writerPointed[GA, W, A]{
+		m: m,
+	}
+}
+
+// Functor implements the functor operations for [Writer]
+func Functor[GB ~func() P.Pair[B, W], GA ~func() P.Pair[A, W], W, A, B any]() functor.Functor[A, B, GA, GB] {
+	return &writerFunctor[GB, GA, W, A, B]{}
+}
+
+// Applicative implements the applicative operations for [Writer]
+func Applicative[GB ~func() P.Pair[B, W], GAB ~func() P.Pair[func(A) B, W], GA ~func() P.Pair[A, W], W, A, B any](m M.Monoid[W]) applicative.Applicative[A, B, GA, GB, GAB] {
+	return &writerApplicative[GB, GAB, GA, W, A, B]{
+		s: M.ToSemigroup(m),
+		m: m,
+	}
+}
+
+// Monad implements the monadic operations for [Writer]
+func Monad[GB ~func() P.Pair[B, W], GAB ~func() P.Pair[func(A) B, W], GA ~func() P.Pair[A, W], W, A, B any](m M.Monoid[W]) monad.Monad[A, B, GA, GB, GAB] {
+	return &writerMonad[GB, GAB, GA, W, A, B]{
+		s: M.ToSemigroup(m),
+		m: m,
+	}
+}

writer/generic/writer.go

@@ -21,133 +21,137 @@ import (
 	FC "github.com/IBM/fp-go/internal/functor"
 	IO "github.com/IBM/fp-go/io/generic"
 	M "github.com/IBM/fp-go/monoid"
+	P "github.com/IBM/fp-go/pair"
 	SG "github.com/IBM/fp-go/semigroup"
-	T "github.com/IBM/fp-go/tuple"
 )
 
-func Tell[GA ~func() T.Tuple3[any, W, SG.Semigroup[W]], W any](s SG.Semigroup[W]) func(W) GA {
-	return F.Flow2(
-		F.Bind13of3(T.MakeTuple3[any, W, SG.Semigroup[W]])(nil, s),
-		IO.Of[GA],
-	)
+var (
+	undefined any = struct{}{}
+)
+
+func Tell[GA ~func() P.Pair[any, W], W any](w W) GA {
+	return IO.Of[GA](P.MakePair[any](undefined, w))
 }
 
-func Of[GA ~func() T.Tuple3[A, W, SG.Semigroup[W]], W, A any](m M.Monoid[W]) func(A) GA {
-	return F.Flow2(
-		F.Bind23of3(T.MakeTuple3[A, W, SG.Semigroup[W]])(m.Empty(), M.ToSemigroup(m)),
-		IO.Of[GA],
-	)
+func Of[GA ~func() P.Pair[A, W], W, A any](m M.Monoid[W], a A) GA {
+	return IO.Of[GA](P.MakePair(a, m.Empty()))
 }
 
 // Listen modifies the result to include the changes to the accumulator
-func Listen[GA ~func() T.Tuple3[A, W, SG.Semigroup[W]], GTA ~func() T.Tuple3[T.Tuple2[A, W], W, SG.Semigroup[W]], W, A any](fa GA) GTA {
-	return func() T.Tuple3[T.Tuple2[A, W], W, SG.Semigroup[W]] {
+func Listen[GA ~func() P.Pair[A, W], GTA ~func() P.Pair[P.Pair[A, W], W], W, A any](fa GA) GTA {
+	return func() P.Pair[P.Pair[A, W], W] {
 		t := fa()
-		return T.MakeTuple3(T.MakeTuple2(t.F1, t.F2), t.F2, t.F3)
+		return P.MakePair(t, P.Tail(t))
 	}
 }
 
 // Pass applies the returned function to the accumulator
-func Pass[GFA ~func() T.Tuple3[T.Tuple2[A, FCT], W, SG.Semigroup[W]], GA ~func() T.Tuple3[A, W, SG.Semigroup[W]], FCT ~func(W) W, W, A any](fa GFA) GA {
-	return func() T.Tuple3[A, W, SG.Semigroup[W]] {
+func Pass[GFA ~func() P.Pair[P.Pair[A, FCT], W], GA ~func() P.Pair[A, W], FCT ~func(W) W, W, A any](fa GFA) GA {
+	return func() P.Pair[A, W] {
 		t := fa()
-		return T.MakeTuple3(t.F1.F1, t.F1.F2(t.F2), t.F3)
+		a := P.Head(t)
+		return P.MakePair(P.Head(a), P.Tail(a)(P.Tail(t)))
 	}
 }
 
-func MonadMap[GB ~func() T.Tuple3[B, W, SG.Semigroup[W]], GA ~func() T.Tuple3[A, W, SG.Semigroup[W]], FCT ~func(A) B, W, A, B any](fa GA, f FCT) GB {
-	return IO.MonadMap[GA, GB](fa, T.Map3(f, F.Identity[W], F.Identity[SG.Semigroup[W]]))
+func MonadMap[GB ~func() P.Pair[B, W], GA ~func() P.Pair[A, W], FCT ~func(A) B, W, A, B any](fa GA, f FCT) GB {
+	return IO.MonadMap[GA, GB](fa, P.Map[W](f))
 }
 
-func Map[GB ~func() T.Tuple3[B, W, SG.Semigroup[W]], GA ~func() T.Tuple3[A, W, SG.Semigroup[W]], FCT ~func(A) B, W, A, B any](f FCT) func(GA) GB {
-	return IO.Map[GA, GB](T.Map3(f, F.Identity[W], F.Identity[SG.Semigroup[W]]))
+func Map[GB ~func() P.Pair[B, W], GA ~func() P.Pair[A, W], FCT ~func(A) B, W, A, B any](f FCT) func(GA) GB {
+	return IO.Map[GA, GB](P.Map[W](f))
 }
 
-func MonadChain[GB ~func() T.Tuple3[B, W, SG.Semigroup[W]], GA ~func() T.Tuple3[A, W, SG.Semigroup[W]], FCT ~func(A) GB, W, A, B any](fa GA, f FCT) GB {
-	return func() T.Tuple3[B, W, SG.Semigroup[W]] {
+func MonadChain[GB ~func() P.Pair[B, W], GA ~func() P.Pair[A, W], FCT ~func(A) GB, W, A, B any](s SG.Semigroup[W], fa GA, f FCT) GB {
+	return func() P.Pair[B, W] {
 		a := fa()
-		b := f(a.F1)()
+		b := f(P.Head(a))()
 
-		return T.MakeTuple3(b.F1, b.F3.Concat(a.F2, b.F2), b.F3)
+		return P.MakePair(P.Head(b), s.Concat(P.Tail(a), P.Tail(b)))
 	}
 }
 
-func Chain[GB ~func() T.Tuple3[B, W, SG.Semigroup[W]], GA ~func() T.Tuple3[A, W, SG.Semigroup[W]], FCT ~func(A) GB, W, A, B any](f FCT) func(GA) GB {
-	return F.Bind2nd(MonadChain[GB, GA, FCT, W, A, B], f)
+func Chain[GB ~func() P.Pair[B, W], GA ~func() P.Pair[A, W], FCT ~func(A) GB, W, A, B any](s SG.Semigroup[W], f FCT) func(GA) GB {
+	return func(fa GA) GB {
+		return MonadChain(s, fa, f)
+	}
 }
 
-func MonadAp[GB ~func() T.Tuple3[B, W, SG.Semigroup[W]], GAB ~func() T.Tuple3[func(A) B, W, SG.Semigroup[W]], GA ~func() T.Tuple3[A, W, SG.Semigroup[W]], W, A, B any](fab GAB, fa GA) GB {
-	return func() T.Tuple3[B, W, SG.Semigroup[W]] {
+func MonadAp[GB ~func() P.Pair[B, W], GAB ~func() P.Pair[func(A) B, W], GA ~func() P.Pair[A, W], W, A, B any](s SG.Semigroup[W], fab GAB, fa GA) GB {
+	return func() P.Pair[B, W] {
 		f := fab()
 		a := fa()
 
-		return T.MakeTuple3(f.F1(a.F1), f.F3.Concat(f.F2, a.F2), f.F3)
+		return P.MakePair(P.Head(f)(P.Head(a)), s.Concat(P.Tail(f), P.Tail(a)))
 	}
 }
 
-func Ap[GB ~func() T.Tuple3[B, W, SG.Semigroup[W]], GAB ~func() T.Tuple3[func(A) B, W, SG.Semigroup[W]], GA ~func() T.Tuple3[A, W, SG.Semigroup[W]], W, A, B any](ga GA) func(GAB) GB {
-	return F.Bind2nd(MonadAp[GB, GAB, GA], ga)
+func Ap[GB ~func() P.Pair[B, W], GAB ~func() P.Pair[func(A) B, W], GA ~func() P.Pair[A, W], W, A, B any](s SG.Semigroup[W], ga GA) func(GAB) GB {
+	return func(fab GAB) GB {
+		return MonadAp[GB](s, fab, ga)
+	}
 }
 
-func MonadChainFirst[GB ~func() T.Tuple3[B, W, SG.Semigroup[W]], GA ~func() T.Tuple3[A, W, SG.Semigroup[W]], FCT ~func(A) GB, W, A, B any](ma GA, f FCT) GA {
+func MonadChainFirst[GB ~func() P.Pair[B, W], GA ~func() P.Pair[A, W], FCT ~func(A) GB, W, A, B any](s SG.Semigroup[W], ma GA, f FCT) GA {
 	return C.MonadChainFirst(
-		MonadChain[GA, GA, func(A) GA],
+		F.Bind1of3(MonadChain[GA, GA, func(A) GA])(s),
 		MonadMap[GA, GB, func(B) A],
 		ma,
 		f,
 	)
 }
 
-func ChainFirst[GB ~func() T.Tuple3[B, W, SG.Semigroup[W]], GA ~func() T.Tuple3[A, W, SG.Semigroup[W]], FCT ~func(A) GB, W, A, B any](f FCT) func(GA) GA {
+func ChainFirst[GB ~func() P.Pair[B, W], GA ~func() P.Pair[A, W], FCT ~func(A) GB, W, A, B any](s SG.Semigroup[W], f FCT) func(GA) GA {
 	return C.ChainFirst(
-		Chain[GA, GA, func(A) GA],
+		F.Bind1st(Chain[GA, GA, func(A) GA], s),
 		Map[GA, GB, func(B) A],
 		f,
 	)
 }
 
-func Flatten[GAA ~func() T.Tuple3[GA, W, SG.Semigroup[W]], GA ~func() T.Tuple3[A, W, SG.Semigroup[W]], W, A any](mma GAA) GA {
-	return MonadChain[GA, GAA, func(GA) GA](mma, F.Identity[GA])
+func Flatten[GAA ~func() P.Pair[GA, W], GA ~func() P.Pair[A, W], W, A any](s SG.Semigroup[W], mma GAA) GA {
+	return MonadChain[GA, GAA, func(GA) GA](s, mma, F.Identity[GA])
 }
 
-func Execute[GA ~func() T.Tuple3[A, W, SG.Semigroup[W]], W, A any](fa GA) W {
-	return fa().F2
+func Execute[GA ~func() P.Pair[A, W], W, A any](fa GA) W {
+	return P.Tail(fa())
 }
 
-func Evaluate[GA ~func() T.Tuple3[A, W, SG.Semigroup[W]], W, A any](fa GA) A {
-	return fa().F1
+func Evaluate[GA ~func() P.Pair[A, W], W, A any](fa GA) A {
+	return P.Head(fa())
 }
 
 // MonadCensor modifies the final accumulator value by applying a function
-func MonadCensor[GA ~func() T.Tuple3[A, W, SG.Semigroup[W]], FCT ~func(W) W, W, A any](fa GA, f FCT) GA {
-	return IO.MonadMap[GA, GA](fa, T.Map3(F.Identity[A], f, F.Identity[SG.Semigroup[W]]))
+func MonadCensor[GA ~func() P.Pair[A, W], FCT ~func(W) W, W, A any](fa GA, f FCT) GA {
+	return IO.MonadMap[GA, GA](fa, P.MapTail[A](f))
 }
 
 // Censor modifies the final accumulator value by applying a function
-func Censor[GA ~func() T.Tuple3[A, W, SG.Semigroup[W]], FCT ~func(W) W, W, A any](f FCT) func(GA) GA {
-	return IO.Map[GA, GA](T.Map3(F.Identity[A], f, F.Identity[SG.Semigroup[W]]))
+func Censor[GA ~func() P.Pair[A, W], FCT ~func(W) W, W, A any](f FCT) func(GA) GA {
+	return IO.Map[GA, GA](P.MapTail[A](f))
 }
 
 // MonadListens projects a value from modifications made to the accumulator during an action
-func MonadListens[GA ~func() T.Tuple3[A, W, SG.Semigroup[W]], GAB ~func() T.Tuple3[T.Tuple2[A, B], W, SG.Semigroup[W]], FCT ~func(W) B, W, A, B any](fa GA, f FCT) GAB {
-	return func() T.Tuple3[T.Tuple2[A, B], W, SG.Semigroup[W]] {
+func MonadListens[GA ~func() P.Pair[A, W], GAB ~func() P.Pair[P.Pair[A, B], W], FCT ~func(W) B, W, A, B any](fa GA, f FCT) GAB {
+	return func() P.Pair[P.Pair[A, B], W] {
 		a := fa()
-		return T.MakeTuple3(T.MakeTuple2(a.F1, f(a.F2)), a.F2, a.F3)
+		t := P.Tail(a)
+		return P.MakePair(P.MakePair(P.Head(a), f(t)), t)
 	}
 }
 
 // Listens projects a value from modifications made to the accumulator during an action
-func Listens[GA ~func() T.Tuple3[A, W, SG.Semigroup[W]], GAB ~func() T.Tuple3[T.Tuple2[A, B], W, SG.Semigroup[W]], FCT ~func(W) B, W, A, B any](f FCT) func(GA) GAB {
+func Listens[GA ~func() P.Pair[A, W], GAB ~func() P.Pair[P.Pair[A, B], W], FCT ~func(W) B, W, A, B any](f FCT) func(GA) GAB {
 	return F.Bind2nd(MonadListens[GA, GAB, FCT], f)
 }
 
-func MonadFlap[FAB ~func(A) B, GFAB ~func() T.Tuple3[FAB, W, SG.Semigroup[W]], GB ~func() T.Tuple3[B, W, SG.Semigroup[W]], W, A, B any](fab GFAB, a A) GB {
+func MonadFlap[FAB ~func(A) B, GFAB ~func() P.Pair[FAB, W], GB ~func() P.Pair[B, W], W, A, B any](fab GFAB, a A) GB {
 	return FC.MonadFlap(
 		MonadMap[GB, GFAB, func(FAB) B],
 		fab,
 		a)
 }
 
-func Flap[FAB ~func(A) B, GFAB ~func() T.Tuple3[FAB, W, SG.Semigroup[W]], GB ~func() T.Tuple3[B, W, SG.Semigroup[W]], W, A, B any](a A) func(GFAB) GB {
+func Flap[FAB ~func(A) B, GFAB ~func() P.Pair[FAB, W], GB ~func() P.Pair[B, W], W, A, B any](a A) func(GFAB) GB {
 	return FC.Flap(Map[GB, GFAB, func(FAB) B], a)
 }

writer/monad.go

@@ -0,0 +1,45 @@
+// Copyright (c) 2024 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 (
+	"github.com/IBM/fp-go/internal/applicative"
+	"github.com/IBM/fp-go/internal/functor"
+	"github.com/IBM/fp-go/internal/monad"
+	"github.com/IBM/fp-go/internal/pointed"
+	M "github.com/IBM/fp-go/monoid"
+	G "github.com/IBM/fp-go/writer/generic"
+)
+
+// Pointed implements the pointed operations for [Writer]
+func Pointed[W, A any](m M.Monoid[W]) pointed.Pointed[A, Writer[W, A]] {
+	return G.Pointed[Writer[W, A], W, A](m)
+}
+
+// Functor implements the pointed operations for [Writer]
+func Functor[W, A, B any]() functor.Functor[A, B, Writer[W, A], Writer[W, B]] {
+	return G.Functor[Writer[W, B], Writer[W, A], W, A, B]()
+}
+
+// Applicative implements the applicative operations for [Writer]
+func Applicative[W, A, B any](m M.Monoid[W]) applicative.Applicative[A, B, Writer[W, A], Writer[W, B], Writer[W, func(A) B]] {
+	return G.Applicative[Writer[W, B], Writer[W, func(A) B], Writer[W, A]](m)
+}
+
+// Monad implements the monadic operations for [Writer]
+func Monad[W, A, B any](m M.Monoid[W]) monad.Monad[A, B, Writer[W, A], Writer[W, B], Writer[W, func(A) B]] {
+	return G.Monad[Writer[W, B], Writer[W, func(A) B], Writer[W, A]](m)
+}

writer/testing/laws.go

@@ -37,39 +37,40 @@ func AssertLaws[W, A, B, C any](t *testing.T,
 	bc func(B) C,
 ) func(a A) bool {
 
-	return L.AssertLaws(t,
+	fofc := WRT.Pointed[W, C](m)
+	fofaa := WRT.Pointed[W, func(A) A](m)
+	fofbc := WRT.Pointed[W, func(B) C](m)
+	fofabb := WRT.Pointed[W, func(func(A) B) B](m)
+
+	fmap := WRT.Functor[W, func(B) C, func(func(A) B) func(A) C]()
+
+	fapabb := WRT.Applicative[W, func(A) B, B](m)
+	fapabac := WRT.Applicative[W, func(A) B, func(A) C](m)
+
+	maa := WRT.Monad[W, A, A](m)
+	mab := WRT.Monad[W, A, B](m)
+	mac := WRT.Monad[W, A, C](m)
+	mbc := WRT.Monad[W, B, C](m)
+
+	return L.MonadAssertLaws(t,
 		WRT.Eq(eqw, eqa),
 		WRT.Eq(eqw, eqb),
 		WRT.Eq(eqw, eqc),
 
-		WRT.Of[A](m),
-		WRT.Of[B](m),
-		WRT.Of[C](m),
+		fofc,
+		fofaa,
+		fofbc,
+		fofabb,
 
-		WRT.Of[func(A) A](m),
-		WRT.Of[func(A) B](m),
-		WRT.Of[func(B) C](m),
-		WRT.Of[func(func(A) B) B](m),
+		fmap,
 
-		WRT.MonadMap[func(A) A, W, A, A],
-		WRT.MonadMap[func(A) B, W, A, B],
-		WRT.MonadMap[func(A) C, W, A, C],
-		WRT.MonadMap[func(B) C, W, B, C],
+		fapabb,
+		fapabac,
 
-		WRT.MonadMap[func(func(B) C) func(func(A) B) func(A) C, W, func(B) C, func(func(A) B) func(A) C],
-
-		WRT.MonadChain[func(A) WRT.Writer[W, A], W, A, A],
-		WRT.MonadChain[func(A) WRT.Writer[W, B], W, A, B],
-		WRT.MonadChain[func(A) WRT.Writer[W, C], W, A, C],
-		WRT.MonadChain[func(B) WRT.Writer[W, C], W, B, C],
-
-		WRT.MonadAp[A, A, W],
-		WRT.MonadAp[B, A, W],
-		WRT.MonadAp[C, B, W],
-		WRT.MonadAp[C, A, W],
-
-		WRT.MonadAp[B, func(A) B, W],
-		WRT.MonadAp[func(A) C, func(A) B, W],
+		maa,
+		mab,
+		mac,
+		mbc,
 
 		ab,
 		bc,

writer/writer.go

@@ -19,30 +19,30 @@ 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"
+	P "github.com/IBM/fp-go/pair"
+	SG "github.com/IBM/fp-go/semigroup"
 	G "github.com/IBM/fp-go/writer/generic"
 )
 
-type Writer[W, A any] IO.IO[T.Tuple3[A, W, S.Semigroup[W]]]
+type Writer[W, A any] IO.IO[P.Pair[A, W]]
 
 // Tell appends a value to the accumulator
-func Tell[W any](s S.Semigroup[W]) func(W) Writer[W, any] {
-	return G.Tell[Writer[W, any]](s)
+func Tell[W any](w W) Writer[W, any] {
+	return G.Tell[Writer[W, any]](w)
 }
 
-func Of[A, W any](m M.Monoid[W]) func(A) Writer[W, A] {
-	return G.Of[Writer[W, A]](m)
+func Of[A, W any](m M.Monoid[W], a A) Writer[W, A] {
+	return G.Of[Writer[W, A]](m, a)
 }
 
 // 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)
+func Listen[W, A any](fa Writer[W, A]) Writer[W, P.Pair[A, W]] {
+	return G.Listen[Writer[W, A], Writer[W, P.Pair[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 Pass[W, A any](fa Writer[W, P.Pair[A, EM.Endomorphism[W]]]) Writer[W, A] {
+	return G.Pass[Writer[W, P.Pair[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] {
@@ -53,32 +53,32 @@ 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)
 }
 
-func MonadChain[FCT ~func(A) Writer[W, B], W, A, B any](fa Writer[W, A], fct FCT) Writer[W, B] {
-	return G.MonadChain[Writer[W, B], Writer[W, A], FCT](fa, fct)
+func MonadChain[FCT ~func(A) Writer[W, B], W, A, B any](s SG.Semigroup[W], fa Writer[W, A], fct FCT) Writer[W, B] {
+	return G.MonadChain[Writer[W, B], Writer[W, A], FCT](s, fa, fct)
 }
 
-func Chain[A, B, W any](fa func(A) Writer[W, B]) func(Writer[W, A]) Writer[W, B] {
-	return G.Chain[Writer[W, B], Writer[W, A], func(A) Writer[W, B]](fa)
+func Chain[A, B, W any](s SG.Semigroup[W], fa func(A) Writer[W, B]) func(Writer[W, A]) Writer[W, B] {
+	return G.Chain[Writer[W, B], Writer[W, A], func(A) Writer[W, B]](s, fa)
 }
 
-func MonadAp[B, A, W any](fab Writer[W, func(A) B], fa Writer[W, A]) Writer[W, B] {
-	return G.MonadAp[Writer[W, B], Writer[W, func(A) B], Writer[W, A]](fab, fa)
+func MonadAp[B, A, W any](s SG.Semigroup[W], fab Writer[W, func(A) B], fa Writer[W, A]) Writer[W, B] {
+	return G.MonadAp[Writer[W, B], Writer[W, func(A) B], Writer[W, A]](s, fab, fa)
 }
 
-func Ap[B, A, W any](fa Writer[W, A]) func(Writer[W, func(A) B]) Writer[W, B] {
-	return G.Ap[Writer[W, B], Writer[W, func(A) B], Writer[W, A]](fa)
+func Ap[B, A, W any](s SG.Semigroup[W], fa Writer[W, A]) func(Writer[W, func(A) B]) Writer[W, B] {
+	return G.Ap[Writer[W, B], Writer[W, func(A) B], Writer[W, A]](s, fa)
 }
 
-func MonadChainFirst[FCT ~func(A) Writer[W, B], W, A, B any](fa Writer[W, A], fct FCT) Writer[W, A] {
-	return G.MonadChainFirst[Writer[W, B], Writer[W, A], FCT](fa, fct)
+func MonadChainFirst[FCT ~func(A) Writer[W, B], W, A, B any](s SG.Semigroup[W], fa Writer[W, A], fct FCT) Writer[W, A] {
+	return G.MonadChainFirst[Writer[W, B], Writer[W, A], FCT](s, fa, fct)
 }
 
-func ChainFirst[FCT ~func(A) Writer[W, B], W, A, B any](fct FCT) func(Writer[W, A]) Writer[W, A] {
-	return G.ChainFirst[Writer[W, B], Writer[W, A], FCT](fct)
+func ChainFirst[FCT ~func(A) Writer[W, B], W, A, B any](s SG.Semigroup[W], fct FCT) func(Writer[W, A]) Writer[W, A] {
+	return G.ChainFirst[Writer[W, B], Writer[W, A], FCT](s, fct)
 }
 
-func Flatten[W, A any](mma Writer[W, Writer[W, A]]) Writer[W, A] {
-	return G.Flatten[Writer[W, Writer[W, A]], Writer[W, A]](mma)
+func Flatten[W, A any](s SG.Semigroup[W], mma Writer[W, Writer[W, A]]) Writer[W, A] {
+	return G.Flatten[Writer[W, Writer[W, A]], Writer[W, A]](s, mma)
 }
 
 // Execute extracts the accumulator
@@ -102,13 +102,13 @@ func Censor[A any, FCT ~func(W) W, W any](f FCT) func(Writer[W, A]) Writer[W, A]
 }
 
 // MonadListens projects a value from modifications made to the accumulator during an action
-func MonadListens[A any, FCT ~func(W) B, W, B any](fa Writer[W, A], f FCT) Writer[W, T.Tuple2[A, B]] {
-	return G.MonadListens[Writer[W, A], Writer[W, T.Tuple2[A, B]]](fa, f)
+func MonadListens[A any, FCT ~func(W) B, W, B any](fa Writer[W, A], f FCT) Writer[W, P.Pair[A, B]] {
+	return G.MonadListens[Writer[W, A], Writer[W, P.Pair[A, B]]](fa, f)
 }
 
 // Listens projects a value from modifications made to the accumulator during an action
-func Listens[A any, FCT ~func(W) B, W, B any](f FCT) func(Writer[W, A]) Writer[W, T.Tuple2[A, B]] {
-	return G.Listens[Writer[W, A], Writer[W, T.Tuple2[A, B]]](f)
+func Listens[A any, FCT ~func(W) B, W, B any](f FCT) func(Writer[W, A]) Writer[W, P.Pair[A, B]] {
+	return G.Listens[Writer[W, A], Writer[W, P.Pair[A, B]]](f)
 }
 
 func MonadFlap[W, B, A any](fab Writer[W, func(A) B], a A) Writer[W, B] {

writer/writer_test.go

@@ -20,24 +20,22 @@ import (
 
 	A "github.com/IBM/fp-go/array"
 	F "github.com/IBM/fp-go/function"
-	S "github.com/IBM/fp-go/semigroup"
-	T "github.com/IBM/fp-go/tuple"
+	P "github.com/IBM/fp-go/pair"
 )
 
 func doubleAndLog(data int) Writer[[]string, int] {
-	return func() T.Tuple3[int, []string, S.Semigroup[[]string]] {
+	return func() P.Pair[int, []string] {
 		result := data * 2
-		return T.MakeTuple3(result, A.Of(fmt.Sprintf("Doubled %d -> %d", data, result)), sg)
+		return P.MakePair(result, A.Of(fmt.Sprintf("Doubled %d -> %d", data, result)))
 	}
 }
 
 func ExampleWriter_logging() {
 
-	res := F.Pipe4(
-		10,
-		Of[int](monoid),
-		Chain(doubleAndLog),
-		Chain(doubleAndLog),
+	res := F.Pipe3(
+		Of[int](monoid, 10),
+		Chain(sg, doubleAndLog),
+		Chain(sg, doubleAndLog),
 		Execute[[]string, int],
 	)