fix: some internal refactorings

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

array/array.go

@@ -58,7 +58,7 @@ func MapWithIndex[A, B any](f func(int, A) B) func([]A) []B {
 }
 
 func Map[A, B any](f func(a A) B) func([]A) []B {
-	return F.Bind2nd(MonadMap[A, B], f)
+	return G.Map[[]A, []B, A, B](f)
 }
 
 func MapRef[A, B any](f func(a *A) B) func([]A) []B {

array/generic/array.go

@@ -147,7 +147,7 @@ func MonadMap[GA ~[]A, GB ~[]B, A, B any](as GA, f func(a A) B) GB {
 }
 
 func Map[GA ~[]A, GB ~[]B, A, B any](f func(a A) B) func(GA) GB {
-	return F.Bind2nd(MonadMap[GA, GB, A, B], f)
+	return array.Map[GA, GB](f)
 }
 
 func MonadMapWithIndex[GA ~[]A, GB ~[]B, A, B any](as GA, f func(int, A) B) GB {

either/either.go

@@ -22,6 +22,7 @@ package either
 import (
 	E "github.com/IBM/fp-go/errors"
 	F "github.com/IBM/fp-go/function"
+	C "github.com/IBM/fp-go/internal/chain"
 	FC "github.com/IBM/fp-go/internal/functor"
 	L "github.com/IBM/fp-go/lazy"
 	O "github.com/IBM/fp-go/option"
@@ -85,9 +86,12 @@ func MonadChain[E, A, B any](fa Either[E, A], f func(a A) Either[E, B]) Either[E
 }
 
 func MonadChainFirst[E, A, B any](ma Either[E, A], f func(a A) Either[E, B]) Either[E, A] {
-	return MonadChain(ma, func(a A) Either[E, A] {
+	return C.MonadChainFirst(
-		return MonadMap(f(a), F.Constant1[B](a))
+		MonadChain[E, A, A],
-	})
+		MonadMap[E, B, A],
+		ma,
+		f,
+	)
 }
 
 func MonadChainTo[A, E, B any](ma Either[E, A], mb Either[E, B]) Either[E, B] {
@@ -114,7 +118,11 @@ func Chain[E, A, B any](f func(a A) Either[E, B]) func(Either[E, A]) Either[E, B
 }
 
 func ChainFirst[E, A, B any](f func(a A) Either[E, B]) func(Either[E, A]) Either[E, A] {
-	return F.Bind2nd(MonadChainFirst[E, A, B], f)
+	return C.ChainFirst(
+		Chain[E, A, A],
+		Map[E, B, A],
+		f,
+	)
 }
 
 func Flatten[E, A any](mma Either[E, Either[E, A]]) Either[E, A] {

either/traverse.go

@@ -19,38 +19,17 @@ import (
 	F "github.com/IBM/fp-go/function"
 )
 
-/*
-*
-We need to pass the members of the applicative explicitly, because golang does neither support higher kinded types nor template methods on structs or interfaces
-
-HKTRB = HKT<Either[B]>
-HKTA = HKT<A>
-HKTB = HKT<B>
-*/
-func traverse[E, A, B, HKTB, HKTRB any](
-	mof func(Either[E, B]) HKTRB,
-	mmap func(func(B) Either[E, B]) func(HKTB) HKTRB,
-) func(Either[E, A], func(A) HKTB) HKTRB {
-
-	left := F.Flow2(Left[B, E], mof)
-	right := mmap(Right[E, B])
-
-	return func(ta Either[E, A], f func(A) HKTB) HKTRB {
-		return MonadFold(ta,
-			left,
-			F.Flow2(f, right),
-		)
-	}
-}
-
 // Traverse converts an [Either] of some higher kinded type into the higher kinded type of an [Either]
 func Traverse[A, E, B, HKTB, HKTRB any](
 	mof func(Either[E, B]) HKTRB,
 	mmap func(func(B) Either[E, B]) func(HKTB) HKTRB,
 ) func(func(A) HKTB) func(Either[E, A]) HKTRB {
-	delegate := traverse[E, A, B](mof, mmap)
+
+	left := F.Flow2(Left[B, E], mof)
+	right := mmap(Right[E, B])
+
 	return func(f func(A) HKTB) func(Either[E, A]) HKTRB {
-		return F.Bind2nd(delegate, f)
+		return Fold(left, F.Flow2(f, right))
 	}
 }
 

internal/array/array.go

@@ -106,6 +106,12 @@ func MonadMap[GA ~[]A, GB ~[]B, A, B any](as GA, f func(a A) B) GB {
 	return bs
 }
 
+func Map[GA ~[]A, GB ~[]B, A, B any](f func(a A) B) func(GA) GB {
+	return func(as GA) GB {
+		return MonadMap[GA, GB](as, f)
+	}
+}
+
 func MonadMapWithIndex[GA ~[]A, GB ~[]B, A, B any](as GA, f func(idx int, a A) B) GB {
 	count := len(as)
 	bs := make(GB, count)

internal/eithert/either.go

@@ -159,3 +159,7 @@ func OrLeft[E1, E2, A, HKTE1A, HKTE2, HKTE2A any](
 func MonadMapLeft[E, A, B, HKTFA, HKTFB any](fmap func(HKTFA, func(ET.Either[E, A]) ET.Either[B, A]) HKTFB, fa HKTFA, f func(E) B) HKTFB {
 	return FC.MonadMap(fmap, ET.MonadMapLeft[E, A, B], fa, f)
 }
+
+func MapLeft[E, A, B, HKTFA, HKTFB any](fmap func(func(ET.Either[E, A]) ET.Either[B, A]) func(HKTFA) HKTFB, f func(E) B) func(HKTFA) HKTFB {
+	return FC.Map(fmap, ET.MapLeft[A, E, B], f)
+}

internal/optiont/option.go

@@ -40,6 +40,12 @@ func MonadMap[A, B, HKTFA, HKTFB any](fmap func(HKTFA, func(O.Option[A]) O.Optio
 	return FC.MonadMap(fmap, O.MonadMap[A, B], fa, f)
 }
 
+func Map[A, B, HKTFA, HKTFB any](fmap func(func(O.Option[A]) O.Option[B]) func(HKTFA) HKTFB, f func(A) B) func(HKTFA) HKTFB {
+	// HKTGA = Either[E, A]
+	// HKTGB = Either[E, B]
+	return FC.Map(fmap, O.Map[A, B], f)
+}
+
 func MonadChain[A, B, HKTFA, HKTFB any](
 	fchain func(HKTFA, func(O.Option[A]) HKTFB) HKTFB,
 	fof func(O.Option[B]) HKTFB,

ioeither/generic/ioeither.go

@@ -156,7 +156,10 @@ func MonadAp[GB ~func() ET.Either[E, B], GAB ~func() ET.Either[E, func(A) B], GA
 }
 
 func Ap[GB ~func() ET.Either[E, B], GAB ~func() ET.Either[E, func(A) B], GA ~func() ET.Either[E, A], E, A, B any](ma GA) func(GAB) GB {
-	return F.Bind2nd(MonadAp[GB, GAB, GA], ma)
+	return eithert.Ap(
+		IO.Ap[GB, func() func(ET.Either[E, A]) ET.Either[E, B], GA, ET.Either[E, B], ET.Either[E, A]],
+		IO.Map[GAB, func() func(ET.Either[E, A]) ET.Either[E, B], ET.Either[E, func(A) B], func(ET.Either[E, A]) ET.Either[E, B]],
+		ma)
 }
 
 func MonadApSeq[GB ~func() ET.Either[E, B], GAB ~func() ET.Either[E, func(A) B], GA ~func() ET.Either[E, A], E, A, B any](mab GAB, ma GA) GB {
@@ -167,7 +170,10 @@ func MonadApSeq[GB ~func() ET.Either[E, B], GAB ~func() ET.Either[E, func(A) B],
 }
 
 func ApSeq[GB ~func() ET.Either[E, B], GAB ~func() ET.Either[E, func(A) B], GA ~func() ET.Either[E, A], E, A, B any](ma GA) func(GAB) GB {
-	return F.Bind2nd(MonadApSeq[GB, GAB, GA], ma)
+	return eithert.Ap(
+		IO.ApSeq[GB, func() func(ET.Either[E, A]) ET.Either[E, B], GA, ET.Either[E, B], ET.Either[E, A]],
+		IO.Map[GAB, func() func(ET.Either[E, A]) ET.Either[E, B], ET.Either[E, func(A) B], func(ET.Either[E, A]) ET.Either[E, B]],
+		ma)
 }
 
 func MonadApPar[GB ~func() ET.Either[E, B], GAB ~func() ET.Either[E, func(A) B], GA ~func() ET.Either[E, A], E, A, B any](mab GAB, ma GA) GB {
@@ -178,7 +184,10 @@ func MonadApPar[GB ~func() ET.Either[E, B], GAB ~func() ET.Either[E, func(A) B],
 }
 
 func ApPar[GB ~func() ET.Either[E, B], GAB ~func() ET.Either[E, func(A) B], GA ~func() ET.Either[E, A], E, A, B any](ma GA) func(GAB) GB {
-	return F.Bind2nd(MonadApPar[GB, GAB, GA], ma)
+	return eithert.Ap(
+		IO.ApPar[GB, func() func(ET.Either[E, A]) ET.Either[E, B], GA, ET.Either[E, B], ET.Either[E, A]],
+		IO.Map[GAB, func() func(ET.Either[E, A]) ET.Either[E, B], ET.Either[E, func(A) B], func(ET.Either[E, A]) ET.Either[E, B]],
+		ma)
 }
 
 func Flatten[GA ~func() ET.Either[E, A], GAA ~func() ET.Either[E, GA], E, A any](mma GAA) GA {
@@ -204,11 +213,18 @@ func Memoize[GA ~func() ET.Either[E, A], E, A any](ma GA) GA {
 }
 
 func MonadMapLeft[GA1 ~func() ET.Either[E1, A], GA2 ~func() ET.Either[E2, A], E1, E2, A any](fa GA1, f func(E1) E2) GA2 {
-	return eithert.MonadMapLeft(IO.MonadMap[GA1, GA2, ET.Either[E1, A], ET.Either[E2, A]], fa, f)
+	return eithert.MonadMapLeft(
+		IO.MonadMap[GA1, GA2, ET.Either[E1, A], ET.Either[E2, A]],
+		fa,
+		f,
+	)
 }
 
 func MapLeft[GA1 ~func() ET.Either[E1, A], GA2 ~func() ET.Either[E2, A], E1, E2, A any](f func(E1) E2) func(GA1) GA2 {
-	return F.Bind2nd(MonadMapLeft[GA1, GA2, E1, E2, A], f)
+	return eithert.MapLeft(
+		IO.Map[GA1, GA2, ET.Either[E1, A], ET.Either[E2, A]],
+		f,
+	)
 }
 
 // Delay creates an operation that passes in the value after some [time.Duration]

iooption/generic/iooption.go

@@ -70,7 +70,7 @@ func MonadMap[GA ~func() O.Option[A], GB ~func() O.Option[B], A, B any](fa GA, f
 }
 
 func Map[GA ~func() O.Option[A], GB ~func() O.Option[B], A, B any](f func(A) B) func(GA) GB {
-	return F.Bind2nd(MonadMap[GA, GB, A, B], f)
+	return optiont.Map(IO.Map[GA, GB, O.Option[A], O.Option[B]], f)
 }
 
 func MonadChain[GA ~func() O.Option[A], GB ~func() O.Option[B], A, B any](fa GA, f func(A) GB) GB {

iterator/stateless/generic/iterator.go

@@ -18,6 +18,7 @@ package generic
 import (
 	A "github.com/IBM/fp-go/array/generic"
 	F "github.com/IBM/fp-go/function"
+	C "github.com/IBM/fp-go/internal/chain"
 	"github.com/IBM/fp-go/internal/utils"
 	IO "github.com/IBM/fp-go/iooption/generic"
 	M "github.com/IBM/fp-go/monoid"
@@ -146,6 +147,23 @@ func MonadChain[GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tupl
 	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 {
+	return C.MonadChainFirst(
+		MonadChain[GU, GU, U, U],
+		MonadMap[GU, GV, V, U],
+		ma,
+		f,
+	)
+}
+
+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 {
+	return C.ChainFirst(
+		Chain[GU, GU, U, U],
+		Map[GU, GV, func(V) U, V, U],
+		f,
+	)
+}
+
 func Flatten[GV ~func() O.Option[T.Tuple2[GV, GU]], GU ~func() O.Option[T.Tuple2[GU, U]], U any](ma GV) GU {
 	return MonadChain(ma, F.Identity[GU])
 }

iterator/stateless/iterator.go

@@ -144,3 +144,11 @@ func FoldMap[U, V any](m M.Monoid[V]) func(func(U) V) func(ma Iterator[U]) V {
 func Fold[U any](m M.Monoid[U]) func(Iterator[U]) U {
 	return G.Fold[Iterator[U]](m)
 }
+
+func MonadChainFirst[U, V any](ma Iterator[U], f func(U) Iterator[V]) Iterator[U] {
+	return G.MonadChainFirst[Iterator[V], Iterator[U], U, V](ma, f)
+}
+
+func ChainFirst[U, V any](f func(U) Iterator[V]) func(Iterator[U]) Iterator[U] {
+	return G.ChainFirst[Iterator[V], Iterator[U], U, V](f)
+}

option/option.go

@@ -18,6 +18,7 @@ package option
 
 import (
 	F "github.com/IBM/fp-go/function"
+	C "github.com/IBM/fp-go/internal/chain"
 	FC "github.com/IBM/fp-go/internal/functor"
 )
 
@@ -95,7 +96,7 @@ func MonadChain[A, B any](fa Option[A], f func(A) Option[B]) Option[B] {
 }
 
 func Chain[A, B any](f func(A) Option[B]) func(Option[A]) Option[B] {
-	return F.Bind2nd(MonadChain[A, B], f)
+	return Fold(None[B], f)
 }
 
 func MonadChainTo[A, B any](ma Option[A], mb Option[B]) Option[B] {
@@ -107,13 +108,20 @@ func ChainTo[A, B any](mb Option[B]) func(Option[A]) Option[B] {
 }
 
 func MonadChainFirst[A, B any](ma Option[A], f func(A) Option[B]) Option[A] {
-	return MonadChain(ma, func(a A) Option[A] {
+	return C.MonadChainFirst(
-		return MonadMap(f(a), F.Constant1[B](a))
+		MonadChain[A, A],
-	})
+		MonadMap[B, A],
+		ma,
+		f,
+	)
 }
 
 func ChainFirst[A, B any](f func(A) Option[B]) func(Option[A]) Option[A] {
-	return F.Bind2nd(MonadChainFirst[A, B], f)
+	return C.ChainFirst(
+		Chain[A, A],
+		Map[B, A],
+		f,
+	)
 }
 
 func Flatten[A any](mma Option[Option[A]]) Option[A] {