fix: add ChainFirstIOK

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

array/generic/uniq.go

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

array/uniq.go

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

array/uniq_test.go

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

either/array.go

@@ -61,14 +61,14 @@ func SequenceArray[E, A any](ma []Either[E, A]) Either[E, []A] {
 	return SequenceArrayG[[]A](ma)
 }
 
-// CompactArrayG discards the none values and keeps the some values
+// CompactArrayG discards the none values and keeps the right values
 func CompactArrayG[A1 ~[]Either[E, A], A2 ~[]A, E, A any](fa A1) A2 {
 	return RA.Reduce(fa, func(out A2, value Either[E, A]) A2 {
 		return MonadFold(value, F.Constant1[E](out), F.Bind1st(RA.Append[A2, A], out))
-	}, make(A2, len(fa)))
+	}, make(A2, 0, len(fa)))
 }
 
-// CompactArray discards the none values and keeps the some values
+// CompactArray discards the none values and keeps the right values
 func CompactArray[E, A any](fa []Either[E, A]) []A {
 	return CompactArrayG[[]Either[E, A], []A](fa)
 }

either/array_test.go

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

either/either.go

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

either/logger.go

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

internal/optiont/option.go

@@ -49,6 +49,16 @@ func MonadChain[A, B, HKTFA, HKTFB any](
 	return fchain(ma, O.Fold(F.Nullary2(O.None[B], fof), f))
 }
 
+func Chain[A, B, HKTFA, HKTFB any](
+	fchain func(HKTFA, func(O.Option[A]) HKTFB) HKTFB,
+	fof func(O.Option[B]) HKTFB,
+	f func(A) HKTFB) func(ma HKTFA) HKTFB {
+	// dispatch to the even more generic implementation
+	return func(ma HKTFA) HKTFB {
+		return MonadChain(fchain, fof, ma, f)
+	}
+}
+
 func MonadAp[A, B, HKTFAB, HKTFGAB, HKTFA, HKTFB any](
 	fap func(HKTFGAB, HKTFA) HKTFB,
 	fmap func(HKTFAB, func(O.Option[func(A) B]) func(O.Option[A]) O.Option[B]) HKTFGAB,

ioeither/ioeither.go

@@ -197,12 +197,12 @@ func GetOrElse[E, A any](onLeft func(E) I.IO[A]) func(IOEither[E, A]) I.IO[A] {
 }
 
 // MonadChainTo composes to the second monad ignoring the return value of the first
-func MonadChainTo[E, A, B any](fa IOEither[E, A], fb IOEither[E, B]) IOEither[E, B] {
+func MonadChainTo[A, E, B any](fa IOEither[E, A], fb IOEither[E, B]) IOEither[E, B] {
 	return G.MonadChainTo(fa, fb)
 }
 
 // ChainTo composes to the second [IOEither] monad ignoring the return value of the first
-func ChainTo[E, A, B any](fb IOEither[E, B]) func(IOEither[E, A]) IOEither[E, B] {
+func ChainTo[A, E, B any](fb IOEither[E, B]) func(IOEither[E, A]) IOEither[E, B] {
 	return G.ChainTo[IOEither[E, A]](fb)
 }
 

iooption/generic/iooption.go

@@ -20,6 +20,7 @@ import (
 
 	ET "github.com/IBM/fp-go/either"
 	F "github.com/IBM/fp-go/function"
+	C "github.com/IBM/fp-go/internal/chain"
 	FI "github.com/IBM/fp-go/internal/fromio"
 	"github.com/IBM/fp-go/internal/optiont"
 	IO "github.com/IBM/fp-go/io/generic"
@@ -76,8 +77,48 @@ func MonadChain[GA ~func() O.Option[A], GB ~func() O.Option[B], A, B any](fa GA,
 	return optiont.MonadChain(IO.MonadChain[GA, GB, O.Option[A], O.Option[B]], IO.MonadOf[GB, O.Option[B]], fa, f)
 }
 
+// MonadChainFirst runs the monad returned by the function but returns the result of the original monad
+func MonadChainFirst[GA ~func() O.Option[A], GB ~func() O.Option[B], A, B any](ma GA, f func(A) GB) GA {
+	return C.MonadChainFirst(
+		MonadChain[GA, GA, A, A],
+		MonadMap[GB, GA, B, A],
+		ma,
+		f,
+	)
+}
+
+// ChainFirst runs the monad returned by the function but returns the result of the original monad
+func ChainFirst[GA ~func() O.Option[A], GB ~func() O.Option[B], A, B any](f func(A) GB) func(GA) GA {
+	return C.ChainFirst(
+		MonadChain[GA, GA, A, A],
+		MonadMap[GB, GA, B, A],
+		f,
+	)
+}
+
+// MonadChainFirstIOK runs the monad returned by the function but returns the result of the original monad
+func MonadChainFirstIOK[GA ~func() O.Option[A], GIOB ~func() B, A, B any](first GA, f func(A) GIOB) GA {
+	return FI.MonadChainFirstIOK(
+		MonadChain[GA, GA, A, A],
+		MonadMap[func() O.Option[B], GA, B, A],
+		FromIO[func() O.Option[B], GIOB, B],
+		first,
+		f,
+	)
+}
+
+// ChainFirstIOK runs the monad returned by the function but returns the result of the original monad
+func ChainFirstIOK[GA ~func() O.Option[A], GIOB ~func() B, A, B any](f func(A) GIOB) func(GA) GA {
+	return FI.ChainFirstIOK(
+		MonadChain[GA, GA, A, A],
+		MonadMap[func() O.Option[B], GA, B, A],
+		FromIO[func() O.Option[B], GIOB, B],
+		f,
+	)
+}
+
 func Chain[GA ~func() O.Option[A], GB ~func() O.Option[B], A, B any](f func(A) GB) func(GA) GB {
-	return F.Bind2nd(MonadChain[GA, GB, A, B], f)
+	return optiont.Chain(IO.MonadChain[GA, GB, O.Option[A], O.Option[B]], IO.MonadOf[GB, O.Option[B]], f)
 }
 
 func MonadChainOptionK[GA ~func() O.Option[A], GB ~func() O.Option[B], A, B any](ma GA, f func(A) O.Option[B]) GB {

iooption/iooption.go

@@ -18,6 +18,7 @@ package iooption
 import (
 	ET "github.com/IBM/fp-go/either"
 	I "github.com/IBM/fp-go/io"
+	IO "github.com/IBM/fp-go/io"
 	G "github.com/IBM/fp-go/iooption/generic"
 	L "github.com/IBM/fp-go/lazy"
 	O "github.com/IBM/fp-go/option"
@@ -143,3 +144,23 @@ func MonadAlt[A any](first IOOption[A], second L.Lazy[IOOption[A]]) IOOption[A]
 func Alt[A any](second L.Lazy[IOOption[A]]) func(IOOption[A]) IOOption[A] {
 	return G.Alt(second)
 }
+
+// MonadChainFirst runs the monad returned by the function but returns the result of the original monad
+func MonadChainFirst[A, B any](ma IOOption[A], f func(A) IOOption[B]) IOOption[A] {
+	return G.MonadChainFirst[IOOption[A], IOOption[B]](ma, f)
+}
+
+// ChainFirst runs the monad returned by the function but returns the result of the original monad
+func ChainFirst[A, B any](f func(A) IOOption[B]) func(IOOption[A]) IOOption[A] {
+	return G.ChainFirst[IOOption[A], IOOption[B]](f)
+}
+
+// MonadChainFirstIOK runs the monad returned by the function but returns the result of the original monad
+func MonadChainFirstIOK[A, B any](first IOOption[A], f func(A) IO.IO[B]) IOOption[A] {
+	return G.MonadChainFirstIOK[IOOption[A], IO.IO[B]](first, f)
+}
+
+// ChainFirstIOK runs the monad returned by the function but returns the result of the original monad
+func ChainFirstIOK[A, B any](f func(A) IO.IO[B]) func(IOOption[A]) IOOption[A] {
+	return G.ChainFirstIOK[IOOption[A], IO.IO[B]](f)
+}

iterator/stateless/uniq.go

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

option/array.go

@@ -65,7 +65,7 @@ func SequenceArray[A any](ma []Option[A]) Option[[]A] {
 func CompactArrayG[A1 ~[]Option[A], A2 ~[]A, A any](fa A1) A2 {
 	return RA.Reduce(fa, func(out A2, value Option[A]) A2 {
 		return MonadFold(value, F.Constant(out), F.Bind1st(RA.Append[A2, A], out))
-	}, make(A2, len(fa)))
+	}, make(A2, 0, len(fa)))
 }
 
 // CompactArray discards the none values and keeps the some values

option/array_test.go

@@ -34,3 +34,14 @@ func TestSequenceArray(t *testing.T) {
 
 	assert.Equal(t, res, Of([]int{1, 2}))
 }
+
+func TestCompactArray(t *testing.T) {
+	ar := []Option[string]{
+		Of("ok"),
+		None[string](),
+		Of("ok"),
+	}
+
+	res := CompactArray(ar)
+	assert.Equal(t, 2, len(res))
+}