fix: bug in compact array

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

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),
 			)
 		}
 	}

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)
 }
 

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))
+}