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fix: add more mostly-adequate examples and solutions

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Signed-off-by: Dr. Carsten Leue <carsten.leue@de.ibm.com>
This commit is contained in:
Dr. Carsten Leue
2023-09-07 17:21:39 +02:00
parent 3ccafb5302
commit 53f4e5ebd7
9 changed files with 386 additions and 37 deletions
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34
either/traverse.go
View File

@@ -27,13 +27,13 @@ HKTRB = HKT<Either[B]>
HKTA = HKT<A>
HKTB = HKT<B>
*/
func traverse[E, A, B, HKTA, HKTB, HKTRB any](
_of func(Either[E, B]) HKTRB,
_map func(HKTB, func(B) Either[E, B]) HKTRB,
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], _of)
right := F.Bind2nd(_map, Right[E, B])
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,
@@ -43,27 +43,21 @@ func traverse[E, A, B, HKTA, HKTB, HKTRB any](
}
}
func Traverse[E, A, B, HKTA, HKTB, HKTRB any](
_of func(Either[E, B]) HKTRB,
_map func(HKTB, func(B) Either[E, B]) HKTRB,
// 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, HKTA](_of, _map)
delegate := traverse[E, A, B](mof, mmap)
return func(f func(A) HKTB) func(Either[E, A]) HKTRB {
return F.Bind2nd(delegate, f)
}
}
/*
*
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
HKTRA = HKT<Either[A]>
HKTA = HKT<A>
HKTB = HKT<B>
*/
// Sequence converts an [Either] of some higher kinded type into the higher kinded type of an [Either]
func Sequence[E, A, HKTA, HKTRA any](
_of func(Either[E, A]) HKTRA,
_map func(HKTA, func(A) Either[E, A]) HKTRA,
mof func(Either[E, A]) HKTRA,
mmap func(func(A) Either[E, A]) func(HKTA) HKTRA,
) func(Either[E, HKTA]) HKTRA {
return Fold(F.Flow2(Left[A, E], _of), F.Bind2nd(_map, Right[E, A]))
return Fold(F.Flow2(Left[A, E], mof), mmap(Right[E, A]))
}

6
either/traverse_test.go
View File

@@ -30,9 +30,9 @@ func TestTraverse(t *testing.T) {
}
return O.None[int]()
}
trav := Traverse[string, int, int, O.Option[Either[string, int]]](
trav := Traverse[int](
O.Of[Either[string, int]],
O.MonadMap[int, Either[string, int]],
O.Map[int, Either[string, int]],
)(f)
assert.Equal(t, O.Of(Left[int]("a")), F.Pipe1(Left[int]("a"), trav))
@@ -44,7 +44,7 @@ func TestSequence(t *testing.T) {
seq := Sequence(
O.Of[Either[string, int]],
O.MonadMap[int, Either[string, int]],
O.Map[int, Either[string, int]],
)
assert.Equal(t, O.Of(Right[string](1)), seq(Right[string](O.Of(1))))