initial checkin

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

internal/record/record.go

@@ -0,0 +1,33 @@
+package record
+
+func Reduce[M ~map[K]V, K comparable, V, R any](r M, f func(R, V) R, initial R) R {
+	current := initial
+	for _, v := range r {
+		current = f(current, v)
+	}
+	return current
+}
+
+func ReduceWithIndex[M ~map[K]V, K comparable, V, R any](r M, f func(K, R, V) R, initial R) R {
+	current := initial
+	for k, v := range r {
+		current = f(k, current, v)
+	}
+	return current
+}
+
+func ReduceRef[M ~map[K]V, K comparable, V, R any](r M, f func(R, *V) R, initial R) R {
+	current := initial
+	for _, v := range r {
+		current = f(current, &v) // #nosec G601
+	}
+	return current
+}
+
+func ReduceRefWithIndex[M ~map[K]V, K comparable, V, R any](r M, f func(K, R, *V) R, initial R) R {
+	current := initial
+	for k, v := range r {
+		current = f(k, current, &v) // #nosec G601
+	}
+	return current
+}

internal/record/traverse.go

@@ -0,0 +1,93 @@
+package record
+
+import (
+	F "github.com/ibm/fp-go/function"
+)
+
+// createEmpty creates a new empty, read-write map
+// this is different to Empty which creates a new read-only empty map
+func createEmpty[N ~map[K]A, K comparable, A any]() N {
+	return make(N)
+}
+
+// inserts the key/value pair into a read-write map for performance
+// order of parameters is adjusted to be curryable
+func addKey[N ~map[K]A, K comparable, A any](key K, m N, value A) N {
+	m[key] = value
+	return m
+}
+
+/*
+*
+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<MB>
+HKTA = HKT<A>
+HKTB = HKT<B>
+HKTAB = HKT<func(A)B>
+*/
+func traverseWithIndex[MA ~map[K]A, MB ~map[K]B, K comparable, A, B, HKTB, HKTAB, HKTRB any](
+	_of func(MB) HKTRB,
+	_map func(HKTRB, func(MB) func(B) MB) HKTAB,
+	_ap func(HKTAB, HKTB) HKTRB,
+
+	ta MA, f func(K, A) HKTB) HKTRB {
+	// this function inserts a value into a map with a given key
+	cb := F.Curry3(addKey[MB, K, B])
+
+	return ReduceWithIndex(ta, func(k K, r HKTRB, a A) HKTRB {
+		return _ap(
+			_map(r, cb(k)),
+			f(k, a),
+		)
+	}, _of(createEmpty[MB]()))
+}
+
+func MonadTraverse[MA ~map[K]A, MB ~map[K]B, K comparable, A, B, HKTB, HKTAB, HKTRB any](
+	_of func(MB) HKTRB,
+	_map func(HKTRB, func(MB) func(B) MB) HKTAB,
+	_ap func(HKTAB, HKTB) HKTRB,
+
+	r MA, f func(A) HKTB) HKTRB {
+	return traverseWithIndex(_of, _map, _ap, r, F.Ignore1st[K](f))
+}
+
+func TraverseWithIndex[MA ~map[K]A, MB ~map[K]B, K comparable, A, B, HKTB, HKTAB, HKTRB any](
+	_of func(MB) HKTRB,
+	_map func(HKTRB, func(MB) func(B) MB) HKTAB,
+	_ap func(HKTAB, HKTB) HKTRB,
+
+	f func(K, A) HKTB) func(MA) HKTRB {
+
+	return func(ma MA) HKTRB {
+		return traverseWithIndex(_of, _map, _ap, ma, f)
+	}
+}
+
+// HKTA = HKT<A>
+// HKTB = HKT<B>
+// HKTAB = HKT<func(A)B>
+// HKTRB = HKT<MB>
+func Traverse[MA ~map[K]A, MB ~map[K]B, K comparable, A, B, HKTB, HKTAB, HKTRB any](
+	_of func(MB) HKTRB,
+	_map func(HKTRB, func(MB) func(B) MB) HKTAB,
+	_ap func(HKTAB, HKTB) HKTRB,
+
+	f func(A) HKTB) func(MA) HKTRB {
+
+	return func(ma MA) HKTRB {
+		return MonadTraverse(_of, _map, _ap, ma, f)
+	}
+}
+
+// HKTA = HKT[A]
+// HKTAA = HKT[func(A)MA]
+// HKTRA = HKT[MA]
+func Sequence[MA ~map[K]A, MKTA ~map[K]HKTA, K comparable, A, HKTA, HKTAA, HKTRA any](
+	_of func(MA) HKTRA,
+	_map func(HKTRA, func(MA) func(A) MA) HKTAA,
+	_ap func(HKTAA, HKTA) HKTRA,
+
+	ma MKTA) HKTRA {
+	return MonadTraverse(_of, _map, _ap, ma, F.Identity[HKTA])
+}