fix: implement foldMap for records

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

record/generic/record.go

@@ -19,6 +19,7 @@ import (
 	"sort"
 
 	F "github.com/IBM/fp-go/function"
+	RAG "github.com/IBM/fp-go/internal/array"
 	FC "github.com/IBM/fp-go/internal/functor"
 	G "github.com/IBM/fp-go/internal/record"
 	Mg "github.com/IBM/fp-go/magma"
@@ -334,6 +335,62 @@ func ToEntries[M ~map[K]V, GT ~[]T.Tuple2[K, V], K comparable, V any](r M) GT {
 	return ToArray[M, GT](r)
 }
 
+// FromFoldableMap uses the reduce method for a higher kinded type to transform
+// its values into a tuple. The key and value are then used to populate the map. Duplicate
+// values are resolved via the provided [Mg.Magma]
+func FromFoldableMap[
+	FCT ~func(A) T.Tuple2[K, V],
+	HKTA any,
+	FOLDABLE ~func(func(M, A) M, M) func(HKTA) M,
+	M ~map[K]V,
+	A any,
+	K comparable,
+	V any](m Mg.Magma[V], fld FOLDABLE) func(f FCT) func(fa HKTA) M {
+	return func(f FCT) func(fa HKTA) M {
+		return fld(func(dst M, a A) M {
+			if IsEmpty(dst) {
+				dst = make(M)
+			}
+			e := f(a)
+			k := T.First(e)
+			old, ok := dst[k]
+			if ok {
+				dst[k] = m.Concat(old, T.Second(e))
+			} else {
+				dst[k] = T.Second(e)
+			}
+			return dst
+		}, Empty[M]())
+	}
+}
+
+func FromFoldable[
+	HKTA any,
+	FOLDABLE ~func(func(M, T.Tuple2[K, V]) M, M) func(HKTA) M,
+	M ~map[K]V,
+	K comparable,
+	V any](m Mg.Magma[V], red FOLDABLE) func(fa HKTA) M {
+	return FromFoldableMap[func(T.Tuple2[K, V]) T.Tuple2[K, V], HKTA, FOLDABLE](m, red)(F.Identity[T.Tuple2[K, V]])
+}
+
+func FromArrayMap[
+	FCT ~func(A) T.Tuple2[K, V],
+	GA ~[]A,
+	M ~map[K]V,
+	A any,
+	K comparable,
+	V any](m Mg.Magma[V]) func(f FCT) func(fa GA) M {
+	return FromFoldableMap[FCT](m, F.Bind23of3(RAG.Reduce[GA, A, M]))
+}
+
+func FromArray[
+	GA ~[]T.Tuple2[K, V],
+	M ~map[K]V,
+	K comparable,
+	V any](m Mg.Magma[V]) func(fa GA) M {
+	return FromFoldable[GA](m, F.Bind23of3(RAG.Reduce[GA, T.Tuple2[K, V], M]))
+}
+
 func FromEntries[M ~map[K]V, GT ~[]T.Tuple2[K, V], K comparable, V any](fa GT) M {
 	m := make(M)
 	for _, t := range fa {

record/record.go

@@ -16,6 +16,7 @@
 package record
 
 import (
+	EM "github.com/IBM/fp-go/endomorphism"
 	Mg "github.com/IBM/fp-go/magma"
 	Mo "github.com/IBM/fp-go/monoid"
 	O "github.com/IBM/fp-go/option"
@@ -291,6 +292,44 @@ func Copy[K comparable, V any](m map[K]V) map[K]V {
 }
 
 // Clone creates a deep copy of the map using the provided endomorphism to clone the values
-func Clone[K comparable, V any](f func(V) V) func(m map[K]V) map[K]V {
+func Clone[K comparable, V any](f EM.Endomorphism[V]) EM.Endomorphism[map[K]V] {
 	return G.Clone[map[K]V](f)
 }
+
+// FromFoldableMap converts from a reducer to a map
+// Duplicate keys are resolved by the provided [Mg.Magma]
+func FromFoldableMap[
+	FOLDABLE ~func(func(map[K]V, A) map[K]V, map[K]V) func(HKTA) map[K]V, // the reduce function
+	A any,
+	HKTA any,
+	K comparable,
+	V any](m Mg.Magma[V], red FOLDABLE) func(f func(A) T.Tuple2[K, V]) func(fa HKTA) map[K]V {
+	return G.FromFoldableMap[func(A) T.Tuple2[K, V]](m, red)
+}
+
+// FromArrayMap converts from an array to a map
+// Duplicate keys are resolved by the provided [Mg.Magma]
+func FromArrayMap[
+	A any,
+	K comparable,
+	V any](m Mg.Magma[V]) func(f func(A) T.Tuple2[K, V]) func(fa []A) map[K]V {
+	return G.FromArrayMap[func(A) T.Tuple2[K, V], []A, map[K]V](m)
+}
+
+// FromFoldable converts from a reducer to a map
+// Duplicate keys are resolved by the provided [Mg.Magma]
+func FromFoldable[
+	HKTA any,
+	FOLDABLE ~func(func(map[K]V, T.Tuple2[K, V]) map[K]V, map[K]V) func(HKTA) map[K]V, // the reduce function
+	K comparable,
+	V any](m Mg.Magma[V], red FOLDABLE) func(fa HKTA) map[K]V {
+	return G.FromFoldable[HKTA, FOLDABLE](m, red)
+}
+
+// FromArray converts from an array to a map
+// Duplicate keys are resolved by the provided [Mg.Magma]
+func FromArray[
+	K comparable,
+	V any](m Mg.Magma[V]) func(fa []T.Tuple2[K, V]) map[K]V {
+	return G.FromArray[[]T.Tuple2[K, V], map[K]V](m)
+}

record/record_test.go

@@ -1,5 +1,5 @@
-// Copyright (c) 2023 IBM Corp.
 // All rights reserved.
+// Copyright (c) 2023 IBM Corp.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -23,8 +23,10 @@ import (
 
 	A "github.com/IBM/fp-go/array"
 	"github.com/IBM/fp-go/internal/utils"
+	Mg "github.com/IBM/fp-go/magma"
 	O "github.com/IBM/fp-go/option"
 	S "github.com/IBM/fp-go/string"
+	T "github.com/IBM/fp-go/tuple"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -149,3 +151,28 @@ func TestCopyVsClone(t *testing.T) {
 	assert.NotEqual(t, cpy, cln)
 	assert.Equal(t, src, cpy)
 }
+
+func TestFromArrayMap(t *testing.T) {
+	src1 := A.From("a", "b", "c", "a")
+	frm := FromArrayMap[string, string](Mg.Second[string]())
+
+	f := frm(T.Replicate2[string])
+
+	res1 := f(src1)
+
+	assert.Equal(t, map[string]string{
+		"a": "a",
+		"b": "b",
+		"c": "c",
+	}, res1)
+
+	src2 := A.From("A", "B", "C", "A")
+
+	res2 := f(src2)
+
+	assert.Equal(t, map[string]string{
+		"A": "A",
+		"B": "B",
+		"C": "C",
+	}, res2)
+}