initial checkin

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

array/monoid.go

@@ -0,0 +1,43 @@
+package array
+
+import (
+	"github.com/ibm/fp-go/internal/array"
+	M "github.com/ibm/fp-go/monoid"
+)
+
+func concat[T any](left, right []T) []T {
+	// some performance checks
+	ll := len(left)
+	lr := len(right)
+	if ll == 0 {
+		return right
+	}
+	if lr == 0 {
+		return left
+	}
+	// need to copy
+	buf := make([]T, ll+lr)
+	copy(buf[copy(buf, left):], right)
+	return buf
+}
+
+func Monoid[T any]() M.Monoid[[]T] {
+	return M.MakeMonoid(concat[T], Empty[T]())
+}
+
+func addLen[A any](count int, data []A) int {
+	return count + len(data)
+}
+
+// ConcatAll efficiently concatenates the input arrays into a final array
+func ArrayConcatAll[A any](data ...[]A) []A {
+	// get the full size
+	count := array.Reduce(data, addLen[A], 0)
+	buf := make([]A, count)
+	// copy
+	array.Reduce(data, func(idx int, seg []A) int {
+		return idx + copy(buf[idx:], seg)
+	}, 0)
+	// returns the final array
+	return buf
+}