fix: introduce stateless iterator

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

lambda/y_test.go

@@ -0,0 +1,34 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package lambda
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestFactorial(t *testing.T) {
+	fct := Y(func(r RecFct[int, int]) RecFct[int, int] {
+		return func(n int) int {
+			if n <= 0 {
+				return 1
+			}
+			return n * r(n-1)
+		}
+	})
+
+	fmt.Println(fct(10))
+}