fix: add some benchmarks

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

iterator/stateless/benchmark_test.go

@@ -0,0 +1,65 @@
+// 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 stateless
+
+import (
+	"testing"
+
+	F "github.com/IBM/fp-go/function"
+)
+
+func BenchmarkMulti(b *testing.B) {
+	// run the Fib function b.N times
+	for n := 0; n < b.N; n++ {
+		single()
+	}
+}
+
+func single() int64 {
+
+	length := 10000
+	nums := make([]int, 0, length)
+	for i := 0; i < length; i++ {
+		nums = append(nums, i+1)
+	}
+
+	return F.Pipe6(
+		nums,
+		FromArray[int],
+		Filter(func(n int) bool {
+			return n%2 == 0
+		}),
+		Map(func(t int) int64 {
+			return int64(t)
+		}),
+		Filter(func(t int64) bool {
+			n := t
+			for n/10 != 0 {
+				if n%10 == 4 {
+					return false
+				}
+				n = n / 10
+			}
+			return true
+		}),
+		Map(func(t int64) int {
+			return int(t)
+		}),
+		Reduce(func(n int64, r int) int64 {
+			return n + int64(r)
+		}, int64(0)),
+	)
+}

iterator/stateless/generic/iterator.go

@@ -82,6 +82,7 @@ func Map[GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tuple2[GU,
 			m,
 		)
 	}
+
 	m = O.Map(T.Map2(recurse, f))
 
 	return recurse