fix: attempt to expose Monad as an interface

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

iterator/stateless/generic/monad.go

@@ -0,0 +1,45 @@
+// Copyright (c) 2024 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 generic
+
+import (
+	"github.com/IBM/fp-go/internal/monad"
+	O "github.com/IBM/fp-go/option"
+	T "github.com/IBM/fp-go/tuple"
+)
+
+type iteratorMonad[A, B any, GA ~func() O.Option[T.Tuple2[GA, A]], GB ~func() O.Option[T.Tuple2[GB, B]], GAB ~func() O.Option[T.Tuple2[GAB, func(A) B]]] struct{}
+
+func (o *iteratorMonad[A, B, GA, GB, GAB]) Of(a A) GA {
+	return Of[GA, A](a)
+}
+
+func (o *iteratorMonad[A, B, GA, GB, GAB]) Map(f func(A) B) func(GA) GB {
+	return Map[GB, GA, func(A) B, A, B](f)
+}
+
+func (o *iteratorMonad[A, B, GA, GB, GAB]) Chain(f func(A) GB) func(GA) GB {
+	return Chain[GB, GA, A, B](f)
+}
+
+func (o *iteratorMonad[A, B, GA, GB, GAB]) Ap(fa GA) func(GAB) GB {
+	return Ap[GAB, GB, GA, A, B](fa)
+}
+
+// Monad implements the monadic operations for iterators
+func Monad[A, B any, GA ~func() O.Option[T.Tuple2[GA, A]], GB ~func() O.Option[T.Tuple2[GB, B]], GAB ~func() O.Option[T.Tuple2[GAB, func(A) B]]]() monad.Monad[A, B, GA, GB, GAB] {
+	return &iteratorMonad[A, B, GA, GB, GAB]{}
+}