Add Do notation support and Bind to Monads (#100)

* fix: implement bind, let, apS for serveral monads

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

* fix: implement bind for maps

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

* fix: implement do notation for more monads

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

* fix: add bind to more monads

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

* fix: add Do and Bind support to Monads

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

---------

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

iterator/stateless/bind.go

@@ -0,0 +1,66 @@
+// 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 (
+	G "github.com/IBM/fp-go/iterator/stateless/generic"
+)
+
+// Bind creates an empty context of type [S] to be used with the [Bind] operation
+func Do[S any](
+	empty S,
+) Iterator[S] {
+	return G.Do[Iterator[S], S](empty)
+}
+
+// Bind attaches the result of a computation to a context [S1] to produce a context [S2]
+func Bind[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) Iterator[T],
+) func(Iterator[S1]) Iterator[S2] {
+	return G.Bind[Iterator[S1], Iterator[S2], Iterator[T], S1, S2, T](setter, f)
+}
+
+// Let attaches the result of a computation to a context [S1] to produce a context [S2]
+func Let[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	f func(S1) T,
+) func(Iterator[S1]) Iterator[S2] {
+	return G.Let[Iterator[S1], Iterator[S2], S1, S2, T](setter, f)
+}
+
+// LetTo attaches the a value to a context [S1] to produce a context [S2]
+func LetTo[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	b T,
+) func(Iterator[S1]) Iterator[S2] {
+	return G.LetTo[Iterator[S1], Iterator[S2], S1, S2, T](setter, b)
+}
+
+// BindTo initializes a new state [S1] from a value [T]
+func BindTo[S1, T any](
+	setter func(T) S1,
+) func(Iterator[T]) Iterator[S1] {
+	return G.BindTo[Iterator[S1], Iterator[T], S1, T](setter)
+}
+
+// ApS attaches a value to a context [S1] to produce a context [S2] by considering the context and the value concurrently
+func ApS[S1, S2, T any](
+	setter func(T) func(S1) S2,
+	fa Iterator[T],
+) func(Iterator[S1]) Iterator[S2] {
+	return G.ApS[Iterator[func(T) S2], Iterator[S1], Iterator[S2], Iterator[T], S1, S2, T](setter, fa)
+}