fix: add monoid for bool

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

boolean/boolean.go

@@ -0,0 +1,59 @@
+// 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 boolean
+
+import (
+	EQ "github.com/IBM/fp-go/eq"
+	M "github.com/IBM/fp-go/monoid"
+	O "github.com/IBM/fp-go/ord"
+)
+
+var (
+	// MonoidAny is the boolean [M.Monoid] under disjunction
+	MonoidAny = M.MakeMonoid(
+		func(l, r bool) bool {
+			return l || r
+		},
+		false,
+	)
+
+	// MonoidAll is the boolean [M.Monoid] under conjuction
+	MonoidAll = M.MakeMonoid(
+		func(l, r bool) bool {
+			return l && r
+		},
+		true,
+	)
+
+	// Eq is the equals predicate for boolean
+	Eq = EQ.FromStrictEquals[bool]()
+
+	// Ord is the strict ordering for boolean
+	Ord = O.MakeOrd(func(l, r bool) int {
+		if l {
+			if r {
+				return 0
+			}
+			return +1
+		}
+		if r {
+			return -1
+		}
+		return 0
+	}, func(l, r bool) bool {
+		return l == r
+	})
+)