fix: add match example

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

samples/match/examples_match_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 match
+
+import (
+	"fmt"
+
+	E "github.com/IBM/fp-go/either"
+	"github.com/IBM/fp-go/errors"
+	F "github.com/IBM/fp-go/function"
+	O "github.com/IBM/fp-go/option"
+	S "github.com/IBM/fp-go/string"
+)
+
+type Thing struct {
+	Name string
+}
+
+func (t Thing) GetName() string {
+	return t.Name
+}
+
+var (
+	// func(Thing) Either[error, string]
+	getName = F.Flow2(
+		Thing.GetName,
+		E.FromPredicate(S.IsNonEmpty, errors.OnSome[string]("value [%s] is empty")),
+	)
+
+	// func(option.Option[Thing]) Either[error, string]
+	GetName = F.Flow2(
+		E.FromOption[Thing](errors.OnNone("value is none")),
+		E.Chain(getName),
+	)
+)
+
+func ExampleEither_match() {
+
+	oThing := O.Of(Thing{"Carsten"})
+
+	res := F.Pipe2(
+		oThing,
+		GetName,
+		E.Fold(S.Format[error]("failed with error %v"), S.Format[string]("get value %s")),
+	)
+
+	fmt.Println(res)
+
+	// Output:
+	// get value Carsten
+
+}