fix: add example for dependency injection using a Reader

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

samples/getting-started-with-fp-ts/reader/example1/reader_test.go

@@ -0,0 +1,75 @@
+// 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 reader implements the example in [https://dev.to/gcanti/getting-started-with-fp-ts-reader-1ie5]
+package example1
+
+import (
+	"fmt"
+
+	F "github.com/IBM/fp-go/function"
+	N "github.com/IBM/fp-go/number"
+	I "github.com/IBM/fp-go/number/integer"
+	"github.com/IBM/fp-go/ord"
+	R "github.com/IBM/fp-go/reader"
+	S "github.com/IBM/fp-go/string"
+)
+
+type (
+	I18n struct {
+		True  string
+		False string
+	}
+
+	Dependencies struct {
+		I18n I18n
+	}
+)
+
+var (
+	// g: func(int) R.Reader[*Dependencies, string], note how the implementation does not depend on the dependencies
+	g = F.Flow2(
+		ord.Gt(I.Ord)(2),
+		f,
+	)
+
+	// h: func(string) R.Reader[*Dependencies, string], note how the implementation does not depend on the dependencies
+	h = F.Flow3(
+		S.Size,
+		N.Add(1),
+		g,
+	)
+)
+
+func f(b bool) R.Reader[*Dependencies, string] {
+	return func(deps *Dependencies) string {
+		if b {
+			return deps.I18n.True
+		}
+		return deps.I18n.False
+	}
+}
+
+func ExampleReader() {
+
+	deps := Dependencies{I18n: I18n{True: "vero", False: "falso"}}
+
+	fmt.Println(h("foo")(&deps))
+	fmt.Println(h("a")(&deps))
+
+	// Output:
+	// vero
+	// falso
+}

samples/getting-started-with-fp-ts/reader/example2/reader_test.go

@@ -0,0 +1,97 @@
+// 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 reader implements the example in [https://dev.to/gcanti/getting-started-with-fp-ts-reader-1ie5]
+package example2
+
+import (
+	"fmt"
+
+	F "github.com/IBM/fp-go/function"
+	ID "github.com/IBM/fp-go/identity"
+	N "github.com/IBM/fp-go/number"
+	I "github.com/IBM/fp-go/number/integer"
+	"github.com/IBM/fp-go/ord"
+	R "github.com/IBM/fp-go/reader"
+	S "github.com/IBM/fp-go/string"
+)
+
+type (
+	I18n struct {
+		True  string
+		False string
+	}
+
+	Dependencies struct {
+		I18n       I18n
+		LowerBound int
+	}
+)
+
+var (
+	// h: func(string) R.Reader[*Dependencies, string], note how the implementation does not depend on the dependencies
+	h = F.Flow3(
+		S.Size,
+		N.Add(1),
+		g,
+	)
+)
+
+func getLowerBound(deps *Dependencies) int {
+	return deps.LowerBound
+}
+
+func g(n int) R.Reader[*Dependencies, string] {
+	return F.Pipe1(
+		R.Ask[*Dependencies](),
+		R.Chain(F.Flow4(
+			getLowerBound,
+			ord.Gt(I.Ord),
+			ID.Flap[bool](n),
+			f,
+		)),
+	)
+}
+
+func f(b bool) R.Reader[*Dependencies, string] {
+	return func(deps *Dependencies) string {
+		if b {
+			return deps.I18n.True
+		}
+		return deps.I18n.False
+	}
+}
+
+func ExampleReader() {
+
+	deps1 := Dependencies{I18n: I18n{True: "vero", False: "falso"}, LowerBound: 2}
+
+	hFoo := h("foo")
+	hA := h("a")
+
+	fmt.Println(hFoo(&deps1))
+	fmt.Println(hA(&deps1))
+
+	deps2 := Dependencies{I18n: I18n{True: "vero", False: "falso"}, LowerBound: 4}
+
+	fmt.Println(hFoo(&deps2))
+	fmt.Println(hA(&deps2))
+
+	// Output:
+	// vero
+	// falso
+	// falso
+	// falso
+}