feat: add Compose in function.go

function/function.go

@@ -1,7 +1,7 @@
 // Copyright 2021 dudaodong@gmail.com. All rights reserved.
 // Use of this source code is governed by MIT license
 
-// Package function implements some functions for functional programming.
+// Package function implements some functions for control the function execution and some is for functional programming.
 
 package function
 
@@ -47,7 +47,22 @@ func (f Fn) Curry(i interface{}) func(...interface{}) interface{} {
 	}
 }
 
-// Delay make the function excution after delayed time
+// Compose compose the functions from right to left
+func Compose(fnList ...func(...string) string) func(...string) string {
+	return func(s... string) string {
+		f := fnList[0]
+		restFn := fnList[1:]
+
+		if len(fnList) == 1 {
+			return f(s...)
+		}
+
+		return f(Compose(restFn...)(s...))
+	}
+}
+
+
+// Delay make the function execution after delayed time
 func Delay(delay time.Duration, fn interface{}, args ...interface{}) {
 	time.Sleep(delay)
 	invokeFunc(fn, args...)

function/function_test.go

@@ -3,6 +3,7 @@ package function
 import (
 	"fmt"
 	"reflect"
+	"strings"
 	"testing"
 	"time"
 )
@@ -69,6 +70,26 @@ func TestCurry(t *testing.T) {
 	}
 }
 
+func TestCompose(t *testing.T) {
+	toUpper := func(a... string) string {
+		return strings.ToUpper(a[0])
+	}
+
+	toLower := func(a... string) string {
+		return strings.ToLower(a[0])
+	}
+
+	expect := toUpper(toLower("aBCde"))
+	cf := Compose(toUpper, toLower)
+	res := cf("aBCde")
+
+	fmt.Println(res, expect)
+	if res != expect {
+		t.FailNow()
+	}
+
+}
+
 func TestDelay(t *testing.T) {
 	var print = func(s string) {
 		fmt.Println(s)