Go - responding to requests - Web Apps - First-class functions, Passing function sto other functions, Functions as types

Head First Go
楽天ブックス 紀伊國屋書店

開発環境

• macOS Mojave - Apple (OS)
• Emacs (Text Editor)
• Windows 10 Pro (OS)
• Visual Studio Code (Text Editor)
• Go (プログラミング言語)

Head First Go (Jay McGavren(著)、O'Reilly Media)のChapter 15(responding to requests - Web Apps)、Pool Puzzle(439)の解答を求めてみる。

コード

package main

import "fmt"

func callFunction(passedFunction func()) {
 passedFunction()
}
func callTwice(passedFunction func()) {
 passedFunction()
 passedFunction()
}
func callWithArguments(passedFunction func(string, bool)) {
 passedFunction("this sentence is", false)
}
func printReturnValue(passedFunction func() string) {
 fmt.Println(passedFunction())
}
func functionA() {
 fmt.Println("function called")
}
func functionB() string {
 fmt.Println("function called")
 return "Returning from function"
}
func functionC(a string, b bool) {
 fmt.Println("function called")
 fmt.Println(a, b)
}
func main() {
 callFunction(functionA)
 callTwice(functionA)
 callWithArguments(functionC)
 printReturnValue(functionB)
}

入出力結果(Bash、cmd.exe(コマンドプロンプト)、Terminal)

$ go run sample2.go
function called
function called
function called
function called
this sentence is false
function called
Returning from function
$