Kotlin - lambdas and higher-order functions - Treating Code Like Data - passing function parameter values

Head First Kotlin
A Brain-Friendly Guide
楽天ブックス(Kobo) 紀伊國屋書店(Kinoppy)

開発環境

• macOS Mojave - Apple (OS)
• Windows 10 Pro (OS)
• IntelliJ IDEA CE(Community Edition) (IDE(統合開発環境))
• Kotlin (プログラミング言語)

Head First Kotlin: A Brain-Friendly Guide (Dawn Griffiths(著)、David Griffiths(著)、O'Reilly Media)のChapter 11(lambdas and higher-order functions - Treating Code Like Data)、Pool Puzzle(346)の解答を求めてみる。

コード

fun unless(condition: Boolean, code: () -> Unit) {
    if (!condition) {
        code()
    }
}

fun main() {
    val options = arrayOf("Red", "Amber", "Green")
    for (n in 1..10) {
        print("n = $n: ")
        var crossWalk = options[kotlin.random.Random.nextInt(options.size)]
        if (crossWalk == "Green") {
            println("Walk!")
        }
        unless(crossWalk == "Green") {
            println("Stop!")
        }
    }
}

入出力結果

n = 1: Stop!
n = 2: Stop!
n = 3: Stop!
n = 4: Stop!
n = 5: Walk!
n = 6: Stop!
n = 7: Walk!
n = 8: Stop!
n = 9: Stop!
n = 10: Stop!

Process finished with exit code 0