Kotlin - lambdas and higher-order functions - Treating Code Like Data - type

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)、WHAT'S MY TYPE?の解答を求めてみる。

コード

fun main() {
    println("lambda1")
    var lambda1: (Double) -> Int
    // 代入できるのはない

    println("lambda2")
    var lambda2: (Int) -> Double

    lambda2 = { it + 7.1 }
    println(lambda2(10))

    println("lambda3")
    var lambda3: (Int) -> Int

    lambda3 = { (it * 3) - 4 }
    println(lambda3(10))

    lambda3 = { x: Int -> x + 56 }
    println(lambda3(10))

    println("lambda4")
    var lambda4: (Double) -> Unit

    lambda4 = { it + 7.1 }
    println(lambda4(1.2))

    lambda4 = { (it * 3) - 4 }
    println(lambda4(1.2))

    lambda4 = { println("Hello!") }
    println(lambda4(1.2))

    lambda4 = { x: Double -> x + 75 }
    println(lambda4(1.2))

    println("lambda5")
    var lambda5 = { x: Int -> x + 56 }
    println(lambda5(10))

    var lambda5_1 = { println("Hello!") }
    println(lambda5_1.invoke())

    var lambda5_2 = { x: Double -> x + 75 }
    println(lambda5_2(1.2))
}

入出力結果

lambda1
lambda2
17.1
lambda3
26
66
lambda4
kotlin.Unit
kotlin.Unit
Hello!
kotlin.Unit
kotlin.Unit
lambda5
66
Hello!
kotlin.Unit
76.2

Process finished with exit code 0