2019年4月5日金曜日

開発環境

Head First Kotlin: A Brain-Friendly Guide (Dawn Griffiths(著)、David Griffiths(著)、O'Reilly Media)のChapter 4(classes and objects - A Bit of Class)、Pool Puzzle(117)の解答を求めてみる。

コード

class Rectangle(var width: Int, var height: Int) {
    val isSquare: Boolean
        get() = width == height
    val area: Int
        get() = width * height
}

fun main() {
    val r = arrayOf(
        Rectangle(1, 1),
        Rectangle(1, 1),
        Rectangle(1, 1),
        Rectangle(1, 1)
    )
    for (x in 0..3) {
        r[x].width = (x + 1) * 3
        r[x].height = x + 5
        print("Rectangle $x has area ${r[x].area}. ")
        println("It is ${if (r[x].isSquare) "" else "not "}a square.")
    }
    println()
    // 他のループでの方法
    for (x in 0 until r.size) {
        r[x].width = (x + 1) * 3
        r[x].height = x + 5
        print("Rectangle $x has area ${r[x].area}. ")
        println("It is ${if (r[x].isSquare) "" else "not "}a square.")
    }
    println()
    for ((x, rect) in r.withIndex()) {
        rect.width = (x + 1) * 3
        rect.height = x + 5
        print("Rectangle $x has area ${rect.area}. ")
        println("It is ${if (rect.isSquare) "" else "not "}a ssquare.")
    }
}

入出力結果

Rectangle 0 has area 15. It is not a square.
Rectangle 1 has area 36. It is a square.
Rectangle 2 has area 63. It is not a square.
Rectangle 3 has area 96. It is not a square.

Rectangle 0 has area 15. It is not a square.
Rectangle 1 has area 36. It is a square.
Rectangle 2 has area 63. It is not a square.
Rectangle 3 has area 96. It is not a square.

Rectangle 0 has area 15. It is not a ssquare.
Rectangle 1 has area 36. It is a ssquare.
Rectangle 2 has area 63. It is not a ssquare.
Rectangle 3 has area 96. It is not a ssquare.

Process finished with exit code 0

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