Kotlin 中使用数据类型 Double 的范围 [英] Ranges in Kotlin using data type Double

问题描述

    fun calcInterest(amount: Double, interest: Double): Double {
    return(amount *(interest/100.0))
}

fun main(args: Array<String>) {

    for (i in 1.0..2.0 step .5) {
        println("&10,000 at 5% interest is = ${calcInterest(10000.0,i)}")
    }

}

我收到错误消息说 For 循环范围必须有一个 'Iterator()' 方法.它强调了我在该部分中的双打(我在 1.0..2.0 中)

I get the error saying the For-loop range must have an 'Iterator()'Method. It underlines my doubles in the section (i in 1.0..2.0)

如何在一个范围内使用双精度数?Ranges Reloaded 网站 (https://blog.jetbrains.com/kotlin/2013/02/ranges-reloaded/ )表明使用数据类型 Double 很好.我不知道我的有什么问题.我需要使用双打，因为我的利率使用小数.对编程完全陌生，所以希望有人能简单地解释一下.谢谢！

How can I use doubles in a range?? A website on Ranges Reloaded (https://blog.jetbrains.com/kotlin/2013/02/ranges-reloaded/ ) shows that using datatype Double is fine. I don't know what's wrong with mine. I need to use doubles for the fact that my interest rates are using decimals. Completely new to programming so hopefully someone can explain simply. Thanks!

添加步骤 .5

推荐答案

从 Kotlin 1.1 开始，ClosedRange不能用于迭代"(rangeTo() - 实用函数 - Ranges - Kotlin 编程语言).

As of Kotlin 1.1, a ClosedRange<Double> "cannot be used for iteration" (rangeTo() - Utility functions - Ranges - Kotlin Programming Language).

但是，您可以定义自己的 step 扩展功能.例如:

You can, however, define your own step extension function for this. e.g.:

infix fun ClosedRange<Double>.step(step: Double): Iterable<Double> {
    require(start.isFinite())
    require(endInclusive.isFinite())
    require(step > 0.0) { "Step must be positive, was: $step." }
    val sequence = generateSequence(start) { previous ->
        if (previous == Double.POSITIVE_INFINITY) return@generateSequence null
        val next = previous + step
        if (next > endInclusive) null else next
    }
    return sequence.asIterable()
}

虽然您可以在使用金钱的情况下执行此操作，但您实际上不应该使用 Double(或 Float).请参阅 Java 实践 -> 代表金钱.

Although you can do this if you are working with money you shouldn't really be using Double (or Float). See Java Practices -> Representing money.

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