为什么 Swift 游乐场显示错误的执行次数? [英] Why does Swift playground shows wrong number of executions?

问题描述

我正在使用完成处理程序来总结数字.我不明白的是，如果我将代码分成 2 行，执行次数将从 6 变为 7！！为什么?

I am using a completion handler to sum up numbers. What I don't understand is if I break my code in 2 lines, the number of executions would change from 6 to 7!! WHY?

 func summer (from : Int, to: Int, handler: (Int) -> (Int)) -> Int {
        var sum = 0
        for i in from...to {
            sum += handler(i)
        }
        return sum

}

summer(1, to:6){ //Shows '21'
    return $0} // shows '(6 times)'


// Same code, but in 1 line
summer(1, to:6){return $0} // shows '(7 times)'

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推荐答案

它显示了在该行调用函数/表达式的次数:

It's showing how many times a function / expression is being called on that line:

由于调用表达式(summer())在同一行，所以算作额外的操作.因此，6 次打印 + 6 次返回 + 1 次 summer() = 13 次该行发生了某些事情.

since the calling expression (summer()) is on the same line, it counts as an extra operation. Hence, 6 prints + 6 returns + 1 summer() = 13 times something happened on that line.

我不确定我是否使用了正确的术语，但这就是正在发生的事情.

I'm not sure if I used the correct terminology, but this is what's going on.

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