优雅的Swift方式来处理for循环中的负指数 [英] Elegant Swift way to handle negative index in for loop

问题描述

我是新来的 Swift ，并试图找到一个优雅的方式来处理一个for循环变量，可以是负面的。

  func funForLoops（_ loop：Int）{
 for i in 0 ..< loop {
 print（Hello \（i） ）
} 
} 
 funForLoops（1）//打印Hello 0 
 funForLoops（0）//不执行
 funForLoops（-1）//运行时错误致命错误：无法形成范围与upperBound< lowerBound
  

是否有更简单这样比这个检查方式：

pre $ code if（loop> = 0）{
for i in 0 .. < loop {
print（Hello \（i））
}
}

或者这个：

  for i in 0 ..<（loop> = 0？循环：0）{
  

解决方案

如果它是消极的，什么都不要做（这不是显而易见的;你可能意思是减量，这就是为什么它会是模棱两可的它不是一个例外）你想要的语法是：

  for i in 0 ..< max（0，loop ）{} 
  

这是一个很好的语法，但在大多数情况下，出乎意料地是消极的，你在程序结构上存在更深层次的问题，应该尽早解决问题。

I'm new to Swift and trying to find an elegant way to handle a for loop variable that can be negative.

func funForLoops(_ loop:Int) {
    for i in 0..<loop {
        print("Hello \(i)")
    }
}
funForLoops(1) // prints Hello 0
funForLoops(0) // doesn't execute
funForLoops(-1) // runtime error "fatal error: Can't form Range with  upperBound < lowerBound"

Is there a simpler way to check this than this:

if (loop >= 0) {
    for i in 0..<loop {
        print("Hello \(i)")
    }
}

Or this:

for i in 0..<(loop >= 0 ? loop : 0) {

解决方案

On the assumption you mean "if it's negative, do nothing," (which is not obvious; you might mean "decrement," which is why it would be ambiguous if it weren't an exception) the syntax you want is:

for i in 0..<max(0, loop) { }

This is a fine syntax when it is necessary, but in most cases if the value can be surprisingly negative, you have a deeper problem in the structure of the program and should have resolved the issue sooner.

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