使用无符号索引执行反向“for"循环的最佳方法是什么? [英] What's the best way to do a reverse 'for' loop with an unsigned index?

问题描述

我第一次尝试 reverse for 循环 做 n 次的事情是这样的:

My first attempt of reverse for loop that does something n times was something like:

for ( unsigned int i = n-1; i >= 0; i-- ) {
    ...     
}

这个失败是因为在无符号算术中i保证总是大于或等于零，因此循环条件总是为真.幸运的是，在我不得不怀疑为什么循环无限执行之前，gcc 编译器警告我毫无意义的比较".

This fails because in unsigned arithmetic i is guaranteed to be always greater or equal than zero, hence the loop condition will always be true. Fortunately, gcc compiler warned me about a 'pointless comparison' before I had to wonder why the loop was executing infinitely.

我正在寻找一种优雅的方式来解决这个问题，请记住:

I'm looking for an elegant way of resolving this issue keeping in mind that:

1. 它应该是一个向后的 for 循环.
2. 循环索引应该是无符号的.
3. n 是无符号常量.
4. 它不应基于无符号整数的晦涩"环算术.

有什么想法吗?谢谢:)

Any ideas? Thanks :)

推荐答案

怎么样:

for (unsigned i = n ; i-- > 0 ; )
{
  // do stuff with i
}

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