当循环正在执行时递减循环计数器 [英] Decrementing a loop counter as loop is executing

问题描述

我试图在循环运行时递减一个for循环的计数器。不幸的是，Lua似乎不允许这样做。这段代码应该永远运行：

  for i = 1，100 do 
 print（i）
i = i  -  1 
 end 
  

事实上， 1-100。这是由设计？如果是这样，我如何减少运行循环的计数器（例如，因为当前的循环被取消资格，应该再次运行）？

解决方案

这是设计。从 Lua参考手册：

3.3.5 - For语句

在循环开始之前，所有三个控制表达式都只计算一次。所以修改 i 的值就可以了。 循环不会改变循环的运行方式。

I'm trying to decrement the counter of a for loop as the loop is running. Unfortunately, Lua doesn't seem to allow that. This piece of code should run forever:

for i = 1, 100 do
    print (i)
    i = i - 1
end

but it does, in fact, simply print the series 1-100. Is that by design? If so, how do I decrement the counter of a running loop (for example because the current cycle was disqualified and should run again)?

解决方案

It's by design. From Lua reference manual:

3.3.5 – For Statement

All three control expressions are evaluated only once, before the loop starts. They must all result in numbers.

So modifying the value of i inside the loop won't change how the loop runs.

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