在循环执行时递减循环计数器

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问题描述

我正在尝试在循环运行时递减 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:

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

但实际上，它只是简单地打印系列 1-100.这是设计的吗?如果是这样，我如何减少正在运行的循环的计数器(例如，因为当前循环被取消资格并应该再次运行)?

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)?

推荐答案

这是设计使然.来自 Lua 参考手册:

It's by design. From Lua reference manual:

在循环开始之前，所有三个控制表达式只计算一次.它们都必须产生数字.

3.3.5 – For Statement

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

因此在循环内修改 i 的值不会改变循环的运行方式.

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

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