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for-loopluacounter

Decrementing a loop counter as loop is executing

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)?

Solution

  • 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.