bug?

[kobi2187]

hi,
I am probably just being stupid, but the following code acts strangely

test_while:func()
{
  seq:=[1]
  x:= seq length

  while(x>=0)
  {
    "%d" printfln(x)
    x -= 1
  }
}

it should just print 1 0, instead the while condition is not checked. it goes to infinite loop.
Why?
if there is no array it seems to work.
I haven't programmed for a long time, so could it be just my empty brain?

PS: can I run a for loop backwards? ( 10:1:-1)

Thanks, kobi

[Amos Wenger]

An array's length is a SizeT, which is unsigned, so it wraps around to 2^32-1 on the first iteration :)

You can cast seq length to an int with:

x := seq length as Int

That, or SSizeT, or whatever type you want.

Here's the C code generated by rock for (something resembling) your sample: https://gist.github.com/fasterthanlime/c4854c9a04a9be004097#file-nonsense-c-L43

Hope that helps!

Cheers,

- Amos

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[kobi2187]

Yes, that really helps. thank you!
I always found overflowing a weird behaviour.
I would much rather see an assert firing instead.
btw, why names like SizeT instead of UInt ?

[Amos Wenger]

Oh but there is UInt, and Int, and UInt32, UInt16, UInt8 — the whole charade. It's based on C types, which, unfortunately, there are many of.

"SizeT" is the size of a pointer on your target platform, usually 4 or 8 bytes.

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