goto

[Rocco Moretti]

> My "favorite" infinte loop with while is:
> 
>    i = 0
>    while i < 20:
>          do_process(i)
> 
> Note the prominent *lack* of any change to i here?
> 
> Oh, for:
> 
>     from i = 0
>     invariant 0 <= i <= 20
>     variant 21 - i
>     until i > 19
>     loop
>         do_process(i)
> 
> which throws an exception at the beginning of the second loop.

What language is that from?

I take it the exception is from the "21-i" not changing as it goes 
around the loop, right? (But why can't "variant i" work just as well?)