Friday Finking: Contorted loops

[Joe Pfeiffer]

ram at zedat.fu-berlin.de (Stefan Ram) writes:

> ram at zedat.fu-berlin.de (Stefan Ram) writes:
>>can be misleading, because the "..." part can still contain
>>"break", "raise", "continue", and "return" statement. So one
>>better should always be on the watch when reading source code
>>of a language like Python than relying only on the condition 
>>behind the "while".
>
>   The existence of statements like "break" renders 
>   proof techniques for loops (such as Hoare's) with
>   their invariants and inference rules unapplicable.

Also the reason to avoid repeat-until loops:  the loop "invariant" isn't
the same on the first iteration as on subsequent iterations.