Guido van Rossum wrote:
> Why are you so excited about having until indented? You didn't give
> any examples with multiple occurrences. A single occurrence works just
> fine unindented, as PEP 315 has already shown.
FWIW, I must say I disagree (about "works just fine"). I find PEP 315
counter-intuitive. There's multi-part blocks in Python, but they all
behave like a step-sequence where you never come back to a previous
step. What I mean is that after entering a finally/except/elif/else,
there's no coming back in the try/if/for/while. My first impression
when looking at:
do:
<block1>
while condition:
<block2>
is that <block1> is executed only once. Yes, it would not make any
sense since you would write instead:
<block1>
while condition:
<block2>
But, FWIW, that's still my impression. I remember reading Stroustrup
saying he was never using do-while loops because he find them
counter-intuitive. I feel the same way. I think this is important,
because it means that even if do-while is available in C++, some
programmers, even the creator himself, are still always using while
loops. Even if different languages, I don't see why that would be
different in Python.
My mental image of a do-while loop looks more like a while-True-if-break
Python loop than a PEP315-like loop. For one thing, since the loop
content is executed at least once, I think about the condition breaking
the loop, not the one maintaining it alive. The keyword 'until' has
been proposed; I guess it would be as in Perl where it is an equivalent
of "while not". Also, the "do" keyword means nothing to me; maybe
something like "loop" would be better. Still, my feeling is that Python
is just getting it right with the status quo.
Regards,
Nicolas
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