On 21Jan2009 14:02, Tres Seaver <[email protected]> wrote:
| Vitor Bosshard wrote:
| > BTW, there is already an "until" keyword in python, it's called "while not"
;)
|
| 'until' is used at least in some languages (Pascal, Modula*, maybe Ada?)
| for a "terminate at bottom" loop (one guaranteed to run at least once):
| in such cases, the predicate has the negative sense.
This is a particular flavour of "do ... while" which just happens
to read a little better in English. It does sometimes bother me that
Python doesn't have do...while when I find my self replicating the loop
bottom above the loop.
Back at uni we had to implement a small language in our compilers class
and the lecturer had specified a proper generic while loop, thus:
loop:
suite
while invariant
suite
endloop
I think the keywords were better than above, but it neatly handled the
fact that the while-test must often be preceeded by some setup that
would be replicated at the loop bottom in Python and many other languages:
setup-invariant-state
while test-invariant
do stuff
setup-invariant-state
of which the bare while... and converse do...while loops are particular
extremes.
Cheers,
--
Cameron Simpson <[email protected]> DoD#743
http://www.cskk.ezoshosting.com/cs/
Why doesn't DOS ever say EXCELLENT command or filename?
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