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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Subject: Re: Local vs global variables in ADA
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Date: Tue, 5 Nov 2002 22:37:51 GMT
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Date: 2002-11-05T22:37:51+00:00
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Stephen Leake <stephen.a.leake.1@gsfc.nasa.gov> writes:

> Never use a "while" loop. Mostly because "exit when" is much clearer,
> partly because I've used other languages that had slightly different
> definitions of "while", and I can't keep them straight.

Like what?  I mean, which languages have different definitions of
"while" loops, and what are the differences.  I thought "while" loops
were one of the few cases where there is pretty much agreement on the
semantics across languages.

I like while loops, and use them in favor of loop/exit whenever the exit
condition happens at the top.

I seem to recall some issue in SPARK, where they discouraged while
loops.  Something about wanting to put a loop-invariant before the exit
condition?  Maybe one of the SPARK folks can comment on that.  I'm happy
to write assertions that help program-proving tools, if they also help
me, the human reader (or at least neutral to the human reader), but I'm
a bit uncomfortable using a style that helps tools, but hinders humans.

- Bob