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From: karl@haddock.ima.isc.com (Karl Heuer)
Newsgroups: comp.lang.c,comp.lang.misc
Subject: do...while vs. repeat...until (was: Errors aren't that simple)
Message-ID: <16188@haddock.ima.isc.com>
Date: 15 Mar 90 23:58:42 GMT
References: <8192@hubcap.clemson.edu> <17000003@hpcvra.CV.HP.COM> <Mar.7.10.43.42.1990.17402@paul.rutgers.edu> <5819.25f7a840@vax1.tcd.ie>
Reply-To: karl@haddock.ima.isc.com (Karl Heuer)
Followup-To: comp.lang.misc
Organization: Interactive Systems, Cambridge, MA 02138-5302
Lines: 20

In article <5819.25f7a840@vax1.tcd.ie> cbuckley@vax1.tcd.ie writes:
>In article <Mar.7.10.43.42.1990.17402@paul.rutgers.edu>, emuleomo@paul.rutgers.edu (Emuleomo) writes:
>> The other less serious flaw in C is the do...while contruct.
>> I kind of prefer PASCAL's repeat....until construct myself.
>
>How can this be a flaw? The two constructs are identical except for the fact
>that the condition is reversed...

That's enough to make it a (minor) flaw.  Judging from my own personal
experience, it is more natural for a test-at-top loop to specify the condition
for continuing (while), but for a test-at-bottom loop to specify the condition
for terminating (until).  I don't know if there's been a study on this; in
fact, I'm not entirely sure how to formalize the concept.

And no, I did *not* learn Pascal before C.  At worst, my opinion may be
slightly polluted from Ratfor; but I believe there's a sense in which
repeat...until is really better.

Karl W. Z. Heuer (karl@ima.ima.isc.com or harvard!ima!karl), The Walking Lint
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