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From: touch@dsl.cis.upenn.edu (Joe Touch)
Newsgroups: comp.lang.modula2
Subject: Re: Why are the loops so awkward?
Message-ID: <26032@netnews.upenn.edu>
Date: 14 Jun 90 19:00:52 GMT
References: <5377.26731960@puddle.fidonet.org> <728.26767558@waikato.ac.nz> <22213@boulder.Colorado.EDU> <747.2677cd57@waikato.ac.nz> <22259@boulder.Colorado.EDU>
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Reply-To: touch@dsl.cis.upenn.edu (Joe Touch)
Organization: University of Pennsylvania
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In article <22259@boulder.Colorado.EDU> wolniewi@tramp.Colorado.EDU (WOLNIEWICZ RICHARD H.) writes:
>
>I would probably write
>
>    stringsSame := TRUE;
>    WHILE stringsSame AND (index <= stringLength) DO
>        stringsSame := (String1[index] = String2[index]);
>        INC(index);
>    END; (* WHILE *)
>

I'd prefer

	WHILE (index <= stringLength) AND (String1[index] = String2[index] DO
		INC(index);
	END; (* WHILE *)

Unless my book is wrong, M2 is defined as having short-circuit evaluation
of conjunctions and disjunctions.  So if the index is out of bounds,
the string element comparison never occurs, and the AND is safe.

This omits the use of a redundant boolean (logical) variable, 
and not only is ir correct, but it will run faster (you don't
really need to store the value of the comparison, do you?)

I'd like to add that loops aren't awkward, but some PROGRAMMERS 
implementation of them IS. ;-)

Joe Touch

PS - A good text for a M2 course is "Modula-2" by Beidler and Jackowitz,
PWS Publishers, 1986 (approx).  It was developed by my advisor
at the University of Scranton when I was there, where M2 has been
used as a primary teaching language since 1984.