Path: utzoo!attcan!uunet!mcsun!unido!uniol!moeller
From: moeller@uniol.UUCP (Klaus Moeller)
Newsgroups: comp.lang.modula2
Subject: Re: Why are the loops so awkward?
Message-ID: <2813@uniol.UUCP>
Date: 14 Jun 90 16:22:58 GMT
References: <5377.26731960@puddle.fidonet.org> <728.26767558@waikato.ac.nz> <22213@boulder.Colorado.EDU> <747.2677cd57@waikato.ac.nz>
Organization: University of Oldenburg, W-Germany
Lines: 39

ccc_ldo@waikato.ac.nz (Lawrence D'Oliveiro, Waikato University) writes:

>This is an unwarranted generalisation. Consider the following example
>(it should be pretty much self-explanatory):

>	LOOP
>	    IF NrCharsLeft = 0 THEN
>		StringsSame := TRUE;
>		EXIT
>	    END (*IF*);
>	    INC(SourceIndex);
>	    DEC(NrCharsLeft);
>	    IF String1[SourceIndex] <> String2[SourceIndex] THEN
>		StringsSame := FALSE;
>		EXIT
>	    END (*IF*)
>	END (*LOOP*)

>Do you think you could write it just as simply and clearly using something
>other than LOOP? I don't think so. Do you think this is an unusual example?
>I find that, in my programs, the majority of my loops are best written
>using LOOP-with-EXIT rather than WHILE, REPEAT or FOR.

Of course no. But this was meant for loops with only one exit.
You must use LOOP for loops that have more than one exit point
simply because you can't do that with FOR, WHILE or REPEAT. But when
you have only one exit point, WHILE, FOR and REPEAT are much clearer.
In C you can have while and for loops with additional exits in them, Modula
prohibits this. I suppose that Wirth wanted to isolate this in pure LOOPs.
The Semantics of while, repeat and for become much easier this way.

					Klaus
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