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From: NOSPAMmbkennelNOSPAM@yahoo.com (Matt Kennel)
Subject: Re: Software landmines (loops)
Date: 1998/10/06
Message-ID: <slrn71j84h.jq0.NOSPAMmbkennelNOSPAM@lyapunov.ucsd.edu>#1/1
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Date: 1998-10-06T04:46:10+00:00
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On Sat, 3 Oct 1998 11:02:08 -0400, John I. Moore, Jr. wrote:
:2.  Mills construct of do-while-do has a single entry and single exit,
:    as do all of the other structured programming constructs.  Using
:    an Ada-like syntax, consider the following:
:
:    loop
:       get x;
:       exit when x satisfies some condition;
:       process x;
:    end loop;
:
:    I contend that this logic is natural, that the loop has only a
:    single entry and exit, and that it doesn't violate any of the
:    structured programming guidelines.  Of course, one can rewrite
:    it by using a standard while-loop, just as one can rewrite any
:    repeat-until loop using a while-loop, but in order to do so you
:    must repeat some part of the logic outside of the loop.

Why is that loop morally superior to one like

    loop
       get x;
       exit when x satisfies some condition;
       partially process x;
       exit if the preliminary processing shows something wrong
       continue to process x;
    end loop;

Which does not have a single exit? 

-- 
*        Matthew B. Kennel/Institute for Nonlinear Science, UCSD           
*
*      "To chill, or to pop a cap in my dome, whoomp! there it is."
*                 Hamlet, Fresh Prince of Denmark.