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From: "Gene Gajewski" <ggajewsk@earthlink.net>
Subject: Re: Software landmines (loops)
Date: 1998/08/31
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X-ELN-Date: Mon Aug 31 20:21:37 1998
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Date: 1998-08-31T00:00:00+00:00
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Matthew Heaney wrote in message ...
>"Robert Martin" <rmartin@oma.com> writes:
>


<schnip>

>The problem with exit at the top is that it defers the actual
>termination.  I have to make sure no code gets executed unintentionally
>between the place at which the exit flag is set, and the bottom of the
>loop.
>
>I can almost live that.  The real problem, however, is that using an
>extra flag to terminate VASTLY complicates the predicate.  In fact, the
>flag doubles the number of states I have to think about when mentally
>evaluating the predicate!  That's the real source of the loop
>termination errors.
>
>(I shouldn't have to remind anyone, but just in case: George Miller did
>a famous study about human cognitive limits, and found that people can
>remember about 7 things, plus or minus 2.  That's why complex predicates
>make a programmer's head spin, and why he often gets loop termination
>wrong.)


I've been following this thread for some time....

I wasn't aware that anyone did any specific research on cognitive limits,
but I posit this is something intuitive. I've made a post to this sometime
before. I believe we encounter such things as a rule that states 'there
shall be but one exit point' because there are those who analyze code
mechanistically, without bothering to aquire an understanding of what the
code is doing. I sat recently sat through a 'code review', which was really
a boss's one-on-one style check, and got hammered severely about some
constructs I used in a particular function. A real knock-down/drag-out bitch
fest. The words 'Well, I understand it NOW that I've read it" were actually
uttered during that session, and not by me....