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From: cslaurie@cybaswan.UUCP (Laurie Moseley )
Newsgroups: comp.lang.pascal
Subject: Re: Overflow error
Message-ID: <2547@cybaswan.UUCP>
Date: 15 Jun 91 20:22:13 GMT
Article-I.D.: cybaswan.2547
References: <2bdd60c9e7152849799c@rose.uucp>
Reply-To: cslaurie@cybaswan.UUCP (Laurie Moseley (Comp Sci))
Lines: 44


Surely any file-reading should be done in a WHILE NOT EOF loop,
rather than a REPEAT UNTIL EOF one. The whole point of the WHILE is
that it may be entered zero times, and therefore you are automatically
guarding against the danger of trying to read from an empty file. In
general the use of WHILE for the traversal of many structures (queues
stacks etc) is good practice anyway, as it removes at a stroke the
need for a lot of special case checking, such as testing for nil pointers.

I reserve the use of REPEAT UNTIL for cases where I know that the loop
will be entered at least once - keyboard input data checking for
example, or a sort routine. It was invented only for convenience 
after all, and can be emulated by a WHILE.

What's all this stuff about GETSTRING; - a parameter-less procedure.
OK, there may be occasions when you need one, but they are rare in
these days when one actually re-uses code. I don't believe that it
is purist to shudder at such constructions, it's simply commonsense.
You may get away with parameter-less procedures occasionally, but
all too frequently one of two things will happen. You'll either get
identifier confusion and manipulate a global unintentionally (and
have some interesting evenings trying to find that !) or you will
find that you have written the same procedure 7 times before you
realise that it IS the same one.

I guess that the point is that if you get into good habits early,
you have fewer disasters later. To put on the humility hat for a
moment - am I missing something important here ?

Laurie

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Laurie Moseley

Computer Science, University College, Swansea SA2 8PP, UK

Tel: +44 792 295399

JANET:	cslaurie@uk.ac.swan.pyr

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"Why does the Turing test set such abysmally low standards ?"
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