Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!pyramid!fmsrl7!metavax!chris
From: chris@metavax.UUCP ( PSA)
Newsgroups: comp.lang.fortran
Subject: Re: Forced variable declaration
Message-ID: <2846@metavax.UUCP>
Date: 29 Jan 88 20:49:17 GMT
References: <445@drilex.UUCP> <50500018@uxe.cso.uiuc.edu>
Reply-To: chris@metavax.UUCP (Chris Collins)
Organization: Meta Systems, Ltd. -- Ann Arbor, MI
Lines: 51

In article <50500018@uxe.cso.uiuc.edu> mcdonald@uxe.cso.uiuc.edu writes:
>
>>I agree.  That's why it's a good idea for FORTRAN programmers  to include 
>>the line IMPLICIT LOGICAL (A-Z) or IMPLICIT CHARACTER (A-Z) in each main  
>>program and subprogram.  Even better, many compilers now make an 
>>IMPLICIT NONE available.  
>
>You must be kidding! Please, please, don't forget the smiley faces when
>saying things like that! 
>
>Doug McDonald
>Professor of Chemistry
>University of Illinois
>

I am so, so, SO glad that smiley faces were NOT added on such a correct
and _necessary_ statement.  For the past 5 years or so, I have had the
inglorious task of maintaining around 200,000 lines of Fortran which was
written without the required declaration of variables.  The failure
of a variable to be declared was responsible for at least 30% of the 
errors which I corrected.  It was only recently that I was able to make
use of IMPLICIT to avoid these problems en masse in our recent new version 
of our software.

Secondly, it is my experience that once software is completed, if in  
testing it appears to be working, cross reference listings generated 
by the compiler are ignored.  Thus an apparently correct output would
indeed be accepted by end users as correct.  This type of error is
particularly painful if some users come to depend upon the incorrectness
and then it is removed (This happened to us, and those who depended 
on the error lost money because of it).

It is my firm belief that the only reason that Fortran does not require
variable declaration is that the original developers were developing
one of the first compiled languages, and thus _didn't know any better_.
There was no experience in the use of higher level programming languages
to be had.
 
Thirdly, the example Professor McDonald sites from his application does
not show that variables shouldn't be declared, only that they should be
declared correctly for the application involved. 


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