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From: mac@harris.cis.ksu.edu (Myron A. Calhoun)
Newsgroups: comp.lang.fortran
Subject: Re: Fortran 77 Style Guide (long, REPOST)
Summary: Do NOT reuse FORMATs!
Message-ID: <1990Sep10.141639.970@maverick.ksu.ksu.edu>
Date: 10 Sep 90 14:16:39 GMT
Expires: 24 September 1990
References: <26B89BE1.4349@ics.uci.edu> <59012@lanl.gov> <1794@ccadfa.adfa.oz.au>
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Organization: Kansas State University, Dept. of Computing and Information Sciences
Lines: 38

In article <1794@ccadfa.adfa.oz.au> you write:

>>>  3) Assign a separate sequence of labels to FORMAT labels that are grouped
>>>     at the end of a subprogram.

>>Same comment about "assign" plus the following: whenever possible, put
>>the format into the I/O statement which uses it.  Use labeled formats
>>only when several I/O statements share the same (long) format.

>I may not have been the only person to contribute this recommendation to David,
>but I did contribute it so I'll defend it.  If you can guarantee that every
>FORMAT statement will appear immediately under (or in) the PRINT statement
>that uses it, fine.  As soon as you start using the same FORMAT statement in
>different places, you either have to hunt through the code or locate the
>FORMAT statement separately, probably at the end.  I feel that it is more 
>consistent to have a simple rule which puts them all in one place.

Unfortunately, re-used FORMATs cause programs to "break" during maintenance.  
The scenario is that someone modifies a FORMAT and ONE of its associated
I/O statements but doesn't notice there are others.

Voila!  Instant "broken" program.

It is EXTREMELY EASY to "guarantee that every FORMAT statement will
appear immediately under (or in) the [I/O] statement that uses it".
Just duplicate it.  Shouldn't take more than a few keystrokes per
FORMAT statement on any reasonable editor; maybe a bit more work if
one is still using cards!

My credentials?  I routinely am called upon to modify programs written
more than 20 years ago.  I've learned a lot in 20 years, and one thing
I've learned is to NOT reuse FORMAT statements.
--Myron.
--
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