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From: burley@world.std.com (James C Burley)
Newsgroups: comp.lang.fortran
Subject: Re: Fortran 77 Style Guide (long, REPOST)
Message-ID: <BURLEY.90Aug4231036@world.std.com>
Date: 5 Aug 90 06:10:36 GMT
References: <26B89BE1.4349@ics.uci.edu> <59012@lanl.gov>
Sender: burley@world.std.com (James C Burley)
Organization: The World
Lines: 31
In-Reply-To: jlg@lanl.gov's message of 3 Aug 90 02:07:18 GMT

I'm not too enamoured with the idea of encoding FORMAT strings as constants
in I/O statements.  Separate FORMAT statements, as ugly as they are, offer
two advantages:

1)  The compiler is forced to check the contents of the format for syntactic
    correctness, at least to parse hollerith and character data.  It is not
    so required for an in-line format, which it need only ensure is a valid
    character constant.  So programmer errors are more likely to be detected
    at compile time with a separate statement.

2)  Some systems are likely to optimize a FORMAT statement by compiling it
    into an intermediate representation at compile time, but postpone doing
    anything about a constant FORMAT specifier in an I/O statement until
    a given execution of that I/O statement.  So formatted I/O is likely to
    take less CPU time with separate FORMAT statements.

Note that a system that translates constant FORMATs in I/O statements also
must effectively check it for legitimacy, so if #2 does not apply to a given
system, #1 probably doesn't also, and vice versa.

Also note that I intend to make GNU Fortran check and compile FORMAT constants
just like FORMAT statements, if I can, because aside from these two
considerations, I think separate FORMAT statements are pretty silly anyway.
Even if you want to use a FORMAT specifier for more than one statement, I'd
prefer people use the more general PARAMETER mechanism to achieve that.

But if your target system(s) suffers from either or both of the above
ailments, then it might be best to stick with separate FORMAT statements
everywhere you can.

James Craig Burley, Software Craftsperson    burley@world.std.com