Path: utzoo!attcan!uunet!husc6!cmcl2!rutgers!gatech!emory!platt
From: platt@emory.uucp (Dan Platt)
Newsgroups: comp.lang.fortran
Subject: Re: Fortran vs C for computations
Message-ID: <3169@emory.uucp>
Date: 8 Sep 88 04:52:01 GMT
References: <962@amelia.nas.nasa.gov> <3290@lanl.gov>
Reply-To: platt@emory.UUCP (Dan Platt)
Organization: Emory University
Lines: 30

>#ifdef is an admission that your compiler isn't any good.  If the
>conditional expression is a constant, a normal if statement should 
>be optimized so that code is only generated for the active branch.  If
>the conditional expression is not a constant, it couldn't be used as
>part of an #ifdef either. 


I object to this argument.  There are some functions provided in certain
environments that are not provided in other environments (specifically,
functions that deal with dates, times, extended function sets such as error
functions or Bessel functions) or which exist but have different forms on
each system.  The biggest problem concerns 'open' statements which seem
to be very system specific; I don't believe that an IF with a constant
expression would let that by, even if the final code generation included the
non-compatible code.  A pre-processed #ifdef would clean up that problem.
It would also provide a clean, convenient way to document the portability 
constraints of the program.  For example, in the PC world, some routines
may be more efficiently compiled if there is no Color card than if there is
(problems with raster syncs).  The easiest way to code this is to include
a function definition in C without the color card, and to use an assembler
routine version if the color card is there.  The inclusion in the module
would depend on the presence of the card.  (An even more sophisticated version
would check the flag at each entry, or load the correct overlay for the
routine at run-time).  One of the biggest problems I've been confronted with
lately is the portability problems of Fortran.  I find C much more portable,
and the new ANSI standards seem to be encouraging portability even more.
I haven't had the opportunity to use 8X (will soon though), so I cannot comment
on the features provided there.

Dan