Path: utzoo!attcan!uunet!husc6!cmcl2!lanl!jlg
From: jlg@lanl.gov (Jim Giles)
Newsgroups: comp.lang.fortran
Subject: Re: Fortran vs C for computations
Message-ID: <3290@lanl.gov>
Date: 7 Sep 88 20:04:39 GMT
References: <962@amelia.nas.nasa.gov>
Organization: Los Alamos National Laboratory
Lines: 37

From article <962@amelia.nas.nasa.gov>, by fouts@lemming.nas.nasa.gov.nas.nasa.gov (Marty Fouts):
> 
> I couldn't pass up making a comment here.  It has been my experience
> that using a preprocessor for Fortran macro expansion is a certain way
> of ensuring nonportable code, since there is no standard preprocessor
> [...]

Write the preprocessor in Fortran.  It is now as portable as the Fortran
environment is.  Besides, my macro expander _never_ produces non-standard
code - it only accepts it.  Output from my macro expander will compile on
any standard conforming Fortran environment.  Finally, my main point was
that C macros don't add functionality - only textual convenience.  My 
Fortran macros do the same.  C does not excel Fortran in this respect.

> I am also a large fan of using #define and #ifdef in C for conditional
> compilation.  When not overused, this is a major win for smoothing
> over portability problems and I've missed it many times in trying to
> make portable programs in Fortran.

#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.  #define is either a _parameter_, an inline
function, or an inline procedure - the first is already in Fortran,
the others are in the proposed 8x extensions.  Besides, as I've already
pointed out, the functionality of #define can already be provided in a
Fortran environment - portably (in fact, the RATFOR preprocessor has its
source given in the original software tools document and includes a
macro facility nearly identical to C macros - including ifdefs).

J. Giles
Los Alamos

Note: RATFOR isn't the best macro facility for Fortran. But it is an
example of a completely portable public domain preprocessor for which
the source is readily available to any interested programmer.