Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!quintus!ok
From: ok@quintus.uucp (Richard A. O'Keefe)
Newsgroups: comp.lang.fortran
Subject: Re: Fortran vs C for computations
Message-ID: <367@quintus.UUCP>
Date: 8 Sep 88 09:57:04 GMT
References: <962@amelia.nas.nasa.gov> <3290@lanl.gov>
Sender: news@quintus.UUCP
Reply-To: ok@quintus.UUCP (Richard A. O'Keefe)
Organization: Quintus Computer Systems, Inc.
Lines: 19

In article <3290@lanl.gov> jlg@lanl.gov (Jim Giles) writes:
>#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.

Spot the hidden assumption?  Right: #ifdef is used more often to select
which header files to #include, which of several sets of declarations
to use, and so on.

For example, how would optimisation of IF statements help someone
who wants the functional equivalent of
	#if	REAL_IS_ENOUGH
		REAL FRED, THOM		
	#else
		DOUBLE PRECISION FRED, THOM
	#endif
(Yes, I know about Fortran 8x parametrised types.  That's not the question.)