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From: torek@elf.ee.lbl.gov (Chris Torek)
Newsgroups: comp.lang.c
Subject: Re: Expressions in initializers
Message-ID: <10592@dog.ee.lbl.gov>
Date: 5 Mar 91 01:03:16 GMT
References: <17270@crdgw1.crd.ge.com> <760@ajpo.sei.cmu.edu> <1991Mar4.144939.8311@ux1.cso.uiuc.edu> <17294@crdgw1.crd.ge.com>
Reply-To: torek@elf.ee.lbl.gov (Chris Torek)
Organization: Lawrence Berkeley Laboratory, Berkeley
Lines: 25
X-Local-Date: Mon, 4 Mar 91 17:03:17 PST

In article <17294@crdgw1.crd.ge.com> volpe@camelback.crd.ge.com
(Christopher R Volpe) writes:
>"The square root of two" can be evaluated at compile time, but "sqrt(2.0)"
>is an invocation of a function. How is the compiler supposed to know
>what sqrt is? I could have in another file:
>
>double sqrt(double x)
>{
>  return x - 1.0;
>}

Not in ANSI C (at least, not if you `#include <math.h>'; I am not sure
about the case where you do not include the standard header).  Compilers
can of course define their own languages and allow

	static double root2 = sqrt(2.0);

but someone writing ANSI C should assume neither this nor that writing

	double sqrt(double x) { return x - 1.0; }

will work.
-- 
In-Real-Life: Chris Torek, Lawrence Berkeley Lab EE div (+1 415 486 5427)
Berkeley, CA		Domain:	torek@ee.lbl.gov