Article View: comp.std.c
Article #1966Re: floating point constant folding
From: Henry Spencer
Date: Tue, 13 Nov 1990 17:40
Date: Tue, 13 Nov 1990 17:40
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1326 bytes
In article <8191@star.cs.vu.nl> eck@cs.vu.nl (Hans van Eck) writes: >Is it allowed to evaluate constant floating point expressions with greater >range and precision than that of the execution environment in contexts >where a constant is not required? > >There are unexpected implications of both allowing and disallowing such >folding, but I cannot find a statement in the standard that unambiguously >says what a translator may or may not do. I believe the relevant statement is the "as if" rule discussed in 2.1.2.3: the compiler can do anything it pleases, provided the observable results are the same. Observable results include overflow exceptions and the values of data items written out to files. Evaluating constant floating-point expressions at compile time using different floating-point hardware strikes me as a minefield of difficulties. -- "I don't *want* to be normal!" | Henry Spencer at U of Toronto Zoology "Not to worry." | henry@zoo.toronto.edu utzoo!henry
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Newsgroups: comp.std.c Path: arc1-ca.pugleaf.net!utzoo!henry From: henry@zoo.toronto.edu (Henry Spencer) Subject: Re: floating point constant folding Message-ID: <1990Nov13.174025.1520@zoo.toronto.edu> Organization: U of Toronto Zoology References: <8191@star.cs.vu.nl> Date: Tue, 13 Nov 90 17:40:25 GMT