Re: IEEE 754 vs Fortran arithmetic

henry@zoo.toronto.edu (Henry Spencer)
Wed, 24 Oct 90 16:25:29 GMT

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[4 later articles]
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Newsgroups: comp.compilers,comp.lang.fortran
From: henry@zoo.toronto.edu (Henry Spencer)
Keywords: Fortran
Organization: U of Toronto Zoology
References: <9010230628.AA22160@admin.ogi.edu>
Date: Wed, 24 Oct 90 16:25:29 GMT

> [our moderator writes]
>... I know of no reason that an IEEE implementation of F77 would be
>nonconforming. ...


I can think of at least one: F77 flatly denies the existence of -0,
while IEEE demands it. (One of Dr. Kahan's favorite examples in his
talks is an algorithm which, when implemented straightforwardly, does
the right thing if -0 is implemented properly and screws up bizarrely
if not, so yes, it does matter.)
--
Henry Spencer at U of Toronto Zoology, henry@zoo.toronto.edu utzoo!henry
[Given that +0 = -0, it's not clear to me that the existence of -0 breaks
anything. Keep in mind that F77 is a permissive standard, extensions are
permitted so long as conforming programs do the right thing. -John]
--

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