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From: ark@alice.UucP (Andrew Koenig)
Newsgroups: net.lang.c
Subject: Re: /-INFINITY and NaN
Message-ID: <4749@alice.UUCP>
Date: Fri, 27-Dec-85 11:30:19 EST
Article-I.D.: alice.4749
Posted: Fri Dec 27 11:30:19 1985
Date-Received: Sat, 28-Dec-85 01:48:20 EST
References: <360@l5.uucp>
Organization: Bell Labs, Murray Hill
Lines: 10

> Sun Unix uses IEEE float.  They provide library routines isnan() and isinf().
> Note that there are two infinite values (positive and negative) and many
> NaNs, so a simple compare to a single value is not good enough.

> These library routines seem to be a good idea, since they can be implemented
> for all kinds of float (eg, Vax, IBM) and increase portability.  (A system
> without infinites or NaNs would always return false of course.)

One does have to be a tiny bit careful on architectures where an attempt
to, say, pass a NaN to a subroutine causes a trap.