Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!uhccux!munnari.oz.au!cs.mu.oz.au!ok
From: ok@cs.mu.oz.au (Richard O'Keefe)
Newsgroups: comp.lang.c
Subject: Re: Bug?
Message-ID: <2412@munnari.oz.au>
Date: 13 Oct 89 06:04:23 GMT
References: <19831@mimsy.UUCP> <15852@dartvax.Dartmouth.EDU> <364@capmkt.COM> <10895@riks.csl.sony.co.jp>
Sender: news@cs.mu.oz.au
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In article <10895@riks.csl.sony.co.jp>, diamond@csl.sony.co.jp (Norman Diamond) writes:
> Sorry Mr. Koenig, it's easy to imagine.  Every hardware floating-point
> system and most software ones have situations where (a-b)==0 but a != b.

My understanding is that IEEE denormalised numbers were introduced
precisely so that subtracting one finite number from another would
yield zero ONLY when the two numbers were equal.

Of course most other floating-point systems haven't got denormalised
numbers, and some systems which use IEEE formats don't obey IEEE rules.