Path: utzoo!censor!geac!yunexus!oz
From: oz@yunexus.yorku.ca (Ozan Yigit)
Newsgroups: comp.lang.c
Subject: Re: Inherent imprecision of floating point variables
Message-ID: <12538@yunexus.YorkU.CA>
Date: 11 Jul 90 16:26:53 GMT
References: <14429@lambda.UUCP> <7906@ncar.ucar.edu> <11035@alice.UUCP>
Sender: news@yunexus.YorkU.CA
Organization: York U. Communications Research & Development
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In article <11035@alice.UUCP> ark@alice.UUCP (Andrew Koenig) writes:

>Interestingly, this does not require that conversion be as accurate
>as possible, and one can reasonably argue that conversions should
>generally *not* be as accurate as possible, because it's quite expensive
>to get it exactly right compared with what it costs to get it
>*almost* right.  In particular, I do not know how to write an
>exact input conversion routine without doing unbounded precision
>arithmetic.

Two excellent papers on this topic that may be of interest can be found in
"Proceedings of the ACM '90 Conference on Programming Language Design and
Implementation" [SIGPLAN NOTICES, v25, #6, June 1990].

Will Clinger: "How to Read Floating Point Numbers Accurately" 

Guy Steel (Jr) and John White: "How to Print Floating Point Numbers
Accurately" 

I suspect the essence of their work will be reflected in various Common Lisp
and Scheme implementations, and their respective standards.

oz
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Sometimes when you fill a vacuum, it still sucks. | oz@nexus.yorku.ca
				  Dennis Ritchie  | or (416) 736 5257