Xref: utzoo comp.lang.pascal:2877 alt.folklore.computers:998
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From: linden@adapt.Sun.COM (Peter van der Linden)
Newsgroups: comp.lang.pascal,alt.folklore.computers
Subject: Re: Problem in Turbo Pascal 4.0
Keywords: Nonterminating Repeat loop, real, representation
Message-ID: <129838@sun.Eng.Sun.COM>
Date: 3 Jan 90 19:01:18 GMT
References: <4658@ur-cc.UUCP> <4660@ur-cc.UUCP> <803@tuewsd.lso.win.tue.nl>
Sender: news@sun.Eng.Sun.COM
Reply-To: linden@sun.UUCP (Peter van der Linden)
Organization: Sun Microsystems, Mountain View
Lines: 16

Kees Huizing - Eindhoven Univ of Techn - The Netherlands,  wants to know:
> the equality operator "=" does not (do) on reals what it pretends to do.  
> I accept that it cannot detect perfect equality of reals, but what it could do 
> is detect equality up to some representation dependent accuracy.   
> Why is it not done this way? 

A very reasonable question Kees!  A number of years ago, a gentleman by the
name of Dijkstra, located not a million miles from where you are, had the very
same thought, and implemented it into an early Algol compiler.

The experiment was soon deemed a failure when it was found that this had the
inadvertent and unwanted side effect that comparison was no longer transitive.
I.e. if A equalled B, and B equalled C, a program could not conclude that A = C !
----------------
Disclaimer: I'm no Jack Kennedy, but I'm no Dan Quayle either.
Peter van der Linden     linden@SuN.cOm    (415) 336-6206