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Mail Archives: djgpp/2002/04/10/05:31:36

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From: Hans-Bernhard Broeker <broeker AT physik DOT rwth-aachen DOT de>
Newsgroups: comp.os.msdos.djgpp,comp.lang.c++
Subject: Re: Weird double problem?!
Date: 10 Apr 2002 09:20:59 GMT
Organization: Aachen University of Technology (RWTH)
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In comp.os.msdos.djgpp Taras <tagas96 AT hotmail DOT com> wrote:

> is assigned the value of 0.1, in the watch window it says the value is
> 0.10000000000000001.  

Memorize this for the future:

	In computing 10.0 times 0.1 is hardly ever 1.0

The problem is that binary floating point can't exactly represent
1/10.  It behaves like 1/7 does in decimal arithmetic: you get an
infinite periodic fraction, which will be cut off somewhere, and thus
lead to rounding error.  As a rule of thumb: never believe the last
digit of a floating point number.

Hans-Bernhard Broeker (broeker AT physik DOT rwth-aachen DOT de)
Even if all the snow were burnt, ashes would remain.

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