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To: Marco Craveiro <soupdragon AT clix DOT pt>
Cc: cygwin AT cygwin DOT com
Subject: Re: atof returns a value that is slightly greater than the original string
References: <1000153353 DOT 1101 DOT 8 DOT camel AT darkroom>
From: Andrew Markebo <flognat AT flognat DOT myip DOT org>
Date: 10 Sep 2001 22:52:47 +0200
In-Reply-To: <1000153353.1101.8.camel@darkroom>
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/ Marco Craveiro <soupdragon AT clix DOT pt> wrote:
| Hello Cygwinners,
| 
| I'm having some strange problems with atof. basically, it returns a
| converted value that is 0.000024 bigger than the one on the string.
| 
| Google searching suggested that the problem was to do with #include
| <stdlib.h>, but I already have that #include in my program and I still
| get strange results. A program like this:
| 

Same problem here if I do:

#include <cstdlib>
#include <iostream>

int main (void)
{
float f=695.40;

cout << f;
}

my gdb says f is 695.400024

If my mind doesn't fail me completely this is a 'misfeature' in float,
the way that the data is stored in can't be exact.. or something..

The recommendations I have seen was to use some alternative
bignum/smallnum package :-) Or if you know how many decimals you can
get, multiply the value by that amount.. and convert to int.

The reason to why you don't see it on cout is that cout prints floats
with 1 or two decimals per default, if you tell it to print.. MANY
decimals.. 

        /Andy

-- 
 The eye of the beholder rests on the beauty!

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