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Bug #55004 Incorrect Modulus calculation
Submitted: 2011-06-06 20:38 UTC Modified: 2011-06-06 22:01 UTC
From: dejagerc at gmail dot com Assigned:
Status: Not a bug Package: Math related
PHP Version: Irrelevant OS: debian
Private report: No CVE-ID: None
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From: dejagerc at gmail dot com
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 [2011-06-06 20:38 UTC] dejagerc at gmail dot com 
Description:
------------
 Modulus calculation not returning correct value as in the example. If I replace 1.001 with 1.002 it works correctly.

Test script:
---------------
<?php
$in = 1.001;
$in2 =  $in * 1000 ;
$decimal = $in2 % 10;
echo $decimal;  // Output 0 ( Wrong )

$in = 1001;
$decimal = $in % 10;
echo $decimal;  // Output 1 ( Correct )
?>

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 [2011-06-06 22:01 UTC] rasmus@php.net
-Status: Open +Status: Bogus
 [2011-06-06 22:01 UTC] rasmus@php.net 
Floating point values have a limited precision. Hence a value might 
not have the same string representation after any processing. That also
includes writing a floating point value in your script and directly 
printing it without any mathematical operations.

If you would like to know more about "floats" and what IEEE
754 is, read this:
http://www.floating-point-gui.de/

Thank you for your interest in PHP.

.
 
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