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Bug #52415 Round Off Error
Submitted: 2010-07-23 12:36 UTC Modified: 2010-07-23 12:41 UTC
From: benjamin at aceinformatique dot com Assigned:
Status: Not a bug Package: *General Issues
PHP Version: 5.2.14 OS: Windows
Private report: No CVE-ID: None
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From: benjamin at aceinformatique dot com
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 [2010-07-23 12:36 UTC] benjamin at aceinformatique dot com 
Description:
------------
There are a round off problems with add/sub of floating values
for instance 0.27+0.34 is not equal to 0.61

0.27+0.34-0.61 != 0

Test script:
---------------
<?php


echo((0.27+0.34)-0.61);


?>

Expected result:
----------------
0

Actual result:
--------------
1.1102230246252E-16

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 [2010-07-23 12:41 UTC] aharvey@php.net
-Status: Open +Status: Bogus
 [2010-07-23 12:41 UTC] aharvey@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://docs.sun.com/source/806-3568/ncg_goldberg.html
 
Thank you for your interest in PHP.
 
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