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Bug #24365 Result problem with soustractions
Submitted: 2003-06-27 13:22 UTC Modified: 2003-06-27 17:35 UTC
From: jump at worldakt dot com Assigned:
Status: Not a bug Package: Scripting Engine problem
PHP Version: 4.3.2 OS: Linux
Private report: No CVE-ID: None
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From: jump at worldakt dot com
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 [2003-06-27 13:22 UTC] jump at worldakt dot com 
Description:
------------
It seems that when I soustract something (float) it returns a wrong result.

Reproduce code:
---------------
<?php
echo 290.34 - (142.00 + 148.34);
?>
-5.68434188608E-14

<?php
echo 142.00 + 148.34;
?>
290.34

<?php
echo 290.34 - 290.34;
?>
0

Expected result:
----------------
<?php
echo 290.34 - (142.00 + 148.34);
?>
0

Actual result:
--------------
<?php
echo 290.34 - (142.00 + 148.34);
?>
-5.68434188608E-14

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 [2003-06-27 14:14 UTC] marcot at tabini dot ca 
This is not really a bug. It's due to normal fluctuations in the way floating-point numbers are handled by the C libraries. Here's another example of this behaviour:

http://bugs.php.net/bug.php?id=22333

You may also want to check out this bit on IEEE representation of floating-point number to understand why some numbers cannot be represented:

http://www.psc.edu/general/software/packages/ieee/ieee.html
 [2003-06-27 17:35 UTC] sniper@php.net 
..
 
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