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Bug #46879 Float addition not always precise
Submitted: 2008-12-16 11:24 UTC Modified: 2008-12-16 11:25 UTC
From: php at thwien dot de Assigned:
Status: Not a bug Package: Variables related
PHP Version: 5.2CVS-2008-12-16 (snap) OS: Linux-Debian 4.0
Private report: No CVE-ID: None
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 [2008-12-16 11:24 UTC] php at thwien dot de 
Description:
------------
Float comparison after addition isn't precise always.

Reproduce code:
---------------
$floatTotal = 19.99 + 39.99;
  
print ($floatTotal - 59.98);

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

Actual result:
--------------
7.105427357601E-15

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 [2008-12-16 11:25 UTC] derick@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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