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Bug #55409 Casting floats containing an integer to ints gives wrong result
Submitted: 2011-08-12 07:48 UTC Modified: 2011-08-13 10:40 UTC
From: php-bugs at nickshanks dot com Assigned:
Status: Not a bug Package: Math related
PHP Version: Irrelevant OS: Irrelevant
Private report: No CVE-ID: None
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 [2011-08-12 07:48 UTC] php-bugs at nickshanks dot com 
Description:
------------
Casting of certain floating-point values, containing just of an integer component 
and a zero fractional component, to an integer results in wrong value.

Test script:
---------------
echo '32.55' * 100;
echo "\n";
echo (int)('32.55' * 100);

Expected result:
----------------
3255
3255

Actual result:
--------------
3255
3254

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 [2011-08-13 10:38 UTC] laruence@php.net 
Float values have a limited precision. Hence a value might 
not have the same string representation after any processing. That also
includes writing a float number in your script and directly printing it without 
any mathematical operations.
 
Thank you for your interest in PHP.
 [2011-08-13 10:40 UTC] laruence@php.net
-Status: Open +Status: Bogus
 [2011-08-13 10:40 UTC] laruence@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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