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Bug #33009 floor does not work with some integers as argument
Submitted: 2005-05-11 20:12 UTC Modified: 2005-05-11 21:03 UTC
From: edelmar at ditech dot com dot br Assigned:
Status: Not a bug Package: *Math Functions
PHP Version: 4.3.11 OS: Win XP
Private report: No CVE-ID: None
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From: edelmar at ditech dot com dot br
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 [2005-05-11 20:12 UTC] edelmar at ditech dot com dot br 
Description:
------------
Using PHP Version 4.3.11 on Windows xp (my development machine).

I believe this behavior of floor function is a bug. The number 7560 passed to it is an integer and would not be changed by floor.

I am using 100 times number because PHP has no function like 'truncate'. I want 2 decimals and there is no way to do it with regular functions.

Its like 7560 has some special properties because this error does not happens with a lot of other numbers.

Thank you.

Reproduce code:
---------------
echo (75.6 * 100).'<br>'; // prints 7560 - OK
echo intval(75.6 * 100).'<br>'; // prints 7559 - ?
echo (int)(75.6 * 100).'<br>'; // prints 7559 - ?
echo floor(75.6 * 100).'<br>'; // prints 7559 - ?
echo ceil(75.6 * 100).'<br>'; // prints 7560 - OK
echo round(75.6 * 100).'<br>'; // prints 7560 - OK



Expected result:
----------------
7560
7560
7560
7560
7560
7560

Actual result:
--------------
7560
7559
7559
7559
7560
7560

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 [2005-05-11 20:41 UTC] edelmar at ditech dot com dot br 
$d = 75.6 * 100;
$d = (string)$d;
echo floor($d).'<br>'; // prints 7560, wich is expected... how embarassing.
 [2005-05-11 21:03 UTC] tony2001@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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