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Bug #43447 comparison in a for-loop is not exact
Submitted: 2007-11-29 12:08 UTC Modified: 2007-11-29 12:12 UTC
From: jumo at gmx dot de Assigned:
Status: Not a bug Package: *General Issues
PHP Version: 5.2.5 OS: Ubuntu Linux
Private report: No CVE-ID: None
View Developer Edit
 [2007-11-29 12:08 UTC] jumo at gmx dot de 
Description:
------------
the comparison in a special for-loop is not correct.

Reproduce code:
---------------
<?php
for($i = 400.84; $i < 400.88; $i = $i + 0.01) {
	echo $i;
	echo "<br>";
}  
?> 

Expected result:
----------------
400.84<br>
400.85<br>
400.86<br>
400.87<br>

Actual result:
--------------
400.84<br>
400.85<br>
400.86<br>
400.87<br>
400.88<br>

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 [2007-11-29 12:12 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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