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Bug #46780 Minus zero returned by simple multiplication of floating numbers
Submitted: 2008-12-06 12:08 UTC Modified: 2008-12-06 13:14 UTC
From: preechaw at gmail dot com Assigned:
Status: Not a bug Package: Math related
PHP Version: 5.2.7 OS: Windows XP
Private report: No CVE-ID: None
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From: preechaw at gmail dot com
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 [2008-12-06 12:08 UTC] preechaw at gmail dot com 
Description:
------------
-0.1 * 0; // returns -0

I believe it should return 0 without the minus sign.

--
I will also submit another bug for the "BC math related" type.
echo bcadd("-0.0", "-0.0", 1); // returns -0.0
echo bccomp("-0.0", "0", 1); // returns -1
--


Reproduce code:
---------------
<?php
echo -0.1 * 0; // returns -0
?>


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

Actual result:
--------------
-0

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 [2008-12-06 13:14 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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