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Bug #50622 minus 0 returned
Submitted: 2009-12-31 14:30 UTC Modified: 2009-12-31 14:38 UTC
From: okycastro at gmail dot com Assigned:
Status: Not a bug Package: *Math Functions
PHP Version: 5.2.12 OS: windows vista
Private report: No CVE-ID: None
 [2009-12-31 14:30 UTC] okycastro at gmail dot com
Description:
------------
-0 is returns under the following example. I believe this is a bug. I see there was a bug about this a long time ago, But I think that the concept of a -0 is an invalid one. it just makes no sense. Even more if you consider  that the following line will never gets executed

if ($x < 0) //$x = -0
   //NEVER EXECUTED

if ($x <= 0) //$x = -0
   //GETS EXECUTED

Reproduce code:
---------------
$i= (float) -90;
$a= (int) 0;
echo floor($i * ($a / 100));

returns -0;//MY OPINION IS AN ERROR

$i= (int) -90;
$a= (int) 0;
echo floor($i * ($a / 100));
returns 0;//OK

Expected result:
----------------
0 should be returned always

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

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 [2009-12-31 14:38 UTC] rasmus@php.net
Computers use IEEE754's two's complement method to store floating point 
numbers.  That standard has both +0 and -0, for better or worse.  When 
computers store integers you only have one 0.  So, in your case, since 
you are obviously interested in the integer floor, you should change 
your code to:

$i= (float) -90;
$a= (int) 0;
echo (int)floor($i * ($a / 100));

We are not going to stray from IEEE754 here.  Every language out there 
does exactly the same.
 
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