#46566 [Opn->Bgs]: wrong calculating
| From: | pajoye@php.net | Date: | Thu, 13 Nov 2008 13:39:36 +0000 |
| Subject: | #46566 [Opn->Bgs]: wrong calculating | ||
| References: | 1 | Groups: | php.bugs |
| Request: | Send a blank email to php-bugs+get-130942@lists.php.net to get a copy of this message | ||
ID: 46566
Updated by: pajoye@php.net
Reported By: krumb at valentins dot de
-Status: Open
+Status: Bogus
Bug Type: Math related
Operating System: Suse Linux
PHP Version: 5.2.6
New Comment:
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.
.
Previous Comments:
------------------------------------------------------------------------
[2008-11-13 13:36:34] krumb at valentins dot de
Description:
------------
Some strange calculating mistake
It seems to happen in the second line at 7/100*100, echos zero, had to
be zero but internal it seems thats not zero
Reproduce code:
---------------
<?
$share=100;
$discount=7/100*$share;
$brutto=5.8824/100*(100+19);
$brutto=round($brutto,2);
echo $brutto."-".$discount."=";
$new=$brutto-$discount;
echo $new;
?>
Expected result:
----------------
7-7=0
Actual result:
--------------
7-7=-8.881784197E-16
------------------------------------------------------------------------
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Edit this bug report at http://bugs.php.net/?id=46566&edit=1