ID: 27744
Updated by: alan_k@php.net
Reported By: t dot steve at ariadne-quatra dot com
Status: Bogus
Bug Type: Math related
Operating System: *
PHP Version: *
New Comment:
create table a ( b float,c float );
Query OK, 0 rows affected (0.11 sec)
mysql> insert into a (b,c) values (141.23,141);
Query OK, 1 row affected (0.07 sec)
mysql> select b-c from a;
+------------------+
| b-c |
+------------------+
| 0.22999572753906 |
+------------------+
1 row in set (0.00 sec)
Previous Comments:
------------------------------------------------------------------------
[2004-03-30 13:45:03] helly@php.net
That is the whole point of the answer. Floating point values are not
accurate and are not nice. And we do not do a bunch of work just to
make them look better in certain circumstances.
------------------------------------------------------------------------
[2004-03-30 12:07:45] garbo_doe at hotmail dot com
IMHO I think this is a bug. Of course there are problems with
floatingpoint values in binary form, especially when rounded many
times. But in an operation like <?php echo (string)(750 - 749.99) ?> it
shouldn't return "0.00999999999999" but "0.01".
I did a quick test in Delphi: showmessage(floattostr(750 - 749.99));
returns "0.01, not "0.00999999999999".
I had to solve it in PHP but multiplying with 100, then subtract and
then divide the result by 100 again.
It's not pretty :-D
(0.00999[infinite 9's] IS exactly the same as 0.01, but it should
remember the "infinite" with a bit or something, so (1/3)*3 = 1 and not
0.999999999)
(this is similar as bug #8164)
------------------------------------------------------------------------
[2004-03-29 01:06:46] alan_k@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.
Thank you for your interest in PHP.
.
------------------------------------------------------------------------
[2004-03-29 01:05:32] t dot steve at ariadne-quatra dot com
Description:
------------
Subtraction does not work as expected.
Windows 2000 Server
SP4
IIS5
PHP5RC1
Reproduce code:
---------------
$result=141.23-141.00;
echo $result;
(or
$result=141.23-141;
echo $result;
- same result)
Expected result:
----------------
0.23
Actual result:
--------------
0.22999999999999
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/?id=27744&edit=1