ID: 27744
Updated by: helly@php.net
Reported By: t dot steve at ariadne-quatra dot com
Status: Bogus
Bug Type: Math related
Operating System: *
PHP Version: *
New Comment:
Since you don't believe us:
http://docs.sun.com/source/806-3568/ncg_goldberg.html
Previous Comments:
------------------------------------------------------------------------
[2004-03-30 21:40:21] gschlossnagle@php.net
Floating point values in computers are never exact.
It's a fact of life, and an issue that is not only
encountered with PHP but other languages as well.
------------------------------------------------------------------------
[2004-03-30 21:35:54] t dot steve at ariadne-quatra dot com
Hi!
I am sure I am something, apologies for that. :(
"Guys, how in the world is PHP supposed to magically guess what
precision you want results displayed in."
141.23 - 141 _is_ precisely 0.23. If I was asking for 1/3, then I would
understand the decimal places. But how come 141.23-141 turns out to
have so many decimal places in the end instead of just being 0.23 - the
mathematically correct and precise result?
------------------------------------------------------------------------
[2004-03-30 19:59:05] rasmus@php.net
Guys, how in the world is PHP supposed to magically guess what
precision you want results displayed in. If you know you always want
lower precision, set that in your php.ini file. Or if you just want it
temporarily simply do:
$old = ini_set('precision',2);
echo (string)(750 - 749.99);
ini_set('precision',$old);
------------------------------------------------------------------------
[2004-03-30 19:47:47] alan_k@php.net
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)
------------------------------------------------------------------------
[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.
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