#37202 [Opn->Bgs]: Iterations with bad precision
| From: | tony2001@php.net | Date: | Tue, 25 Apr 2006 20:43:51 +0000 |
| Subject: | #37202 [Opn->Bgs]: Iterations with bad precision | ||
| References: | 1 | Groups: | php.bugs |
| Request: | Send a blank email to php-bugs+get-96229@lists.php.net to get a copy of this message | ||
ID: 37202
Updated by: tony2001@php.net
Reported By: ruben_ruben at yahoo dot com
-Status: Open
+Status: Bogus
Bug Type: Variables related
Operating System: win xp pro sp2
PHP Version: 5.1.2
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:
------------------------------------------------------------------------
[2006-04-25 20:42:21] ruben_ruben at yahoo dot com
Description:
------------
In loops like While and For with increases with point decimal fails the
precision.
Reproduce code:
---------------
$i=71;
$i2 = 82;
$increases = .1;
for($i; $i <= $i2; $i = $i + $increases)
{
echo "$i<br>";
}
//**** or ******
$i=1.5;
$i2 = 2;
$increases = .001;
while($i <= $i2)
{
echo "$i<br>";
$i = $i + $increases;
}
Expected result:
----------------
with
$i=71;
$i2 = 82;
$increases = .1;
it must be:
71
71.1
.
.
.
81.9
82
***************
with
$i=1.5;
$i2 = 2;
$increases = .001;
it must be:
1.5
1.501
1.502
.
.
.
1.999
2
Actual result:
--------------
both with
$i=71;
$i2 = 82;
generates:
71
71.1
.
.
79.8
79.899999999999
79.999999999999
.
.
81.899999999999
81.999999999999
***************
both with
$i=1.5;
$i2 = 2;
$increases = .001;
generates:
1.5
1.501
1.502
.
.
1.954
1.9549999999999
1.9559999999999
.
.
1.9989999999999
1.9999999999999
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/?id=37202&edit=1