ID: 16366
Updated by: [EMAIL PROTECTED]
Reported By: [EMAIL PROTECTED]
Status: Closed
Bug Type: Math related
Operating System: WinXP
PHP Version: 4.1.2
New Comment:
Daniel: 32 columns or 1 integer, I'd take the integer anytime.
The problem is, that large integers are converted to floats:
<?php
$number=11;
$bigint=$number * 10000000000000000000000000000000;
$bigint_nocalc=1100000000000000000000000000000000;
echo("Using values: $number - $bigint - $bigint_nocalc\n");
var_dump($number);
var_dump($bigint);
var_dump($bigint_nocalc);
echo ("\nNumber shift 34\n");
echo ($number>>34);
echo ("\nNumber shift 2\n");
echo ($number>>2);
echo("\nBigint shift 29\n");
echo($bigint>>29);
echo("\nBigint shift 30\n");
echo($bigint>>30);
echo("\nBigint shift 31\n");
echo($bigint>>31);
echo("\nBigint shift 32\n");
echo($bigint>>32);
echo("\nBigint shift 33\n");
echo($bigint>>33);
echo("\nBigint shift 1\n");
echo($bigint>>1);
?>
Output:
$ ./test_bit.php
Using values: 11 - 1.1E+32 - 1.1E+33
int(11)
float(1.1E+32)
float(1.1E+33)
Number shift 34
2
Number shift 2
2
Bigint shift 29
0
Bigint shift 30
0
Bigint shift 31
0
Bigint shift 32
0
Bigint shift 33
0
Bigint shift 1
0
Previous Comments:
------------------------------------------------------------------------
[2002-03-31 12:49:34] [EMAIL PROTECTED]
> I think I will switch to blobs or something.
the problem is PHP-related. Switching to BLOBs won't solve it.
Why don't you use the ENUM('0','1') data field instead? It is more
humand-friendly (better readable) and somewhat more what the inventor
of databases wanted to do.
You can forget all database-related optimizations because the database
does not understand what you want to do.
------------------------------------------------------------------------
[2002-03-31 12:43:26] [EMAIL PROTECTED]
why store boolean values in a bigint if someone invented "columns" in
SQL? it's a useful thing, you know.
but to get your script working, why don't you just binary "&" ?
if($data & 2)
would check if register two was set.
------------------------------------------------------------------------
[2002-03-31 12:27:36] [EMAIL PROTECTED]
Hmm well the bug of (11>>34) still exists.. anything >>32 or more
should be zero.
I'm not really doing math, I am just storing boolean values in all the
bits of a bigint, and trying to access the high bits has become a
problem. I could always divide by 2 34 times but that kinda sucks.
I think I will switch to blobs or something.
------------------------------------------------------------------------
[2002-03-31 12:21:09] [EMAIL PROTECTED]
and besides, you should consider using more accurate operators for
sensitive data:
http://www.php.net/manual/en/ref.bc.php
PHP is not actually meant to do real-time calculations or to write
3D-engines in. Also, there is no precalculated sine table and no int
13h in PHP :)
11/34 or bcdiv(11, 34) should do the trick.
------------------------------------------------------------------------
[2002-03-31 11:54:25] [EMAIL PROTECTED]
AFAIK, PHP stores any number from MySQL as a string, until you access
it as a number. If you try to do some math on that number, that will
probably not work as expected. Bitshifting won't work either.
------------------------------------------------------------------------
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the rest of the comments, please view the bug report online at
http://bugs.php.net/16366
--
Edit this bug report at http://bugs.php.net/?id=16366&edit=1
