Bug #16366 Updated: bit shifting error

ID: 16366 Updated by: daniel@php.net Reported By: adam@adeptsoftware.com -Status: Closed +Status: Open -Bug Type: Math related +Bug Type: Documentation problem Operating System: WinXP PHP Version: 4.1.2 New Comment: are you sure? there is already a bunch of reports on "floating-point bugs" in PHP. That's why I didn't reopen it. Previous Comments: ------------------------------------------------------------------------ [2002-03-31 13:38:51] adam@adeptsoftware.com Well I have 200 groups of 64 on/off's.. I can name the 200 bigint groups but there is no way in hell I am going to name 12,800 bools, not to mention that they would take up 8x more space in the database.. Each group has the same structure - somebody needs to write a DB that uses structures as custom fields. This may be the way they work but this is ancient design - I was surprised as hell when I started learning MySQL and realized that they are still doing things this way. But anyway. Now I am thinking "char binary" since it can be fixed size, but the documentation on PHP's conversions of MySQL is sparse. If someone would like to pursue this in private email please write. The original bug was about bit shifting, which I don't think would involve a conversion to float.. unless PHP is doing something weird. It looks like someone is just not expecting a shift greater than 32. ------------------------------------------------------------------------ [2002-03-31 13:27:30] sander@php.net Good point. Reopening as documentation problem. ------------------------------------------------------------------------ [2002-03-31 13:23:52] msopacua@idg.nl Related to the bug only: <?php $int=2; for($i=25;$i<33;$i++) { $check=pow($int, $i); $check2=(int)$check; $check2 += 1; $check3=(int)$check; $check3 -= 1; echo("i is $i\n"); var_dump($check); var_dump($check2); var_dump($check3); echo("\n"); } ?> Gives some weird results: $ ./test_float_conversion.php i is 25 int(33554432) int(33554433) int(33554431) i is 26 int(67108864) int(67108865) int(67108863) i is 27 int(134217728) int(134217729) int(134217727) i is 28 int(268435456) int(268435457) int(268435455) i is 29 int(536870912) int(536870913) int(536870911) i is 30 int(1073741824) int(1073741825) int(1073741823) i is 31 float(2147483648) int(-2147483647) float(-2147483649) i is 32 float(4294967296) int(1) int(-1) I guess the manual should be appended, in the 'typecasting' section, to not cast to integer, when it's larger than 2^30 and that those numbers are automatically converted to floats. (http://www.php.net/manual/en/language.types.type-juggling.php#language.types.typecasting) ------------------------------------------------------------------------ [2002-03-31 13:10:38] derick@php.net Can you please stop this discussion in the bug system. Fighting about what is best can be done in private mail just fine. Derick ------------------------------------------------------------------------ [2002-03-31 13:09:00] daniel@php.net I'm sorry, but this is not flipcode.com - this is web-development. Not performance, but maintaineability and readability are crucial. Always write your code in a way someone else could easily understand what you are trying to do (even if you'll never release your sourcecode). ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view 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