Bug #6260 Updated: xor operator not working correctly

ID: 6260 Updated by: derick Reported By: fredrik@devibe.net Old-Status: Suspended Status: Closed Bug Type: Scripting Engine problem Operating system: PHP Version: 4.0.1pl2 Assigned To: Comments: This is not a bug in PHP, so closing. Previous Comments: --------------------------------------------------------------------------- [2000-08-20 09:50:47] stas@php.net PHP integers are signed longs. If you want to go outside signed long, you should use bcmath library. I do not close it since PHP has showed some very strange behaviour on large numbers, which might be useful to investigate and decide what to do. --------------------------------------------------------------------------- [2000-08-20 09:44:58] fredrik@devibe.net I Compiled php with MySQL and apxs. php.ini shouldn't be relevant. It was not included in the install (btw. why?) and I've only created one with only session related stuff. I found this thing on a newsgroup, alt.php, a new group not yet found on many servers, but you *can* find it on news.cis.dfn.de. The thread is named "a little maths problem", started 08/15/00 11:07. I've considered it for some time now, and I can't find any explanation: the code snippet <?php $val = 2634023077 ^ 407240870; echo $val; ?> outputs "-1740242778". This can't to my knowledge be correct. I mean, 2634023077 would normally be an unsigned integer, but I haven't found any way to specify signed/unsigned integers. In addition, the answer should be 2235957251, and -1740242778 is not the signed representation of that number. 1001 1101 0000 0000 0000 0000 1010 0101 - 2634023077 ^ 0001 1000 0100 0110 0000 0000 1010 0110 - 0407240870 = 1000 0101 0100 0110 0000 0000 0000 0011 - 2235957251 The result from an xor operation performed on these two integers in php is -1740242778. 1740242778 (positive) is in binary: 0110 0111 1011 1001 1111 1111 0101 1010 Then the negative representation should be (negating each bit and "adding" one): 1001 1000 0100 0110 0000 0000 1010 0110 which unsigned is 2554724518, not 2235957251. All this taken into consideration, is this a bug/flaw or am I wrong? --Fredrik de Vibe --------------------------------------------------------------------------- ATTENTION! Do NOT reply to this email! To reply, use the web interface found at http://bugs.php.net/?id=6260&edit=2