#18401 [Ana->Csd]: shuffle() broken

ID: 18401 Updated by: kalowsky@php.net Reported By: adam@trachtenberg.com -Status: Analyzed +Status: Closed Bug Type: Arrays related Operating System: Redhat 7.3 PHP Version: 4CVS-2002-08-12 New Comment: Fixed in CVS now. Thanks for your patch. Please follow up on any fallout too :) Previous Comments: ------------------------------------------------------------------------ [2002-08-14 11:59:51] adam@trachtenberg.com Yes, this is the Fisher-Yates algorithm. See Perl Cookbook or "perldoc -f shuffle" for supporting details. ------------------------------------------------------------------------ [2002-08-14 03:27:49] yohgaki@php.net Oops. Now I see what's the point. This patch seems good to me. There is no point changing cur_elem. Anyone? ------------------------------------------------------------------------ [2002-08-14 03:04:50] yohgaki@php.net - if (rnd_idx != cur_elem) { - temp = elems[cur_elem]; - elems[cur_elem] = elems[rnd_idx]; + RAND_RANGE(rnd_idx, 0, n_left, PHP_RAND_MAX); + if (rnd_idx != n_left) { + temp = elems[n_left]; + elems[n_left] = elems[rnd_idx]; elems[rnd_idx] = temp; Thanks for detailed report. This diff clearly show where to fix. Swapping values requires 3 lines!! ------------------------------------------------------------------------ [2002-08-12 03:10:28] adam@trachtenberg.com I have just tried it with the latest CVS and I still get the same results. Brad's changes were in a different section of the file. ------------------------------------------------------------------------ [2002-08-11 02:30:52] kalowsky@php.net I'm pretty Brad has been playing with this code. Can you test again, and report back with a new snapshot? ------------------------------------------------------------------------ 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/18401 -- Edit this bug report at http://bugs.php.net/?id=18401&edit=1