note 124307 added to language.operators.bitwise

A fast algorithm (Brian Kernighan's) to count all bits set to 1 in an integer, modified to work with signed ints. It does the same as https://php.net/gmp_popcount except for ordinary integers. <?php function count_set_bits( $n ){ if( $n >= 0 ){ for( $count = 0; $n; ++$count ) $n &= $n - 1; } else{ for( $count = 1; $n << 1; ++$count ) $n &= $n - 1; } return $count; } echo 'This PHP uses ' . count_set_bits(-1) .'-bit integers.'; ?> ---- Server IP: 208.43.231.9 Probable Submitter: 185.85.3.168 (proxied: 62.165.224.226) ---- Manual Page -- http://php.net/manual/en/language.operators.bitwise.php Edit -- https://master.php.net/note/edit/124307 Del: integrated -- https://master.php.net/note/delete/124307/integrated Del: useless -- https://master.php.net/note/delete/124307/useless Del: bad code -- https://master.php.net/note/delete/124307/bad+code Del: spam -- https://master.php.net/note/delete/124307/spam Del: non-english -- https://master.php.net/note/delete/124307/non-english Del: in docs -- https://master.php.net/note/delete/124307/in+docs Del: other reasons-- https://master.php.net/note/delete/124307 Reject -- https://master.php.net/note/reject/124307 Search -- https://master.php.net/manage/user-notes.php