Re: Data Structures

At 04:43 09.02.2003, Laborda said: --------------------[snip]-------------------- >Does anyone know where can I find information about data structures >implemented in PHP. I need to find something about Linked Lists, implemented >in PHP.. If anyone has any info, I'd appreciate it. I've tried to google it >out but I can't find anything. Thanks. --------------------[snip]-------------------- As another poster already pointed out associative arrays may be one way to go /although there are multiple solutions to linked lists, as in many languages). However there is one caveat you absolutely need to observe: in PHP there are NO POINTERS. "Normally" assigning variables of any type will create a copy of the variable. like this: $a1 = array(1,2,3); $a2 = $a1; Here, $a2 is a COPY of $a1: $a2[3] = 4; echo join(',',$a1), ' - ', join(',',$a2); will produce 1,2,3 - 1,2,3,4 OTOH, you may use REFERENCES: $a2 =& $a1; $a2[3] = 4; echo join(',',$a1), ' - ', join(',',$a2); will now produce 1,2,3,4 - 1,2,3,4 This said, using array entries for linked lists, you must absolutely make sure to always use references, not simple assignments. Assuming a "structure" built as PHP array (unfortunately there's no such thing as a typedef): $start = array('prev' => null, 'next' => null, 'data' => 'First entry'); $elem = array('prev' => &$start, 'next' => null, 'data' => 'Second entry'); $start['next'] =& $elem; You get the picture, I believe. Just make sure the "pointers" are actually references to the list elements, or everything will break up. HTH, -- >O Ernest E. Vogelsinger (\) ICQ #13394035 ^ http://www.vogelsinger.at/