note 59811 deleted from language.functions by nlopess

Note Submitter: budzynowski at hot dot NOSPAM dot mail dot com ---- If you're having stack problems with recursive subroutines, you can just make your own stack. Simply use an array, to which you add a value that you need to return to later. (I.e. rather than calling the function again, save the variables you would pass to it into an array) When you would normally 'return', just load up the last set of values from the array and continue from there. array_push() and array_pop() may be helpful. Here is yasuo_ohgaki AT hotmail DOT com's program modified to use no recursion: <?php echo('<br>Recursion-free TEST<br>'); function swap(&$v, $i, $j) { $temp = $v[$i]; $v[$i] = $v[$j]; $v[$j] = $temp; } // Quick Sort integer array - $int_array[$left] .. $int_array[$right] function qsort(&$int_array, $left, $right) { for(;;){ //keep repeating this until we reach return statement while ($left >= $right){ if (($right=array_pop($stack))==NULL) return; // Quit if the array is empty $left=array_pop($stack); //Otherwise load another $left and $right to process } swap ($int_array, $left, intval(($left+$right)/2)); $last = $left; for ($i = $left + 1; $i <= $right; $i++) if ($int_array[$i] < $int_array[$left]) swap($int_array, ++$last, $i); swap($int_array, $left, $last); $stack[]=$left; // Store the left and right values we need to process later $stack[]=$last-1; $left=$last+1; //$right is unchanged. } } $val = array(406,12,92,1,75,237,1,16,55,23,204,2,14,16); qsort($val, 0, count($val)-1); echo '<pre>'; print_r ($val); echo '</pre>'; ?> Also, some algorithms perform better when you *don't* stick to the order in the stack, by "typing up loose ends", as I have found with floodfill algorithms, for example. You can either pick and remove random stack elements, or swap a random element with the last one, then pop it off. One other thing- don't use recursion unless it gives a large advantage, as there is quite a bit of overhead in calling functions. germanAlonso at keltoi-web dot com's factorial program is fine as a demonstration of recursion, but I think a method like this would be more efficient: function fact($i){ for($j = $i; $j; $i*=$j--){} return $i; }