drupol / phpermutations

  }

  function point_to_hilbert($x, $y, $order = 16, $map = "hilbert_map_1", $mode = "hilbert") {

    $current_square = 'a';

    $position = 0;

    foreach (range($order - 1, 0, -1) as $i) {

      $position <<= 2;

      $quad_x = $x & (1 << $i) ? 1 : 0;

      $quad_y = $y & (1 << $i) ? 1 : 0;

      list($quad_position, $current_square) = $this->{$map}[$current_square]["$quad_x, $quad_y"];

      $position |= $quad_position;

    }

    return $position;

  }

  function hilbert_to_point($hilbert, $order) {

    $current_square = "a";

  }

  function xy2d($x, $y, $order = 16) {

    $current_square = 'a';

    $position = 0;

    foreach (range($order - 1, 0, -1) as $i) {

      $position <<= 2;

      $quad_x = $x & (1 << $i) ? 1 : 0;

      $quad_y = $y & (1 << $i) ? 1 : 0;

      list($quad_position, $current_square) = $this->hilbert_map[$current_square]["$quad_x, $quad_y"];

      $position |= $quad_position;

    }

    return $position;

  }

  function d2xy($hilbert, $order = 16) {

    $current_square = "a";