/* Sort the array interval a[from..to] */
void quicksort(element a[], index from, index to){
  index point1, point2;

  if (from < to){
    do_partitioning(a, from, to, &point1, &point2); 
    partitioning_info(a, from, to, point1, point2);
    quicksort(a, from, point1);
    quicksort(a, point2, to);
  }
}