struct pavl_node *x = y->pavl_link[0];
if (x->pavl_balance == -1)
  {
    w = x;
    y->pavl_link[0] = x->pavl_link[1];
    x->pavl_link[1] = y;
    x->pavl_balance = y->pavl_balance = 0;
    x->pavl_parent = y->pavl_parent;
    y->pavl_parent = x;
    if (y->pavl_link[0] != NULL)
      y->pavl_link[0]->pavl_parent = y;
  }
else
  {
    assert (x->pavl_balance == +1);
    w = x->pavl_link[1];
    x->pavl_link[1] = w->pavl_link[0];
    w->pavl_link[0] = x;
    y->pavl_link[0] = w->pavl_link[1];
    w->pavl_link[1] = y;
    if (w->pavl_balance == -1)
      x->pavl_balance = 0, y->pavl_balance = +1;
    else if (w->pavl_balance == 0)
      x->pavl_balance = y->pavl_balance = 0;
    else /* |w->pavl_balance == +1| */
      x->pavl_balance = -1, y->pavl_balance = 0;
    w->pavl_balance = 0;
    w->pavl_parent = y->pavl_parent;
    x->pavl_parent = y->pavl_parent = w;
    if (x->pavl_link[1] != NULL)
      x->pavl_link[1]->pavl_parent = x;
    if (y->pavl_link[0] != NULL)
      y->pavl_link[0]->pavl_parent = y;
  }
