TRS:
 {        qsort(nil()) -> nil(),
        qsort(.(x, y)) -> ++(qsort(lowers(x, y)), .(x, qsort(greaters(x, y)))),
      lowers(x, nil()) -> nil(),
    lowers(x, .(y, z)) -> if(<=(y, x), .(y, lowers(x, z)), lowers(x, z)),
    greaters(x, nil()) -> nil(),
  greaters(x, .(y, z)) -> if(<=(y, x), greaters(x, z), .(y, greaters(x, z)))}
 Fail