let power = (* power x y = x^y *)
  fun f (x:int) (y:int): int =>
    if y = 0 then 1
    else if y = 1 then x
         else if y = 2 then x * x
              else let t = f (x) (y / 2) in
                     if y mod 2 = 0 then t * t else x * t * t
in
    power 2 10