Min

( symbol ack
  (int :m int :n ==> int :o)
  (
    (
      ((m 0 ==) (n 1 +))
      ((n 0 ==) (m 1 - 1 ack))
      ((true) (m 1 - m n 1 - ack ack))
    ) case @o
  )
) operator

(0 3) range (:m
  (0 4) range (:n
    m n ack
  ) map
) map