ackermann (n) (m) :
  ? n = 0
    :> m+1
  ? m = 0
    :> ackermann (n-1) 1
  :> ackermann (n-1) ackermann n (m-1) \ = ackermann (n-1) (ackermann n (m-1))
\ test it
main(params):+
  p1 =: string params[1] as integer else 3
  p2 =: string params[2] as integer else 5
  print "ackermann(" _ p1 _ "," _ p2 _ ") = " _ ackermann p1 p2