REBOL [ Title: "Ackermann" Author: "Aldo Calpini" Date: 03-Jul-2001 File: %ackermann.r ] Ack: func [M N] [ return either M > 0 [ either N > 0 [ Ack M - 1 Ack M N - 1 ] [ Ack M - 1 1 ] ] [ N + 1 ] ] NUM: to-integer to-string first system/script/args NUM: either NUM < 1 [ 1 ] [ NUM ] R: Ack 3 NUM print rejoin [ "Ack(3," NUM "): " R ]