RosettaCodeData/Task/Ackermann-function/Golfscript/ackermann-function.golf

{
  :_n; :_m;
  _m 0= {_n 1+}
        {_n 0= {_m 1- 1 ack}
               {_m 1- _m _n 1- ack ack}
               if}
        if
}:ack;