RosettaCodeData/Task/Ackermann-function/BCPL/ackermann-function.bcpl

GET "libhdr"

LET ack(m, n) = m=0 -> n+1,
                n=0 -> ack(m-1, 1),
                ack(m-1, ack(m, n-1))

LET start() = VALOF
{ FOR i = 0 TO 6 FOR m = 0 TO 3 DO
    writef("ack(%n, %n) = %n*n", m, n, ack(m,n))
  RESULTIS 0
}