acker.s 275 Bytes
# solution of fast growing recursive function ackerman(mc,nc)

MC : int = 3;
NC : int = 8;

acker = map (m, n) [
    ? [ m=0 -> ^ n+1
      | n=0 -> ^ @(m-1, 1)
      |  *  -> ^ @(m-1, @(m, n-1)) ]
];

program = map () -> () [
    writeInt (acker (MC, NC)); writeChar (10)
]