fun ackermann ← <int m, int n|when(m æ 0,
  n + 1,
  when(n æ 0,
  ackermann(m - 1, 1),
  ackermann(m - 1, ackermann(m, n - 1))))
for int m ← 0; m ≤ 3; ++m
  for int n ← 0; n ≤ 6; ++n
    writeLine("Ackermann(" + m + ", " + n + ") = ", ackermann(m, n))
  end
end