language-benchmarks/Interpreted/ackermann-function/ack.lua

function ack(M,N)
    if M == 0 then return N + 1 end
    if N == 0 then return ack(M-1,1) end
    return ack(M-1,ack(M, N-1))
end

print(ack(tonumber(arg[1]), tonumber(arg[2])))