Tarai function in Haskell

Tarai.hs

main :: IO ()
main = print (tarai 13 8 0)
　
tarai :: Int -> Int -> Int -> Int
tarai x y z
    | x <= y    = y
    | otherwise = tarai (tarai (x-1) y z)
                        (tarai (y-1) z x)
                        (tarai (z-1) x y)

{-
   % ghc --make -O3 Tarai.hs
   [1 of 1] Compiling Main             ( Tarai.hs, Tarai.o )
   Linking Tarai ...
   % time ./Tarai
   13
   ./Tarai  0.00s user 0.00s system 95% cpu 0.004 total
-}