Some Haskell fun with Fibonacci and the tower of Hanoi

HaskellFibAndHanoiFun.hs

main = do 
        putStrLn . show . last . fib' $ 30000
        putStrLn . show  $ move 4 1 2 3

fib :: (Eq a, Num a) => a -> a
fib 0 = 0
fib 1 = 1
fib n = fib (n-1) + fib (n-2)

fib' :: (Eq a, Num a) => a -> [a]
fib' n = reverse $ grow n [1, 0]
    where grow n xs = case n of 0 -> xs
                                _ -> grow (n-1) $ [first xs + second xs] ++ xs
          first  = head
          second = flip (!!) 1
          
fibs :: [Integer]
fibs = 0 : 1 : zipWith (+) fibs (tail fibs)

move :: Integer -> Integer -> Integer -> Integer -> [String]
move = move' []
    where move' xs x from to spare | x <= 1 = ["Move from: " ++ (show from) ++ " to: " ++ (show to)]
                                   | otherwise = xs ++ 
                                                 move' xs (x-1) from spare to ++ 
                                                 move' xs 1 from to spare ++ 
                                                 move' xs (x-1) spare to from