import Data.Function.YaMemo
import Data.Map

fibF :: (Num a, Eq a, Num b, Eq b) => (a -> b) -> a -> b
fibF _ 0 = 0
fibF _ 1 = 1
fibF f n = f (n-2) + f (n-1)

fib :: Integer -> Integer
fib = memo (undefined :: (Memo Map) Integer Integer) fibF

fib' :: Int -> Integer
fib' = memo (undefined :: (Memo Map) Int Integer) fibF