f :: (,) a [b] -> a				-- constructor de tip
f x = fst x

g :: [] Integer -> Integer		-- constructor de tip
g l = 1 + head l


d = [(1, 'a'), (2, 'b'), (3, 'c'), (2, 'd')]

search k dict = case res of
      [] -> Nothing
      v:_ -> Just v
    where res = [val | (key, val) <- dict, key == k]

fromMaybe Nothing = undefined
fromMaybe (Just x) = x

s :: String
s = "abc"

--a :: []
--a = []

t :: (,,,) Integer Char [Char] Bool
t = (1, 'a', "abc", True)

-- fx x = (x x)