SOE ex.1.3
[(2,3),(4,5)] :: Num a, b => [(a,b)]
['z', 42] :: error, elements of list must have the same type.
('z', -42) :: Num a => (Char, a)
simple 'a' 'b' 'c' :: error, need Integer parameters.
(simple 1 2 3, simple) :: (Integer, Integer -> Integer -> Integer -> Integer)