functors

-- fmap :: (a -> b) -> f a -> f b

-- (.) :: (b -> c) -> (a -> b) -> a -> c

-- (a -> b) -> (e -> a) -> e -> b
-- 
instance Functor ((->) e) where
	fmap g h = g . h 


-- (e, v) where e is an annotation and v a value
instance Functor ((,) e) where
	fmap f ((,) e v) = ((,) e (f v)) 


instance Functor (Either e) where
	fmap _ (Left x) = Left x
	fmap f (Right v) = Right $ f v 

class Functor f => Pointed f where
	pure :: a -> f a


instance Pointed ((->) e) where
	pure a = \ e -> a