class Functor f => Applicative f where
pure :: a->f a
<*> :: f (a->b)->f a->f b
class Foldable t where
foldr :: (a->b->b)->b->t a->b
foldr f b = foldMap (`f` b)
foldMap :: Monoid m => (a->m)->t a->m
foldMap f = foldr (mappend . f) mempty
class (Functor t, Foldable t) => Traversable t where
traverse :: (Applicative f) => (a -> f b) -> t a -> f (t b)
sequenceA :: Applicative f => t (f a)->f (t a)
class Functor f where
fmap :: (a->b)->f a->f b
instance Functor [] where
fmap g x:xs = g x:g xs
instance Traversable List where
sequenceA [] = pure []
sequenceA x:xs = (:) <$> x <*> sequenceA xs
traverse g [] = pure []
traverse g x:xs = fmap (:) (g x) <*> traverse g xs
(:) :: a->[a]->[a]
(a->b)->f a->f b
(+1) :: Int->Int
fmap (+1) :: f Int->f Int
read :: String->Int
fmap (+1) read :: String->Int
((:[]).(+1)) :: Int->[Int]
fmap ((:[]).(+1)) :: f Int->f [Int]
fmap ((:[]).(+1)) read ::
