Portability | portable |
---|---|
Stability | provisional |
Maintainer | Edward Kmett <ekmett@gmail.com> |
- class Functor g => Distributive g where
- distribute :: Functor f => f (g a) -> g (f a)
- collect :: Functor f => (a -> g b) -> f a -> g (f b)
- distributeM :: Monad m => m (g a) -> g (m a)
- collectM :: Monad m => (a -> g b) -> m a -> g (m b)
- fmapDefault :: Distributive g => (a -> b) -> g a -> g b
- cotraverse :: (Functor f, Distributive g) => (f a -> b) -> f (g a) -> g b
- comapM :: (Monad m, Distributive g) => (m a -> b) -> m (g a) -> g b
Documentation
class Functor g => Distributive g whereSource
This is the categorical dual of Traversable
. However, there appears
to be little benefit to allow the distribution via an arbitrary comonad
so we restrict ourselves to Functor
.
Minimal complete definition: distribute
or collect
To be distributable a container will need to have a way to consistently zip a potentially infinite number of copies of itself. This effectively means that the holes in all values of that type, must have the same cardinality, fixed sized vectors, infinite streams, functions, etc. and no extra information to try to merge together.
distribute :: Functor f => f (g a) -> g (f a)Source
The dual of Data.Traversable.sequence
distribute = collect id
collect :: Functor f => (a -> g b) -> f a -> g (f b)Source
collect = distribute . fmap f
distributeM :: Monad m => m (g a) -> g (m a)Source
distributeM = fmap unwrapMonad . distribute . WrapMonad
collectM :: Monad m => (a -> g b) -> m a -> g (m b)Source
collectM = distributeM . liftM f
Distributive Identity | |
Distributive ((->) e) | |
Distributive g => Distributive (IdentityT g) | |
Distributive g => Distributive (ReaderT e g) |
fmapDefault :: Distributive g => (a -> b) -> g a -> g bSource
Every Distributive
is a Functor
. This is a valid default definition.
cotraverse :: (Functor f, Distributive g) => (f a -> b) -> f (g a) -> g bSource
comapM :: (Monad m, Distributive g) => (m a -> b) -> m (g a) -> g bSource