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) | |

(Distributive f, Distributive g) => Distributive (Compose f g) | |

(Distributive f, Distributive g) => Distributive (Product f 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