Portability | non-portable (class-associated types) |
---|---|

Stability | experimental |

Maintainer | Edward Kmett <ekmett@gmail.com> |

NB: this contradicts another common meaning for an `Associative`

`Category`

, which is one
where the pentagonal condition does not hold, but for which there is an identity.

- class Bifunctor p => Associative p where
- associate :: p (p a b) c -> p a (p b c)

- class Bifunctor s => Coassociative s where
- coassociate :: s a (s b c) -> s (s a b) c

# Documentation

class Bifunctor p => Associative p whereSource

A category with an associative bifunctor satisfying Mac Lane's pentagonal coherence identity law:

bimap id associate . associate . bimap associate id = associate . associate

class Bifunctor s => Coassociative s whereSource

A category with a coassociative bifunctor satisyfing the dual of Mac Lane's pentagonal coherence identity law:

bimap coassociate id . coassociate . bimap id coassociate = coassociate . coassociate

coassociate :: s a (s b c) -> s (s a b) cSource