Portability | GADTs, TFs, MPTCs |
---|---|

Stability | provisional |

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

Safe Haskell | Trustworthy |

Yoneda Reduction of presheafs

- data Yoneda f a where
- liftYoneda :: f a -> Yoneda f a
- lowerYoneda :: Contravariant f => Yoneda f a -> f a

# Documentation

A `Contravariant`

functor (aka presheaf) suitable for Yoneda reduction.

Contravariant (Yoneda f) | |

Valued f => Valued (Yoneda f) | |

Coindexed f => Coindexed (Yoneda f) | |

Representable f => Representable (Yoneda f) | |

Adjunction f g => Adjunction (Yoneda f) (Yoneda g) |

liftYoneda :: f a -> Yoneda f aSource

Yoneda expansion of a presheaf

`liftYoneda`

.`lowerYoneda`

≡`id`

`lowerYoneda`

.`liftYoneda`

≡`id`

lowerYoneda :: Contravariant f => Yoneda f a -> f aSource

Yoneda reduction on a presheaf