# free-functors: Provides free functors that are adjoint to functors that forget class constraints.

Versions | 0, 0.1, 0.1.1, 0.1.2, 0.2, 0.3, 0.4, 0.4.1, 0.5, 0.6, 0.6.1, 0.6.1.1, 0.6.2, 0.6.3, 0.6.3.1, 0.6.3.2, 0.6.3.3, 0.6.4, 0.6.4.1, 0.6.5, 0.7, 0.7.1, 0.7.2, 0.8, 0.8.1, 0.8.2, 0.8.3, 0.8.4 |
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Dependencies | base (>=4.4 && <5), comonad (==3.0.*), constraints (>=0.3.2 && <0.4), transformers (>=0.2.0.0 && <0.4), void (>=0.4 && <0.6) [details] |

License | BSD-3-Clause |

Author | Sjoerd Visscher |

Maintainer | sjoerd@w3future.com |

Category | Data, Math |

Home page | http://github.com/sjoerdvisscher/free-functors |

Bug tracker | http://github.com/sjoerdvisscher/free-functors/issues |

Source repo | head: git clone git://github.com/sjoerdvisscher/free-functors.git |

Uploaded | by SjoerdVisscher at Tue Jul 24 22:36:52 UTC 2012 |

Distributions | NixOS:0.8.4 |

Downloads | 7689 total (141 in the last 30 days) |

Rating | (no votes yet) [estimated by rule of succession] |

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Status | Docs uploaded by user Build status unknown [no reports yet] Hackage Matrix CI |

A free functor is a left adjoint to a forgetful functor. It used to be the case that the only category that was easy to work with in Haskell was Hask itself, so there were no interesting forgetful functors.

But the new ConstraintKinds feature of GHC provides an easy way of creating subclasses of Hask. That brings interesting opportunities for free (and cofree) functors.

The examples directory contains an implementation of non-empty lists as free semigroups, and automata as free actions. The standard example of free higher order functors is free monads, and this definition can be found in Data.Functor.HFree.

## Downloads

- free-functors-0.1.tar.gz [browse] (Cabal source package)
- Package description (as included in the package)