# free-functors: Free functors, adjoint to functors that forget class constraints.

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 subcategories 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.

Versions [faq] | 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, 0.9, 1.0, 1.0.1, 1.1, 1.1.1, 1.1.2, 1.2, 1.2.1 |
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Change log | CHANGELOG |

Dependencies | base (>=4.13 && <4.16), bifunctors (==5.*), comonad (==5.*), contravariant (==1.5.*), derive-lifted-instances (>=0.2.2 && <0.3), profunctors (==5.*), template-haskell (>=2.15 && <2.18), transformers (==0.5.*) [details] |

License | BSD-3-Clause |

Author | Sjoerd Visscher |

Maintainer | sjoerd@w3future.com |

Category | Data, Math |

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

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

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

Uploaded | by SjoerdVisscher at 2020-10-05T09:24:44Z |

Distributions | NixOS:1.2.1 |

Downloads | 20774 total (889 in the last 30 days) |

Rating | (no votes yet) [estimated by Bayesian average] |

Your Rating | |

Status | Docs uploaded by user [build log] All reported builds failed as of 2020-10-05 [all 2 reports] |

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## Downloads

- free-functors-1.2.1.tar.gz [browse] (Cabal source package)
- Package description (as included in the package)