# The free package

Free monads are useful for many tree-like structures and domain specific languages.

If `f` is a `Functor` then the free `Monad` on `f` is the type
of trees whose nodes are labeled with the constructors of `f`. The word
"free" is used in the sense of "unrestricted" rather than "zero-cost":
`Free f` makes no constraining assumptions beyond those given by `f` and the
definition of `Monad`. As used here it is a standard term from the
mathematical theory of adjoint functors.

Cofree comonads are dual to free monads. They provide convenient ways to talk
about branching streams and rose-trees, and can be used to annotate syntax
trees. The cofree comonad can be seen as a stream parameterized by a `Functor`
that controls its branching factor.

More information on free monads, including examples, can be found in the following blog posts: http://comonad.com/reader/2008/monads-for-free/ http://comonad.com/reader/2011/free-monads-for-less/

## Properties

Versions | 0.1.0, 0.1.1, 0.2.0, 0.2.1, 0.2.2, 0.2.3, 1.8.0, 1.8.0.1, 1.8.0.3, 1.8.0.4, 2.0, 2.0.1, 2.0.1.1, 2.0.2, 2.0.3, 2.1, 2.1.1, 2.1.1.1, 2.2, 3.0, 3.1, 3.1.1, 3.2, 3.3, 3.3.0.1, 3.3.0.2, 3.3.1, 3.4, 3.4.1, 3.4.2, 4.0, 4.1, 4.2, 4.4, 4.5, 4.6, 4.6.1, 4.7, 4.7.1, 4.8, 4.8.0.1, 4.9, 4.10.0.1 |
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Dependencies | base (>=4 && <4.8), bifunctors (==4.*), comonad (==4.*), distributive (>=0.2.1), mtl (>=2.0.1.0 && <2.2), prelude-extras (>=0.4 && <1), profunctors (==4.*), semigroupoids (==4.*), semigroups (>=0.8.3.1 && <1), template-haskell (>=2.7.0.0 && <3), transformers (>=0.2.0 && <0.4) |

License | BSD3 |

Copyright | Copyright (C) 2008-2013 Edward A. Kmett |

Author | Edward A. Kmett |

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

Stability | provisional |

Category | Control, Monads |

Home page | http://github.com/ekmett/free/ |

Bug tracker | http://github.com/ekmett/free/issues |

Source repository | head: git clone git://github.com/ekmett/free.git |

Uploaded | Sat Apr 19 06:23:19 UTC 2014 by EdwardKmett |

Updated | Tue Dec 2 10:54:46 UTC 2014 by HerbertValerioRiedel to revision 1 |

Distributions | Debian:4.9, NixOS:4.10.0.1, Stackage:4.9 |

Downloads | 88814 total (6283 in last 30 days) |

Status | Docs available [build log] Successful builds reported [all 1 reports] |

## Modules

*Control**Alternative**Applicative**Comonad**Monad*

[Index]

## Downloads

- free-4.7.tar.gz [browse] (Cabal source package)
- Package description (included in the package)

#### Maintainers' corner

For package maintainers and hackage trustees