# free: Monads for free

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/

[Skip to Readme]

Versions [faq] | 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, 4.11, 4.12, 4.12.1, 4.12.2, 4.12.3, 4.12.4, 5, 5.0.1, 5.0.2, 5.1, 5.1.1, 5.1.2, 5.1.3, 5.1.4, 5.1.5, 5.1.6, 5.1.7 (info) |
---|---|

Change log | CHANGELOG.markdown |

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) [details] |

License | BSD-3-Clause |

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

Author | Edward A. Kmett |

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

Revised | Revision 1 made by HerbertValerioRiedel at 2014-12-02T10:54:46Z |

Category | Control, Monads |

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

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

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

Uploaded | by EdwardKmett at 2014-04-19T06:23:19Z |

Distributions | Arch:5.1.7, Debian:5.0.2, Fedora:5.1.3, FreeBSD:4.12.1, LTSHaskell:5.1.5, NixOS:5.1.7, Stackage:5.1.5, openSUSE:5.1.3 |

Downloads | 221097 total (2496 in the last 30 days) |

Rating | 2.5 (votes: 5) [estimated by Bayesian average] |

Your Rating | |

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

## Downloads

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

Note: This package has metadata revisions in the cabal description newer than included in the tarball. To unpack the package including the revisions, use 'cabal get'.