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|
|Dependencies||base (>=4.4 && <5), comonad (==3.0.*), constraints (>=0.3.2 && <0.4), transformers (>=0.2.0.0 && <0.4), void (>=0.4 && <0.7) [details]|
|Source repo||head: git clone git://github.com/sjoerdvisscher/free-functors.git|
|Uploaded||by SjoerdVisscher at Sat Mar 23 20:24:10 UTC 2013|
|Downloads||7687 total (144 in the last 30 days)|
|Rating||(no votes yet) [estimated by rule of succession]|
|Status||Docs uploaded by user
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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.
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