@hackage / free-operational

A reimplementation of the operational package (http://hackage.haskell.org/package/operational) using free monads (from http://hackage.haskell.org/package/free). This implements ideas discussed here:

• http://stackoverflow.com/questions/14263363/is-operational-really-isomorphic-to-a-free-monad

• http://www.reddit.com/r/haskell/comments/17a33g/free_functors_the_reason_free_and_operational_are/

To understand the basic concepts you can do no better than read Heinrich Apfelmus' operational tutorial:

• http://apfelmus.nfshost.com/articles/operational-monad.html

In addition to that, this package supplies operational-style modules for Applicative, Alternative and MonadPlus. Applicative and Alternative programs easily admit of static analysis. See these references for discussion and examples:

• http://gergo.erdi.hu/blog/2012-12-01-static_analysis_with_applicatives/ (discussion: http://www.reddit.com/r/haskell/comments/143wpd/static_analysis_with_applicatives/)

• http://paolocapriotti.com/blog/2013/04/03/free-applicative-functors/ (discussion: http://www.reddit.com/r/haskell/comments/1bnql3/free_applicative_functors_icfp_submission/)

See Control.Applicative.Operational for the bulk of the documentation. Control.Alternative.Operational also has some significant examples.