Free Category

This package introduces variouos presentations of free categories in Haskell.

Free categories are useful to model state machines in a simple yet type safe way and for that purpose Kleisli categroies are a very useful target which allows to include monadic computations. This packge contains a useful generalisation of Kliesli categories captured by EffCategory class (effectful categories), and a (free) transformer which lifts a category to an effectful one.

Some examples

• LoginStateMachine: based on State Machines All The Way Down by Edwin Bradly, 2017 You can run it with cabal new-run examples:login-state-machine.
• Read more here on a simple example of a finite state machine encoded using a free category using a simple GADT.
• Another example.
• Blog post on Keleisli categories.