This package contains efficient implementations of free categories. There are various representations available:
- real-time queues (C. Okasaki 'Pure Functional Data Structures')
- type aligned lists
- continuation passing style (Church encoding)
Free arrows and free Kleisli categories are also included.
Free categories are useful to model state machines in a simple yet type safe
manner. For that purpose Kleisli categories are a very useful target which
allows to include monadic computations. This package contains a useful
generalisation of Kleisli categories captured by EffectCategory class
(categories with effects), and a (free) transformer which lifts a category to
a category with effects.
Check performance characteristics of various representations:
- 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 Kleisli categories.