efficient data types for free categories and arrows.
This package provides various data types for free categories, type aligned queues, arrows and type classes which allow to write abstract categories with side effects (Kleisli like categories). These are useful for encoding type safe state machines. Free arrows are also provided.
Free Category
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.
Benchmarks
Check performance characteristics of various representations:
Resources
- 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.