brandonbloom / cleff

Algebraic Effect Handlers for Clojure

Cleff

Cleff provides a framework for extensible handling of computational effects.

The design is heavily inspired by the Eff programming language. This project aims to provide a proof of concept implementation of all of the examples in Programming with Algebraic Effects and Handlers by Bauer and Pretnar.

Status

The basics of first-class effects and handlers are working.

Here's a simple non-deterministic choice effect:

(defn choose-all [c]
  (handler
    (value [x] [x])
    c
    (decide []
      (concat (continue true) (continue false)))))

(let [c (choice)]
  (handle-with (choose-all c)
    (let [x (if (effect c 'decide) 10 20)
          y (if (effect c 'decide) 0 5)]
      (- x y))))
;;=> (10 5 20 15)

Lots left to do:

• Polish up the syntax
• defprotocol-style defeffect
• Subroutines for coping with core.async's lexical IOC

See the test/ directory for some more examples.

License

Copyright © 2013 Brandon Bloom

Distributed under the Eclipse Public License, the same as Clojure.