This is a simple and easy to use Actor system in Common Lisp.


Requires Bordeaux threads. 2. Just load actors.lisp and start using it. If you have Quicklisp, (ql:quickload "cl-actors")


An small manual can be found at :

  • Creating an actor class or template lisp (defactor Actor-Class (state) (message-vars) behavior)

  • Creating an actor instance

        (setq my-actor (Actor-Class (:state-var_1 value_1 ...
                    :state-var_n value_n)))
  • Sending a message lisp (send my-actor message_args)


  1. Concurrency using the actors model.
  2. Dynamic behavior change of actors.


  • A ticker: Keeps printing out a count every 2 seconds, starting from 0 and incrementing it every 2 seconds.

lisp ;create the ticker template (defactor ticker ((counter 0)) (m) (sleep 2) (pr counter) (incf counter) (send self nil) next) ; Create an instance (setf t1 (ticker)) ; send a message (async) (send t1 nil) ; to stop use (stop-actor t1)

  • A print actor: Prints the message which was sent to it. A very useful utility actor.

lisp ;create the actor template (defactor print-actor () (val) (pr val) next) ; initialize a new instance (setf printer (print-actor)) ;send values for printing (send printer "hello, world")

  • A factorial computing actor : The name says it all :)

lisp ;create the template (defactor fact ((temp 1)) (n cust) (if (equal 1 n) (progn (send cust (* temp 1)) (setf temp 1) next) (progn (setf temp (* n temp)) (send self (- n 1) cust) next))) ;create a new instance (setf f (fact)) ; send a value (send f 4 print-actor)

  • A nagger for fun : Works only in Mac OS X. Keeps saying out aloud "please work" every 10 seconds :)

lisp (defactor nagger () () (sleep 10) (trivial-shell:shell-command "say please work") (send self) next) ; anonymous actor , no way to stop the nagging (send (nagger))

More Resources

  1. [Meta-Circular Adventures in Functional Abstraction ?Challenging Clojure in Common Lisp] (
Naveen Sundar G. <>