Non Blocking Channel Operations in Lisp

Our example demonstrates non-blocking operations on channels in Lisp. While Lisp doesn’t have built-in channels like Go, we can simulate similar behavior using queues and multiple threads.

(defpackage :non-blocking-channel-operations
  (:use :cl :bordeaux-threads :jpl-queues))

(in-package :non-blocking-channel-operations)

(defun main ()
  (let ((messages (make-instance 'synchronized-queue))
        (signals (make-instance 'synchronized-queue)))

    ;; Here's a non-blocking receive. If a value is
    ;; available in `messages` then it will be retrieved.
    ;; If not, it will immediately take the default case.
    (if (queue-empty-p messages)
        (format t "no message received~%")
        (format t "received message ~a~%" (dequeue messages)))

    ;; A non-blocking send works similarly. Here `msg`
    ;; is attempted to be sent to the `messages` queue.
    (let ((msg "hi"))
      (if (enqueue messages msg)
          (format t "sent message ~a~%" msg)
          (format t "no message sent~%")))

    ;; We can implement a multi-way non-blocking select
    ;; by checking multiple queues. Here we attempt
    ;; non-blocking receives on both `messages` and `signals`.
    (cond
      ((not (queue-empty-p messages))
       (format t "received message ~a~%" (dequeue messages)))
      ((not (queue-empty-p signals))
       (format t "received signal ~a~%" (dequeue signals)))
      (t
       (format t "no activity~%")))))

(main)

To run this program, you would need to ensure you have the necessary libraries installed (bordeaux-threads for multi-threading support and a queue implementation like jpl-queues). Then, you can load this file into your Lisp environment and execute the main function.

The output will depend on the state of the queues, but if they’re empty, you’ll see:

no message received
no message sent
no activity

This example demonstrates how to perform non-blocking operations in Lisp, simulating channel-like behavior using queues. The synchronized-queue ensures thread-safety for these operations.

Note that this is a simplification and doesn’t capture all the nuances of Go’s channel operations. In a real-world scenario, you might need more sophisticated mechanisms to fully replicate Go’s channel behavior in Lisp.

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Non Blocking Channel Operations in Lisp