Channel Synchronization in Lisp

Our example demonstrates how to synchronize execution across multiple processes using channels. In Lisp, we’ll use threads and a semaphore to achieve a similar effect.

(defpackage :channel-synchronization
  (:use :cl :bordeaux-threads))

(in-package :channel-synchronization)

;; This is the function we'll run in a separate thread. The
;; semaphore will be used to notify the main thread that this
;; function's work is done.
(defun worker (semaphore)
  (format t "working...")
  (sleep 1)
  (format t "done~%")
  ;; Signal the semaphore to notify that we're done.
  (signal-semaphore semaphore))

(defun main ()
  ;; Create a semaphore with an initial count of 0
  (let ((done (make-semaphore :count 0)))
    ;; Start a worker thread, giving it the semaphore to signal on.
    (make-thread (lambda () (worker done)))
    ;; Block until we receive a notification from the worker
    ;; via the semaphore.
    (wait-on-semaphore done)))

;; Run the main function
(main)

To run this program:

$ sbcl --load channel-synchronization.lisp
working...done

If you removed the (wait-on-semaphore done) line from this program, the program would exit before the worker even started.

In this Lisp version:

1. We use the bordeaux-threads library for multi-threading support.
2. Instead of a channel, we use a semaphore for synchronization.
3. The worker function is similar to the original, but it signals a semaphore instead of sending a value to a channel.
4. In the main function, we create a semaphore, start a new thread running the worker function, and then wait on the semaphore.
5. The wait-on-semaphore call blocks until the worker thread signals the semaphore, similar to the channel receive in the original example.

This approach provides similar synchronization between threads as the original Go example did with goroutines and channels.