syndicate-rkt/syndicate-examples/box-and-client.rkt

31 lines
1.1 KiB
Racket

;;; SPDX-License-Identifier: LGPL-3.0-or-later
;;; SPDX-FileCopyrightText: Copyright © 2010-2024 Tony Garnock-Jones <tonyg@leastfixedpoint.com>
#lang syndicate
;; Simple mutable box and count-to-infinity box client.
(message-struct set-box (new-value))
(assertion-struct box-state (value))
(module+ main
(standard-actor-system/no-services (ds)
(spawn #:name 'box
(define-field current-value 0)
(at ds
(assert (box-state (current-value)))
(on (message (set-box $new-value))
(log-info "box: taking on new-value ~v" new-value)
(current-value new-value)))
(stop-on-true (= (current-value) 10)
(log-info "box: terminating")))
(spawn #:name 'client
(at ds
(stop-on (retracted (Observe (:pattern (set-box ,_)) _))
(log-info "client: box has gone"))
(on (asserted (box-state $v))
(log-info "client: learned that box's value is now ~v" v)
(send! (set-box (+ v 1))))
(on (retracted (box-state _))
(log-info "client: box state disappeared"))))))