syndicate-2017/racket/syndicate/examples/actor/f-to-c3.rkt

34 lines
1.2 KiB
Racket

#lang syndicate
;; After the Fahrenheit-to-Celsius converter example in "Fabrik - A
;; Visual Programming Environment", Ingalls, Wallace, Chow, Ludolph
;; and Doyle, OOPSLA 1988.
(struct temperature (unit value) #:prefab)
(struct set-temperature (unit value) #:prefab)
(spawn #:name 'track-celsius
(field [temp 0])
(assert (temperature 'C (temp)))
(on (message (set-temperature 'C $new-temp)) (temp new-temp)))
(spawn #:name 'track-fahrenheit
(field [temp 32])
(assert (temperature 'F (temp)))
(on (message (set-temperature 'F $new-temp)) (temp new-temp)))
(spawn #:name 'convert-C-to-F
(on (asserted (temperature 'C $other-temp))
(send! (set-temperature 'F (+ (* other-temp 9/5) 32)))))
(spawn #:name 'convert-F-to-C
(on (asserted (temperature 'F $other-temp))
(send! (set-temperature 'C (* (- other-temp 32) 5/9)))))
(spawn (on (asserted (temperature $unit $value))
(printf "Temperature in ~a is ~a\n" unit (exact->inexact value))))
(spawn (on (asserted (observe (set-temperature _ _)))
;; (send! (set-temperature 'C 20))
(send! (set-temperature 'F 90))
))