Glitching example

racket/syndicate/examples/actor/example-glitch.rkt

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+#lang syndicate/actor
+;; Demonstrate FRP-like "glitching"
+;;
+;; Based on an example from the FRP survey of Bainomugisha et al.
+;; 2013:
+;;
+;;     var1 = 1
+;;     var2 = var1 * 1
+;;     var3 = var1 + var2
+;;
+;; Sample output; notice doubled 'var3 printing:
+;;
+;; 'var1 = 1
+;; 'var2 = 1
+;; 'var3 = 2
+;; ---
+;; 'var1 = 2
+;; 'var2 = 2
+;; 'var3 = 3
+;; 'var3 = 4
+;; ---
+;; 'var1 = 3
+;; 'var2 = 3
+;; 'var3 = 5
+;; 'var3 = 6
+;; ---
+;; 'var1 = 4
+;; 'var2 = 4
+;; 'var3 = 7
+;; 'var3 = 8
+;; ---
+
+(require/activate syndicate/drivers/timestate)
+
+(actor (field [var1 1])
+       (assert (list 'var1 (var1)))
+       (on (message 'tick)
+           (var1 (+ (var1) 1))))
+
+(actor (during (list 'var1 $v)
+         (assert (list 'var2 (* v 1)))))
+
+(actor (during (list 'var1 $v1)
+         (during (list 'var2 $v2)
+           (assert (list 'var3 (+ v1 v2))))))
+
+(actor (on (asserted (list $k $v))
+           (printf "~v = ~v\n" k v)))
+
+(actor* (until (asserted (observe 'tick)))
+        (sleep 0.1)
+        (printf "---\n")
+        (send! 'tick)
+        (sleep 0.1)
+        (printf "---\n")
+        (send! 'tick)
+        (sleep 0.1)
+        (printf "---\n")
+        (send! 'tick)
+        (sleep 0.1)
+        (printf "---\n"))