Example for os2

os2-example.rkt

@@ -0,0 +1,30 @@
+#lang racket/base
+;; Trivial demonstration of an os2.rkt virtual machine.
+
+(require "os2.rkt")
+(require racket/pretty)
+
+(define (super-alarm msecs)
+  (wrap-evt (alarm-evt msecs) (lambda (_) (current-inexact-milliseconds))))
+
+(define (sleep n k)
+  (transition k
+    (add-role (topic-subscriber (super-alarm (+ (current-inexact-milliseconds) n)))
+	      (handlers #f #f (lambda (eid topic now)
+				(lambda (k)
+				  (extend-transition (k)
+				    (delete-role eid))))))))
+
+(define (example-process delay)
+  (write `(sleeping for ,delay milliseconds))
+  (newline)
+  (sleep delay (lambda ()
+		 (write `(awoke after ,delay milliseconds))
+		 (newline)
+		 (transition 'no-state (kill)))))
+
+(ground-vm (lambda ()
+	     (transition 'no-state
+	       (spawn (lambda () (example-process 1000)))
+	       (spawn (lambda () (example-process 2000)))
+	       (kill))))