Split out call to ground-vm from definition of main

os-big-bang-example.rkt

@@ -37,7 +37,7 @@
 			     (send-message `(tick ,counter ,now))
 			     (loop now (+ counter 1)))]))))
 
-(ground-vm
+(define main
   (os-big-bang 'none
 	       (subscribe 'display-driver display-driver-handler)
 	       (subscribe 'read-line-driver read-line-driver-handler)
@@ -71,3 +71,5 @@
 					(unsubscribe 'ticker)
 					(send-message 'greet-loop)
 					)]))))
+
+(ground-vm main)