running-total.rkt

racket/syndicate/examples/actor/running-total.rkt

@@ -0,0 +1,15 @@
+#lang syndicate
+;; Terminal I/O demo program.
+
+(require (only-in racket/port read-bytes-line-evt))
+
+(define e (read-bytes-line-evt (current-input-port) 'any))
+
+(spawn (field [total 0])
+       (begin/dataflow (printf "The total is ~a.\n" (total)))
+       (on-stop (printf "Goodbye!\n"))
+       (on (message (inbound (external-event e (list $input))))
+           (cond
+             [(eof-object? input) (stop-current-facet)]
+             [(string->number (bytes->string/utf-8 input)) => (lambda (n) (total (+ (total) n)))]
+             [else (void)])))