Experimental begin/dataflow and define/dataflow facilities

racket/syndicate/actor.rkt

@@ -19,6 +19,8 @@
          on
          during
          during/actor
+         begin/dataflow
+         define/dataflow
 
          asserted
          retracted
@@ -377,6 +379,30 @@
               (react (stop-when (retracted p #:meta-level L.level))
                      O ...)))))]))
 
+(define-syntax (begin/dataflow stx)
+  (syntax-parse stx
+    [(_ expr ...)
+     (quasisyntax/loc stx
+       (let ()
+         (add-endpoint! #,(source-location->string stx)
+                        (lambda ()
+                          (define subject-id (current-dataflow-subject-id))
+                          (schedule-script!
+                           #f
+                           (lambda ()
+                             (parameterize ((current-dataflow-subject-id subject-id))
+                               expr ...)))
+                          patch-empty)
+                        void)))]))
+
+(define-syntax (define/dataflow stx)
+  (syntax-parse stx
+    [(_ fieldname expr)
+     (quasisyntax/loc stx
+       (begin
+         (field [fieldname #f])
+         (begin/dataflow (fieldname expr))))]))
+
 (define-syntax (asserted stx) (raise-syntax-error #f "asserted: Used outside event spec" stx))
 (define-syntax (retracted stx) (raise-syntax-error #f "retracted: Used outside event spec" stx))
 (define-syntax (rising-edge stx) (raise-syntax-error #f "rising-edge: Used outside event spec" stx))

racket/syndicate/examples/actor/query-set.rkt

@@ -11,6 +11,19 @@
         (define/query-hash as-hash `(item ,$a ,$b) a b)
         (define/query-hash-set as-hash-set `(item ,$a ,$b) a b)
 
+        (field [as-value-notification-counter 0])
+
+        (begin/dataflow
+          (log-info "Notification counter: ~v" (as-value-notification-counter))
+          (local-require (only-in racket/base sleep))
+          (sleep 1))
+
+        (let ((shadow-counter 0))
+          (begin/dataflow
+            (log-info "as-value is now: ~v" (as-value))
+            (set! shadow-counter (+ shadow-counter 1))
+            (as-value-notification-counter shadow-counter)))
+
         (on (message 'dump)
             (printf "----------------------------------------\n")
             (printf "Queried as-value: ~v\n" (as-value))