with promises

beautiful-racket-demo/wires-demo/with-promises.rkt

@@ -0,0 +1,33 @@
+#lang br/quicklang
+(require "main.rkt")
+(provide (all-from-out "main.rkt"))
+
+(module+ reader
+  (provide read-syntax))
+
+(define (read-syntax path port)
+  (define wire-datums
+    (for/list ([wire-str (in-lines port)])
+      (format-datum '(wire ~a) wire-str)))
+  (strip-bindings
+   #`(module wires-mod wires-demo/with-promises
+       #,@wire-datums)))
+
+(define-macro-cases wire
+  [(wire ARG -> WIRE) #'(define/display (WIRE)
+                          (val ARG))]
+  [(wire OP ARG -> WIRE) #'(define/display (WIRE)
+                             (OP (val ARG)))]
+  [(wire ARG1 OP ARG2 -> WIRE) #'(define/display (WIRE)
+                                   (OP (val ARG1) (val ARG2)))]
+  [else #'(void)])
+(provide wire)
+
+(define-macro (define/display (WIRE) BODY)
+  #'(begin
+      (define WIRE (delay BODY))
+      (module+ main
+        (displayln 'promises)
+        (displayln (format "~a: ~a" 'WIRE (val WIRE))))))
+
+(define (val num-or-wire) (force num-or-wire))