funstacker

beautiful-racket/br/demo/funstacker.rkt

@@ -1,26 +1,29 @@
 #lang br/quicklang
-(provide read-syntax
-         (rename-out [stacker-module-begin #%module-begin])
-         + *)
 
-(define (read-syntax src-path in-port)
-  (define args (port->list read in-port))
-  (define module-datum `(module funstacker-mod br/demo/funstacker
-                          ,@args))
+(define (read-syntax path port)
+  (define args (port->lines port))
+  (define arg-datums (format-datums '~a args))
+  (define module-datum `(module stacker-mod br/demo/funstacker
+                          (handle-args ,@arg-datums)))
   (datum->syntax #f module-datum))
+(provide read-syntax)
 
-(define-macro (stacker-module-begin ARG ...)
+(define-macro (stacker-module-begin HANDLE-ARGS-EXPR)
   #'(#%module-begin
-     (define stack-result
-       (for/fold ([stack empty])
-                 ([arg (in-list (list ARG ...))])
-         (push arg stack)))
-     (display (first stack-result))))
+     (display (first HANDLE-ARGS-EXPR))))
+(provide (rename-out [stacker-module-begin #%module-begin]))
 
-(define (push arg stack)
-  (if (number? arg)
-      (cons arg stack)
-      (cons (arg (first stack) (second stack)) (drop stack 2))))
+(define (handle-args . args)
+  (for/fold ([stack empty])
+            ([arg (in-list (filter-not void? args))])
+    (cond
+      [(number? arg) (cons arg stack)]
+      [(or (equal? * arg) (equal? + arg))
+       (define op-result (arg (first stack) (second stack)))
+       (cons op-result (drop stack 2))])))
+(provide handle-args)
+
+(provide + *)
 
 (module+ test 
   (require rackunit)