add stacker to demo

beautiful-racket/br/demo/stacker.rkt

@@ -0,0 +1,33 @@
+#lang br
+(define (read-syntax source-path input-port)
+  (define src-strs (remove-blank-lines (port->lines input-port)))
+  (define (make-datum str) (format-datum '(dispatch ~a) str))
+  (define src-exprs (map make-datum src-strs))
+  (strip-context
+   (inject-syntax ([#'(SRC-EXPR ...) src-exprs])
+                  #'(module stacker-mod br/demo/stacker
+                      SRC-EXPR ...))))
+(provide read-syntax)
+
+(define #'(stacker-module-begin READER-LINE ...)
+  #'(#%module-begin
+     READER-LINE ...
+     (display (first stack))))
+(provide (rename-out [stacker-module-begin #%module-begin]))
+(provide #%top-interaction)
+
+(define stack empty)
+(define (push num) (set! stack (cons num stack)))
+(provide push)
+
+(define (dispatch arg-1 [arg-2 #f])
+  (cond
+    [(number? arg-2) (push arg-2)]
+    [else
+     (define op arg-1)
+     (define op-result (op (first stack) (second stack)))
+     (set! stack (cons op-result (drop stack 2)))]))
+(provide dispatch)
+
+(provide + *)
+(provide #%app #%datum)