From 8a319647f7a5378a26aa57344dc9ed299e1bb791 Mon Sep 17 00:00:00 2001
From: Jean Carass <jeancarass@gmail.com>
Date: Sun, 31 Dec 2017 00:43:31 -0500
Subject: [PATCH] Create stacker-extended.rkt

---
 .../stacker-demo/stacker-extended.rkt         | 38 +++++++++++++++++++
 1 file changed, 38 insertions(+)
 create mode 100644 beautiful-racket-demo/stacker-demo/stacker-extended.rkt

diff --git a/beautiful-racket-demo/stacker-demo/stacker-extended.rkt b/beautiful-racket-demo/stacker-demo/stacker-extended.rkt
new file mode 100644
index 0000000..8ef8af7
--- /dev/null
+++ b/beautiful-racket-demo/stacker-demo/stacker-extended.rkt
@@ -0,0 +1,38 @@
+#lang br/quicklang
+
+(define (read-syntax path port)
+  (define args (port->lines port))
+  (define handle-datums (format-datums '(handle ~a) args))
+  (define module-datum `(module stacker-mod stacker-demo/stacker
+                          ,@handle-datums))
+  (datum->syntax #f module-datum))
+(provide read-syntax)
+
+(define-macro (stacker-module-begin HANDLE-EXPR ...)
+  #'(#%module-begin
+     HANDLE-EXPR ...
+     (display (first stack))))
+(provide (rename-out [stacker-module-begin #%module-begin]))
+
+(define stack empty)
+
+(define (pop-stack!)
+  (define arg (first stack))
+  (set! stack (rest stack))
+  arg)
+
+(define (push-stack! arg)
+  (set! stack (cons arg stack)))
+
+(define (handle [arg #f])
+  (cond
+    [(number? arg) (push-stack! arg)]
+    [(or (equal? * arg) (equal? + arg) (equal? - arg) (equal? / arg))
+     ; This will ensure that stacker can be extended to support - and / operations while keeping the RPN notation
+     (define operand2 (pop-stack!))
+     (define operand1 (pop-stack!))
+     (define op-result (arg operand1 operand2)) 
+     (push-stack! op-result)]))
+(provide handle)
+
+(provide + * - /)