make non-mutating `stacker`

beautiful-racket/br/demo/stacker-test.rkt

@@ -1,6 +1,6 @@
 #lang reader br/demo/stacker
-push 4
-push 8
+4
+8
 +
-push 3
+3
 *

beautiful-racket/br/demo/stacker.rkt

@@ -1,32 +1,30 @@
-#lang br
+#lang br/quicklang
 
 (define (read-syntax src-path in-port)
-  (define lines (remove-blank-lines (port->lines in-port)))
-  (define (make-exec-datum line) (format-datum '(exec ~a) line))
-  (define exec-exprs (map make-exec-datum lines))
-  (strip-context (with-pattern ([(EXEC-EXPR ...) exec-exprs])
+  (define stack-args (port->list read in-port))
+  (strip-context (with-pattern ([(STACK-ARG ...) stack-args])
                    #'(module stacker-mod br/demo/stacker
-                       EXEC-EXPR ...))))
+                       (push STACK-ARG) ...))))
 (provide read-syntax)
 
-(define-macro (stacker-module-begin SRC-LINE ...)
+(define-macro (stacker-module-begin PUSH-STACK-ARG ...)
   #'(#%module-begin
-     SRC-LINE ...
+     PUSH-STACK-ARG ...
      (display (first stack))))
 (provide (rename-out [stacker-module-begin #%module-begin]))
 
 (define stack empty)
-(define (push num) (set! stack (cons num stack)))
-(provide push)
 
-(define-cases exec
-  [(_ func num) (func num)]
-  [(_ op) (define result (op (first stack) (second stack)))
-          (set! stack (cons result (drop stack 2)))])
-(provide exec)
+(define (push arg)
+  (cond
+    [(number? arg) (set! stack (cons arg stack))]
+    [else
+     (define result (arg (first stack) (second stack)))
+     (set! stack (cons result (drop stack 2)))]))
+(provide push)
 
-(provide + * #%app #%datum #%top-interaction)
+(provide + *)
 
-(module+ test 
+#;(module+ test 
   (require rackunit)
   (check-equal? (with-output-to-string (λ () (dynamic-require "stacker-test.rkt" #f))) "36"))

beautiful-racket/br/demo/stacker2-test.rkt

@@ -0,0 +1,8 @@
+#lang reader br/demo/stacker2
+4
+8
+
++
+3
+
+*

beautiful-racket/br/demo/stacker2.rkt

@@ -0,0 +1,32 @@
+#lang br/quicklang
+
+
+(define (read-syntax src-path in-port)
+  (define stack-args (port->list read in-port))
+  (strip-context
+   (with-pattern ([(STACK-ARG ...) stack-args])
+     #'(module stacker2-mod br/demo/stacker2
+         STACK-ARG ...))))
+(provide read-syntax)
+
+(define-macro (stacker-module-begin STACK-ARG ...)
+  #'(#%module-begin
+     (define stack-result
+       (for/fold ([stack null])
+                 ([arg (in-list (list STACK-ARG ...))])
+         (push arg stack)))
+     (display (first stack-result))))
+(provide (rename-out [stacker-module-begin #%module-begin]))
+
+(define (push arg stack)
+  (if (number? arg)
+      (cons arg stack)
+      (let* ([op arg]
+             [result (op (first stack) (second stack))])
+        (cons result (drop stack 2)))))
+
+(provide + * #%app #%datum #%top-interaction)
+
+(module+ test 
+  (require rackunit)
+  (check-equal? (with-output-to-string (λ () (dynamic-require "stacker2-test.rkt" #f))) "36"))