Open DrRacket. Start a new file called "funstacker.rkt" and save it in a convenient location. Paste in the source code that we had at the end of the stacker tutorial, with one change: for our module-datum, change the expander name from "stacker.rkt" to "funstacker.rkt":
#lang br/quicklang
(define (read-syntax path port)
(define src-lines (port->lines port))
(define src-datums (format-datums '(handle ~a) src-lines))
(define module-datum `(module stacker-mod "funstacker.rkt"
,@src-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))
(define op-result (arg (pop-stack!) (pop-stack!)))
(push-stack! op-result)]))
(provide handle)
(provide + *)
In the same directory, create a second file called "funstacker-test.rkt", and paste in our stacker demo program, but with an updated #lang line:
#lang reader "funstacker.rkt"
4
8
+
3
*
We should be able to run this file and get 36, same as usual.
Now we’re ready to break things.