[racket] rudimentary macro Q.

Thank you. Maybe I can make the question a tiny bit less dumb (though still really dumb). 

In this example, when I use the syntax macro 'public-proc', it keeps the 'private-proc' binding from the 'inner' submodule. 

Q: How could I invoke 'public-proc' for its syntax-generating effect in the main module, yet have it adopt the binding of 'private-proc' in the main module? 

I gather roughly that it requires tampering with the lexical information of the syntax objects. Then things get hazy.

;;;;;;;;;;;;;;;;;;;;;;;;;
#lang racket

(module inner racket
  (provide public-proc)
  (define-syntax-rule (public-proc x) (private-proc x))
  (define (private-proc x) (format "Inner private proc says ~a" x)))

(require 'inner)

(define (private-proc x) (format "Outer private proc says ~a" x))

(syntax->datum (expand #'(public-proc 'hi)))
;> '(#%app private-proc 'hi)
(public-proc 'hi)
;> "Inner private proc says hi"

(syntax->datum (expand #'(private-proc 'hi)))
;> '(#%app private-proc 'hi)
(private-proc 'hi)
;> "Outer private proc says hi"
;;;;;;;;;;;;;;;;;;;;;;;;;



On Feb 26, 2014, at 10:22 AM, Matthias Felleisen <matthias at ccs.neu.edu> wrote:

> 
> That's precisely the behavior you want: 
> -- what's exported is the public name, which would usually check/do things before it calls private 
> -- while the unprotected private one is not provided and should not be visilble. 
> 
> How does the mechanics work? Well it delivers path names to these private identifier that in principle you can find too. So you can get around provided/not-provided but you don't want to 
> 
> -- Matthias
> 
> 
> 
> 
> 
> 
> On Feb 26, 2014, at 11:51 AM, Matthew Butterick <mb at mbtype.com> wrote:
> 
>> In this example, why can syntax produced via macro reach the private function, while the ordinary syntax cannot?
>> 
>> 
>> ;;;;;;;;;;;;;;;;;;;;;;;;
>> ;; one.rkt
>> #lang racket/base
>> 
>> (provide public-proc)
>> 
>> (define (private-proc x)
>> (format "The private proc says ~a" x))
>> 
>> (define-syntax-rule (public-proc x)
>> (private-proc x))
>> ;;;;;;;;;;;;;;;;;;;;;;;;
>> 
>> ;;;;;;;;;;;;;;;;;;;;;;;;
>> ;; two.rkt
>> #lang racket/base
>> (require "one.rkt")
>> ;;;;;;;;;;;;;;;;;;;;;;;;
>> 
>> Running two.rkt:
>>> (public-proc 'hi)
>> "The private proc says hi"
>>> (private-proc 'hi)
>> private-proc: undefined
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>