[racket-dev] using module system for alternate namespaces

Matthias -

Hello... so, yes, Jay and I continued our discussion on the IRC channel.

To answer your question, yes, the code as written should behave as it does.

What I wanted was to make "a" not visible to the enclosing module unless it
was exported via "provide" or an analogous operation. Jay's idea was to use
"define" to create a module binding from "a" to a generated or decorated
name, provide "a" (or not), and put the generated name in the hash table.
I'm pursuing that approach currently.

Dan


PS: The motivation for this is to finally get our custom language "DC" to
be implemented as a proper Racket module language.  It's turning out to be
a bit of a nightmare since we rely so heavily on the side effects of "load"
and we have 4 different namespaces active at once.  This example is just
one small piece.





On Mon, Nov 3, 2014 at 5:31 AM, Matthias Felleisen <matthias at ccs.neu.edu>
wrote:

>
> On Oct 27, 2014, at 7:00 PM, Dan Liebgold wrote:
>
> I have a namespace behind a particular API. I'd love to hook into the
> module system to control compilation, visibility, etc. of all the
> definitions and references.
>
> Here's an example. 'a' is available in the top level module even though it
> was defined by module 'm1' and not provided by any explicit mechanism.
> (Also, order dependencies seem imminent.)
>
>
> Since you didn't reply to Jay's response, let me resume the thread. You
> had written not quite this:
>
> #lang racket
>
>
> (module base racket
>   (define my-table (make-hasheq))
>
>   (define-syntax (my-define stx)
>     (syntax-case stx ()
>       [(_ my-id expr) (identifier? #'my-id)
>                       #'(hash-set! my-table 'my-id expr)]))
>
>   (define-syntax (my-eval stx)
>     (syntax-case stx ()
>       [(_ my-id)
>        #'(hash-ref my-table 'my-id #f)])) ;; <--- my first change
>
>   (provide my-define my-eval))
>
> (module m1 racket
>   (require (submod ".." base))
>   (my-define a (+ 1 2)))
>
> (require 'base 'm1)
>
> (my-eval a) ;; <--- my second change
>
>
> ;; ---
>
> When you write 'a' is available in the top-level module, even though you
> didn't import it, I don't see it. You imported all of base into the top
> level and m1. These imports include accessors to 'my-table' and 'm1'
> happened to store a key in this table. Why should you not be able to
> retrieve the value of 'a'?
>
> -- Matthias
>
>
>
>
>


-- 
Dan Liebgold    [dan.liebgold at gmail.com]
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