[racket] Controlling module bindings with filtered-out?

I originally had something like that in mind, but then I figured that going with a plain `lambda' gives you all of these tweaks that you'd possibly want to do, and while they're a bit more verbose, they have the advantage of being readable without reading up on yet another provide variant.  BTW, I'd use a plain `regexp-match' instead of `match' -- seems mentally shorter to me...


On Sep 19, 2011, at 1:18 PM, Danny Yoo <dyoo at cs.wpi.edu> wrote:

> Sometimes I want to write a module language that extends the
> functionality of another, but I want to write that extension in
> racket/base, not in the extending language.
> 
> At the moment, I do this like this:
> 
> 
> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
> #lang racket/base
> 
> (require racket/provide
>         (for-syntax racket/base)
>         (for-syntax racket/match))
> 
> (require (prefix-in whalesong-kernel: (planet dyoo/whalesong/lang/kernel)))
> (provide (filtered-out
>          (lambda (name)
>            (match  name
>              [(regexp #rx"^whalesong-kernel:(.+)$" (list _ real-name))
>               real-name]
>              [else
>               #f]))
>          (all-from-out (planet dyoo/whalesong/lang/kernel))))
> 
> ;; definitions/provides for the other language extensions here...
> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
> 
> 
> This feels verbose, and I imagine that some people do this frequently.
> Is there an easier way to do this?
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