On Friday, July 15, 2016 at 2:22:50 PM UTC+10, Jack Firth wrote:
> I've got a macro that extends function definition by letting the user rebind
> some identifiers with different values, which are then only available in a
> certain context. For the sake of simplicity suppose it looks like this:
>
> (define/foo (func v ...)
> #:bind [helper1 expr]
> #:bind [helper2 other-expr]
> (helper1 v ...)
> (helper2 v ...))
>
> I would like helper1 and helper2 to have their normal meaning unless I'm
> inside a special `with-foo` form like so:
>
> (helper1 'a) ; normal behavior
>
> (with-foo func
> ; in here, helper1 and helper2 are bound to expr and other-expr instead
> (helper1 'a))
>
> I'd also like `with-foo` to be the only way to access the versions of helper1
> and helper2 that have this alternate behavior. I'm attempting to do this with
> some submodule hackery, essentially I'm expanding the above to this:
>
> (define (func v ...)
> (helper1 v ...)
> (helper2 v ...))
>
> (module foo racket/base
> (module+ func
> (define helper1 expr)
> (define helper2 other-expr)
> (provide (all-defined-out
>
> (begin
> (require (submod ".." foo func))
> (helper 1))
>
> My reasoning is that by letting "func" double as a submodule identifier, I
> can easily bring all the specially-bound identifiers associated with func
> into scope, and by putting that submodule in a "foo" submodule I can hide the
> existence of the foo submodule so only `with-foo` knows how to require the
> correct "func" module. But I'm hitting scope issues - I'm not sure hot to
> make the redefinitions of func available in (body ...) in a (with-foo func
> body ...) use, naively adding the require imports fails to bring them into
> scope. Various combinations of using syntax/loc and datum->syntax on the
> require statement, the require submod path, and/or the body are all failing
> to do what I want.
>
> How can I achieve this? Is there a better way to try and do this?
Although I'm not experienced enough to understand all that's going on in your
design, I wanted to remind you of (require (for-syntax )) since you're using
the required module in the macro?
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