[racket] Macros that use local-require (hygiene issues?)

I understand why the begin and [a a] work, but what I'm wondering is why
the others didn't work. For example, why didn't `begin` work in my second
example? Is the lexical information for the bindings just coming form
somewhere really weird?

On Thu Nov 06 2014 at 5:18:59 PM Jay McCarthy <jay.mccarthy at gmail.com>
wrote:

> The begin works because the macro use is at the top-level and the
> thing gets pulled up and spliced in, I believe.
>
> The [a a] works because the second a is detected as a binder so it
> gets matched up mark-wise with the second one rather than having them
> erased? Hygiene? Marks? Dye packets?
>
> Jay
>
> On Thu, Nov 6, 2014 at 4:36 PM, Spencer Florence <spencer at florence.io>
> wrote:
> > Thanks! That fixed it!
> >
> > Although I'm still curious as to why the error happens in the first
> place.
> >
> > On Thu Nov 06 2014 at 3:32:02 PM Alexander D. Knauth <
> alexander at knauth.org>
> > wrote:
> >>
> >> I think I had a similar sort of problem about a year ago (I was at
> either
> >> RacketCon or a Hackathon that same weekend and Mathew Flatt figured it
> out),
> >> and the solution was changing (only-in path a) to (only-in path [a a]).
> >>
> >> #lang racket/load
> >> ;;provider
> >> (module T racket
> >>   (provide a)
> >>   (define a 1))
> >> ;; requirer
> >> (module R racket
> >>   (require (for-syntax syntax/parse))
> >>   (define-syntax (test-binding stx)
> >>     (syntax-parse stx
> >>       [(_ path)
> >>        #'(let () (local-require (only-in path [a a])) a)]))
> >>   (test-binding 'T))
> >> ;; go
> >> (require ‘R)
> >>
> >>
> >> On Nov 6, 2014, at 4:09 PM, Spencer Florence <spencer at florence.io>
> wrote:
> >>
> >> > Hi All,
> >> >
> >> > I've been struggling to have a macro be given a path then require
> >> > something from that path. The following code produces and "Unbound
> >> > Identifier" error, although I would expect it to evaluate to 1. Could
> >> > someone provide insight into what is going on?
> >> >
> >> > #lang racket/load
> >> > ;;provider
> >> > (module T racket
> >> >   (provide a)
> >> >   (define a 1))
> >> > ;; requirer
> >> > (module R racket
> >> >   (require (for-syntax syntax/parse))
> >> >   (define-syntax (test-binding stx)
> >> >     (syntax-parse stx
> >> >       [(_ path)
> >> >        #'(let () (local-require (only-in path a)) a)]))
> >> >   (test-binding 'T))
> >> > ;; go
> >> > (require 'R)
> >> >
> >> >
> >> > P.S. I attempted to do this with `dynamic-require,` but that failed
> >> > because in my actual program `path` is sometimes `(submod "..")`,
> which
> >> > caused an error about not having a base path.
> >> >
> >> > ____________________
> >> >  Racket Users list:
> >> >  http://lists.racket-lang.org/users
> >>
> >
> > ____________________
> >   Racket Users list:
> >   http://lists.racket-lang.org/users
> >
>
>
>
> --
> Jay McCarthy
> http://jeapostrophe.github.io
>
>            "Wherefore, be not weary in well-doing,
>       for ye are laying the foundation of a great work.
> And out of small things proceedeth that which is great."
>                           - D&C 64:33
>
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