[racket-dev] A strange problem with namespaces

No, the `evaluator` module wasn't available anywhere.

I'll work on the definition of "available" in the docs. "Available at
phase 0" implies that you can use macros that are bound at phase 0 and
whose implementations live at phase 1.

At Wed, 7 May 2014 10:03:25 -0500, Robby Findler wrote:
> Oh! So the evaluator module is available in phase 0 in 'ns', but not
> in 'namespace'. Is that right?
> 
> Robby
> 
> On Wed, May 7, 2014 at 9:58 AM, Matthew Flatt <mflatt at cs.utah.edu> wrote:
> > I think the right change might be
> >
> >  (module evaluator racket
> >    ....
> >    (define (prep!)
> >      (parameterize ([current-namespace namespace])
> >        (dynamic-require (variable-reference->module-path-index
> >                          (#%variable-reference))
> >                         0)))
> >    ....
> >    (define-syntax phase1-phase0-eval
> >      (syntax-parser
> >       [(_ form:expr ...)
> >        #'(begin
> >            (prep!)
> >            (eval-syntax .....))])))
> >
> > The `prep!` function ensures that the enclosing module is available.
> >
> > At Wed, 7 May 2014 10:11:49 -0400, Sam Tobin-Hochstadt wrote:
> >> This program: https://gist.github.com/samth/e7b55fcef66da9b8416a works
> >> when line 33 is uncommented, otherwise it gives the error:
> >>
> >> ?: module mismatch;
> >>  attempted to use a module that is not available
> >>   possible cause:
> >>    using (dynamic-require .... #f)
> >>    but need (dynamic-require .... 0)
> >>   module: (submod "weird.rkt" evaluator)
> >>   phase: 0
> >>   in: phase1-phase0-run
> >>   context...:
> >>    weird.rkt: [running body]
> >>
> >> From reading the docs on `dynamic-require`, I can see that
> >> `(dynamic-require m 'f)` doesn't make anything available for higher
> >> phases.  However, the actual `dynamic-require` in the program is just
> >> for a function -- the need for higher phases is an implementation
> >> detail that's leaking in because it doesn't behave like a regular
> >> value wrt `dynamic-require`.
> >>
> >> Is there something I can change in the implementation of the internals
> >> of `f` so that clients of `f` don't need to do the extra
> >> `(dynamic-require m 0)` in order for `f` to work?
> >>
> >> Sam
> >> _________________________
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