Progress is a new error! I don't think I understand how
syntax-local-bind-syntaxes is supposed to work. I extended the previous
program:
#lang racket
(require (for-syntax syntax/parse))
(define-syntax (test stx)
(syntax-parse stx
[(_ e)
(define ctx
(if (list? (syntax-local-context))
(cons (gensym) (syntax-local-context))
(list (gensym))))
(define def-ctx (syntax-local-make-definition-context))
(define expd (local-expand #'e ctx (list #'define-values) def-ctx))
(define ids (syntax-parse expd [(def (id) _) (list #'id)]))
(syntax-local-bind-syntaxes ids #f def-ctx)
(internal-definition-context-seal def-ctx)
expd]))
(let ()
(test (define x 1))
x)
And now I receive the error: `x: unbound identifier in module in: x`
Looking at the docs for `syntax-local-make-definition-context` it seems
like I need to provide it with the parent definition-context, but I'm not
sure how to get a hold of that.
--spf
On Mon Jan 05 2015 at 10:00:53 AM Matthew Flatt <mfl...@cs.utah.edu> wrote:
> The error message is intended for "end users" and turns out to be
> misleading for the implementor of an internal-definition context. The
> documentation for `define-values` has essentially the same problem: it
> describes how `define-values` should work in an internal-definition
> context, but it doesn't say how the form interacts with `local-expand`.
>
> A `define-values` form will only expand in a module or top-level
> context. To implement an internal-definition context, you must expand
> only far enough to see `define-values` form; in other words, supply
> `#'define-values` in the stop list. Then, a partially expanded
> `define-values` form must be recognized and handled explicitly, with
> tools like `syntax-local-bind-syntaxes` or re-writing to
> `letrec-values`, as appropriate for the definition context.
>
> At Mon, 05 Jan 2015 14:49:03 +0000, Spencer Florence wrote:
> > Hey all,
> >
> > I'm trying to use 'local-expand', however it seems to think its never in
> a
> > definition context. For example:
> >
> > (require (for-syntax syntax/parse))
> > (define-syntax (test stx)
> > (syntax-parse stx
> > [(_ e)
> > (define ctx
> > (if (list? (syntax-local-context))
> > (cons (gensym) (syntax-local-context))
> > (list (gensym))))
> > (local-expand
> > #'e ctx null
> > ;; result is the same with this uncommented
> > #;(syntax-local-make-definition-context))]))
> > (let ()
> > (test (define x 1))
> > x)
> >
> > errors with a "define-values: not in a definition context in:
> > (define-values (x) 1)"
> >
> > Can anyone provide any insight into what is going on?
> >
> > --spf
> > ____________________
> > Racket Users list:
> > http://lists.racket-lang.org/users
>
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