To match a literal ellipses in syntax-parse use #:literal [(ellipses ...)] and
match on the term `ellipses', then to use a literal ellipses in the template
use (... ...) instead of just ...
It looks like you only want the latter, so
(define-syntax (example stx)
(syntax-parse stx
[(_ name:id) #'(define-syntax (name stx)
(syntax-parse stx
[(_ args (... ...)) #'(args (... ...)))])]))
On 08/02/2012 11:30 PM, Nick Sivo wrote:
> Hi,
>
> I'm trying to use ... in the inner macro of a macro defining macro,
> but can't figure out the right way to escape it.
>
> Here's a minimal (pointless) example:
>
> (require (for-syntax syntax/parse))
>
> (define-syntax (example stx)
> (syntax-parse
> stx
> ;#:literals (...) ; Doesn't help :(
> [(_ name:id)
> #'(define-syntax (name stx)
> (syntax-parse
> stx
> [(_ args ...) #'(args ...)]))]))
>
> The goal is to have (example invisible) define a macro called
> invisible that erases itself.
>
> Any ideas? The full code I'm trying to enable follows below if you'd
> like more context.
>
> Thanks,
> Nick
>
> #lang racket
>
> (require (for-syntax syntax/parse)
> racket/splicing)
>
> ;;;
> ;;; Procedure Application
> ;;;
>
> (define arc-nil #f)
>
> (define-syntax (arc-#%app stx)
> (syntax-parse
> stx
> [(_ fn:expr arg:expr)
> #'(let ([efn fn])
> (cond [(procedure? efn) (#%app efn arg)]
> [(pair? efn) (#%app list-ref efn arg)]
> [(string? efn) (#%app string-ref efn arg)]
> [(hash? efn) (#%app hash-ref efn arg arc-nil)]
> [else (#%app efn arg)]))]
> [(_ fn:expr arg1:expr arg2:expr)
> #'(let ([efn fn])
> (if (hash? efn)
> ; Have to use the lamda in case arg2 is a function
> ; See hash-ref docs for more info
> (#%app hash-ref fn arg1 (lambda () arg2))
> (#%app fn arg1 arg2)))]
> [(_ args ...)
> #'(#%app args ...)]))
>
> ; This allows cross module mutation of globals
> (define-syntax (declare-with-set-transformer stx)
> (syntax-parse
> stx
> ;#:literals (...) ; Doesn't help :(
> [(_ var:id)
> #'(declare-with-set-transformer var (gensym 'unintialized))]
> [(_ var:id init-val:expr)
> (let ([store-name (gensym (syntax->datum #'var))])
> #`(begin
> (define #,store-name init-val)
> (splicing-let ([set (lambda (val)
> (set! #,store-name val))])
> (define-syntax var
> (make-set!-transformer
> (lambda (stx)
> (syntax-case stx (set!)
> [(set! id val) #'(set val)]
> ; Uses Racket's #%app, which doesn't work for arc
> [(id . args) #'(#,store-name . args)] ; function
> application
> ; Obviously invalid syntax
> ;[(id . args) #'(arc-#%app #,store-name . args)]
> ; Errors because ... isn't recognized as a literal
> ;[(id args ...) #'(arc-#%app #,store-name args ...)]
> [id (identifier? #'id) #'#,store-name])))))))]))
>
> ; Demo of what I'm looking for
> (define test (make-hash))
> (hash-set! test 'key 'value)
> (displayln (arc-#%app test 'key))
>
> ; Example of what doesn't work right now
> (declare-with-set-transformer test2 (make-hash))
> (hash-set! test2 'key 'value)
> (displayln (test2 'key))
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