Hi Mattias, On Fri, 2011-07-29 at 09:39 -0400, Matthias Felleisen wrote: > On Jul 29, 2011, at 8:35 AM, Maurizio Giordano wrote: > > > (require (for syntax multiset)) ;; import mset? for macro > > > > (define-syntax (mm stx) > > (syntax-case stx () > > [(_ input ...) > > (let* ((l1 (syntax '(input ...))) > > (l2 '(input ...))) > > (map (lambda (x) (print-type x)) l2) ; assume print-type is > > imported for syntax > > (datum->syntax stx `(map (lambda (x) (print-type x)) ,l1) > > stx))])) > > > Are you sure you don't just want to do something like this: > > > (define-syntax (mm stx) > (syntax-case stx () > [(_ input ...) > (let* ((l1 (syntax '(input ...))) > (l2 '(input ...))) > (map (lambda (x) (print-type x)) l2) ; assume print-type is > imported for syntax > #'(begin (print-type 'input) ...))])) > > As for your l2, you are just quoting the symbol 'input here. So either this > isn't really your macro or you sketched the output The macro I have reported is merely an example trying to reproduce the problem I have in the "real" macro I am trying to implement. If you remember my last post and discussion, you may figure out why I am using "(datum->syntax stx `(... (unquote ...))" instead of your "(syntax (begin ...))" proposal... you can find all the boring details in my last thread of discussion. > Your question isn't clear. You are right! I try to clarify my point... The problem is in the "(map (lambda ... l2)" expression, not in the syntax the macro produces. It is ok when I reference "l1" in the line: "(datum->syntax stx `(map (lambda (x) (print-type x)) ,l1)" In fact, the struct "<...>" is recognized correctly in l1 as a "mset" type. It is not in the "(map (lambda ... l2)". For some reason (I bet you know) the same struct "<...>" IS NOT recognized as a "mset" in the map. I suppose the input list (l2), when parsed, is stripped out of some information about user defined (not-prefab) struct. But more likely I am simply using the macro in a wrong way.
Thank you for your prompt answer. Cheers, Maurizio. _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
