Whoa, very nice! IIUC, you could get rid of syntax-local-eval because you have a sub-macro, so the overall macro puts the content of id-rename inside a sub-macro that is then evaluated. This is also why id is correctly "bound" inside (begin body ...) : after the first expansion, it is not really body ..., but the full expression containing id. It is definitely better. Also, the first let () is not really needed I guess. Thank you very much. Laurent <div class="gmail_quote">On Mon, Apr 18, 2011 at 20:42, Jon Rafkind <<a href="mailto:rafkind@cs.utah.edu" target="_blank">rafkind@cs.utah.edu</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> <div text="#000000" bgcolor="#ffffff"> Here is an alternative implementation that makes the example you showed at the very bottom of your emails work. I don't know if its "better" but using `syntax-local-eval' looks somewhat dangerous to me. This is mostly straight-forward except that to get the right lexical scope for `get-x1' we need to do a little hack (by assuming the argument list has at least one thing in it). Of course the original macro could enforce such a property as well. #lang racket<div> (define-syntax (define-syntax-rule/id stx) (syntax-case stx () </div> [(_ (name arg ...) [id id-rename] body ...) (let () #'(define-syntax (name stx) (syntax-case stx () [(_ arg ...) ;; we want the defined procedure to have the same lexical scope as ;; the arguments given to the syntax-rule ;; we can't use #'(arg ...) as the thing to get the lexical scope ;; because #' will create a new syntax object using the lexical ;; scope of the code right here. so instead we take out the first ;; object from the argument list which should have the right scope. (with-syntax ([id (datum->syntax (car (syntax->list #'(arg ...))) (string->symbol (let ([arg (syntax-e #'arg)] ...) id-rename)) (car (syntax->list #'(arg ...))))]) #'(begin body ...))])) )])) (define-syntax-rule/id (make-getter xid) [id2 (format "get-~a" xid)] (define (id2) xid)) (define x1 5) (make-getter x1) (get-x1)<div><div></div><div> On 04/18/2011 12:03 PM, Laurent wrote: </div></div><blockquote type="cite"><div><div></div><div>Found! After having read more carefully Eli's very good post (<a href="http://blog.racket-lang.org/2011/04/writing-syntax-case-macros.html" target="_blank">http://blog.racket-lang.org/2011/04/writing-syntax-case-macros.html</a>), it became clearer that the problem was that the context of the created identifier was wrong. Deconstructing and reconstructing the id syntax object did the trick: (define-syntax (define-syntax-rule/id stx) (syntax-case stx () [(_ [id id-gen] body) (with-syntax ([id-def (to-syntax (syntax-e (syntax-local-eval #'id-gen)) #:stx stx)]) #'(splicing-let-syntax ([tmp-form (syntax-rules () [(_ id) (begin (displayln 'body) body)])]) (tmp-form id-def)) )] )) Now if anyone knows a better way to implement this or can point out problems with this implementation, I'd be glad to know about it. Thanks for listening :) Laurent <div class="gmail_quote">On Mon, Apr 18, 2011 at 18:21, Laurent <<a href="mailto:laurent.orseau@gmail.com" target="_blank">laurent.orseau@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204, 204, 204);padding-left:1ex"> Dear Racket list, Once again, I need a little help on a macro definition. I want to define the following (simplified[1]) macro: (define-syntax-rule/id [id id-gen] body) where id is replaced with the result of id-gen inside body. For example: (define-syntax-rule/id [x #'foo] (begin (define x 5) (displayln x))) is supposed to bind foo to 5 in the top-level at run-time. (You can replace #'foo by some complex identifier-making expression using format-id.) Here is what I have right now, after much trial&error: #lang racket (require (for-syntax unstable/syntax) (for-syntax errortrace/errortrace-key) racket/splicing ) (provide (all-defined-out)) ;; Like define-syntax-rule, ;; but id is replaced with the result of id-gen in body. ;; id-gen is eval'ed at macro-time. (define-syntax (define-syntax-rule/id stx) (syntax-case stx () [(_ [id id-gen] body) (with-syntax ([id-def (syntax-local-eval #'id-gen)]) #'(splicing-let-syntax ([tmp-form (syntax-rules () [(_ id) (begin (displayln 'body) body)])]) (tmp-form id-def)) )] )) ;;; TESTS (define-syntax-rule/id [x #'foo] (begin (define x 5) (displayln x) (displayln 'x) )) It works (foo is bound to 5), except that foo is unknown (undefined identifier) after the (begin ...). I suspect this is because of syntax-local-eval, but I don't know what to use instead. There is another intriguing thing: if just after (define x 5) we add (provide x), and in another file we require the first file, then foo is actually defined and can be used normally! Why is that and why does this not work when there is no (provide x) ? [note that there is a (provide (all-defined out)).] Can someone give me a hint as to what is going on? I also suspect that using splicing-let-syntax is not the way to go, but again I don't know what to use otherwise, that would let me replace id with id-def. Thank you very much, Laurent [1] To explain the name: once finished, this macro will be supposed to behave like an augmented version of define-syntax-rule but with explicit hygiene breaking: (define-syntax-rule/id (make-getter id) [id2 (format-id #'here "get-~a" id)] (define (id2) id)) which, when called on (make-getter foo) would create the get-foo function. </blockquote> </div> </div></div><pre><fieldset></fieldset> _________________________________________________ For list-related administrative tasks: <a href="http://lists.racket-lang.org/listinfo/users" target="_blank">http://lists.racket-lang.org/listinfo/users</a></pre> </blockquote> </div> _________________________________________________ For list-related administrative tasks: <a href="http://lists.racket-lang.org/listinfo/users" target="_blank">http://lists.racket-lang.org/listinfo/users</a> </blockquote></div>