Well that works fine when it’s in the same module (or namespace), but when I put it in a #lang, it breaks and I get this error: experiment-with-hygenic-reader-extensions/try-it.rkt: #lang experiment-with-hygenic-reader-extensions $ ; g15667: unbound identifier in module in: g15667
That’s one problem with unhygienic reader extensions. Since you used (datum->syntax #f ‘(GENSYM …)), it eventually took on the lexical context of try-it.rkt, where the GENSYM name isn’t there. Though strangely, if I put some lexical context on GENSYM by using (datum->syntax #f `(,#'GENSYM …)), then it gives me this error: experiment-with-hygenic-reader-extensions-2/try-it.rkt: #lang experiment-with-hygenic-reader-extensions-2 $ ; require: namespace mismatch; ; reference to a module that is not available ; reference phase: 0 ; referenced module: “…/experiment-with-hygenic-reader-extensions-2/lang/reader.rkt" ; referenced phase level: 0 in: g24 https://github.com/AlexKnauth/experiment-with-hygenic-reader-extensions On Jul 28, 2014, at 3:49 AM, Roman Klochkov <[email protected]> wrote: > > You may use such macro for making hygienic read-macros > > (define-syntax (make-reader stx) > (syntax-case stx () > [(_ NAME BODY ...) > (with-syntax ([GENSYM (datum->syntax stx (gensym))]) > #'(begin > (define-syntax (GENSYM stx) > (syntax-case stx () > [(_ in src line col pos) BODY ...])) > (provide GENSYM) > (define NAME > (case-lambda > [(ch in) > (datum->syntax #f '(GENSYM in #f #f #f #f))] > [(ch in src line col pos) > (datum->syntax #f '(GENSYM in src line col pos))]))))])) > > Usage example: > (make-reader read-dollar > #'(lambda (x) x)) > > (current-readtable > (make-readtable (current-readtable) > #\$ 'terminating-macro read-dollar)) > > Test: >> $ > #<procedure> >> (let ([lambda 1]) $) > #<procedure> > > All works just fine > > Sun, 27 Jul 2014 20:10:48 -0400 от "Alexander D. Knauth" > <[email protected]>: >> It seems like “hygienic reader extensions” still work when a module-level >> definition conflicts with it, but it seems like if it’s a local binding the >> local binding overrides the one in the reader extension. >> >> For example: >> #lang rackjure >> ;; this works: >> (define lambda "module-level-whatever") >> #λ(void %1) ; #<procedure> >> ;; this doesn't work >> (let ([lambda "local-whatever"] >> [%1 void] >> [define-syntax void] >> [% void]) >> #λ(void %1)) ; application: not a procedure; >> ; ; expected a procedure that can be applied to arguments >> ; ; given: "local-whatever" >> ; ; arguments…: >> >> Why does it work at the module-level and not within a let? >> >> Is this a bug, or should reader extensions not be used this way, or what? >> >> What’s going on here? >> >> >> ____________________ >> Racket Users list: >> http://lists.racket-lang.org/users >> > > > -- > Roman Klochkov ____________________ Racket Users list: http://lists.racket-lang.org/users
