On Jul 28, 2014, at 11:41 AM, Roman Klochkov <[email protected]> wrote:
> I tried to make it with module > (module m racket > (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))]))))])) > (make-reader read-dollar > #'(lambda (x) x)) > > (current-readtable > (make-readtable (current-readtable) > #\$ 'terminating-macro read-dollar))) > > (require 'm) > > Works just fine Yes because GENSYM was provided by ‘m, but if it’s a #lang then that doesn’t matter unless you specifically require experiment-with-hygenic-reader-extensions/lang/reader. And as I say below, I shouldn’t have to do that, and I shouldn’t have to provide GENSYM either. > I'm not very proficient with lang, but you should require module with > `make-reader' to you last module. > > I installed your package via `raco pkg install > git://github.com/AlexKnauth/experiment-with-hygenic-reader-extensions', but > > $ /usr/racket/bin/racket try-it.rkt > default-load-handler: cannot open module file > module path: experiment-with-hygenic-reader-extensions/lang/reader > path: > /home/monk/.racket/6.0.1/pkgs/experiment-with-hygenic-reader-extensions/experiment-with-hygenic-reader-extensions/lang/reader.rkt > system error: No such file or directory; errno=2 > > Maybe something wrong. Hmm, it doesn't do that for me. But I’m just wondering, when you look at …/pkgs/experiment-with-hygenic-reader-extensions, does it have …extensions/langreader.rkt instead of …extensions/lang/reader.rkt ? > I think you should add (require (submod > experiment-with-hygenic-reader-extensions/lang/reader reader)) to try-it. Or > make another module with make-reader, which will be required by lang and > result program. Well another good thing about hygienic macros and syntax-objects is encapsulation so that a macro can use GENSYM without having to provide GENSYM, so that GENSYM does not have visible to the user of the macro. So you shouldn’t have to add a (require experiment-…/lang/reader) to try-it.rkt. But for some reason that’s not always working for reader extensions. It seems to work when the binding is from racket/base and there’s no local binding conflicting with it (but module-level bindings conflicting with it are ok), but not when it’s from a different module other than racket/base? I don’t know. > > Mon, 28 Jul 2014 11:08:20 -0400 от "Alexander D. Knauth" > <[email protected]>: >> 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 >> > > > -- > Roman Klochkov ____________________ Racket Users list: http://lists.racket-lang.org/users
