<HTML><BODY>Great! Thank you! (with- ...) is the best approach for such in-place substitutions. I missed this opportunity. Вторник, 30 июля 2013, 0:40 -04:00 от Ryan Culpepper <ryanc@ccs.neu.edu>: <BLOCKQUOTE style="BORDER-LEFT: #0857a6 1px solid; PADDING-BOTTOM: 0px; MARGIN: 10px; PADDING-LEFT: 10px; PADDING-RIGHT: 0px; PADDING-TOP: 0px" class=mailru-blockquote> <DIV> <DIV class="js-helper js-readmsg-msg"> <STYLE type=text/css></STYLE> <DIV id=style_13751592230000000019 class=mr_read__body><BASE href="https://e.mail.ru/" target=_self> <DIV id=style_13751592230000000019_BODY>I don't think read-time computation is the right approach for Racket. Here's a compile/expand-time alternative that lets you use unsyntax as a compile-time escape. (require (for-syntax racket/syntax)) (define-syntax (with-compile-time-unsyntax stx)    (syntax-case stx ()      [(wctu form ...)       (syntax-local-introduce        (syntax-local-eval #'(quasisyntax (begin form ...))))])) Here's an example use: (begin-for-syntax    (define the-symbol 'apple)) (with-compile-time-unsyntax   (define (f x)     (case x       ((#,the-symbol) 'yes)       (else 'no)))) (f 'apple) ;; => 'yes (f 'pear) ;; => 'no If you wanted, you could make a custom language (see #%module-begin) that implicitly wrapped the whole module body with with-compile-time-unsyntax automatically. You might find it difficult to use quasisyntax and unsyntax within such a module. I haven't tried it or thought through how it would interact with quasisyntax "levels". You could of course implement your own quasisyntax-like form with a different escape binding. Ryan On 07/29/2013 10:07 PM, Roman Klochkov wrote: > Yes. Really it is read-time. > > In CL every top level expression read-compile-load or simply load if it > is compiled. > > So in Racket would be natural to have (for-syntax ...) environment in #. > I hope, that Racket also read toplevel form, loads it, then reads next > (not reads all at once, then load first form , second form and so on). > > Can you invent such read-macro? > > > Понедельник, 29 июля 2013, 21:44 -04:00 от Sam Tobin-Hochstadt > <<A href="https://e.mail.ru/messages/sentmsg?compose&To=samth@ccs.neu.edu">samth@ccs.neu.edu</A>>: > > On Mon, Jul 29, 2013 at 1:53 PM, Vincent St-Amour > <<A href="https://e.mail.ru/messages/sentmsg?compose&To=stamourv@ccs.neu.edu">stamourv@ccs.neu.edu</A> > <<A href="https://e.mail.ru/messages/sentmsg?compose&To=stamourv@ccs.neu.edu" target=_blank>https://e.mail.ru/messages/sentmsg?compose&To=stamourv@ccs.neu.edu</A>>> wrote: > > Here's a quick solution: > > > > #lang racket > > > > (define-syntax-rule (hash-dot e) > > (let-syntax ([computed-e (lambda (stx) (datum->syntax #'e e))]) > > (computed-e))) > > > > (hash-dot (+ 2 3)) > > > > In CL, #. is read-time, not compile-time, evaluation, so this isn't > quite the same. It would be easy to create a read-table that enabled > this, though. You'd have to make some decision about what environment > the read-time expression sees -- I don't know what CL does here. > > Sam > > > > -- > Roman Klochkov > > > > ____________________ > Racket Users list: > <A href="http://lists.racket-lang.org/users" target=_blank>http://lists.racket-lang.org/users</A> > </DIV><BASE href="https://e.mail.ru/" target=_self></DIV></DIV></DIV></BLOCKQUOTE> -- Roman Klochkov </BODY></HTML>