<HTML><BODY><BR> <DIV class="js-helper js-readmsg-msg"> <STYLE type=text/css></STYLE> <DIV class=mr_read__body id=style_13751452590000000043><BASE href="https://e.mail.ru/" target=_self> <DIV id=style_13751452590000000043_BODY>#. calcuclates its argument and place it in the program code.<BR>Now I have to write something like <BR><BR>(case state-number<BR>  ((0 1) ; state in init, stage1<BR>     (initialize))<BR>   ((2) ; state = process<BR>       (function1)<BR>   ((3) ; state = abort<BR>       (function2)))<BR><BR>I want to have<BR><BR>(define (state x)<BR>  (let rec ([states '(init stage1 process fail)]<BR>            [pos 0])<BR>    (cond<BR>      [(null? states) #f]<BR>      [(eq? (car states) x) pos]<BR>      [else (rec (cdr states) (add1 pos))])))<BR><BR>(case state-number<BR>  ((#.(state 'init) #.(state 'stage1))<BR>     (initialize))<BR>   ((#.(state 'process))<BR>       (function1)<BR>   ((#.(state 'fail))<BR>       (function2)))<BR><BR>So the code becomes self-documenting. Like using enum values in C or Pascal.<BR><BR>Понедельник, 29 июля 2013, 13:32 -04:00 от Asumu Takikawa <asumu@ccs.neu.edu>:<BR> <BLOCKQUOTE style="PADDING-BOTTOM: 0px; PADDING-TOP: 0px; PADDING-LEFT: 10px; MARGIN: 10px; BORDER-LEFT: #0857a6 1px solid; PADDING-RIGHT: 0px"> <DIV> <DIV> <DIV id=style_13751191470000000143> <DIV id=style_13751191470000000143_BODY>On 2013-07-29 06:25:21 +0400, Roman Klochkov wrote:<BR>> Is there simple way to calculate during compilation. Something like #.<BR>> in Common Lisp.<BR><BR>Can you tell us what #. means in Common Lisp?<BR><BR>I am guessing that you want to do something like the following:<BR><BR>  #lang racket<BR>  (require (for-syntax syntax/parse))<BR><BR>  ;; functions to compute costly constants<BR>  ;; at compile-time<BR>  (begin-for-syntax<BR>    (define (compute-x) ...)<BR>    (define (compute-y) ...)<BR>    (define (compute-z) ...))<BR><BR>  ;; macro that defines x, y, z assuming<BR>  ;; suitable definitions of compute-x, etc.<BR>  (define-syntax (define-constants stx)<BR>    (syntax-parse stx<BR>      [(_ x:id y:id z:id)<BR>       #`(begin (define x #,(compute-x))<BR>                (define y #,(compute-y))<BR>                (define z #,(compute-z)))]))<BR><BR>  (define-constants my-x my-y my-z)<BR><BR>This will work if the `compute-` functions produce flat data that can be<BR>embedded in syntax, like numbers.<BR><BR>Cheers,<BR>Asumu<BR></DIV></DIV></DIV></DIV></BLOCKQUOTE><BR><BR>-- <BR>Roman Klochkov<BR></DIV><BASE href="https://e.mail.ru/" target=_self></DIV></DIV><BR> <HR> <BR>-- <BR>Roman Klochkov<BR></BODY></HTML>