<HTML><BODY>Thank you. Yet one question^ is it possible to control, what will be in stacktrace. Because, I have (macro generated) (class base object% (define/public (write stream) (write-value l1 stream field1) (write-value l1 stream field2) (write-value l1 stream field3) ...)) Where l1 -- function, that takes its param and it to bytestream. (class derived base (define/override (write stream) (super write stream))) Then I have in stacktrace (super write stream), and then instantly body of l1. But no string "(write-value l1 stream field2)" where I could see, what field caouse error. Is it possible to add it to stacktrace? Or how Racket decides, what expressions will be in stacktrace? Wed, 17 Sep 2014 14:15:17 -0400 от Marc Burns <m4burns@uwaterloo.ca>: <blockquote style="border-left:1px solid #0857A6; margin:10px; padding:0 0 0 10px;"> <div id=""> <div class="js-helper js-readmsg-msg"> <style type="text/css"></style> <div> <base target="_self" href="https://e.mail.ru/"> <div id="style_14109777310000000733_BODY">It's not generally possible to edit the message contained in an exception. However, you can add information to the program's stack using continuation marks. Here's an example: (define my-cont-mark-key (gensym)) (define (parse-item item) (with-continuation-mark my-cont-mark-key item ...)) (with-handlers ([exn? (lambda(e) ((error-display-handler) (format "Parser exception at item ~a:\n~a" (first (continuation-mark-set->list (exn-continuation-marks e) my-cont-mark-key)) (exn-message e)) e))]) (parse-item start-item)) The exception captures the continuation marks installed when it is thrown. You can extract the information you added to the stack with these marks in the exception handler. On Wed, Sep 17, 2014 at 08:59:15PM +0400, Roman Klochkov wrote: > I'm writeing a parser. > So I want to see in parser exception what happend and when (not only where). > > (define (parse-item item) > ?? ??(with-handlers ([exn? (lambda (e) (raise (struct-copy exn e [message (format "At item ~a\n~a" item (exn-message e))])))]) > ?? ?? ?? ?? ??....)) > > But this way I lose all exception types. Is there a way to change exception message, saving its type, except long copy/paste like > (with-handlers ([exn:fail:contract:arity? (raise (struct-copy exn:fail:contract:arity ...))] > ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??[exn:fil:contract? (raise??(struct-copy exn:fail:contract ...))] > ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??...) > ?? ??...) > > ? > > -- > Roman Klochkov > ____________________ > Racket Users list: > <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a> </div> <base target="_self" href="https://e.mail.ru/"> </div> </div> </div> </blockquote> -- Roman Klochkov </BODY></HTML>