[racket] Exception decorator. is it possible?

 Thank you very much!
I didn't find struct-info function. This is enough for my needs.


Wed, 24 Sep 2014 00:22:28 -0300 от Gustavo Massaccesi <gustavo at oma.org.ar>:
> This code works, but it needs a lot more of error checking.
> 
> It uses that all the built-in exceptions are transparent and that all
> of them inherit from exn, so the first field is the message.
> 
> ;---
> #lang racket
> 
> (define (copy-struct/new-first str first)
>   (define-values (str-struct-info _) (struct-info str))
>   (define str-maker (struct-type-make-constructor str-struct-info))
>   (apply str-maker first (cdr (cdr (vector->list (struct->vector str))))))
> 
> (define (parse-item item)
>   (with-handlers ([exn? (lambda (e) (raise (copy-struct/new-first e
> (format "At item ~a\n~a" item (exn-message e)))))])
>     (cons 1 2 3) ;==> cons: arity mismatch;
>     #;(/ 1 0) ;==> /: division by zero
>     ))
> 
> (parse-item "Hello")
> ;---
> 
> Gustavo
> 
> 
> 
> 
> On Wed, Sep 17, 2014 at 1:59 PM, Roman Klochkov <kalimehtar at mail.ru> 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:
> >   http://lists.racket-lang.org/users
> >
> 

-- 
Roman Klochkov