On Wed, 8 Dec 2010 16:13:08 -0500
Matthias Felleisen <matth...@ccs.neu.edu>
wrote:
> ;;
> -----------------------------------------------------------------------------
> ;;
> usage example (could be separate module) (define detail-default "?")
> (struct/kw book (author title [details detail-default]) #:transparent)
>
> (define book1 (book/kw #:title "The Client" #:author "John Grisham"))
>
> (define book2 (book/kw #:title "The Client" #:author "John Grisham"
> #:details "?"))
>
> (string=? (book-author book1) "John Grisham")
> (string=? (book-details book2) "?")
>
>
If for instance I write book1 to a file (using write) and read it back
using read this works fine.
However, if I then try to use it as a struct/kw this will fail.
Example:
(call-with-output-file "books"
(lambda (out) (write book1 out)))
; works fine
(define bookx (call-with-input-file "books"
(lambda (in) (read in))))
; gives error
(string=? (book-author book1) (book-author bookx))
book-author: expects argument of type <struct:book>; given
'#(struct:book "John Grisham" "The Client" "")
=== context ===
/usr/lib/racket/collects/racket/private/misc.rkt:85:7
Indeed they are different:
> book1
(book "John Grisham" "The Client" "")
> bookx
'#(struct:book "John Grisham" "The Client" "")
Can this be solved within the definition of struct/kw or do I have to
work around it.
--
Manfred
--
Manfred
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