[racket] Generics and gen:custom-write

Anyone has an answer to this?

Thanks,
Laurent


On Tue, Nov 12, 2013 at 1:58 PM, Laurent <laurent.orseau at gmail.com> wrote:

> I'm trying to implement a custom writer for a struct with generics, but I
> think I'm misunderstanding something.
>
> What I want to do is specialize only the behavior for `write' and
> `display', but leave the behavior for `print' untouched. So I thought that
> is what define/generic was for, but the following loops indefinitely:
>
> #lang racket
> (require racket/generic)
>
> (struct A (x y)
>   #:transparent
>   #:methods gen:custom-write
>   [(define/generic super-write write-proc)
>    (define (write-proc a port mode)
>      (case mode
>        [(#t) (write (list (A-x a) (A-y a)) port)]
>        [(#f) (display (list (A-x a) (A-y a)) port)]
>        [else (super-write a port mode)]))])
>
> (define a (A 1 'b))
> (displayln a) ; ok
> (write a)(newline) ; ok
> (print a)(newline) ; infinite loop
>
> What's the correct way to do that then?
>
> Thanks,
> Laurent
>
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