<div dir="ltr">Thanks for your answer. Too bad -- I guess I'll have to rewrite the custom print then. Laurent </div><div class="gmail_extra"> <div class="gmail_quote">On Mon, Dec 2, 2013 at 9:16 PM, Vincent St-Amour <<a href="mailto:stamourv@ccs.neu.edu" target="_blank">stamourv@ccs.neu.edu</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">`define/generic' binds the specified generic function to a new identifier, to allow methods to call the generic function recursively. In your case, your `write-proc' calls `super-write' which, after dispatch, calls your `write-proc' again. What you want would be some a bit like CLOS's `call-next-method', which Racket's generics don't have. I can't think of a way to do what you want, short of reimplementing the behavior for `print' in your method. The interface for `gen:custom-write' (which it inherited from `prop:custom-write') is not great. IMO, it would be nicer to have `write', `display' and `print' be separate methods (which would support your use case), but I don't know how to retrofit that on top of the existing custom-write interface provided by runtime system. Vincent At Mon, 2 Dec 2013 18:05:59 +0100, Laurent wrote: > > [1 <multipart/alternative (7bit)>] > [1.1 <text/plain; ISO-8859-1 (7bit)>] <div><div class="h5">> Anyone has an answer to this? > > Thanks, > Laurent > > > On Tue, Nov 12, 2013 at 1:58 PM, Laurent <<a href="mailto:laurent.orseau@gmail.com">laurent.orseau@gmail.com</a>> 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 > > </div></div>> [1.2 <text/html; ISO-8859-1 (quoted-printable)>] > > [2 <text/plain; us-ascii (7bit)>] > ____________________ > Racket Users list: > <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a> </blockquote></div> </div>