On 13 Nov 2009, at 08:13, Mark Engelberg wrote: > Is there a way to customize the way that types defined by deftype > print in the REPL?
Implement the multimethod clojure.core/print-method for the associated type tag: (deftype Foo ...) (defmethod clojure.core/print-method ::Foo [x] ...) > While these datatype and protocol constructs are taking shape, maybe > now is the time to discuss what kind of "privacy" settings are > worthwhile in a language like Clojure. I think Java's system of > private/public/protected is probably overkill for Clojure. But do > people feel that some degree of data hiding is worthwhile? For > example, might you want to hide some deftype fields from keyword > lookup? Coming from a Python background, I don't think access restrictions are necessary. However, flagging fields as "not meant for use by outsiders" could be of interest for documentation tools, to make it clear what client code can safely rely on. Note also that you can always make the deftype private (it's a var like any other) and restrict all use of it to public functions defined in the same namespace. That doesn't exclude defining protocols and multimethods on this type elsewhere, because its type tag is a namespace-qualified symbol that can be used anywhere. > Protocols: > > I don't understand whether there's any way to provide a partial > implementation or default implementation of a given > protocol/interface, and I believe this to be an important issue. I don't think that partial implementations are possible at the moment, but I agree that it would be useful. A default implementation can be provided as an implementation of Object. It's not quite the same as a default implementation for a multimethod, as it doesn't apply to types identified by a metadata type tag, but in practice it can be good enough or even better. > For example, a protocol for < and > that provides a default > implementation of > in terms of < and a default implementation of < in > terms of >, so that you only need to implement one and you get the > other for free. Right. I have such a case in my test implementation for multiarrays (soon to be put on Google Code...), where I'd want to define a default implementation for "rank" as "length of the shape vector". Konrad. -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
