On Sat, Oct 29, 2011 at 7:02 AM, David McNeil <mcneil.da...@gmail.com> wrote: > A couple of more thoughts on this. > > On Oct 28, 12:46 pm, Howard Lewis Ship <hls...@gmail.com> wrote: >> (extend-type cascade.Asset >> ToAttributeValueString >> (to-attribute-value-string [asset] (:client-url asset))) > > The reason this is probably not what you really want is that the set > of types which satisfy the Asset protocol is a superset of the set of > types which satisfy the cascade.Asset interface. This is certainly not > immediately obvious, but one way to understand it is that if you > extend a built-in Java type to implement your protocol, it does not > change the underlying type to implement the protocol's interface. > Rather it provides machinery in the protocol itself that knows how to > use the built-in Java type to satisfy the protocol. > >> I don't think it is useful to try and think of this as interface >> inheritance because it is not the same as interface inheritance in >> Java. > > I wasn't used to thinking of it as inheritance, but after thinking > about it more it seems like "inheritance" is a reasonable way to think > of it. Adapting protocol A to protocol B is like saying that all types > satisfying protocol B can also be used as if they satisfy protocol A > and furthermore there is a default implementation (that can be over- > ridden) of protocol A for them.
And then, before you know it, you've created Haskell type classes. > > -David > > -- > 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 -- Howard M. Lewis Ship Creator of Apache Tapestry The source for Tapestry training, mentoring and support. Contact me to learn how I can get you up and productive in Tapestry fast! (971) 678-5210 http://howardlewisship.com -- 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
