I feel like I've seen an answer to this before, but I can't find the specific thread now. However, the following two threads seem to have very closely related info (including a reply or two from Rich).
http://groups.google.com/group/clojure/browse_thread/thread/a5e0ba6480d04829/e8e2a14c77f5babf?hl=en&lnk=gst&q=struct#e8e2a14c77f5babf http://groups.google.com/group/clojure/browse_thread/thread/74d430f8e4353725/cc8ad0b22adf60cc?hl=en&lnk=gst&q=struct#cc8ad0b22adf60cc -Jason On Jan 21, 10:48 pm, Mark Engelberg <mark.engelb...@gmail.com> wrote: > Is there any way to determine whether something is a "struct" (versus > an ordinary hash map), and if so, determine which kind of struct it > was built from? > > For example, in Scheme, consider (define-struct circle (x y radius)), > you get a circle? predicate for free that knows how to distinguish > between circle structs and other kinds of structs. Anything like that > in Clojure? If not, how do you discriminate between various structs > in multimethods? > > In the docs for multimethods, the circle/rect example is given, and > I'm imagining it would be nice to be able to write the example like > this: > ; rather than making special constructors, let's just use structs > (defstruct rect :wd :ht) > (defstruct circle :radius) > > (defmulti area :struct) ;let's pretend structs tag their structs with > some :struct keyword that gives you the struct used to build it. > (defmethod area rect [r] > (* (:wd r) (:ht r))) > (defmethod area circle [c] > (* (. Math PI) (* (:radius c) (:radius c)))) > (defmethod area :default [x] :oops) > (def r (struct rect 4 13)) > (def c (struct circle 12)) > > Any way to make this approach work? --~--~---------~--~----~------------~-------~--~----~ 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 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 -~----------~----~----~----~------~----~------~--~---
