core.clj

(defmacro proxy-meta
  "This macro emits a function that can then be called with the appropriate
args to proxy a given class, extending it to implement the `IObj' interface.
"
  [class]
  `(fn make#
     [infile# & [moremeta#]]
     (let [metadata# (merge {:filename infile#} moremeta#)]
       (proxy [~class clojure.lang.IObj] [infile#]
         (withMeta [newmeta#] (make# infile# newmeta#))
         (meta [] metadata#)))))