fooling around with Clojure interfaces, part 1

type-fun.clj

(deftype Foo [x y z]
  clojure.lang.IKeywordLookup
  (getLookupThunk
   [self k]
   (reify
    clojure.lang.ILookupThunk
    (get
     [self k]
     (if-let [v (k {:x x :y y :z z})]
       (inc v)))))
  clojure.lang.IFn
  (invoke
   [self k]
   (.get (.getLookupThunk self k) k))
  clojure.lang.ILookup
  (valAt
   [self k]
   ({:x x :y y :z z} k))
  (valAt
   [self k nf]
   ({:x x :y y :z z} k nf)))