protocol.clj

(defprotocol F
  (echo [this msg]))

(def anon (reify F (echo [this msg] (str msg " anon " this))))

(echo anon "bar")
;;=> "bar anon yetibot.core.adapters.adapter$reify__8141@6ebc46fd"

(deftype Foo [x y]
  F
  (echo [this msg] (str "Foo " msg this x y)))

(echo (->Foo 1 3) "hello?")
;;=> "Foo hello?yetibot.core.adapters.adapter.Foo@4db20e4c13"


(extend-type java.lang.String
  F
  (echo [this msg] (str "It's a String `" this "` with message: " msg)))

(echo "foo" "bar")
;;=> "It's a String `foo` with message: bar"