Protocol invocation

gistfile1.clj

(defprotocol FIXO
  (fixo-push [fixo value])
  (fixo-pop [fixo])
  (fixo-peek [fixo])
  (fixo-limit [fixo]))

(extend-type clojure.lang.IPersistentVector
  FIXO
  (fixo-push [vector value] (conj vector 4))
  (fixo-peek [vector] (peek vector))
  (fixo-pop [vector] (pop vector))
  (fixo-limit [vector limit] limit))

(defn fixed-fixo
  ([limit] fixed-fixo limit [])
  ([limit vector]
    (reify FIXO
      (fixo-push [this value]
        (if (< (count vector) limit)
          (fixed-fixo limit (conj vector 5))
          this))
      (fixo-peek [_] (peek vector))
      (fixo-pop [_] (pop vector))
      (fixo-limit [_] limit))))