Stack implementation in Clojure using Protocols and Records

;; Stack example abstract data type using Clojure protocols and records
;; viksit at gmail dot com
;; 2010

(ns viksit.stack
  (:refer-clojure :exclude [pop]))

(defprotocol PStack
  "A stack protocol"
  (push [this val] "Push element into the stack")
  (pop [this] "Pop element from stack")
  (top [this] "Get top element from stack"))

(defrecord Stack [coll]
  PStack
  (push [_ val]
        (swap! coll conj val))
  (pop [_]
       (let [ret (first @coll)]
         (swap! coll rest)
         ret))
  (top [_]
       (first @coll)))

;; Testing
stack> (def s (Stack. (atom '())))
#'stack/s
stack> (push s 10)
(10)
stack> (push s 20)
(20 10)
stack> (top s)
20
stack> s
#:stack.Stack{:coll #<Atom@d2c9015: (20 10)>}
stack> (pop s)
20