stack.clj

(ns algo.stack)

(defn make-stack [] {:first nil})

(defn is-empty? [stack] (nil? (:first stack)))

(defn stack-push [stack item]
  (let [previous (:first stack)]
    {:first
     {:item item :next previous}}))

(defn stack-pop [stack]
  (:next (:first stack)))

(defn stack-popped [stack]
  (:item (:first stack)))