Data commit

Task/Stack/Clojure/stack-1.clj

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+(deftype Stack [elements])
+
+(def stack (Stack (ref ())))
+
+(defn push-stack
+  "Pushes an item to the top of the stack."
+  [x] (dosync (alter (:elements stack) conj x)))
+
+(defn pop-stack
+  "Pops an item from the top of the stack."
+  [] (let [fst (first (deref (:elements stack)))]
+       (dosync (alter (:elements stack) rest)) fst))
+
+(defn top-stack
+  "Shows what's on the top of the stack."
+  [] (first (deref (:elements stack))))
+
+(defn empty-stack?
+  "Tests whether or not the stack is empty."
+  [] (= () (deref (:elements stack))))