Data commit

Task/Stack/Clojure/stack-1.clj

@@ -0,0 +1,20 @@
+(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))))

Task/Stack/Clojure/stack-2.clj

@@ -0,0 +1,14 @@
+(defprotocol StackOps
+  (push-stack [this x] "Pushes an item to the top of the stack.")
+  (pop-stack [this] "Pops an item from the top of the stack.")
+  (top-stack [this] "Shows what's on the top of the stack.")
+  (empty-stack? [this] "Tests whether or not the stack is empty."))
+(deftype Stack [elements]
+  StackOps
+   (push-stack [x] (dosync (alter elements conj x)))
+   (pop-stack [] (let [fst (first (deref elements))]
+		   (dosync (alter elements rest)) fst))
+   (top-stack [] (first (deref elements)))
+   (empty-stack? [] (= () (deref elements))))
+
+(def stack (Stack (ref ())))