checks if a given code snippet parentheses are balanced

src.balanced-check.clj

(ns balance-check.core)

(defn balanced? [s]
  (-> (reduce (fn [[h & r :as stack] c] 
                (case c
                  \( (conj stack 42)
                  \) (if (= h 42) 
                       r 
                       (conj stack "unbalanced"))
                  stack)) 
              '() s)
      empty?))

test.balanced-check.clj

(ns balance-check.test.core
  (:use [balance-check.core]
        [clojure.test]))

(deftest check-balanced
  (is (balanced? "()"))
  (is (balanced? "(a)"))
  (is (balanced? "((a))"))
  (is (balanced? "((a)(b))"))
  (is (balanced? "(((a)(b)c))"))
  (is (balanced? "(a (b (c d k (m)) v))")))

(deftest check-unbalanced
  (is (not (balanced? ")(")))
  (is (not (balanced? "()(")))
  (is (not (balanced? ")())")))
  (is (not (balanced? "(()(")))
  (is (not (balanced? "(a (b (c d k (m) v))")))
  (is (not (balanced? ")(a (b (c d k (m) v))")))
  (is (not (balanced? "(a (b (c d( k (m) v)((()")))
  (is (not (balanced? "(a (b (c d( k (m) v)(((")))
  (is (not (balanced? "(a (b) (c d k (m) )))v))"))))