Clojure - Match Parantheses

;; The purpose of the function is to match all unmatched parentheses in a given string
;; ") (()(" ===> "() (()())"

;; The function will loop through a given string one character at a time.
;; The count of (currently) unmatched left parentheses will be increased by one for each "(" found.
;; For each ")" found, two things might happen:
;; If there's currently any unmatched lefties, decrease the count of unmatched left parentheses by 1
;; (since we've found a matched pair)
;; Otherwise, if there's no unmatched "(", increase the count of unmatched right parenthesis by 1
;; (since the found ")" has no preceding partner)
;; Finally, add the appropriate amount of left and right parenthesis on each side of the string
;; so that every parenthesis has a matching partner in the returned result

(defn match-parantheses [the-string]
  (loop [index 0
         unmatched-left 0
         unmatched-right 0]
    (if (< index (count the-string))
      (let [char (get the-string index)]
        (cond
          (= \( char) (recur (inc index) (inc unmatched-left) unmatched-right)
          (= \) char) (if (= unmatched-left 0)
                        (recur (inc index) unmatched-left (inc unmatched-right))
                        (recur (inc index) (dec unmatched-left) unmatched-right))
          :else (recur (inc index) unmatched-left unmatched-right)))
      (str
        (apply str (repeat unmatched-right "( "))
        the-string
        (apply str (repeat unmatched-left ") "))))))