recursive-descent.clj

;; return one sequence from s along with the unread input
(defn read-seq [s]
  (loop [input (rest s) acc ()]
    (let [[c & more] input]
      (cond (= \) c) [(reverse acc) more]
            (= \( c) (let [[term input] (read-seq input)]
                       (recur input (cons term acc)))
            :else    (recur more (cons c acc))))))

(println (first (read-seq (vec "(ABC(DE(FGH)I)J)"))))