isopsephile

(defn pair-brackets [indexed]
  (reduce
    (fn [pairs cur]
      (condp = (cur 1)
        \[ (merge-with conj pairs {:pend (cur 0)})
        \] (merge pairs
                  {(first (pairs :pend)) (cur 0)
                   (cur 0) (first (pairs :pend))
                   :pend (pop (pairs :pend))})
        pairs))