brainfuck interpreter in Clojure, transient vector version

bf2.clj

(defn brainfuck2 [s]
  (let [c (transient (vec (repeat 30000 (byte 0))))]
    (letfn [(fmb [[t p] f ip]           ; find matching bracket
              ((fn [ip n]
                 (condp = (nth s ip)
                   t (if (= n 0) ip (recur (f ip) (dec n)))
                   p (recur (f ip) (inc n))
                   (recur (f ip) n)))
               ip 0))]
      ((fn [dp ip]
         (if (< ip (count s))
           (let [[dp ip]
                 (condp = (nth s ip)
                   \< [(dec dp) ip]
                   \> [(inc dp) ip]
                   \+ (do (assoc! c dp (inc (c dp))) [dp ip])
                   \- (do (assoc! c dp (dec (c dp))) [dp ip])
                   \. (do (print (char (c dp))) [dp ip])
                   \, (do (assoc! c dp (byte (. System/in read))) [dp ip])
                   \[ (if (= (c dp) 0) [dp (fmb "][" inc ip)] [dp ip])
                   \] (if (= (c dp) 0) [dp ip] [dp (fmb "[]" dec (dec ip))])
                   [dp ip])]
             (recur dp (inc ip)))))
       0 0))))