temp

(declare S U V Q)
(defn S [x] ;Start Status
  (case x :a U :b V))

(defn U [x]
  (case x :a Q :b V))

(defn V [x]
  (case x :a U :b Q))

(defn Q [x] ;End Status
  Q)

(defn judge [coll]
  (loop [reading (first coll) 
         right-hand (rest coll) 
         current-status S]
    (if (empty? right-hand)
      (= current-status Q)
      (recur (first right-hand)
             (rest right-hand)
             (current-status reading)))))