Post

(defn try-change [i w [u v]]
  (loop [w w, u u]
    (let [[hw tw] ((juxt peek pop) w)
          [hu tu] ((juxt first rest) u)]
      (cond (nil? hu) [(inc i) (reduce conj w v)]
            (nil? hw) nil
            (= hw hu) (recur tw tu)
            :else     nil))))

(defn new-word [system i word]
  (first (keep (partial try-change i word) system)))

(defn run [path word]
  (let [system (read-psy path)]
    (as-> word $
      (vector 0 (reduce conj clojure.lang.PersistentQueue/EMPTY $))
      (iterate (fn [[i w]] (new-word system i w)) $)
      (take-while identity $)
      ((fn [ws] [(take 1000 ws) (last ws)]) $)
      ((fn [[ws [i w]]] [ws i (apply str w)]) $))))

(defn try-change* [w [u v]]
  (loop [w w, u u]
    (let [[hw tw] ((juxt peek pop) w)
          [hu tu] ((juxt first rest) u)]
      (cond (nil? hu) (reduce conj w v)
            (nil? hw) nil
            (= hw hu) (recur tw tu)
            :else     nil))))

(defn new-word* [system word]
  (first (keep (partial try-change* word) system)))

(defn run* [system word]
  (let [system' (read-psy system)
        w'      (reduce conj clojure.lang.PersistentQueue/EMPTY word)]
    (loop [w w', ws [], n 1000, i 0]
      (let [nw  (new-word* system' w)
            nws (if (> n 0) (conj ws (str i ": " (apply str w))) ws)]
        (if (nil? nw)
          [nws (dec i) (apply str w)]
          (recur nw nws (dec n) (inc i)))))))