gistfile1.clj

(defn- with-index
  "Maps a token's sequential position to its 
   entry."
  [{:keys [count] :as accum} x]
  (-> accum
      (update-in [:by-index] assoc (inc count) x)
      (update-in [:count] inc)))

(defn- with-key
  "Maps a token's normalized string-based key
   to its entry."
  [accum {:keys [token] :as x}]
  (let [key (lower-case token)]
    (update-in accum [:by-key] assoc key x)))

(defn- index
  "Indexes tokens by their sequential position
   (:by-index) and their normalized string key
   (:by-key)."
  [xs]
  (reduce (fn [accum x]
            (-> accum
             (with-index x)
             (with-key   x)))
          {:count    0
           :by-index {}
           :by-key   {}}
          xs))