gistfile1.clj

    (defmap AList [entries meta]
      IPersistentMap
      (count [this]
             (count entries))
      (valAt [this k not-found]
             (if-let [e (find this k)]
               (val e)
               not-found))
      (entryAt [this k]
               (first (filter #(= k (key %)) entries)))
      (empty [this]
             (AList. () meta))
      (seq [this]
           (seq entries))
      (assoc [this k v]
        (AList. (cons (MapEntry. k v) entries) meta))
      (without [this k]
               (AList. (->> entries (remove #(= k (key %)))
                            (apply list))
                       meta))

      IObj
      (meta [this]
            meta)
      (withMeta [this meta]
                (AList. entries meta)))