Vector

(deftype Vector [meta array ^:mutable __hash]
  Object
  (toString [this]
    (pr-str this))

  IWithMeta
  (-with-meta [coll meta] (Vector. meta array __hash))

  IMeta
  (-meta [coll] meta)

  IStack
  (-peek [coll]
    (let [count (alength array)]
      (when (> count 0)
        (aget array (dec count)))))
  (-pop [coll]
    (if (> (alength array) 0)
      (let [new-array (aclone array)]
        (. new-array (pop))
        (Vector. meta new-array nil))
      (throw (js/Error. "Can't pop empty vector"))))

  ICollection
  (-conj [coll o]
    (let [new-array (aclone array)]
      (.push new-array o)
      (Vector. meta new-array nil)))

  IEmptyableCollection
  (-empty [coll] (with-meta cljs.core.Vector/EMPTY meta))

  ISequential
  IEquiv
  (-equiv [coll other] (equiv-sequential coll other))

  IHash
  (-hash [coll] (caching-hash coll hash-coll __hash))

  ISeqable
  (-seq [coll]
    (when (> (alength array) 0)
      (let [vector-seq
             (fn vector-seq [i]
               (lazy-seq
                 (when (< i (alength array))
                   (cons (aget array i) (vector-seq (inc i))))))]
        (vector-seq 0))))

  ICounted
  (-count [coll] (alength array))

  IIndexed
  (-nth [coll n]
    (if (and (<= 0 n) (< n (alength array)))
      (aget array n)
      #_(throw (js/Error. (str "No item " n " in vector of length " (alength array))))))
  (-nth [coll n not-found]
    (if (and (<= 0 n) (< n (alength array)))
      (aget array n)
      not-found))

  ILookup
  (-lookup [coll k] (-nth coll k nil))
  (-lookup [coll k not-found] (-nth coll k not-found))

  IAssociative
  (-assoc [coll k v]
    (let [new-array (aclone array)]
      (aset new-array k v)
      (Vector. meta new-array nil)))

  IVector
  (-assoc-n [coll n val] (-assoc coll n val))

  IReduce
  (-reduce [v f]
    (ci-reduce array f))
  (-reduce [v f start]
    (ci-reduce array f start))

  IFn
  (-invoke [coll k]
    (-lookup coll k))
  (-invoke [coll k not-found]
    (-lookup coll k not-found)))