nicer-ll.clj

;; Singly-Linked List
(definterface INode
  (getCar [])
  (getCdr [])
  (setCar [x])
  (setCdr [x]))

(deftype Node
  [^:volatile-mutable car ^:volatile-mutable cdr]
  INode
  (getCar [_] car)
  (getCdr [_] cdr)
  (setCar [this x] (set! car x) this)
  (setCdr [this x] (set! cdr x) this)

  clojure.lang.IPersistentCollection
  (cons [this _] this))

(definterface ILinkedList
  (getHead []))

(deftype LinkedList
  [^:volatile-mutable head]
  ILinkedList
  (getHead [_] head)

  clojure.lang.IPersistentCollection
  (cons [this x] (set! head (Node. x head)) this)

  clojure.lang.Seqable
  (seq [this]
    (loop [cur head acc ()]
      (if-not cur
        acc
        (recur (.getCdr cur)
               (concat acc (list [cur (.getCar cur) (.getCdr cur)]))))))

  clojure.lang.ISeq
  (first [_] head)
  (next [this] (drop 1 (seq this)))
  (more [this] (if-let [n (next this)] n ()))

  clojure.lang.Reversible
  (rseq [this]
    (loop [new-head nil cur head nex (.getCdr cur)]
     (if-not cur
       (do (set! head new-head) this)
       (do (.setCdr cur new-head) (recur cur nex (if nex (.getCdr nex))))))))

(defn linked-list [& [cars]]
  (let [ll (LinkedList. (Node. (first cars) nil))]
    (reduce conj ll (rest cars))))