Clojure Zipper Lazy Visitors

zip_visitors.clj

(require 'clojure.zip :as zip)

;;; see also
;;; https://gist.github.com/luxbock/4a4cafdcf2522ede6575
;;; http://stackoverflow.com/a/11426326

(defn depth-first [loc]
  (take-while (complement zip/end?) (iterate zip/next loc)))

;;; (peek PQueue) -> head
;;; (pop PQueue) -> but head
;;; (conj PQueue x) -> append

(defn- zip-children [loc]
  (when-let [child (zip/down loc)]
    (take-while (complement nil?) (iterate zip/right child))))

(defn breadth-first [loc]
  ((fn bfs [queue]
     (lazy-seq
      (when (seq queue)
        (let [new-loc  (peek queue)
              children (zip-children new-loc)]
          (cons new-loc (bfs (into (pop queue) children)))))))
   (conj clojure.lang.PersistentQueue/EMPTY loc)))