Create persistent queue

;; I found having to explicitly use clojure.lang.PersistentQueue/EMPTY ugly and
;; takes up too much real estate in a Clojure source file. I wrote this to
;; emulate the core `list' and `vector' functions.

(defn- queue
  "For any number of parameters, create a persistent queue."
  ([]
   clojure.lang.PersistentQueue/EMPTY)
  ([x]
   (conj clojure.lang.PersistentQueue/EMPTY x))
  ([x & xs]
   (into clojure.lang.PersistentQueue/EMPTY (cons x xs))))