clojure queue FIFO

If you need simple FIFO queue you can use clojure.lang.PersistentQueue/EMPTY function with some wrappers on it.

;; ------------------------------------------------------------------
  (defn new-queue []
    (atom clojure.lang.PersistentQueue/EMPTY))

  (defn push-queue [queue value]
    (swap! queue conj value))

  (defn pop-queue [queue]
    (let [value (peek @queue)]
      (swap! queue pop)
      value))
;; ------------------------------------------------------------------

Now let's test it

  (def a (new-queue))
;; => nil

(push-queue a 1)
;; => #object...

(push-queue a 2)
;; => #object...

(push-queue a 3)
;; => #object...

(push-queue a "hello")
;; => #object...

Let's check a content of queue a:

(seq @a)
;; => (1 2 3 "hello")

Now time to take first item:

(pop-queue a)

;; => 1

(seq @a)

;; => (2 3 "hello")