Data commit

Task/Queue-Definition/Clojure/queue-definition.clj

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+user=> (def empty-queue clojure.lang.PersistentQueue/EMPTY)
+#'user/empty-queue
+user=> (def aqueue (atom empty-queue))
+#'user/aqueue
+; Check if queue is empty
+user=> (empty? @aqueue)
+true
+; As with other Clojure data structures, you can add items using conj and into
+user=> (swap! aqueue conj 1)
+user=> (swap! aqueue into [2 3 4])
+user=> (pprint @aqueue)
+<-(1 2 3 4)-<
+; You can read the head of the queue with peek
+user=> (peek @aqueue)
+1
+; You can remove the head producing a new queue using pop
+user=> (pprint (pop @aqueue))
+<-(2 3 4)-<
+; pop returns a new queue, the original is still intact
+user=> (pprint @aqueue)
+<-(1 2 3 4)-<
+; you can treat a queue as a sequence
+user=> (into [] @aqueue)
+[1 2 3 4]
+; but remember that using rest or next converts the queue to a seq. Compare:
+user=> (-> @aqueue rest (conj 5) pprint)
+(5 2 3 4)
+; with:
+user=> (-> @aqueue pop (conj 5) pprint)
+<-(2 3 4 5)-<