structure Std.Queue (α : Type u) :
  • eList : List α

    The enqueue list, which stores elements that have just been pushed (with the most recently enqueued elements at the head).

  • dList : List α

    The dequeue list, which buffers elements ready to be dequeued (with the head being the next item to be yielded by dequeue?).

A functional queue data structure, using two back-to-back lists. If we think of the queue as having elements pushed on the front and popped from the back, then the queue itself is effectively eList ++ dList.reverse.

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    def Std.Queue.empty {α : Type u} :

    O(1). The empty queue.

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      def Std.Queue.isEmpty {α : Type u} (q : Std.Queue α) :

      O(1). Is the queue empty?

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        def Std.Queue.enqueue {α : Type u} (v : α) (q : Std.Queue α) :

        O(1). Push an element on the front of the queue.

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          def Std.Queue.enqueueAll {α : Type u} (vs : List α) (q : Std.Queue α) :

          O(|vs|). Push a list of elements vs on the front of the queue.

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            def Std.Queue.dequeue? {α : Type u} (q : Std.Queue α) :

            O(1) amortized, O(n) worst case. Pop an element from the back of the queue, returning the element and the new queue.

            Instances For
              def Std.Queue.toArray {α : Type u} (q : Std.Queue α) :
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