structure Std.Queue (α : Type u) : Type u

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.

• 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?).

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

O(1). The empty queue.

instance Std.Queue.instEmptyCollection {α : Type u} : EmptyCollection (Queue α)

instance Std.Queue.instInhabited {α : Type u} : Inhabited (Queue α)

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

O(1). Is the queue empty?

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

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

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

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

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

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

@[specialize #[]]

def Std.Queue.filterM {m : Type → Type v} [Monad m] {α : Type} (p : α → m Bool) (q : Queue α) : m (Queue α)

O(n). Applies the monadic predicate p to every element in the queue, and returns the queue of elements for which p returns true. Note that there are currently no guarantees for the order that p is applied in.