The type of queues containing elements of type 'a.

Raised when Queue.take or Queue.peek is applied to an empty queue.

Return a new queue, initially empty.

add x q adds the element x at the end of the queue q.

push is a synonym for add.

take q removes and returns the first element in queue q, or raises Empty if the queue is empty.

take_opt q removes and returns the first element in queue q, or returns None if the queue is empty.

• since 4.08

pop is a synonym for take.

peek q returns the first element in queue q, without removing it from the queue, or raises Empty if the queue is empty.

peek_opt q returns the first element in queue q, without removing it from the queue, or returns None if the queue is empty.

• since 4.08

top is a synonym for peek.

Discard all elements from a queue.

Return a copy of the given queue.

Return true if the given queue is empty, false otherwise.

Return the number of elements in a queue.

iter f q applies f in turn to all elements of q, from the least recently entered to the most recently entered. The queue itself is unchanged.

fold f accu q is equivalent to List.fold_left f accu l, where l is the list of q's elements. The queue remains unchanged.

transfer q1 q2 adds all of q1's elements at the end of the queue q2, then clears q1. It is equivalent to the sequence iter (fun x -> add x q2) q1; clear q1, but runs in constant time.

Iterate on the queue, in front-to-back order. The behavior is not specified if the queue is modified during the iteration.

• since 4.07

Add the elements from a sequence to the end of the queue.

• since 4.07

Create a queue from a sequence.

• since 4.07