The type of queues containing elements of type 'a.

Raised when dequeue is applied to an empty queue.

Return a new queue, initially empty.

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

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

peek q returns the first element in queue q, or raises Empty if the queue is empty. The queue itself is unchanged.

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

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.

drop ~f q applies f in turn to all elements of q and discard all elements of q.

Return the number of elements in a queue.

to_list q returns a list of q's elements.

transfer q returns new queue in which we have added all of q's elements, then clears q. It's an atomically safe equivalent to the sequence let q' = make () in drop ~f:(fun x -> enqueue q' x) q; q'.