The type of queues containing elements of type 'a.

Raised when peek_exn or pop_exn is applied to an empty queue.

An empty queue.

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

Number of elements in the queue.

Push element at the end of the queue.

Push element at the front of the queue.

peek q returns the first element in the queue q, without removing it from the queue. If q is empty, it returns None.

Same as peek but it raises an exception if q is empty.

Get and remove the first element. If q is empty, it returns None.

Same as pop but it raises an exception if q is empty.

Get and remove the last element. If q is empty, it returns None.

Same as tail but it raises an exception if q is empty.

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.

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

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

Pretty-printer of t.

Human-readable pretty-printer of t.