Type of work-stealing queue

create () returns a new empty work-stealing queue.

push t v adds v to the front of the queue q. It should only be invoked by the domain which owns the queue q.

pop q removes and returns the first element in queue q.It should only be invoked by the domain which owns the queue q.

• raises Exit

  if the queue is empty.

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

steal q removes and returns the last element from queue q. It should only be invoked by domain which doesn't own the queue q.

• raises Exit

  if the queue is empty.

steal_opt q removes and returns the last element from queue q, or returns None if the queue is empty. It should only be invoked by domain which doesn't own the queue q.