Add this item to the queue q.

Return the count of items currently in the queue q.

Lock the queue q.

True if this queue q is locked, else false.

Apply this process, assumed to be a function of one argument, to the next item in the queue q, if the queue is not currently locked; return the value returned by process.

Create a new queue

Look at the next item which could be removed from the queue q.

True if x is a queue, else false.

Return the first item from the queue q, rebind the queue to the remaining items. If the queue is empty return nil.

Unlock the queue q if not value is supplied; if a value is supplied, unlock only if that value is true, otherwise lock.