queue

Queue[A, E]: an async queue fibers can share.

Capacity and overflow behavior are fixed at creation:

• "suspend" (default): offer waits while the queue is full. Capacity 0 is a rendezvous: an offer completes when a taker takes it.
• "dropping": offer on a full queue drops the new item.
• "sliding": offer on a full queue drops the oldest item. As in Effect, sliding(0) keeps the newest offered item, while offer_all to it keeps nothing.

A queue can be finished. After fail(error) (or interrupt()), new offers return False, but takers still drain the items and the offers that were already waiting, and then fail with error. A queue that should be endable declares it in its type, Queue[int, Done]; only then do end() and into(eff) type-check, takers fail with Done() once it drains, and collect / clear / await_done take Done out of the error type. shutdown() drops everything at once: items are cleared, waiting offers return False and takers are interrupted.

Enqueue and Dequeue are the write-only and read-only views of a queue, for passing it to code that only offers or only takes.

The unsafe_* methods act at once, outside an effect; call them on the scheduler thread of the fibers that use the queue.

Classes#