The Concurrency Problem in APIs

The trick is to separate the two problems. So we're no longer talking about the problem of actually modifying a collection to put another thing in it. Those are functions on values. But, but if two people do that at the same time from different threats, then you run into concurrency issues. Except that these reference types have concurity semantics. That's their job. Okay. And how does this go ahead? Go ahead.