[cpp-threads] Asynchronous Function Proposal

[Peter Dimov]

Beman Dawes:
> As Herb pointed out, this makes it look like we have serious problems with 
> the current future interface and/or the current thread interface. I very 
> much want to hear what Howard, Anthony, and others with a deep 
> understanding of standard library threads/futures/promises have to say 
> about these issues.

I've pointed out many times that the thread class needs "proper" join 
semantics, including try_join and timed_join.

> I also share Herb's concern about the apparent complexity of an eight 
> function interface. We can do better than that!

This is an implementation detail. It's possible to collapse the eight 
functions into two by using

concept AsyncPolicy<typename T> {};

async( F&& f, Args&&... args );
async( AsyncPolicy policy, F&& f, Args&&... args );