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From: Peter Dimov (pdimov_at_[hidden])
Date: 2008-04-11 10:36:43

Braddock Gaskill:

>> pair<promise,future> pc = create_channel();
> The thought crossed my mind, but there are too many places in real-world
> usage (I've had a lot now) where I find I want to get a future from a
> promise. I think it might be awkward to store both, and defeats the
> intention of automatic cancelation.

Can you please go into more detail?

It seems to me that if you need to create futures on demand, then the
non-automatic cancelation should not be used. If some future holder calls
cancel, later futures created by this promise will not work. I can't think
of a situation where this would be desirable.

Storing a future in addition to the promise does disable the implicit
cancelation - by design; presumably if you need the capability to create
more futures at some later point, you don't want the task canceled in the
meantime. And if you don't mind the task being canceled since you no longer
need to create futures, you just reset() your local future copy.

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