Re: [boost] [future] Early draft of wait for multiple futures interface

From: Peter Dimov (pdimov_at_[hidden])
Date: 2008-05-30 10:25:01

Johan Torp:

> is_ready doesn't trigger the callback, so this won't work.
>
> OTOH, I think is_ready should trigger the callback, even for the "run 
> extra
> work in wait()" thread pool use case.

ready() should trigger a separate "ready callback", since its semantics are 
not the same.

(f1 || f2).ready :- f1.ready || f2.ready
(f1 || f2).wait :- wait_for_any(f1, f2)

(Ignoring the problem in which f1 completes with an exception and f2 is 
still active.)

Java futures don't have this callback proliferation problem because they are 
abstract.

class future
{
public:

    virtual void wait() = 0;
    virtual bool ready() = 0;
};

but we'd rather like to pass and return futures by value. :-)