Re: [boost] future/packaged_task Sean Parent designn

Subject: Re: [boost] future/packaged_task Sean Parent designn
From: Giovanni Piero Deretta (gpderetta_at_[hidden])
Date: 2015-06-24 12:52:24

On 24 Jun 2015 4:48 pm, "Niall Douglas" <s_sourceforge_at_[hidden]> wrote:
>
> On 24 Jun 2015 at 16:30, Neil Groves wrote:
>
> > > There is no reason for a packaged task implementation to be more heavy
> > > weight than a promise. If the packaged task is [](T x) { return x; }
then
> > > it is also semantically equivalent to promise<T>, just in a nicer
> > > interface. Bonus points it works beautifully with ASIO without any
explicit
> > > support from ASIO itself.
> >
> > I think this is a very important point. Of course the interaction is
better
> > with most existing code bases of which ASIO is merely one (important)
> > example. It is clear that in at least some cases the packaged task
> > implementation need not add overhead. Does anyone have any examples
where
> > one needs the additional abstraction for optimal performance?
>
> Yes:
> https://boostgsoc13.github.io/boost.afio/doc/html/afio/reference/class
> es/enqueued_task_r___.html
>
> std::packaged_task has a very unhelpful design for real world
> programming. The ability to extract its its internally held promise,
> and optionally set it early within the task is exactly what
> afio::enqueued_task does.
>

A Packaged task is for all intent and purposes a promise. How exactly would
you use the underlying promise and in which scenarios?

-- gpd