Re: [boost] Re view Request: future library (N2561/Williams version)

From: Frank Mori Hess (frank.hess_at_[hidden])
Date: 2008-05-23 12:01:26

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On Friday 23 May 2008 10:50 am, Johan Torp wrote:
> Frank Mori Hess wrote:
> > How about an additional future_select overload which accepts two
> > boost::shared_container_iterators as arguments, and returns a
> > future<shared_container_iterator>?  The returned iterator would point at
> > the
> > future which is ready or has an exception.  Then the caller could use the
> > returned iterator to erase the element from the container before calling
> > future_select again.  The shared_container_iterator would insure the
> > input container of futures doesn't die before the return future becomes
> > ready.
>
> That would restrict users to put their futures in a container created as a
> shared_ptr, right? 

Yes, but the shared_container_iterator isn't really necessary, I could make 
future_select return a future<Iterator> for any type of iterator input.  I 
was just trying to make it safer.  Unfortunately, even using 
shared_container_iterator still wouldn't prevent the user from modifying the 
container so as to invalidate the returned future iterator anyways.  Maybe 
I'll just suggest using shared_container_iterator in the docs.

> Yes, I'm thinking of a passive function which doesn't have an internal
> thread associated with it. One that is evaluated lazily as soon as someone
> is interested in it.
>
> I think this could be very useful, do you? 

I don't know, it might be.  I've never tried to program something using a lot 
of nested lazy evaluation.  Could you use boost::bind to achieve the same 
effect?  Doesn't it do something like this by default if you do a recursive 
bind of a function to a parameter, and don't wrap the function in 
boost::protect()?
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