On Thu, Jun 27, 2013 at 9:01 PM, Vicente J. Botet Escriba <vicente.botet@wanadoo.fr> wrote:

I guess you need to call fut.then() before the value is set. I will need to check if this works when the future is not created with async().

If the callback isn't called when set using then() if the value is already acquired, I don't see the point of then().

Between the time you retrieve a future from any function returning it and the time you call then(), the value could have been set.

So I expect ft.then( task ) to call immediately task if the value have already been set.

"- If the parent was created with promise<< or with a packaged_task<> (has no associated launch policy), the continuation behaves the same as the third overload with a policy argument of launch::async | launch::deferred and the same argument for func.
"

Or maybe I didn't understood correctly what you meant?

On a related topic: I just upgraded to the latest SVN and forced Boost to use decltype as result_of, which fixed a problem already mentionned.

Just in case it is not already known:

1.

   ft.then( []( future<T> f ) { return 42; } ); 

This will not compile (VS2012U3) because there is an attempt to copy future<T> (which looks like a bug I reported where returning a future would

trigger copy instead of moving the future, bug fixed since then so I'm a bit surprise about this one)

2. 

  ft.then( []( future<T>& f ) { return 42; } );

This trigger the following warning:

1>e:\projects\sdk\boost\boost\include\boost-1_54\boost\thread\future.hpp(3956): warning C4715: 'boost::future<aosd::backend::Id<aosd::backend::Project> >::then<<lambda_f0fec0502a034b6d05aaa9610f9b705e> >' : not all control paths return a value

Indeed the then() implementation have a series of if-else ending with an else with assert false forced.

The compiler can't catch the assertion I suppose something have to be written there after the assertion

to silence the warning.