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. 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