"vicente.botet" <vicente.botet@wanadoo.fr> writes:
Hi,
The function get is defined in the documentation with following prototypes
R&& unique_future::get(); R& unique_future<R&>::get(); void unique_future<void>::get();
But when the move semantic is emulated this is just translated as
move_dest_type get()
with move_dest_type defined depending on the future template parameter as follows
typedef typename detail::future_traits<R>::move_dest_type move_dest_type;
template<typename T> struct future_traits { #ifdef BOOST_HAS_RVALUE_REFS typedef T const& source_reference_type; struct dummy; typedef typename boost::mpl::if_<boost::is_fundamental<T>,dummy&,T&&>::type rvalue_source_type; typedef typename boost::mpl::if_<boost::is_fundamental<T>,T,T&&>::type move_dest_type; #else typedef T& source_reference_type; typedef typename boost::mpl::if_<boost::is_convertible<T&,boost::detail::thread_move_t<T> >,boost::detail::thread_move_t<T>,T const&>::type rvalue_source_type; typedef typename boost::mpl::if_<boost::is_convertible<T&,boost::detail::thread_move_t<T> >,boost::detail::thread_move_t<T>,T>::type move_dest_type; #endif
};
Generic libraries using the futures needs to get the type returned by get. What do you think about making the move_dest_type public at least when BOOST_HAS_RVALUE_REFS is not defined? Another option would be to make public the future_traits class.
That's an interesting idea. I can see the benefit of being able to know the type of unique_future<T>::get() without having to use decltype/BOOST_TYPEOF. Maybe a unique_future<T>::get_result_type typedef would be most appropriate. Anthony -- Author of C++ Concurrency in Action | http://www.manning.com/williams just::thread C++0x thread library | http://www.stdthread.co.uk Just Software Solutions Ltd | http://www.justsoftwaresolutions.co.uk 15 Carrallack Mews, St Just, Cornwall, TR19 7UL, UK. Company No. 5478976