----- Original Message ----- From: "Anthony Williams" <anthony.ajw@gmail.com> To: <boost@lists.boost.org> Sent: Tuesday, February 10, 2009 6:22 PM Subject: Re: [boost] [repost] Futures Review - can move_dest_type be public?
"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.
This will be Ok to my needs. Thanks, Vicente