Re: [boost] Futures Review - can move_dest_type be public?

Subject: Re: [boost] Futures Review - can move_dest_type be public?
From: vicente.botet (vicente.botet_at_[hidden])
Date: 2009-01-23 18:38:32

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.

Best,
Vicente