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Subject: Re: [boost] [repost] Futures Review - can move_dest_type be public?
From: Anthony Williams (anthony.ajw_at_[hidden])
Date: 2009-02-10 12:22:09

"vicente.botet" <vicente.botet_at_[hidden]> 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
>> {
>> 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

Maybe a unique_future<T>::get_result_type typedef would be most


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