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Use an internal forward_from_tuple as the std:: one isn't constexpr in C++11 or libstdc++ 5

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Peter Dimov
2020-05-24 06:14:18 +03:00
parent 588bc4458a
commit e653eb3e8b
1 changed files with 19 additions and 13 deletions
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32
include/boost/mp11/tuple.hpp
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@@ -93,48 +93,54 @@ template<class Tp, class F> BOOST_MP11_CONSTEXPR F tuple_for_each( Tp && tp, F &
namespace detail
{
template<std::size_t J, class... Tp>
BOOST_MP11_CONSTEXPR auto tp_extract( Tp&&... tp )
-> decltype( std::forward_as_tuple( std::get<J>( std::forward<Tp>( tp ) )... ) )
// std::forward_as_tuple is not constexpr in C++11 or libstdc++ 5.x
template<class... T> BOOST_MP11_CONSTEXPR auto tp_forward_r( T&&... t ) -> std::tuple<T&&...>
{
return std::forward_as_tuple( std::get<J>( std::forward<Tp>( tp ) )... );
return std::tuple<T&&...>( std::forward<T>( t )... );
}
template<class... T> BOOST_MP11_CONSTEXPR auto tp_forward( T&&... t ) -> std::tuple<T...>
template<class... T> BOOST_MP11_CONSTEXPR auto tp_forward_v( T&&... t ) -> std::tuple<T...>
{
return std::tuple<T...>( std::forward<T>( t )... );
}
template<std::size_t J, class... Tp>
BOOST_MP11_CONSTEXPR auto tp_extract( Tp&&... tp )
-> decltype( tp_forward_r( std::get<J>( std::forward<Tp>( tp ) )... ) )
{
return tp_forward_r( std::get<J>( std::forward<Tp>( tp ) )... );
}
#if !BOOST_MP11_WORKAROUND( BOOST_MP11_MSVC, < 1900 )
template<class F, class... Tp, std::size_t... J>
BOOST_MP11_CONSTEXPR auto tuple_transform_impl( integer_sequence<std::size_t, J...>, F const& f, Tp&&... tp )
-> decltype( tp_forward( tuple_apply( f, tp_extract<J>( std::forward<Tp>(tp)... ) )... ) )
-> decltype( tp_forward_v( tuple_apply( f, tp_extract<J>( std::forward<Tp>(tp)... ) )... ) )
{
return tp_forward( tuple_apply( f, tp_extract<J>( std::forward<Tp>(tp)... ) )... );
return tp_forward_v( tuple_apply( f, tp_extract<J>( std::forward<Tp>(tp)... ) )... );
}
#else
template<class F, class Tp1, std::size_t... J>
BOOST_MP11_CONSTEXPR auto tuple_transform_impl( integer_sequence<std::size_t, J...>, F const& f, Tp1&& tp1 )
-> decltype( tp_forward( f( std::get<J>( std::forward<Tp1>(tp1) ) )... ) )
-> decltype( tp_forward_v( f( std::get<J>( std::forward<Tp1>(tp1) ) )... ) )
{
return tp_forward( f( std::get<J>( std::forward<Tp1>(tp1) ) )... );
return tp_forward_v( f( std::get<J>( std::forward<Tp1>(tp1) ) )... );
}
template<class F, class Tp1, class Tp2, std::size_t... J>
BOOST_MP11_CONSTEXPR auto tuple_transform_impl( integer_sequence<std::size_t, J...>, F const& f, Tp1&& tp1, Tp2&& tp2 )
-> decltype( tp_forward( f( std::get<J>( std::forward<Tp1>(tp1) ), std::get<J>( std::forward<Tp2>(tp2) ) )... ) )
-> decltype( tp_forward_v( f( std::get<J>( std::forward<Tp1>(tp1) ), std::get<J>( std::forward<Tp2>(tp2) ) )... ) )
{
return tp_forward( f( std::get<J>( std::forward<Tp1>(tp1) ), std::get<J>( std::forward<Tp2>(tp2) ) )... );
return tp_forward_v( f( std::get<J>( std::forward<Tp1>(tp1) ), std::get<J>( std::forward<Tp2>(tp2) ) )... );
}
template<class F, class Tp1, class Tp2, class Tp3, std::size_t... J>
BOOST_MP11_CONSTEXPR auto tuple_transform_impl( integer_sequence<std::size_t, J...>, F const& f, Tp1&& tp1, Tp2&& tp2, Tp3&& tp3 )
-> decltype( tp_forward( f( std::get<J>( std::forward<Tp1>(tp1) ), std::get<J>( std::forward<Tp2>(tp2) ), std::get<J>( std::forward<Tp3>(tp3) ) )... ) )
-> decltype( tp_forward_v( f( std::get<J>( std::forward<Tp1>(tp1) ), std::get<J>( std::forward<Tp2>(tp2) ), std::get<J>( std::forward<Tp3>(tp3) ) )... ) )
{
return tp_forward( f( std::get<J>( std::forward<Tp1>(tp1) ), std::get<J>( std::forward<Tp2>(tp2) ), std::get<J>( std::forward<Tp3>(tp3) ) )... );
return tp_forward_v( f( std::get<J>( std::forward<Tp1>(tp1) ), std::get<J>( std::forward<Tp2>(tp2) ), std::get<J>( std::forward<Tp3>(tp3) ) )... );
}
#endif // !BOOST_MP11_WORKAROUND( BOOST_MP11_MSVC, < 1900 )