| #ifndef BOOST_TYPE_TRAITS_COMMON_TYPE_HPP_INCLUDED |
| #define BOOST_TYPE_TRAITS_COMMON_TYPE_HPP_INCLUDED |
| |
| // |
| // Copyright 2015 Peter Dimov |
| // |
| // Distributed under the Boost Software License, Version 1.0. |
| // See accompanying file LICENSE_1_0.txt or copy at |
| // http://www.boost.org/LICENSE_1_0.txt |
| // |
| |
| #include <boost/config.hpp> |
| #include <boost/type_traits/decay.hpp> |
| #include <boost/type_traits/declval.hpp> |
| #include <boost/detail/workaround.hpp> |
| #include <boost/type_traits/is_complete.hpp> |
| #include <boost/type_traits/is_void.hpp> |
| #include <boost/type_traits/is_array.hpp> |
| #include <boost/static_assert.hpp> |
| |
| #if defined(BOOST_NO_CXX11_DECLTYPE) |
| #include <boost/type_traits/detail/common_type_impl.hpp> |
| #endif |
| |
| #if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES) && !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) |
| #include <boost/type_traits/detail/mp_defer.hpp> |
| #endif |
| |
| namespace boost |
| { |
| |
| // variadic common_type |
| |
| #if !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) |
| |
| template<class... T> struct common_type |
| { |
| }; |
| |
| #if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES) |
| |
| template<class... T> using common_type_t = typename common_type<T...>::type; |
| |
| namespace type_traits_detail |
| { |
| |
| template<class T1, class T2, class... T> using common_type_fold = common_type_t<common_type_t<T1, T2>, T...>; |
| |
| } // namespace type_traits_detail |
| |
| template<class T1, class T2, class... T> |
| struct common_type<T1, T2, T...>: type_traits_detail::mp_defer<type_traits_detail::common_type_fold, T1, T2, T...> |
| { |
| }; |
| |
| #else |
| |
| template<class T1, class T2, class... T> |
| struct common_type<T1, T2, T...>: common_type<typename common_type<T1, T2>::type, T...> |
| { |
| }; |
| |
| #endif // !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES) |
| |
| #else |
| |
| template< |
| class T1 = void, class T2 = void, class T3 = void, |
| class T4 = void, class T5 = void, class T6 = void, |
| class T7 = void, class T8 = void, class T9 = void |
| > |
| struct common_type: common_type<typename common_type<T1, T2>::type, T3, T4, T5, T6, T7, T8, T9> |
| { |
| }; |
| |
| #endif // !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) |
| |
| // one argument |
| |
| template<class T> struct common_type<T>: boost::decay<T> |
| { |
| BOOST_STATIC_ASSERT_MSG(::boost::is_complete<T>::value || ::boost::is_void<T>::value || ::boost::is_array<T>::value, "Arguments to common_type must both be complete types"); |
| }; |
| |
| // two arguments |
| |
| namespace type_traits_detail |
| { |
| |
| // binary common_type |
| |
| #if !defined(BOOST_NO_CXX11_DECLTYPE) |
| |
| #if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES) && !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) |
| |
| #if !defined(BOOST_MSVC) || BOOST_MSVC > 1800 |
| |
| // internal compiler error on msvc-12.0 |
| |
| template<class T1, class T2> using builtin_common_type = typename boost::decay<decltype( boost::declval<bool>()? boost::declval<T1>(): boost::declval<T2>() )>::type; |
| |
| template<class T1, class T2> struct common_type_impl: mp_defer<builtin_common_type, T1, T2> |
| { |
| }; |
| |
| #else |
| |
| template<class T1, class T2> using builtin_common_type = decltype( boost::declval<bool>()? boost::declval<T1>(): boost::declval<T2>() ); |
| |
| template<class T1, class T2> struct common_type_impl_2: mp_defer<builtin_common_type, T1, T2> |
| { |
| }; |
| |
| template<class T1, class T2> using decay_common_type = typename boost::decay<typename common_type_impl_2<T1, T2>::type>::type; |
| |
| template<class T1, class T2> struct common_type_impl: mp_defer<decay_common_type, T1, T2> |
| { |
| }; |
| |
| #endif // !defined(BOOST_MSVC) || BOOST_MSVC > 1800 |
| |
| #else |
| |
| template<class T1, class T2> struct common_type_impl: boost::decay<decltype( boost::declval<bool>()? boost::declval<T1>(): boost::declval<T2>() )> |
| { |
| }; |
| |
| #endif // #if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES) && !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) |
| |
| #endif // #if !defined(BOOST_NO_CXX11_DECLTYPE) |
| |
| // decay helper |
| |
| template<class T1, class T2, class T1d = typename boost::decay<T1>::type, class T2d = typename boost::decay<T2>::type> struct common_type_decay_helper: boost::common_type<T1d, T2d> |
| { |
| }; |
| |
| template<class T1, class T2> struct common_type_decay_helper<T1, T2, T1, T2>: common_type_impl<T1, T2> |
| { |
| }; |
| |
| } // type_traits_detail |
| |
| template<class T1, class T2> struct common_type<T1, T2>: type_traits_detail::common_type_decay_helper<T1, T2> |
| { |
| BOOST_STATIC_ASSERT_MSG(::boost::is_complete<T1>::value || ::boost::is_void<T1>::value || ::boost::is_array<T1>::value, "Arguments to common_type must both be complete types"); |
| BOOST_STATIC_ASSERT_MSG(::boost::is_complete<T2>::value || ::boost::is_void<T2>::value || ::boost::is_array<T2>::value, "Arguments to common_type must both be complete types"); |
| }; |
| |
| } // namespace boost |
| |
| #endif // #ifndef BOOST_TYPE_TRAITS_COMMON_TYPE_HPP_INCLUDED |