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- #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
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