ceph/src/boost/libs/type_traits/include/boost/type_traits/common_type.hpp

   1 #ifndef BOOST_TYPE_TRAITS_COMMON_TYPE_HPP_INCLUDED
   2 #define BOOST_TYPE_TRAITS_COMMON_TYPE_HPP_INCLUDED
   3
   4 //
   5 //  Copyright 2015 Peter Dimov
   6 //
   7 //  Distributed under the Boost Software License, Version 1.0.
   8 //  See accompanying file LICENSE_1_0.txt or copy at
   9 //  http://www.boost.org/LICENSE_1_0.txt
  10 //
  11
  12 #include <boost/config.hpp>
  13 #include <boost/type_traits/decay.hpp>
  14 #include <boost/type_traits/declval.hpp>
  15 #include <boost/detail/workaround.hpp>
  16
  17 #if defined(BOOST_NO_CXX11_DECLTYPE)
  18 #include <boost/type_traits/detail/common_type_impl.hpp>
  19 #endif
  20
  21 #if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES) && !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
  22 #include <boost/type_traits/detail/mp_defer.hpp>
  23 #endif
  24
  25 namespace boost
  26 {
  27
  28 // variadic common_type
  29
  30 #if !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
  31
  32 template<class... T> struct common_type
  33 {
  34 };
  35
  36 #if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES)
  37
  38 template<class... T> using common_type_t = typename common_type<T...>::type;
  39
  40 namespace type_traits_detail
  41 {
  42
  43 template<class T1, class T2, class... T> using common_type_fold = common_type_t<common_type_t<T1, T2>, T...>;
  44
  45 } // namespace type_traits_detail
  46
  47 template<class T1, class T2, class... T>
  48 struct common_type<T1, T2, T...>: type_traits_detail::mp_defer<type_traits_detail::common_type_fold, T1, T2, T...>
  49 {
  50 };
  51
  52 #else
  53
  54 template<class T1, class T2, class... T>
  55 struct common_type<T1, T2, T...>: common_type<typename common_type<T1, T2>::type, T...>
  56 {
  57 };
  58
  59 #endif // !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES)
  60
  61 #else
  62
  63 template<
  64     class T1 = void, class T2 = void, class T3 = void,
  65     class T4 = void, class T5 = void, class T6 = void,
  66     class T7 = void, class T8 = void, class T9 = void
  67 >
  68 struct common_type: common_type<typename common_type<T1, T2>::type, T3, T4, T5, T6, T7, T8, T9>
  69 {
  70 };
  71
  72 #endif // !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
  73
  74 // one argument
  75
  76 template<class T> struct common_type<T>: boost::decay<T>
  77 {
  78 };
  79
  80 // two arguments
  81
  82 namespace type_traits_detail
  83 {
  84
  85 // binary common_type
  86
  87 #if !defined(BOOST_NO_CXX11_DECLTYPE)
  88
  89 #if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES) && !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
  90
  91 #if !defined(BOOST_MSVC) || BOOST_MSVC > 1800
  92
  93 // internal compiler error on msvc-12.0
  94
  95 template<class T1, class T2> using builtin_common_type = typename boost::decay<decltype( boost::declval<bool>()? boost::declval<T1>(): boost::declval<T2>() )>::type;
  96
  97 template<class T1, class T2> struct common_type_impl: mp_defer<builtin_common_type, T1, T2>
  98 {
  99 };
 100
 101 #else
 102
 103 template<class T1, class T2> using builtin_common_type = decltype( boost::declval<bool>()? boost::declval<T1>(): boost::declval<T2>() );
 104
 105 template<class T1, class T2> struct common_type_impl_2: mp_defer<builtin_common_type, T1, T2>
 106 {
 107 };
 108
 109 template<class T1, class T2> using decay_common_type = typename boost::decay<typename common_type_impl_2<T1, T2>::type>::type;
 110
 111 template<class T1, class T2> struct common_type_impl: mp_defer<decay_common_type, T1, T2>
 112 {
 113 };
 114
 115 #endif // !defined(BOOST_MSVC) || BOOST_MSVC > 1800
 116
 117 #else
 118
 119 template<class T1, class T2> struct common_type_impl: boost::decay<decltype( boost::declval<bool>()? boost::declval<T1>(): boost::declval<T2>() )>
 120 {
 121 };
 122
 123 #endif // #if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES) && !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
 124
 125 #endif // #if !defined(BOOST_NO_CXX11_DECLTYPE)
 126
 127 // decay helper
 128
 129 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>
 130 {
 131 };
 132
 133 template<class T1, class T2> struct common_type_decay_helper<T1, T2, T1, T2>: common_type_impl<T1, T2>
 134 {
 135 };
 136
 137 } // type_traits_detail
 138
 139 template<class T1, class T2> struct common_type<T1, T2>: type_traits_detail::common_type_decay_helper<T1, T2>
 140 {
 141 };
 142
 143 } // namespace boost
 144
 145 #endif // #ifndef BOOST_TYPE_TRAITS_COMMON_TYPE_HPP_INCLUDED