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 |
146 | |