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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 |