1/*!
2@file
3Defines `boost::hana::pair`.
4
5Copyright Louis Dionne 2013-2022
6Distributed under the Boost Software License, Version 1.0.
7(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
8 */
9
10#ifndef BOOST_HANA_PAIR_HPP
11#define BOOST_HANA_PAIR_HPP
12
13#include <boost/hana/fwd/pair.hpp>
14
15#include <boost/hana/config.hpp>
16#include <boost/hana/detail/decay.hpp>
17#include <boost/hana/detail/ebo.hpp>
18#include <boost/hana/detail/intrinsics.hpp>
19#include <boost/hana/detail/operators/adl.hpp>
20#include <boost/hana/detail/operators/comparable.hpp>
21#include <boost/hana/detail/operators/orderable.hpp>
22#include <boost/hana/fwd/core/make.hpp>
23#include <boost/hana/fwd/first.hpp>
24#include <boost/hana/fwd/second.hpp>
25
26#include <type_traits>
27#include <utility>
28
29
30namespace boost { namespace hana {
31 namespace detail {
32 template <int> struct pix; // pair index
33 }
34
35 //////////////////////////////////////////////////////////////////////////
36 // pair
37 //////////////////////////////////////////////////////////////////////////
38 //! @cond
39 template <typename First, typename Second>
40#ifdef BOOST_HANA_WORKAROUND_MSVC_EMPTYBASE
41 struct __declspec(empty_bases) pair : detail::operators::adl<pair<First, Second>>
42#else
43 struct pair : detail::operators::adl<pair<First, Second>>
44#endif
45 , private detail::ebo<detail::pix<0>, First>
46 , private detail::ebo<detail::pix<1>, Second>
47 {
48 // Default constructor
49 template <typename ...dummy, typename = typename std::enable_if<
50 BOOST_HANA_TT_IS_CONSTRUCTIBLE(First, dummy...) &&
51 BOOST_HANA_TT_IS_CONSTRUCTIBLE(Second, dummy...)
52 >::type>
53 constexpr pair()
54 : detail::ebo<detail::pix<0>, First>()
55 , detail::ebo<detail::pix<1>, Second>()
56 { }
57
58 // Variadic constructors
59 template <typename ...dummy, typename = typename std::enable_if<
60 BOOST_HANA_TT_IS_CONSTRUCTIBLE(First, First const&, dummy...) &&
61 BOOST_HANA_TT_IS_CONSTRUCTIBLE(Second, Second const&, dummy...)
62 >::type>
63 constexpr pair(First const& fst, Second const& snd)
64 : detail::ebo<detail::pix<0>, First>(fst)
65 , detail::ebo<detail::pix<1>, Second>(snd)
66 { }
67
68 template <typename T, typename U, typename = typename std::enable_if<
69 BOOST_HANA_TT_IS_CONVERTIBLE(T&&, First) &&
70 BOOST_HANA_TT_IS_CONVERTIBLE(U&&, Second)
71 >::type>
72 constexpr pair(T&& t, U&& u)
73 : detail::ebo<detail::pix<0>, First>(static_cast<T&&>(t))
74 , detail::ebo<detail::pix<1>, Second>(static_cast<U&&>(u))
75 { }
76
77
78 // Possibly converting copy and move constructors
79 template <typename T, typename U, typename = typename std::enable_if<
80 BOOST_HANA_TT_IS_CONSTRUCTIBLE(First, T const&) &&
81 BOOST_HANA_TT_IS_CONSTRUCTIBLE(Second, U const&) &&
82 BOOST_HANA_TT_IS_CONVERTIBLE(T const&, First) &&
83 BOOST_HANA_TT_IS_CONVERTIBLE(U const&, Second)
84 >::type>
85 constexpr pair(pair<T, U> const& other)
86 : detail::ebo<detail::pix<0>, First>(hana::first(other))
87 , detail::ebo<detail::pix<1>, Second>(hana::second(other))
88 { }
89
90 template <typename T, typename U, typename = typename std::enable_if<
91 BOOST_HANA_TT_IS_CONSTRUCTIBLE(First, T&&) &&
92 BOOST_HANA_TT_IS_CONSTRUCTIBLE(Second, U&&) &&
93 BOOST_HANA_TT_IS_CONVERTIBLE(T&&, First) &&
94 BOOST_HANA_TT_IS_CONVERTIBLE(U&&, Second)
95 >::type>
96 constexpr pair(pair<T, U>&& other)
97 : detail::ebo<detail::pix<0>, First>(hana::first(static_cast<pair<T, U>&&>(other)))
98 , detail::ebo<detail::pix<1>, Second>(hana::second(static_cast<pair<T, U>&&>(other)))
99 { }
100
101
102 // Copy and move assignment
103 template <typename T, typename U, typename = typename std::enable_if<
104 BOOST_HANA_TT_IS_ASSIGNABLE(First&, T const&) &&
105 BOOST_HANA_TT_IS_ASSIGNABLE(Second&, U const&)
106 >::type>
107 constexpr pair& operator=(pair<T, U> const& other) {
108 hana::first(*this) = hana::first(other);
109 hana::second(*this) = hana::second(other);
110 return *this;
111 }
112
113 template <typename T, typename U, typename = typename std::enable_if<
114 BOOST_HANA_TT_IS_ASSIGNABLE(First&, T&&) &&
115 BOOST_HANA_TT_IS_ASSIGNABLE(Second&, U&&)
116 >::type>
117 constexpr pair& operator=(pair<T, U>&& other) {
118 hana::first(*this) = hana::first(static_cast<pair<T, U>&&>(other));
119 hana::second(*this) = hana::second(static_cast<pair<T, U>&&>(other));
120 return *this;
121 }
122
123 // Prevent the compiler from defining the default copy and move
124 // constructors, which interfere with the SFINAE above.
125 ~pair() = default;
126
127 friend struct first_impl<pair_tag>;
128 friend struct second_impl<pair_tag>;
129 template <typename F, typename S> friend struct pair;
130 };
131 //! @endcond
132
133 template <typename First, typename Second>
134 struct tag_of<pair<First, Second>> {
135 using type = pair_tag;
136 };
137
138 //////////////////////////////////////////////////////////////////////////
139 // Operators
140 //////////////////////////////////////////////////////////////////////////
141 namespace detail {
142 template <>
143 struct comparable_operators<pair_tag> {
144 static constexpr bool value = true;
145 };
146 template <>
147 struct orderable_operators<pair_tag> {
148 static constexpr bool value = true;
149 };
150 }
151
152 //////////////////////////////////////////////////////////////////////////
153 // Product
154 //////////////////////////////////////////////////////////////////////////
155 template <>
156 struct make_impl<pair_tag> {
157 template <typename F, typename S>
158 static constexpr pair<
159 typename detail::decay<F>::type,
160 typename detail::decay<S>::type
161 > apply(F&& f, S&& s) {
162 return {static_cast<F&&>(f), static_cast<S&&>(s)};
163 }
164 };
165
166 template <>
167 struct first_impl<pair_tag> {
168 template <typename First, typename Second>
169 static constexpr decltype(auto) apply(hana::pair<First, Second>& p) {
170 return detail::ebo_get<detail::pix<0>>(
171 static_cast<detail::ebo<detail::pix<0>, First>&>(p)
172 );
173 }
174 template <typename First, typename Second>
175 static constexpr decltype(auto) apply(hana::pair<First, Second> const& p) {
176 return detail::ebo_get<detail::pix<0>>(
177 static_cast<detail::ebo<detail::pix<0>, First> const&>(p)
178 );
179 }
180 template <typename First, typename Second>
181 static constexpr decltype(auto) apply(hana::pair<First, Second>&& p) {
182 return detail::ebo_get<detail::pix<0>>(
183 static_cast<detail::ebo<detail::pix<0>, First>&&>(p)
184 );
185 }
186 };
187
188 template <>
189 struct second_impl<pair_tag> {
190 template <typename First, typename Second>
191 static constexpr decltype(auto) apply(hana::pair<First, Second>& p) {
192 return detail::ebo_get<detail::pix<1>>(
193 static_cast<detail::ebo<detail::pix<1>, Second>&>(p)
194 );
195 }
196 template <typename First, typename Second>
197 static constexpr decltype(auto) apply(hana::pair<First, Second> const& p) {
198 return detail::ebo_get<detail::pix<1>>(
199 static_cast<detail::ebo<detail::pix<1>, Second> const&>(p)
200 );
201 }
202 template <typename First, typename Second>
203 static constexpr decltype(auto) apply(hana::pair<First, Second>&& p) {
204 return detail::ebo_get<detail::pix<1>>(
205 static_cast<detail::ebo<detail::pix<1>, Second>&&>(p)
206 );
207 }
208 };
209}} // end namespace boost::hana
210
211#endif // !BOOST_HANA_PAIR_HPP
212

source code of boost/libs/hana/include/boost/hana/pair.hpp