3 Defines function-like equivalents to the standard `<type_traits>`, and also
4 to some utilities like `std::declval`.
6 @copyright Louis Dionne 2013-2017
7 Distributed under the Boost Software License, Version 1.0.
8 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
11 #ifndef BOOST_HANA_TRAITS_HPP
12 #define BOOST_HANA_TRAITS_HPP
14 #include <boost/hana/config.hpp>
15 #include <boost/hana/integral_constant.hpp>
16 #include <boost/hana/type.hpp>
19 #include <type_traits>
22 BOOST_HANA_NAMESPACE_BEGIN namespace traits {
24 // We use this instead of hana::integral because we want to return
25 // hana::integral_constants instead of std::integral_constants.
26 template <template <typename ...> class F>
28 template <typename ...T>
29 constexpr auto operator()(T const& ...) const {
30 using Result = typename F<typename T::type...>::type;
31 return hana::integral_c<typename Result::value_type, Result::value>;
36 ///////////////////////
38 ///////////////////////
39 // Primary type categories
40 constexpr auto is_void = detail::hana_trait<std::is_void>{};
41 constexpr auto is_null_pointer = detail::hana_trait<std::is_null_pointer>{};
42 constexpr auto is_integral = detail::hana_trait<std::is_integral>{};
43 constexpr auto is_floating_point = detail::hana_trait<std::is_floating_point>{};
44 constexpr auto is_array = detail::hana_trait<std::is_array>{};
45 constexpr auto is_enum = detail::hana_trait<std::is_enum>{};
46 constexpr auto is_union = detail::hana_trait<std::is_union>{};
47 constexpr auto is_class = detail::hana_trait<std::is_class>{};
48 constexpr auto is_function = detail::hana_trait<std::is_function>{};
49 constexpr auto is_pointer = detail::hana_trait<std::is_pointer>{};
50 constexpr auto is_lvalue_reference = detail::hana_trait<std::is_lvalue_reference>{};
51 constexpr auto is_rvalue_reference = detail::hana_trait<std::is_rvalue_reference>{};
52 constexpr auto is_member_object_pointer = detail::hana_trait<std::is_member_object_pointer>{};
53 constexpr auto is_member_function_pointer = detail::hana_trait<std::is_member_function_pointer>{};
55 // Composite type categories
56 constexpr auto is_fundamental = detail::hana_trait<std::is_fundamental>{};
57 constexpr auto is_arithmetic = detail::hana_trait<std::is_arithmetic>{};
58 constexpr auto is_scalar = detail::hana_trait<std::is_scalar>{};
59 constexpr auto is_object = detail::hana_trait<std::is_object>{};
60 constexpr auto is_compound = detail::hana_trait<std::is_compound>{};
61 constexpr auto is_reference = detail::hana_trait<std::is_reference>{};
62 constexpr auto is_member_pointer = detail::hana_trait<std::is_member_pointer>{};
65 constexpr auto is_const = detail::hana_trait<std::is_const>{};
66 constexpr auto is_volatile = detail::hana_trait<std::is_volatile>{};
67 constexpr auto is_trivial = detail::hana_trait<std::is_trivial>{};
68 constexpr auto is_trivially_copyable = detail::hana_trait<std::is_trivially_copyable>{};
69 constexpr auto is_standard_layout = detail::hana_trait<std::is_standard_layout>{};
70 constexpr auto is_pod = detail::hana_trait<std::is_pod>{};
71 constexpr auto is_literal_type = detail::hana_trait<std::is_literal_type>{};
72 constexpr auto is_empty = detail::hana_trait<std::is_empty>{};
73 constexpr auto is_polymorphic = detail::hana_trait<std::is_polymorphic>{};
74 constexpr auto is_abstract = detail::hana_trait<std::is_abstract>{};
75 constexpr auto is_signed = detail::hana_trait<std::is_signed>{};
76 constexpr auto is_unsigned = detail::hana_trait<std::is_unsigned>{};
78 // Supported operations
79 constexpr auto is_constructible = detail::hana_trait<std::is_constructible>{};
80 constexpr auto is_trivially_constructible = detail::hana_trait<std::is_trivially_constructible>{};
81 constexpr auto is_nothrow_constructible = detail::hana_trait<std::is_nothrow_constructible>{};
83 constexpr auto is_default_constructible = detail::hana_trait<std::is_default_constructible>{};
84 constexpr auto is_trivially_default_constructible = detail::hana_trait<std::is_trivially_default_constructible>{};
85 constexpr auto is_nothrow_default_constructible = detail::hana_trait<std::is_nothrow_default_constructible>{};
87 constexpr auto is_copy_constructible = detail::hana_trait<std::is_copy_constructible>{};
88 constexpr auto is_trivially_copy_constructible = detail::hana_trait<std::is_trivially_copy_constructible>{};
89 constexpr auto is_nothrow_copy_constructible = detail::hana_trait<std::is_nothrow_copy_constructible>{};
91 constexpr auto is_move_constructible = detail::hana_trait<std::is_move_constructible>{};
92 constexpr auto is_trivially_move_constructible = detail::hana_trait<std::is_trivially_move_constructible>{};
93 constexpr auto is_nothrow_move_constructible = detail::hana_trait<std::is_nothrow_move_constructible>{};
95 constexpr auto is_assignable = detail::hana_trait<std::is_assignable>{};
96 constexpr auto is_trivially_assignable = detail::hana_trait<std::is_trivially_assignable>{};
97 constexpr auto is_nothrow_assignable = detail::hana_trait<std::is_nothrow_assignable>{};
99 constexpr auto is_copy_assignable = detail::hana_trait<std::is_copy_assignable>{};
100 constexpr auto is_trivially_copy_assignable = detail::hana_trait<std::is_trivially_copy_assignable>{};
101 constexpr auto is_nothrow_copy_assignable = detail::hana_trait<std::is_nothrow_copy_assignable>{};
103 constexpr auto is_move_assignable = detail::hana_trait<std::is_move_assignable>{};
104 constexpr auto is_trivially_move_assignable = detail::hana_trait<std::is_trivially_move_assignable>{};
105 constexpr auto is_nothrow_move_assignable = detail::hana_trait<std::is_nothrow_move_assignable>{};
107 constexpr auto is_destructible = detail::hana_trait<std::is_destructible>{};
108 constexpr auto is_trivially_destructible = detail::hana_trait<std::is_trivially_destructible>{};
109 constexpr auto is_nothrow_destructible = detail::hana_trait<std::is_nothrow_destructible>{};
111 constexpr auto has_virtual_destructor = detail::hana_trait<std::has_virtual_destructor>{};
114 constexpr auto alignment_of = detail::hana_trait<std::alignment_of>{};
115 constexpr auto rank = detail::hana_trait<std::rank>{};
116 constexpr struct extent_t {
117 template <typename T, typename N>
118 constexpr auto operator()(T const&, N const&) const {
119 constexpr unsigned n = N::value;
120 using Result = typename std::extent<typename T::type, n>::type;
121 return hana::integral_c<typename Result::value_type, Result::value>;
124 template <typename T>
125 constexpr auto operator()(T const& t) const
126 { return (*this)(t, hana::uint_c<0>); }
129 // Type relationships
130 constexpr auto is_same = detail::hana_trait<std::is_same>{};
131 constexpr auto is_base_of = detail::hana_trait<std::is_base_of>{};
132 constexpr auto is_convertible = detail::hana_trait<std::is_convertible>{};
134 ///////////////////////
135 // Type modifications
136 ///////////////////////
137 // Const-volatility specifiers
138 constexpr auto remove_cv = metafunction<std::remove_cv>;
139 constexpr auto remove_const = metafunction<std::remove_const>;
140 constexpr auto remove_volatile = metafunction<std::remove_volatile>;
142 constexpr auto add_cv = metafunction<std::add_cv>;
143 constexpr auto add_const = metafunction<std::add_const>;
144 constexpr auto add_volatile = metafunction<std::add_volatile>;
147 constexpr auto remove_reference = metafunction<std::remove_reference>;
148 constexpr auto add_lvalue_reference = metafunction<std::add_lvalue_reference>;
149 constexpr auto add_rvalue_reference = metafunction<std::add_rvalue_reference>;
152 constexpr auto remove_pointer = metafunction<std::remove_pointer>;
153 constexpr auto add_pointer = metafunction<std::add_pointer>;
156 constexpr auto make_signed = metafunction<std::make_signed>;
157 constexpr auto make_unsigned = metafunction<std::make_unsigned>;
160 constexpr auto remove_extent = metafunction<std::remove_extent>;
161 constexpr auto remove_all_extents = metafunction<std::remove_all_extents>;
163 // Miscellaneous transformations
164 constexpr struct aligned_storage_t {
165 template <typename Len, typename Align>
166 constexpr auto operator()(Len const&, Align const&) const {
167 constexpr std::size_t len = Len::value;
168 constexpr std::size_t align = Align::value;
169 using Result = typename std::aligned_storage<len, align>::type;
170 return hana::type_c<Result>;
173 template <typename Len>
174 constexpr auto operator()(Len const&) const {
175 constexpr std::size_t len = Len::value;
176 using Result = typename std::aligned_storage<len>::type;
177 return hana::type_c<Result>;
181 constexpr struct aligned_union_t {
182 template <typename Len, typename ...T>
183 constexpr auto operator()(Len const&, T const&...) const {
184 constexpr std::size_t len = Len::value;
185 using Result = typename std::aligned_union<len, typename T::type...>::type;
186 return hana::type_c<Result>;
190 constexpr auto decay = metafunction<std::decay>;
195 constexpr auto common_type = metafunction<std::common_type>;
196 constexpr auto underlying_type = metafunction<std::underlying_type>;
197 constexpr auto result_of = metafunction<std::result_of>;
200 ///////////////////////
202 ///////////////////////
204 template <typename T>
205 typename std::add_rvalue_reference<
207 >::type operator()(T const&) const;
210 constexpr declval_t declval{};
211 } BOOST_HANA_NAMESPACE_END
213 #endif // !BOOST_HANA_TRAITS_HPP