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2 Copyright 2007 John Maddock.
3 Distributed under the Boost Software License, Version 1.0.
4 (See accompanying file LICENSE_1_0.txt or copy at
5 http://www.boost.org/LICENSE_1_0.txt).
6]
7
8[section:value_traits Type Traits that Describe the Properties of a Type]
9
10These traits are all /value traits/, which is to say the traits classes all
11inherit from __integral_constant, and are used to access some numerical
12property of a type. Often this is a simple true or false Boolean value,
13but in a few cases may be some other integer value (for example when dealing
14with type alignments, or array bounds: see `__alignment_of`, `__rank` and `__extent`).
15
16[section:primary Categorizing a Type]
17
18These traits identify what "kind" of type some type `T` is. These are split into
19two groups: primary traits which are all mutually exclusive, and composite traits
20that are compositions of one or more primary traits.
21
22For any given type, exactly one primary type trait will inherit from
23__true_type, and all the others will inherit from __false_type, in other
24words these traits are mutually exclusive.
25
26This means that `__is_integral<T>::value` and `__is_floating_point<T>::value`
27will only ever be true for built-in types; if you want to check for a
28user-defined class type that behaves "as if" it is an integral or floating point type,
29then use the `std::numeric_limits template` instead.
30
31[*Synopsis:]
32
33 template <class T>
34 struct __is_array;
35
36 template <class T>
37 struct __is_class;
38
39 template <class T>
40 struct __is_complex;
41
42 template <class T>
43 struct __is_enum;
44
45 template <class T>
46 struct __is_floating_point;
47
48 template <class T>
49 struct __is_function;
50
51 template <class T>
52 struct __is_integral;
53
54 template <class T>
55 struct __is_member_function_pointer;
56
57 template <class T>
58 struct __is_member_object_pointer;
59
60 template <class T>
61 struct __is_pointer;
62
63 template <class T>
64 struct __is_lvalue_reference;
65
66 template <class T>
67 struct __is_rvalue_reference;
68
69 template <class T>
70 struct __is_union;
71
72 template <class T>
73 struct __is_void;
74
75The following traits are made up of the union of one or more type
76categorizations. A type may belong to more than one of these categories,
77in addition to one of the primary categories.
78
79 template <class T>
80 struct __is_arithmetic;
81
82 template <class T>
83 struct __is_compound;
84
85 template <class T>
86 struct __is_fundamental;
87
88 template <class T>
89 struct __is_member_pointer;
90
91 template <class T>
92 struct __is_object;
93
94 template <class T>
95 struct __is_reference;
96
97 template <class T>
98 struct __is_scalar;
99
100[endsect]
101
102[section:properties General Type Properties]
103
104The following templates describe the general properties of a type.
105
106[*Synopsis:]
107
108 template <class T>
109 struct __alignment_of;
110
111 template <class T>
112 struct __has_new_operator;
113
114 template <class T>
115 struct __has_nothrow_assign;
116
117 template <class T>
118 struct __has_nothrow_constructor;
119
120 template <class T>
121 struct __has_nothrow_default_constructor;
122
123 template <class T>
124 struct __has_nothrow_copy;
125
126 template <class T>
127 struct __has_nothrow_copy_constructor;
128
129 template <class T>
130 struct __has_nothrow_destructor;
131
132 template <class T>
133 struct __has_trivial_assign;
134
135 template <class T>
136 struct __has_trivial_constructor;
137
138 template <class T>
139 struct __has_trivial_default_constructor;
140
141 template <class T>
142 struct __has_trivial_copy;
143
144 template <class T>
145 struct __has_trivial_copy_constructor;
146
147 template <class T>
148 struct __has_trivial_destructor;
149
150 template <class T>
151 struct __has_virtual_destructor;
152
153 template <class T>
154 struct __is_abstract;
155
156 template <class T, class U>
157 struct __is_assignable;
158
159 template <class T>
160 struct __is_copy_constructible;
161
162 template <class T>
163 struct __is_copy_assignable;
164
165 template <class T, class... Args>
166 struct __is_constructible;
167
168 template <class T>
169 struct __is_default_constructible;
170
171 template <class T, class... Args>
172 struct __is_list_constructible;
173
174 template <class T>
175 struct __is_destructible;
176
177 template <class T>
178 struct __is_const;
179
180 template <class T>
181 struct __is_empty;
182
183 template <class T>
184 struct __is_final;
185
186 template <class T>
187 struct __is_stateless;
188
189 template <class T>
190 struct __is_pod;
191
192 template <class T>
193 struct __is_polymorphic;
194
195 template <class T>
196 struct __is_signed;
197
198 template <class T>
199 struct __is_unsigned;
200
201 template <class T>
202 struct __is_volatile;
203
204 template <class T, std::size_t N = 0>
205 struct __extent;
206
207 template <class T>
208 struct __rank;
209
210[endsect]
211
212[section:relate Relationships Between Two Types]
213
214These templates determine the whether there is a relationship
215between two types:
216
217[*Synopsis:]
218
219 template <class Base, class Derived>
220 struct __is_base_of;
221
222 template <class Base, class Derived>
223 struct __is_virtual_base_of;
224
225 template <class From, class To>
226 struct __is_convertible;
227
228 template <class T, class U>
229 struct __is_same;
230
231[endsect]
232
233[include operators.qbk]
234
235[endsect]