ceph/src/boost/libs/type_traits/doc/value_traits.qbk

   1 [/
   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
  10 These traits are all /value traits/, which is to say the traits classes all
  11 inherit from __integral_constant, and are used to access some numerical
  12 property of a type.  Often this is a simple true or false Boolean value,
  13 but in a few cases may be some other integer value (for example when dealing
  14 with type alignments, or array bounds: see `__alignment_of`, `__rank` and `__extent`).
  15
  16 [section:primary Categorizing a Type]
  17
  18 These traits identify what "kind" of type some type `T` is.  These are split into
  19 two groups: primary traits which are all mutually exclusive, and composite traits
  20 that are compositions of one or more primary traits.
  21
  22 For 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
  24 words these traits are mutually exclusive.
  25
  26 This means that `__is_integral<T>::value` and `__is_floating_point<T>::value`
  27 will only ever be true for built-in types; if you want to check for a
  28 user-defined class type that behaves "as if" it is an integral or floating point type,
  29 then 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
  75 The following traits are made up of the union of one or more type
  76 categorizations. A type may belong to more than one of these categories,
  77 in 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
 104 The 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>
 172    struct __is_destructible;
 173
 174    template <class T>
 175    struct __is_const;
 176
 177    template <class T>
 178    struct __is_empty;
 179
 180    template <class T>
 181    struct __is_final;
 182
 183    template <class T>
 184    struct __is_stateless;
 185
 186    template <class T>
 187    struct __is_pod;
 188
 189    template <class T>
 190    struct __is_polymorphic;
 191
 192    template <class T>
 193    struct __is_signed;
 194
 195    template <class T>
 196    struct __is_unsigned;
 197
 198    template <class T>
 199    struct __is_volatile;
 200
 201    template <class T, std::size_t N = 0>
 202    struct __extent;
 203
 204    template <class T>
 205    struct __rank;
 206
 207 [endsect]
 208
 209 [section:relate Relationships Between Two Types]
 210
 211 These templates determine the whether there is a relationship
 212 between two types:
 213
 214 [*Synopsis:]
 215
 216    template <class Base, class Derived>
 217    struct __is_base_of;
 218
 219    template <class Base, class Derived>
 220    struct __is_virtual_base_of;
 221
 222    template <class From, class To>
 223    struct __is_convertible;
 224
 225    template <class T, class U>
 226    struct __is_same;
 227
 228 [endsect]
 229
 230 [include operators.qbk]
 231
 232 [endsect]