ceph/src/boost/libs/mpl/doc/src/refmanual/IntegralConstant.rst

   1 .. Data Types/Concepts//Integral Constant
   2
   3 Integral Constant
   4 =================
   5
   6 Description
   7 -----------
   8
   9 An |Integral Constant| is a holder class for a compile-time value of an
  10 integral type. Every |Integral Constant| is also a nullary |Metafunction|,
  11 returning itself. An integral constant *object* is implicitly convertible to the
  12 corresponding run-time value of the wrapped integral type.
  13
  14 Expression requirements
  15 -----------------------
  16
  17 |In the following table...| ``n`` is a model of |Integral Constant|.
  18
  19 +-----------------------------------+---------------------------------------+---------------------------+
  20 | Expression                        | Type                                  | Complexity                |
  21 +===================================+=======================================+===========================+
  22 | ``n::tag``                        | ``integral_c_tag``                    | Constant time.            |
  23 +-----------------------------------+---------------------------------------+---------------------------+
  24 | ``n::value_type``                 | An integral type                      | Constant time.            |
  25 +-----------------------------------+---------------------------------------+---------------------------+
  26 | ``n::value``                      | An integral constant expression       | Constant time.            |
  27 +-----------------------------------+---------------------------------------+---------------------------+
  28 | ``n::type``                       | |Integral Constant|                   | Constant time.            |
  29 +-----------------------------------+---------------------------------------+---------------------------+
  30 | ``next<n>::type``                 | |Integral Constant|                   | Constant time.            |
  31 +-----------------------------------+---------------------------------------+---------------------------+
  32 | ``prior<n>::type``                | |Integral Constant|                   | Constant time.            |
  33 +-----------------------------------+---------------------------------------+---------------------------+
  34 | ``n::value_type const c = n()``   |                                       | Constant time.            |
  35 +-----------------------------------+---------------------------------------+---------------------------+
  36
  37
  38 Expression semantics
  39 --------------------
  40
  41 +---------------------------------------+-----------------------------------------------------------+
  42 | Expression                            | Semantics                                                 |
  43 +=======================================+===========================================================+
  44 | ``n::tag``                            | ``n``\ 's tag type; ``n::tag::value`` is ``n``\ 's        |
  45 |                                       | *conversion rank*.                                        |
  46 +---------------------------------------+-----------------------------------------------------------+
  47 | ``n::value_type``                     | A cv-unqualified type of ``n::value``.                    |
  48 +---------------------------------------+-----------------------------------------------------------+
  49 | ``n::value``                          | The value of the wrapped integral constant.               |
  50 +---------------------------------------+-----------------------------------------------------------+
  51 | ``n::type``                           | ``is_same<n::type,n>::value == true``.                    |
  52 +---------------------------------------+-----------------------------------------------------------+
  53 | ``next<n>::type``                     | An |Integral Constant| ``c`` of type ``n::value_type``    |
  54 |                                       | such that ``c::value == n::value + 1``.                   |
  55 +---------------------------------------+-----------------------------------------------------------+
  56 | ``prior<n>::type``                    | An |Integral Constant| ``c`` of type ``n::value_type``    |
  57 |                                       | such that ``c::value == n::value - 1``.                   |
  58 +---------------------------------------+-----------------------------------------------------------+
  59 | ``n::value_type const c = n()``       | ``c == n::value``.                                        |
  60 +---------------------------------------+-----------------------------------------------------------+
  61
  62
  63 Models
  64 ------
  65
  66 * |bool_|
  67 * |int_|
  68 * |long_|
  69 * |char_|
  70 * |integral_c|
  71
  72
  73 See also
  74 --------
  75
  76 |Data Types|, |Integral Sequence Wrapper|, |integral_c|
  77
  78
  79 .. copyright:: Copyright ©  2001-2009 Aleksey Gurtovoy and David Abrahams
  80    Distributed under the Boost Software License, Version 1.0. (See accompanying
  81    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)