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

   1 .. Macros/Asserts//BOOST_MPL_ASSERT_RELATION
   2
   3 BOOST_MPL_ASSERT_RELATION
   4 =========================
   5
   6 Synopsis
   7 --------
   8
   9 .. parsed-literal::
  10
  11     #define BOOST_MPL_ASSERT_RELATION( x, relation, y ) \\
  12         |unspecified-token-seq| \\
  13     /\*\*/
  14
  15
  16
  17 Description
  18 -----------
  19
  20 A specialized assertion macro for checking numerical conditions. Generates
  21 a compilation error when the condition ``( x relation y )``
  22 doesn't hold.
  23
  24
  25 Header
  26 ------
  27
  28 .. parsed-literal::
  29
  30     #include <boost/mpl/assert.hpp>
  31
  32
  33 Parameters
  34 ----------
  35
  36 +---------------+-----------------------------------+-----------------------------------------------+
  37 | Parameter     | Requirement                       | Description                                   |
  38 +===============+===================================+===============================================+
  39 | ``x``         | An integral constant              | Left operand of the checked relation.         |
  40 +---------------+-----------------------------------+-----------------------------------------------+
  41 | ``y``         | An integral constant              | Right operand of the checked relation.        |
  42 +---------------+-----------------------------------+-----------------------------------------------+
  43 | ``relation``  | A C++ operator token              | An operator token for the relation being      |
  44 |               |                                   | checked.                                      |
  45 +---------------+-----------------------------------+-----------------------------------------------+
  46
  47
  48 Expression semantics
  49 --------------------
  50
  51 For any integral constants ``x``, ``y`` and a legal C++ operator token ``op``:
  52
  53
  54 .. parsed-literal::
  55
  56     BOOST_MPL_ASSERT_RELATION( x, op, y );
  57
  58 :Return type:
  59     None.
  60
  61 :Semantics:
  62     Generates a compilation error if ``( x op y ) != true``, otherwise
  63     has no effect.
  64
  65     When possible within the compiler's diagnostic capabilities,
  66     the error message will include a name of the relation being checked,
  67     the actual values of both operands, and have a general form of:
  68
  69     .. parsed-literal::
  70
  71         |...| \*\*\*\*\*\*\*\*\*\*\*\*\ |...|\ assert_relation<op, x, y>::\*\*\*\*\*\*\*\*\*\*\*\*) |...|
  72
  73
  74 Example
  75 -------
  76
  77 ::
  78
  79     template< typename T, typename U > struct my
  80     {
  81         // ...
  82         BOOST_MPL_ASSERT_RELATION( sizeof(T), <, sizeof(U) );
  83     };
  84
  85     my<char[50],char[10]> test;
  86
  87     // In instantiation of `my<char[50], char[10]>':
  88     //   instantiated from here
  89     // conversion from `
  90     //   mpl_::failed************mpl_::assert_relation<less, 50, 10>::************'
  91     //   to non-scalar type `mpl_::assert<false>' requested
  92
  93
  94 See also
  95 --------
  96
  97 |Asserts|, |BOOST_MPL_ASSERT|, |BOOST_MPL_ASSERT_NOT|, |BOOST_MPL_ASSERT_MSG|
  98
  99
 100 .. copyright:: Copyright ©  2001-2009 Aleksey Gurtovoy and David Abrahams
 101    Distributed under the Boost Software License, Version 1.0. (See accompanying
 102    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)