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

   1 .. Macros/Asserts//BOOST_MPL_ASSERT
   2
   3 BOOST_MPL_ASSERT
   4 ================
   5
   6 Synopsis
   7 --------
   8
   9 .. parsed-literal::
  10
  11     #define BOOST_MPL_ASSERT( pred ) \\
  12         |unspecified-token-seq| \\
  13     /\*\*/
  14
  15
  16 Description
  17 -----------
  18
  19 Generates a compilation error when the predicate ``pred`` holds false.
  20
  21
  22 Header
  23 ------
  24
  25 .. parsed-literal::
  26
  27     #include <boost/mpl/assert.hpp>
  28
  29
  30 Parameters
  31 ----------
  32
  33 +---------------+-----------------------------------+-------------------------------+
  34 | Parameter     | Requirement                       | Description                   |
  35 +===============+===================================+===============================+
  36 | ``pred``      | Boolean nullary |Metafunction|    | A predicate to be asserted.   |
  37 +---------------+-----------------------------------+-------------------------------+
  38
  39
  40 Expression semantics
  41 --------------------
  42
  43 For any boolean nullary |Metafunction| ``pred``:
  44
  45
  46 .. parsed-literal::
  47
  48     BOOST_MPL_ASSERT(( pred ));
  49
  50 :Return type:
  51     None.
  52
  53 :Semantics:
  54     Generates a compilation error if ``pred::type::value != true``, otherwise
  55     has no effect. Note that double parentheses are required even if no commas
  56     appear in the condition.
  57
  58     When possible within the compiler's diagnostic capabilities,
  59     the error message will include the predicate's full type name, and have a
  60     general form of:
  61
  62     .. parsed-literal::
  63
  64        |...| \*\*\*\*\*\*\*\*\*\*\*\* pred::\*\*\*\*\*\*\*\*\*\*\*\* |...|
  65
  66
  67 Example
  68 -------
  69
  70 ::
  71
  72     template< typename T, typename U > struct my
  73     {
  74         // ...
  75         BOOST_MPL_ASSERT(( is_same< T,U > ));
  76     };
  77
  78     my<void*,char*> test;
  79
  80     // In instantiation of `my<void, char*>':
  81     //   instantiated from here
  82     // conversion from `
  83     //   mpl_::failed************boost::is_same<void, char*>::************' to
  84     //   non-scalar type `mpl_::assert<false>' requested
  85
  86
  87 See also
  88 --------
  89
  90 |Asserts|, |BOOST_MPL_ASSERT_NOT|, |BOOST_MPL_ASSERT_MSG|, |BOOST_MPL_ASSERT_RELATION|
  91
  92
  93 .. copyright:: Copyright ©  2001-2009 Aleksey Gurtovoy and David Abrahams
  94    Distributed under the Boost Software License, Version 1.0. (See accompanying
  95    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)