ceph/src/boost/libs/core/doc/is_same.qbk

   1 [/
   2   Copyright 2014 Peter Dimov
   3
   4   Distributed under the Boost Software License, Version 1.0.
   5
   6   See accompanying file LICENSE_1_0.txt
   7   or copy at http://boost.org/LICENSE_1_0.txt
   8 ]
   9
  10 [section:is_same is_same]
  11
  12 [simplesect Authors]
  13
  14 * Peter Dimov
  15
  16 [endsimplesect]
  17
  18 [section Header <boost/core/is_same.hpp>]
  19
  20 The header `<boost/core/is_same.hpp>` defines the class template
  21 `boost::core::is_same<T1,T2>`. It defines a nested integral constant
  22 `value` which is `true` when `T1` and `T2` are the same type, and
  23 `false` when they are not.
  24
  25 In tandem with `BOOST_TEST_TRAIT_TRUE` and `BOOST_TEST_TRAIT_FALSE`,
  26 `is_same` is useful for writing tests for traits classes that have
  27 to define specific nested types.
  28
  29 [section Synopsis]
  30
  31 ``
  32 namespace boost
  33 {
  34
  35 namespace core
  36 {
  37     template<class T1, class T2> struct is_same;
  38 }
  39
  40 }
  41 ``
  42
  43 [endsect]
  44
  45 [section Example]
  46
  47 ``
  48 #include <boost/core/lightweight_test_trait.hpp>
  49 #include <boost/core/is_same.hpp>
  50
  51 template<class T> struct X
  52 {
  53     typedef T& type;
  54 };
  55
  56 using boost::core::is_same;
  57
  58 int main()
  59 {
  60     BOOST_TEST_TRAIT_TRUE(( is_same<X<int>::type, int&> ));
  61     return boost::report_errors();
  62 }
  63 ``
  64
  65 [endsect]
  66
  67 [endsect]
  68
  69 [endsect]