ceph/src/boost/libs/type_traits/doc/user_defined.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:user_defined User Defined Specializations]
   9
  10 Occationally the end user may need to provide their own specialization
  11 for one of the type traits - typically where intrinsic compiler support
  12 is required to implement a specific trait fully.
  13 These specializations should derive from boost::__true_type or boost::__false_type
  14 as appropriate:
  15
  16    #include <boost/type_traits/is_pod.hpp>
  17    #include <boost/type_traits/is_class.hpp>
  18    #include <boost/type_traits/is_union.hpp>
  19
  20    struct my_pod{};
  21    struct my_union
  22    {
  23       char c;
  24       int i;
  25    };
  26
  27    namespace boost
  28    {
  29       template<>
  30       struct __is_pod<my_pod> : public __true_type{};
  31
  32       template<>
  33       struct __is_pod<my_union> : public __true_type{};
  34
  35       template<>
  36       struct __is_union<my_union> : public __true_type{};
  37
  38       template<>
  39       struct __is_class<my_union> : public __false_type{};
  40    }
  41
  42 [endsect]
  43