ceph/src/boost/libs/type_erasure/example/concept_map.cpp

   1 // Boost.TypeErasure library
   2 //
   3 // Copyright 2011 Steven Watanabe
   4 //
   5 // Distributed under the Boost Software License Version 1.0. (See
   6 // accompanying file LICENSE_1_0.txt or copy at
   7 // http://www.boost.org/LICENSE_1_0.txt)
   8 //
   9 // $Id$
  10
  11 #include <boost/type_erasure/operators.hpp>
  12 #include <typeinfo>
  13
  14 namespace mpl = boost::mpl;
  15 using namespace boost::type_erasure;
  16
  17 //[concept_map1
  18 /*`
  19     Sometimes it is useful to non-intrusively adapt a
  20     type to model a concept.  For example, suppose that
  21     we want to make `std::type_info` model __less_than_comparable.
  22     To do this, we simply specialize the concept definition.
  23 */
  24 namespace boost {
  25 namespace type_erasure {
  26
  27 template<>
  28 struct less_than_comparable<std::type_info>
  29 {
  30     static bool apply(const std::type_info& lhs, const std::type_info& rhs)
  31     { return lhs.before(rhs) != 0; }
  32 };
  33
  34 }
  35 }
  36
  37 /*`
  38     [note Most, but not all of the builtin concepts can be specialized.
  39     Constructors, destructors, and RTTI need special treatment from the
  40     library and cannot be specialized.  Only primitive concepts can
  41     be specialized, so the iterator concepts are also out.]
  42 */
  43
  44 //]
  45
  46 //[concept_map
  47 //` (For the source of the examples in this section see
  48 //` [@boost:/libs/type_erasure/example/concept_map.cpp concept_map.cpp])
  49 //` [concept_map1]
  50 //]