ceph/src/boost/boost/flyweight/tag.hpp

   1 /* Copyright 2006-2008 Joaquin M Lopez Munoz.
   2  * Distributed under the Boost Software License, Version 1.0.
   3  * (See accompanying file LICENSE_1_0.txt or copy at
   4  * http://www.boost.org/LICENSE_1_0.txt)
   5  *
   6  * See http://www.boost.org/libs/flyweight for library home page.
   7  */
   8
   9 #ifndef BOOST_FLYWEIGHT_TAG_HPP
  10 #define BOOST_FLYWEIGHT_TAG_HPP
  11
  12 #if defined(_MSC_VER)
  13 #pragma once
  14 #endif
  15
  16 #include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
  17 #include <boost/parameter/parameters.hpp>
  18 #include <boost/type_traits/is_base_and_derived.hpp>
  19
  20 /* A type T can be used as a tag in the specification of a flyweight
  21  * by passing it wrapped in the form tag<T>.
  22  */
  23
  24 namespace boost{
  25
  26 namespace flyweights{
  27
  28 namespace detail{
  29
  30 struct tag_marker{};
  31
  32 template<typename T>
  33 struct is_tag:is_base_and_derived<tag_marker,T>
  34 {};
  35
  36 } /* namespace flyweights::detail */
  37
  38 template<typename T=parameter::void_>
  39 struct tag:parameter::template_keyword<tag<>,T>,detail::tag_marker
  40 {};
  41
  42 } /* namespace flyweights */
  43
  44 } /* namespace boost */
  45
  46 #endif