boost/flyweight/factory_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_FACTORY_TAG_HPP
  10 #define BOOST_FLYWEIGHT_FACTORY_TAG_HPP
  11
  12 #if defined(_MSC_VER)&&(_MSC_VER>=1200)
  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 namespace boost{
  21
  22 namespace flyweights{
  23
  24 /* Three ways to indicate that a given class T is a factory specifier:
  25  *   1. Make it derived from factory_marker.
  26  *   2. Specialize is_factory to evaluate to boost::mpl::true_.
  27  *   3. Pass it as factory<T> when defining a flyweight type.
  28  */
  29
  30 struct factory_marker{};
  31
  32 template<typename T>
  33 struct is_factory:is_base_and_derived<factory_marker,T>
  34 {};
  35
  36 template<typename T=parameter::void_>
  37 struct factory:parameter::template_keyword<factory<>,T>
  38 {};
  39
  40 } /* namespace flyweights */
  41
  42 } /* namespace boost */
  43
  44 #endif