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)
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
20namespace boost{
21
22namespace 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
30struct factory_marker{};
31
32template<typename T>
33struct is_factory:is_base_and_derived<factory_marker,T>
34{};
35
36template<typename T=parameter::void_>
37struct factory:parameter::template_keyword<factory<>,T>
38{};
39
40} /* namespace flyweights */
41
42} /* namespace boost */
43
44#endif
45

source code of boost/libs/flyweight/include/boost/flyweight/factory_tag.hpp