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 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 45