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 47