boost/flyweight/tag.hpp
/* Copyright 2006-2008 Joaquin M Lopez Munoz. * Distributed under the Boost Software License, Version 1.0. * (See accompanying file LICENSE_1_0.txt or copy at * http://www.boost.org/LICENSE_1_0.txt) * * See http://www.boost.org/libs/flyweight for library home page. */ #ifndef BOOST_FLYWEIGHT_TAG_HPP #define BOOST_FLYWEIGHT_TAG_HPP #if defined(_MSC_VER) #pragma once #endif #include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */ #include <boost/parameter/parameters.hpp> #include <boost/type_traits/is_base_and_derived.hpp> /* A type T can be used as a tag in the specification of a flyweight * by passing it wrapped in the form tag<T>. */ namespace boost{ namespace flyweights{ namespace detail{ struct tag_marker{}; template<typename T> struct is_tag:is_base_and_derived<tag_marker,T> {}; } /* namespace flyweights::detail */ template<typename T=parameter::void_> struct tag:parameter::template_keyword<tag<>,T>,detail::tag_marker {}; } /* namespace flyweights */ } /* namespace boost */ #endif