45 lines
1.1 KiB
C++
45 lines
1.1 KiB
C++
/* Copyright 2006-2008 Joaquin M Lopez Munoz.
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* Distributed under the Boost Software License, Version 1.0.
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* (See accompanying file LICENSE_1_0.txt or copy at
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* http://www.boost.org/LICENSE_1_0.txt)
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*
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* See http://www.boost.org/libs/flyweight for library home page.
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*/
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#ifndef BOOST_FLYWEIGHT_TRACKING_TAG_HPP
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#define BOOST_FLYWEIGHT_TRACKING_TAG_HPP
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#if defined(_MSC_VER)
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#pragma once
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#endif
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#include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
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#include <boost/parameter/parameters.hpp>
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#include <boost/type_traits/is_base_and_derived.hpp>
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namespace boost{
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namespace flyweights{
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/* Three ways to indicate that a given class T is a tracking policy:
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* 1. Make it derived from tracking_marker.
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* 2. Specialize is_tracking to evaluate to boost::mpl::true_.
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* 3. Pass it as tracking<T> when defining a flyweight type.
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*/
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struct tracking_marker{};
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template<typename T>
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struct is_tracking:is_base_and_derived<tracking_marker,T>
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{};
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template<typename T=parameter::void_>
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struct tracking:parameter::template_keyword<tracking<>,T>
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{};
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} /* namespace flyweights */
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} /* namespace boost */
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#endif
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