| 1 | /* Copyright 2006-2008 Joaquin M Lopez Munoz. |
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| 2 | * Distributed under the Boost Software License, Version 1.0. |
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| 3 | * (See accompanying file LICENSE_1_0.txt or copy at |
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| 4 | * http://www.boost.org/LICENSE_1_0.txt) |
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| 5 | * |
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| 6 | * See http://www.boost.org/libs/flyweight for library home page. |
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| 7 | */ |
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| 8 | |
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| 9 | #ifndef BOOST_FLYWEIGHT_TRACKING_TAG_HPP |
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| 10 | #define BOOST_FLYWEIGHT_TRACKING_TAG_HPP |
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| 11 | |
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| 12 | #if defined(_MSC_VER) |
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| 13 | #pragma once |
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| 14 | #endif |
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| 15 | |
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| 16 | #include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */ |
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| 17 | #include <boost/parameter/parameters.hpp> |
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| 18 | #include <boost/type_traits/is_base_and_derived.hpp> |
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| 19 | |
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| 20 | namespace boost{ |
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| 21 | |
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| 22 | namespace flyweights{ |
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| 23 | |
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| 24 | /* Three ways to indicate that a given class T is a tracking policy: |
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| 25 | * 1. Make it derived from tracking_marker. |
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| 26 | * 2. Specialize is_tracking to evaluate to boost::mpl::true_. |
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| 27 | * 3. Pass it as tracking<T> when defining a flyweight type. |
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| 28 | */ |
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| 29 | |
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| 30 | struct tracking_marker{}; |
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| 31 | |
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| 32 | template<typename T> |
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| 33 | struct is_tracking:is_base_and_derived<tracking_marker,T> |
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| 34 | {}; |
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| 35 | |
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| 36 | template<typename T=parameter::void_> |
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| 37 | struct tracking:parameter::template_keyword<tracking<>,T> |
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| 38 | {}; |
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| 39 | |
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| 40 | } /* namespace flyweights */ |
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| 41 | |
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| 42 | } /* namespace boost */ |
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| 43 | |
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| 44 | #endif |
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| 45 | |
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