/*
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* Copyright Andrey Semashev 2007 - 2015.
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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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/*!
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* \file value_extraction_fwd.hpp
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* \author Andrey Semashev
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* \date 01.03.2008
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*
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* The header contains forward declaration of tools for extracting attribute values
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* from the view.
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*/
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#ifndef BOOST_LOG_ATTRIBUTES_VALUE_EXTRACTION_FWD_HPP_INCLUDED_
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#define BOOST_LOG_ATTRIBUTES_VALUE_EXTRACTION_FWD_HPP_INCLUDED_
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#include <boost/log/detail/config.hpp>
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#include <boost/log/attributes/fallback_policy_fwd.hpp>
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#ifdef BOOST_HAS_PRAGMA_ONCE
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#pragma once
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#endif
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namespace boost {
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BOOST_LOG_OPEN_NAMESPACE
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namespace result_of {
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/*!
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* \brief A metafunction that allows to acquire the result of the value extraction
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*/
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template< typename T, typename DefaultT = T, typename TagT = void >
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struct extract_or_default;
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/*!
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* \brief A metafunction that allows to acquire the result of the value extraction
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*/
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template< typename T, typename TagT = void >
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struct extract_or_throw;
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/*!
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* \brief A metafunction that allows to acquire the result of the value extraction
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*/
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template< typename T, typename TagT = void >
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struct extract;
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} // namespace result_of
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/*!
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* \brief Generic attribute value extractor
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*/
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template< typename T, typename FallbackPolicyT = fallback_to_none, typename TagT = void >
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class value_extractor;
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BOOST_LOG_CLOSE_NAMESPACE // namespace log
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} // namespace boost
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#endif // BOOST_LOG_ATTRIBUTES_VALUE_EXTRACTION_FWD_HPP_INCLUDED_
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