/*
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* Copyright Andrey Semashev 2020.
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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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* https://www.boost.org/LICENSE_1_0.txt)
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*/
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/*!
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* \file utility/manipulators/optional.hpp
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* \author Andrey Semashev
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* \date 12.05.2020
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*
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* The header contains implementation of a stream manipulator for inserting an optional value.
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*/
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#ifndef BOOST_LOG_UTILITY_MANIPULATORS_OPTIONAL_HPP_INCLUDED_
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#define BOOST_LOG_UTILITY_MANIPULATORS_OPTIONAL_HPP_INCLUDED_
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#include <cstddef>
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#include <boost/core/enable_if.hpp>
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#include <boost/type_traits/is_array.hpp>
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#include <boost/type_traits/is_scalar.hpp>
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#include <boost/type_traits/conditional.hpp>
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#include <boost/log/detail/config.hpp>
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#include <boost/log/detail/is_ostream.hpp>
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#include <boost/log/detail/header.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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/*!
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* Stream manipulator for inserting an optional value.
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*/
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template< typename OptionalT, typename NoneT >
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class optional_manipulator
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{
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private:
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typedef typename conditional<
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is_scalar< OptionalT >::value,
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OptionalT,
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OptionalT const&
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>::type stored_optional_type;
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typedef typename conditional<
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is_scalar< NoneT >::value,
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NoneT,
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NoneT const&
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>::type stored_none_type;
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private:
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stored_optional_type m_optional;
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stored_none_type m_none;
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public:
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//! Initializing constructor
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optional_manipulator(stored_optional_type opt, stored_none_type none) BOOST_NOEXCEPT :
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m_optional(opt),
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m_none(none)
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{
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}
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//! The method outputs the value, if it is present, otherwise outputs the "none" marker
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template< typename StreamT >
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void output(StreamT& stream) const
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{
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if (!!m_optional)
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stream << *m_optional;
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else
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stream << m_none;
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}
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};
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/*!
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* Stream manipulator for inserting an optional value. Specialization for no "none" marker.
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*/
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template< typename OptionalT >
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class optional_manipulator< OptionalT, void >
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{
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private:
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typedef typename conditional<
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is_scalar< OptionalT >::value,
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OptionalT,
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OptionalT const&
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>::type stored_optional_type;
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private:
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stored_optional_type m_optional;
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public:
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//! Initializing constructor
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optional_manipulator(stored_optional_type opt) BOOST_NOEXCEPT :
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m_optional(opt)
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{
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}
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//! The method outputs the value, if it is present
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template< typename StreamT >
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void output(StreamT& stream) const
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{
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if (!!m_optional)
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stream << *m_optional;
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}
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};
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/*!
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* Stream output operator for \c optional_manipulator. Outputs the optional value or the "none" marker, if one was specified on manipulator construction.
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*/
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template< typename StreamT, typename OptionalT, typename NoneT >
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inline typename boost::enable_if_c< log::aux::is_ostream< StreamT >::value, StreamT& >::type operator<< (StreamT& strm, optional_manipulator< OptionalT, NoneT > const& manip)
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{
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manip.output(strm);
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return strm;
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}
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/*!
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* Optional manipulator generator function.
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*
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* \param opt Optional value to output. The optional value must support contextual conversion to \c bool and dereferencing, and its dereferencing result must support stream output.
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* \param none Marker used to indicate when the value is not present. Optional. If not specified, nothing is output if the value is not present.
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* \returns Manipulator to be inserted into the stream.
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*
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* \note Both \a opt and \a none objects must outlive the created manipulator object.
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*/
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template< typename OptionalT, typename NoneT >
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inline typename boost::enable_if_c<
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is_scalar< OptionalT >::value && is_scalar< NoneT >::value,
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optional_manipulator< OptionalT, NoneT >
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>::type optional_manip(OptionalT opt, NoneT none) BOOST_NOEXCEPT
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{
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return optional_manipulator< OptionalT, NoneT >(opt, none);
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}
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/*!
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* Optional manipulator generator function.
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*
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* \param opt Optional value to output. The optional value must support contextual conversion to \c bool and dereferencing, and its dereferencing result must support stream output.
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* \param none Marker used to indicate when the value is not present. Optional. If not specified, nothing is output if the value is not present.
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* \returns Manipulator to be inserted into the stream.
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*
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* \note Both \a opt and \a none objects must outlive the created manipulator object.
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*/
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template< typename OptionalT, typename NoneT >
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inline typename boost::enable_if_c<
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is_scalar< OptionalT >::value && !is_scalar< NoneT >::value,
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optional_manipulator< OptionalT, NoneT >
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>::type optional_manip(OptionalT opt, NoneT const& none) BOOST_NOEXCEPT
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{
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return optional_manipulator< OptionalT, NoneT >(opt, none);
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}
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/*!
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* Optional manipulator generator function.
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*
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* \param opt Optional value to output. The optional value must support contextual conversion to \c bool and dereferencing, and its dereferencing result must support stream output.
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* \param none Marker used to indicate when the value is not present. Optional. If not specified, nothing is output if the value is not present.
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* \returns Manipulator to be inserted into the stream.
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*
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* \note Both \a opt and \a none objects must outlive the created manipulator object.
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*/
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template< typename OptionalT, typename NoneElementT, std::size_t N >
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inline typename boost::enable_if_c<
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is_scalar< OptionalT >::value,
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optional_manipulator< OptionalT, NoneElementT* >
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>::type optional_manip(OptionalT opt, NoneElementT (&none)[N]) BOOST_NOEXCEPT
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{
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return optional_manipulator< OptionalT, NoneElementT* >(opt, none);
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}
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/*!
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* Optional manipulator generator function.
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*
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* \param opt Optional value to output. The optional value must support contextual conversion to \c bool and dereferencing, and its dereferencing result must support stream output.
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* \param none Marker used to indicate when the value is not present. Optional. If not specified, nothing is output if the value is not present.
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* \returns Manipulator to be inserted into the stream.
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*
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* \note Both \a opt and \a none objects must outlive the created manipulator object.
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*/
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template< typename OptionalT, typename NoneT >
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inline typename boost::enable_if_c<
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!is_scalar< OptionalT >::value && !is_array< OptionalT >::value && is_scalar< NoneT >::value,
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optional_manipulator< OptionalT, NoneT >
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>::type optional_manip(OptionalT const& opt, NoneT none) BOOST_NOEXCEPT
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{
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return optional_manipulator< OptionalT, NoneT >(opt, none);
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}
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/*!
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* Optional manipulator generator function.
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*
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* \param opt Optional value to output. The optional value must support contextual conversion to \c bool and dereferencing, and its dereferencing result must support stream output.
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* \param none Marker used to indicate when the value is not present. Optional. If not specified, nothing is output if the value is not present.
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* \returns Manipulator to be inserted into the stream.
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*
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* \note Both \a opt and \a none objects must outlive the created manipulator object.
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*/
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template< typename OptionalT, typename NoneT >
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inline typename boost::enable_if_c<
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!is_scalar< OptionalT >::value && !is_array< OptionalT >::value && !is_scalar< NoneT >::value,
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optional_manipulator< OptionalT, NoneT >
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>::type optional_manip(OptionalT const& opt, NoneT const& none) BOOST_NOEXCEPT
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{
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return optional_manipulator< OptionalT, NoneT >(opt, none);
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}
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/*!
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* Optional manipulator generator function.
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*
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* \param opt Optional value to output. The optional value must support contextual conversion to \c bool and dereferencing, and its dereferencing result must support stream output.
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* \param none Marker used to indicate when the value is not present. Optional. If not specified, nothing is output if the value is not present.
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* \returns Manipulator to be inserted into the stream.
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*
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* \note Both \a opt and \a none objects must outlive the created manipulator object.
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*/
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template< typename OptionalT, typename NoneElementT, std::size_t N >
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inline typename boost::enable_if_c<
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!is_scalar< OptionalT >::value && !is_array< OptionalT >::value,
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optional_manipulator< OptionalT, NoneElementT* >
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>::type optional_manip(OptionalT const& opt, NoneElementT (&none)[N]) BOOST_NOEXCEPT
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{
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return optional_manipulator< OptionalT, NoneElementT* >(opt, none);
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}
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/*!
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* Optional manipulator generator function.
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*
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* \param opt Optional value to output. The optional value must support contextual conversion to \c bool and dereferencing, and its dereferencing result must support stream output.
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* \returns Manipulator to be inserted into the stream.
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*
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* \note \a opt object must outlive the created manipulator object.
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*/
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template< typename OptionalT >
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inline typename boost::enable_if_c<
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is_scalar< OptionalT >::value,
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optional_manipulator< OptionalT, void >
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>::type optional_manip(OptionalT opt) BOOST_NOEXCEPT
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{
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return optional_manipulator< OptionalT, void >(opt);
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}
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/*!
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* Optional manipulator generator function.
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*
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* \param opt Optional value to output. The optional value must support contextual conversion to \c bool and dereferencing, and its dereferencing result must support stream output.
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* \returns Manipulator to be inserted into the stream.
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*
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* \note \a opt object must outlive the created manipulator object.
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*/
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template< typename OptionalT >
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inline typename boost::enable_if_c<
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!is_scalar< OptionalT >::value && !is_array< OptionalT >::value,
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optional_manipulator< OptionalT, void >
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>::type optional_manip(OptionalT const& opt) BOOST_NOEXCEPT
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{
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return optional_manipulator< OptionalT, void >(opt);
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}
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BOOST_LOG_CLOSE_NAMESPACE // namespace log
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} // namespace boost
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#include <boost/log/detail/footer.hpp>
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#endif // BOOST_LOG_UTILITY_MANIPULATORS_OPTIONAL_HPP_INCLUDED_
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