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49 lines
1.5 KiB
C++
49 lines
1.5 KiB
C++
// Copyright (C) 2003, Fernando Luis Cacciola Carballal.
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// Copyright (C) 2014, 2024 Andrzej Krzemienski.
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//
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// Use, modification, and distribution is subject to the Boost Software
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// License, Version 1.0. (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/optional for documentation.
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//
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// You are welcome to contact the author at:
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// fernando_cacciola@hotmail.com
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//
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#ifndef BOOST_NONE_T_17SEP2003_HPP
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#define BOOST_NONE_T_17SEP2003_HPP
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#include <boost/config.hpp>
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#if defined (BOOST_NO_CXX11_RVALUE_REFERENCES) || defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) || defined(BOOST_NO_CXX11_REF_QUALIFIERS) \
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|| defined(BOOST_NO_CXX11_LAMBDAS) || defined(BOOST_NO_CXX11_DECLTYPE_N3276) || defined(BOOST_NO_CXX11_NOEXCEPT) || defined(BOOST_NO_CXX11_DELETED_FUNCTIONS) || defined(BOOST_NO_CXX11_DEFAULTED_FUNCTIONS) || defined(BOOST_NO_CXX11_DEFAULTED_MOVES) || defined(BOOST_NO_CXX11_EXPLICIT_CONVERSION_OPERATORS)
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#error "Boost.Optional requires C++11 or later. If you have an older C++ version use Boost.Optional version 1.86 or earlier."
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#endif
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namespace boost {
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#ifdef BOOST_OPTIONAL_USE_OLD_DEFINITION_OF_NONE
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namespace detail { struct none_helper{}; }
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typedef int detail::none_helper::*none_t ;
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#elif defined BOOST_OPTIONAL_USE_SINGLETON_DEFINITION_OF_NONE
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class none_t {};
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#else
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struct none_t
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{
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struct init_tag{};
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explicit BOOST_CONSTEXPR none_t(init_tag){} // to disable default constructor
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};
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#endif // old implementation workarounds
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} // namespace boost
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#endif // header guard
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