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40 lines
953 B
40 lines
953 B
3 years ago
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// Copyright (C) 2003, Fernando Luis Cacciola Carballal.
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// Copyright (C) 2014, 2015 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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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 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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