整理

include/boost/none_t.hpp

@@ -0,0 +1,55 @@
+// Copyright (C) 2003, Fernando Luis Cacciola Carballal.
+// Copyright (C) 2014, 2024 Andrzej Krzemienski.
+//
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/libs/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  fernando_cacciola@hotmail.com
+//
+#ifndef BOOST_NONE_T_17SEP2003_HPP
+#define BOOST_NONE_T_17SEP2003_HPP
+
+#include <boost/config.hpp>
+#include <boost/config/pragma_message.hpp>
+
+#if defined (BOOST_NO_CXX11_RVALUE_REFERENCES) || defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) \
+|| defined(BOOST_NO_CXX11_LAMBDAS) || defined(BOOST_NO_CXX11_DECLTYPE_N3276)  \
+|| defined(BOOST_NO_CXX11_DELETED_FUNCTIONS) || defined(BOOST_NO_CXX11_DEFAULTED_FUNCTIONS) \
+|| defined(BOOST_NO_CXX11_EXPLICIT_CONVERSION_OPERATORS) || defined(BOOST_NO_CXX11_STATIC_ASSERT)
+
+#error "Boost.Optional requires some C++11 features since version 1.87. If you have an older C++ version use Boost.Optional version 1.86 or earlier."
+
+#elif defined(BOOST_NO_CXX11_REF_QUALIFIERS) || defined(BOOST_NO_CXX11_NOEXCEPT) || defined(BOOST_NO_CXX11_DEFAULTED_MOVES)
+
+BOOST_PRAGMA_MESSAGE("C++03 support is deprecated in Boost.Optional 1.83 and will be removed in Boost.Optional 1.88.")
+
+#endif
+
+namespace boost {
+
+#ifdef BOOST_OPTIONAL_USE_OLD_DEFINITION_OF_NONE
+
+namespace detail { struct none_helper{}; }
+typedef int detail::none_helper::*none_t ;
+
+#elif defined BOOST_OPTIONAL_USE_SINGLETON_DEFINITION_OF_NONE
+
+class none_t {};
+
+#else
+
+struct none_t
+{
+  struct init_tag{};
+  explicit BOOST_CONSTEXPR none_t(init_tag){} // to disable default constructor
+};
+
+#endif // old implementation workarounds
+
+} // namespace boost
+
+#endif // header guard