sol2/include/sol/optional.hpp

// sol3 

// The MIT License (MIT)

// Copyright (c) 2013-2018 Rapptz, ThePhD and contributors

// Permission is hereby granted, free of charge, to any person obtaining a copy of
// this software and associated documentation files (the "Software"), to deal in
// the Software without restriction, including without limitation the rights to
// use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
// the Software, and to permit persons to whom the Software is furnished to do so,
// subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
// FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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#ifndef SOL_OPTIONAL_HPP
#define SOL_OPTIONAL_HPP

#include "forward.hpp"
#include "in_place.hpp"
#if defined(SOL_USE_BOOST) && SOL_USE_BOOST
#include <boost/optional.hpp>
#else
#include "optional_implementation.hpp"
#endif // Boost vs. Better optional

#if defined(SOL_CXX17_FEATURES) && SOL_CXX17_FEATURES
#include <optional>
#endif

namespace sol {

#if defined(SOL_USE_BOOST) && SOL_USE_BOOST
	template <typename T>
	using optional = boost::optional<T>;
	using nullopt_t = boost::none_t;
	const nullopt_t nullopt = boost::none;
#endif // Boost vs. Better optional

	namespace meta {
		template <typename T>
		struct is_optional : std::false_type {};
		template <typename T>
		struct is_optional<optional<T>> : std::true_type {};
#if defined(SOL_CXX17_FEATURES) && SOL_CXX17_FEATURES
		template <typename T>
		struct is_optional<std::optional<T>> : std::true_type {};
#endif
	} // namespace meta
} // namespace sol

#endif // SOL_OPTIONAL_HPP