/*
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Copyright 2018 Glen Joseph Fernandes
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(glenjofe@gmail.com)
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Distributed under the Boost Software License, Version 1.0.
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(http://www.boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_CORE_EMPTY_VALUE_HPP
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#define BOOST_CORE_EMPTY_VALUE_HPP
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#include <boost/config.hpp>
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#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
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#include <utility>
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#endif
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#if defined(BOOST_GCC_VERSION) && (BOOST_GCC_VERSION >= 40700)
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#define BOOST_DETAIL_EMPTY_VALUE_BASE
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#elif defined(BOOST_INTEL) && defined(_MSC_VER) && (_MSC_VER >= 1800)
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#define BOOST_DETAIL_EMPTY_VALUE_BASE
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#elif defined(BOOST_MSVC) && (BOOST_MSVC >= 1800)
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#define BOOST_DETAIL_EMPTY_VALUE_BASE
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#elif defined(BOOST_CLANG) && !defined(__CUDACC__)
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#if __has_feature(is_empty) && __has_feature(is_final)
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#define BOOST_DETAIL_EMPTY_VALUE_BASE
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#endif
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#endif
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namespace boost {
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template<class T>
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struct use_empty_value_base {
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enum {
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#if defined(BOOST_DETAIL_EMPTY_VALUE_BASE)
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value = __is_empty(T) && !__is_final(T)
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#else
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value = false
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#endif
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};
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};
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struct empty_init_t { };
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namespace empty_ {
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template<class T, unsigned N = 0,
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bool E = boost::use_empty_value_base<T>::value>
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class empty_value {
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public:
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typedef T type;
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#if !defined(BOOST_NO_CXX11_DEFAULTED_FUNCTIONS)
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empty_value() = default;
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#else
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empty_value() { }
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#endif
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empty_value(boost::empty_init_t)
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: value_() { }
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#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
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#if !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
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template<class U, class... Args>
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empty_value(boost::empty_init_t, U&& value, Args&&... args)
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: value_(std::forward<U>(value), std::forward<Args>(args)...) { }
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#else
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template<class U>
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empty_value(boost::empty_init_t, U&& value)
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: value_(std::forward<U>(value)) { }
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#endif
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#else
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template<class U>
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empty_value(boost::empty_init_t, const U& value)
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: value_(value) { }
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template<class U>
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empty_value(boost::empty_init_t, U& value)
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: value_(value) { }
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#endif
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const T& get() const BOOST_NOEXCEPT {
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return value_;
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}
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T& get() BOOST_NOEXCEPT {
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return value_;
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}
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private:
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T value_;
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};
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#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
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template<class T, unsigned N>
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class empty_value<T, N, true>
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: T {
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public:
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typedef T type;
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#if !defined(BOOST_NO_CXX11_DEFAULTED_FUNCTIONS)
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empty_value() = default;
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#else
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empty_value() { }
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#endif
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empty_value(boost::empty_init_t)
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: T() { }
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#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
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#if !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
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template<class U, class... Args>
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empty_value(boost::empty_init_t, U&& value, Args&&... args)
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: T(std::forward<U>(value), std::forward<Args>(args)...) { }
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#else
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template<class U>
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empty_value(boost::empty_init_t, U&& value)
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: T(std::forward<U>(value)) { }
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#endif
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#else
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template<class U>
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empty_value(boost::empty_init_t, const U& value)
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: T(value) { }
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template<class U>
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empty_value(boost::empty_init_t, U& value)
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: T(value) { }
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#endif
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const T& get() const BOOST_NOEXCEPT {
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return *this;
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}
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T& get() BOOST_NOEXCEPT {
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return *this;
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}
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};
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#endif
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} /* empty_ */
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using empty_::empty_value;
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BOOST_INLINE_CONSTEXPR empty_init_t empty_init = empty_init_t();
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} /* boost */
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#endif
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