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Headers: Implement <optional>
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/* Copyright (C) 2019 Povilas Kanapickas <povilas@radix.lt>
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This file is part of cppreference-doc
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This work is licensed under the Creative Commons Attribution-ShareAlike 3.0
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Unported License. To view a copy of this license, visit
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http://creativecommons.org/licenses/by-sa/3.0/ or send a letter to Creative
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Commons, 444 Castro Street, Suite 900, Mountain View, California, 94041, USA.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with no
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Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
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*/
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#ifndef CPPREFERENCE_OPTIONAL_H
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#define CPPREFERENCE_OPTIONAL_H
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#if CPPREFERENCE_STDVER >= 2017
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#include <functional> // hash
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#include <utility> // in_place_t, ...
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#include <type_traits> // decay_t
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#include <exception> // exception
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namespace std {
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struct nullopt_t {};
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inline constexpr nullopt_t nullopt;
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class bad_optional_access : public exception {
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public:
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~bad_optional_access() override;
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const char * what() const override;
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};
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template<class T>
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class optional {
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public:
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using value_type = T;
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constexpr optional();
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constexpr optional(std::nullopt_t);
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constexpr optional(const optional& other);
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constexpr optional(optional&& other);
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template <class U>
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optional(const optional<U>& other);
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template<class U>
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optional(optional<U>&& other);
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template<class... Args>
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constexpr explicit optional(in_place_t, Args&&... args);
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template<class U, class... Args>
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constexpr explicit optional(in_place_t,
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initializer_list<U> ilist,
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Args&&... args);
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template<class U = value_type>
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constexpr optional(U&& value);
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~optional();
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optional& operator=(std::nullopt_t);
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constexpr optional& operator=(const optional& other);
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constexpr optional& operator=(optional&& other);
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template<class U = T>
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optional& operator=(U&& value);
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template<class U>
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optional& operator=(const optional<U>& other);
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template<class U>
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optional& operator=(optional<U>&& other);
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constexpr const T* operator->() const;
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constexpr T* operator->();
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constexpr const T& operator*() const&;
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constexpr T& operator*() &;
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constexpr const T&& operator*() const&&;
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constexpr T&& operator*() &&;
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constexpr explicit operator bool() const;
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constexpr bool has_value() const;
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constexpr T& value() &;
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constexpr const T & value() const &;
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constexpr T&& value() &&;
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constexpr const T&& value() const &&;
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template< class U >
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constexpr T value_or(U&& default_value) const&;
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template< class U >
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constexpr T value_or(U&& default_value) &&;
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void swap(optional& other);
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void reset();
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template<class... Args>
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T& emplace(Args&&... args);
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template<class U, class... Args>
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T& emplace(initializer_list<U> ilist, Args&&... args);
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};
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template<class T, class U>
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constexpr bool operator==(const optional<T>& lhs, const optional<U>& rhs);
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template<class T, class U>
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constexpr bool operator!=(const optional<T>& lhs, const optional<U>& rhs);
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template<class T, class U>
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constexpr bool operator<(const optional<T>& lhs, const optional<U>& rhs);
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template<class T, class U>
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constexpr bool operator<=(const optional<T>& lhs, const optional<U>& rhs);
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template<class T, class U>
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constexpr bool operator>(const optional<T>& lhs, const optional<U>& rhs);
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template<class T, class U>
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constexpr bool operator>=(const optional<T>& lhs, const optional<U>& rhs);
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template<class T>
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constexpr bool operator==(const optional<T>& opt, nullopt_t);
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template<class T>
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constexpr bool operator==(nullopt_t, const optional<T>& opt);
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template<class T>
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constexpr bool operator!=(const optional<T>& opt, nullopt_t);
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template<class T>
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constexpr bool operator!=(nullopt_t, const optional<T>& opt);
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template<class T>
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constexpr bool operator<(const optional<T>& opt, nullopt_t);
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template<class T>
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constexpr bool operator<(nullopt_t, const optional<T>& opt);
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template<class T>
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constexpr bool operator<=(const optional<T>& opt, nullopt_t);
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template<class T>
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constexpr bool operator<=(nullopt_t, const optional<T>& opt);
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template<class T>
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constexpr bool operator>(const optional<T>& opt, nullopt_t);
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template<class T>
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constexpr bool operator>(nullopt_t, const optional<T>& opt);
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template<class T>
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constexpr bool operator>=(const optional<T>& opt, nullopt_t);
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template<class T>
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constexpr bool operator>=(nullopt_t, const optional<T>& opt);
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template<class T, class U>
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constexpr bool operator==(const optional<T>& opt, const U& value);
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template<class T, class U>
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constexpr bool operator==(const T& value, const optional<U>& opt);
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template<class T, class U>
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constexpr bool operator!=(const optional<T>& opt, const U& value);
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template<class T, class U>
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constexpr bool operator!=(const T& value, const optional<U>& opt);
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template<class T, class U>
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constexpr bool operator<(const optional<T>& opt, const U& value);
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template<class T, class U>
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constexpr bool operator<(const T& value, const optional<U>& opt);
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template<class T, class U>
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constexpr bool operator<=(const optional<T>& opt, const U& value);
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template<class T, class U>
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constexpr bool operator<=(const T& value, const optional<U>& opt);
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template<class T, class U>
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constexpr bool operator>(const optional<T>& opt, const U& value);
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template<class T, class U>
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constexpr bool operator>(const T& value, const optional<U>& opt);
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template<class T, class U>
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constexpr bool operator>=(const optional<T>& opt, const U& value);
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template<class T, class U>
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constexpr bool operator>=(const T& value, const optional<U>& opt);
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template<class T >
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constexpr optional<decay_t<T>> make_optional(T&& value);
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template<class T, class... Args >
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constexpr optional<T> make_optional(Args&&... args);
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template<class T, class U, class... Args >
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constexpr optional<T> make_optional(initializer_list<U> il, Args&&... args);
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template<class T>
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void swap(optional<T>& lhs, optional<T>& rhs);
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template<class T>
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struct hash<std::optional<T>> {};
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} // namespace std
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#endif // CPPREFERENCE_STDVER >= 2017
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#endif // CPPREFERENCE_OPTIONAL_H

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