23 General utilities library [utilities]

23.6 Optional objects [optional]

23.6.7 Comparison with nullopt [optional.nullops]

template <class T> constexpr bool operator==(const optional<T>& x, nullopt_t) noexcept; template <class T> constexpr bool operator==(nullopt_t, const optional<T>& x) noexcept;

1
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Returns: !x.

template <class T> constexpr bool operator!=(const optional<T>& x, nullopt_t) noexcept; template <class T> constexpr bool operator!=(nullopt_t, const optional<T>& x) noexcept;

2
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Returns: bool(x).

template <class T> constexpr bool operator<(const optional<T>& x, nullopt_t) noexcept;

3
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Returns: false.

template <class T> constexpr bool operator<(nullopt_t, const optional<T>& x) noexcept;

4
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Returns: bool(x).

template <class T> constexpr bool operator<=(const optional<T>& x, nullopt_t) noexcept;

5
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Returns: !x.

template <class T> constexpr bool operator<=(nullopt_t, const optional<T>& x) noexcept;

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Returns: true.

template <class T> constexpr bool operator>(const optional<T>& x, nullopt_t) noexcept;

7
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Returns: bool(x).

template <class T> constexpr bool operator>(nullopt_t, const optional<T>& x) noexcept;

8
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Returns: false.

template <class T> constexpr bool operator>=(const optional<T>& x, nullopt_t) noexcept;

9
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Returns: true.

template <class T> constexpr bool operator>=(nullopt_t, const optional<T>& x) noexcept;

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Returns: !x.