23 General utilities library [utilities]

23.6 Optional objects [optional]

23.6.7 Comparison with nullopt [optional.nullops]

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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
#
Returns: !x.
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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
#
Returns: bool(x).
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template <class T> constexpr bool operator<(const optional<T>& x, nullopt_t) noexcept;
3
#
Returns: false.
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template <class T> constexpr bool operator<(nullopt_t, const optional<T>& x) noexcept;
4
#
Returns: bool(x).
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template <class T> constexpr bool operator<=(const optional<T>& x, nullopt_t) noexcept;
5
#
Returns: !x.
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template <class T> constexpr bool operator<=(nullopt_t, const optional<T>& x) noexcept;
6
#
Returns: true.
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template <class T> constexpr bool operator>(const optional<T>& x, nullopt_t) noexcept;
7
#
Returns: bool(x).
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template <class T> constexpr bool operator>(nullopt_t, const optional<T>& x) noexcept;
8
#
Returns: false.
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template <class T> constexpr bool operator>=(const optional<T>& x, nullopt_t) noexcept;
9
#
Returns: true.
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template <class T> constexpr bool operator>=(nullopt_t, const optional<T>& x) noexcept;
10
#
Returns: !x.