20 General utilities library [utilities]

20.6 Optional objects [optional]

20.6.8 Comparison with T [optional.comp.with.t]

template<class T, class U> constexpr bool operator==(const optional<T>& x, const U& v);
Mandates: The expression *x == v is well-formed and its result is convertible to bool.
[Note 1:
T need not be Cpp17EqualityComparable.
— end note]
Effects: Equivalent to: return x.has_­value() ? *x == v : false;
template<class T, class U> constexpr bool operator==(const T& v, const optional<U>& x);
Mandates: The expression v == *x is well-formed and its result is convertible to bool.
Effects: Equivalent to: return x.has_­value() ? v == *x : false;
template<class T, class U> constexpr bool operator!=(const optional<T>& x, const U& v);
Mandates: The expression *x != v is well-formed and its result is convertible to bool.
Effects: Equivalent to: return x.has_­value() ? *x != v : true;
template<class T, class U> constexpr bool operator!=(const T& v, const optional<U>& x);
Mandates: The expression v != *x is well-formed and its result is convertible to bool.
Effects: Equivalent to: return x.has_­value() ? v != *x : true;
template<class T, class U> constexpr bool operator<(const optional<T>& x, const U& v);
Mandates: The expression *x < v is well-formed and its result is convertible to bool.
Effects: Equivalent to: return x.has_­value() ? *x < v : true;
template<class T, class U> constexpr bool operator<(const T& v, const optional<U>& x);
Mandates: The expression v < *x is well-formed and its result is convertible to bool.
Effects: Equivalent to: return x.has_­value() ? v < *x : false;
template<class T, class U> constexpr bool operator>(const optional<T>& x, const U& v);
Mandates: The expression *x > v is well-formed and its result is convertible to bool.
Effects: Equivalent to: return x.has_­value() ? *x > v : false;
template<class T, class U> constexpr bool operator>(const T& v, const optional<U>& x);
Mandates: The expression v > *x is well-formed and its result is convertible to bool.
Effects: Equivalent to: return x.has_­value() ? v > *x : true;
template<class T, class U> constexpr bool operator<=(const optional<T>& x, const U& v);
Mandates: The expression *x <= v is well-formed and its result is convertible to bool.
Effects: Equivalent to: return x.has_­value() ? *x <= v : true;
template<class T, class U> constexpr bool operator<=(const T& v, const optional<U>& x);
Mandates: The expression v <= *x is well-formed and its result is convertible to bool.
Effects: Equivalent to: return x.has_­value() ? v <= *x : false;
template<class T, class U> constexpr bool operator>=(const optional<T>& x, const U& v);
Mandates: The expression *x >= v is well-formed and its result is convertible to bool.
Effects: Equivalent to: return x.has_­value() ? *x >= v : false;
template<class T, class U> constexpr bool operator>=(const T& v, const optional<U>& x);
Mandates: The expression v >= *x is well-formed and its result is convertible to bool.
Effects: Equivalent to: return x.has_­value() ? v >= *x : true;
template<class T, class U> requires (!is-optional<U>) && three_­way_­comparable_­with<T, U> constexpr compare_three_way_result_t<T, U> operator<=>(const optional<T>& x, const U& v);
Effects: Equivalent to: return x.has_­value() ? *x <=> v : strong_­ordering​::​less;