23 General utilities library [utilities]

23.6 Optional objects [optional]

23.6.6 Relational operators [optional.relops]

template<class T, class U> constexpr bool operator==(const optional<T>& x, const optional<U>& y);
Requires: The expression *x == *y shall be well-formed and its result shall be convertible to bool.
[Note
:
T need not be EqualityComparable.
end note
]
Returns: If bool(x) != bool(y), false; otherwise if bool(x) == false, true; otherwise *x == *y.
Remarks: Specializations of this function template for which *x == *y is a core constant expression shall be constexpr functions.
template<class T, class U> constexpr bool operator!=(const optional<T>& x, const optional<U>& y);
Requires: The expression *x != *y shall be well-formed and its result shall be convertible to bool.
Returns: If bool(x) != bool(y), true; otherwise, if bool(x) == false, false; otherwise *x != *y.
Remarks: Specializations of this function template for which *x != *y is a core constant expression shall be constexpr functions.
template<class T, class U> constexpr bool operator<(const optional<T>& x, const optional<U>& y);
Requires: *x < *y shall be well-formed and its result shall be convertible to bool.
Returns: If !y, false; otherwise, if !x, true; otherwise *x < *y.
Remarks: Specializations of this function template for which *x < *y is a core constant expression shall be constexpr functions.
template<class T, class U> constexpr bool operator>(const optional<T>& x, const optional<U>& y);
Requires: The expression *x > *y shall be well-formed and its result shall be convertible to bool.
Returns: If !x, false; otherwise, if !y, true; otherwise *x > *y.
Remarks: Specializations of this function template for which *x > *y is a core constant expression shall be constexpr functions.
template<class T, class U> constexpr bool operator<=(const optional<T>& x, const optional<U>& y);
Requires: The expression *x <= *y shall be well-formed and its result shall be convertible to bool.
Returns: If !x, true; otherwise, if !y, false; otherwise *x <= *y.
Remarks: Specializations of this function template for which *x <= *y is a core constant expression shall be constexpr functions.
template<class T, class U> constexpr bool operator>=(const optional<T>& x, const optional<U>& y);
Requires: The expression *x >= *y shall be well-formed and its result shall be convertible to bool.
Returns: If !y, true; otherwise, if !x, false; otherwise *x >= *y.
Remarks: Specializations of this function template for which *x >= *y is a core constant expression shall be constexpr functions.