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);
1
#
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
 ]
2
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Returns: If bool(x) != bool(y), false; otherwise if bool(x) == false, true; otherwise *x == *y.
3
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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);
4
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Requires: The expression *x != *y shall be well-formed and its result shall be convertible to bool.
5
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Returns: If bool(x) != bool(y), true; otherwise, if bool(x) == false, false; otherwise *x != *y.
6
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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);
7
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Requires: *x < *y shall be well-formed and its result shall be convertible to bool.
8
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Returns: If !y, false; otherwise, if !x, true; otherwise *x < *y.
9
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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);
10
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Requires: The expression *x > *y shall be well-formed and its result shall be convertible to bool.
11
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Returns: If !x, false; otherwise, if !y, true; otherwise *x > *y.
12
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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);
13
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Requires: The expression *x <= *y shall be well-formed and its result shall be convertible to bool.
14
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Returns: If !x, true; otherwise, if !y, false; otherwise *x <= *y.
15
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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);
16
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Requires: The expression *x >= *y shall be well-formed and its result shall be convertible to bool.
17
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Returns: If !y, true; otherwise, if !x, false; otherwise *x >= *y.
18
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Remarks: Specializations of this function template for which *x >= *y is a core constant expression shall be constexpr functions.