std::partial_order
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partial_order
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Defined in header
<compare>
inline namespace /* unspecified */ {
(since C++20)
inline constexpr /* unspecified */ partial_order = /* unspecified */;
Call signature
template< class T, class U >
requires /* see below */
constexpr std::partial_ordering
Compares two values using 3-way comparison and produces a result of type std::partial_ordering.
Let t and u be expressions and T and U denote decltype((t)) and decltype((u)) respectively, std::partial_order(t, u) is expression-equivalent to:
- If std::is_same_v <std::decay_t <T>, std::decay_t <U>> is true:
- std::partial_ordering (partial_order(t, u)), if it is a well-formed expression with overload resolution performed in a context that does not include a declaration of
std::partial_order, - otherwise, std::partial_ordering (std::compare_three_way ()(t, u)), if it is well-formed,
- otherwise, std::partial_ordering (std::weak_order (t, u)), if it is well-formed.
- std::partial_ordering (partial_order(t, u)), if it is a well-formed expression with overload resolution performed in a context that does not include a declaration of
- In all other cases, the expression is ill-formed, which can result in substitution failure when it appears in the immediate context of a template instantiation.
Customization point objects
The name std::partial_order denotes a customization point object, which is a const function object of a literal semiregular class type. See CustomizationPointObject for details.
[edit] Example
This section is incomplete
Reason: no example
Reason: no example
[edit] See also
(C++20)
(class) [edit]
(C++20)
std::strong_ordering(customization point object)[edit]
(C++20)
std::weak_ordering(customization point object)[edit]
(C++20)
std::partial_ordering, even if operator<=> is unavailable(customization point object)[edit]