std::partial_order
From cppreference.com
| Defined in header <compare>
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| inline namespace /* unspecified */ { inline constexpr /* unspecified */ partial_order = /* unspecified */; |
(since C++20) | |
| Call signature |
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| template< class T, class U > requires /* see below */ |
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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 |
[edit] See also
| (C++20) |
the result type of 3-way comparison that supports all 6 operators, is not substitutable, and allows incomparable values (class) |
| (C++20) |
performs 3-way comparison and produces a result of type std::strong_ordering(customization point object) |
| (C++20) |
performs 3-way comparison and produces a result of type std::weak_ordering(customization point object) |
performs 3-way comparison and produces a result of type std::partial_ordering, even if operator<=> is unavailable(customization point object) |
