std::common_comparison_category - cppreference.com (original) (raw)

| | | | | --------------------------------------------------------------------------------------------------- | | ------------- | | template< class... Ts > struct common_comparison_category { using type = /* see below */ ; }; | | (since C++20) |

The class template std::common_comparison_category provides an alias (as the member typedef type) for the strongest comparison category to which all of the template arguments Ts... can be converted.

In detail, the common comparison type of a list of n types T0...Tn-1 is defined as follows:

• If any Ti is not a comparison category type (std::partial_ordering, std::weak_ordering, std::strong_ordering), U is void.
• Otherwise, if at least one Ti is std::partial_ordering, U is std::partial_ordering.
• Otherwise, if at least one Ti is std::weak_ordering, U is std::weak_ordering.
• Otherwise (if every Ti is std::strong_ordering, or if the list is empty), U is std::strong_ordering.

Contents

• 1 Template parameters
• 2 Helper template
• 3 Member types
• 4 Possible implementation
• 5 Example
• 6 See also

[edit] Template parameters

[edit] Helper template

| template< class... Ts > using common_comparison_category_t = common_comparison_category<Ts...>::type; | | (since C++20) | | ------------------------------------------------------------------------------------------------------------- | | ------------- |

[edit] Member types

[edit] Possible implementation

[edit] Example

[edit] See also

| | the result type of 3-way comparison that supports all 6 operators and is substitutable (class) [edit] | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | | the result type of 3-way comparison that supports all 6 operators and is not substitutable (class) [edit] | | | the result type of 3-way comparison that supports all 6 operators, is not substitutable, and allows incomparable values (class) [edit] |