17 Language support library [support]

17.11 Comparisons [cmp]

17.11.3 Class template common_comparison_category [cmp.common]

The type common_comparison_category provides an alias for the strongest comparison category to which all of the template arguments can be converted.

[Note 1:

A comparison category type is stronger than another if they are distinct types and an instance of the former can be converted to an instance of the latter.

— end note]

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template<class... Ts>
struct common_comparison_category {
  using type = see below;
};

Remarks: The member typedef-name type denotes the common comparison type ([class.spaceship]) of Ts..., the expanded parameter pack, or void if any element of Ts is not a comparison category type.

[Note 2:

This is std::strong_ordering if the expansion is empty.

— end note]