std::common_type<tuple-like>

 

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语言支持 Type support (基本类型, RTTI) Library feature-test macros (C++20) 程序工具 可变参数函数 initializer_list (C++11) is_constant_evaluated (C++20) is_within_lifetime (C++26) source_location (C++20) Coroutine support (C++20) Contract support (C++26) 三路比较 three_way_comparablethree_way_comparable_with (C++20)(C++20) strong_ordering (C++20) weak_ordering (C++20) partial_ordering (C++20) common_comparison_category (C++20) compare_three_way_result (C++20) compare_three_way (C++20) strong_order (C++20) weak_order (C++20) partial_order (C++20) compare_strong_order_fallback (C++20) compare_weak_order_fallback (C++20) compare_partial_order_fallback (C++20)   is_eqis_ltis_lteq (C++20)(C++20)(C++20)   is_neqis_gtis_gteq (C++20)(C++20)(C++20)

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tuple-like (C++23)

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tuple_size<std::tuple>

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basic_common_reference<std::tuple> (C++23)

common_type<std::tuple> (C++23)

formatter<std::tuple> (C++23)

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定义于头文件 <tuple>
template< tuple-like TTuple, tuple-like UTuple >     requires /* see below */ struct common_type<TTuple, UTuple>;		(since C++23)

两个 tuple-like 类型的共同类型是一个 std::tuple，它由两种类型的所有对应元素类型对的共同类型组成。

给定

• TTypes as the pack formed by the sequence of std::tuple_element_t<i, TTuple> for every integer i in [​0, std::tuple_size_v<TTuple>), and
• UTypes as the pack formed by the sequence of std::tuple_element_t<i, UTuple> for every integer i in [​0, std::tuple_size_v<UTuple>),

the following constraints need to be satisfied

• TTuple or UTuple is a std::tuple specialization.
• std::is_same_v<TTuple, std::decay_t<TTuple>> is true.
• std::is_same_v<UTuple, std::decay_t<UTuple>> is true.
• std::tuple_size_v<TTuple> equals std::tuple_size_v<UTuple> (TTuple and UTuple have the same number of elements).
• std::tuple<std::common_type_t<TTypes, UTypes>...> denotes a type.

成员类型

成员类型	定义
type	std::tuple<std::common_type_t<TTypes, UTypes>...>

参见

common_type (C++11)	确定一组类型的共同类型 (class template)
std::common_type<std::pair> (C++23)	determines the common type of two pairs (class template specialization)