# std::common_type<tuple-like>

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< cpp‎ | utility‎ | tuple

Defined in header `<tuple>` |  |
template< tuple-like TTuple, tuple-like UTuple > requires /* see below */ struct common_type<TTuple, UTuple>; |  | (since C++23)

The common type of two `tuple-like` types is a std::tuple consists of the common types of all corresponding element type pairs of both types.

Given

- `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.

### Member types

Member type | Definition
`type` | std::tuple < std::common_type_t <TTypes, UTypes>...>

### Example

| This section is incomplete Reason: no example

### See also

common_type (C++11) | determines the common type of a group of types (class template)
std::common_type<std::pair> (C++23) | determines the common type of two `pair`s (class template specialization)

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