# tuple-like, pair-like

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< cpp‎ | utility‎ | tuple

template< class T > concept tuple-like = /* see below */; | (1) | (since C++23) (exposition only*)
template< class T > concept pair-like = tuple-like<T> && std::tuple_size_v < std::remove_cvref_t <T>> == 2; | (2) | (since C++23) (exposition only*)

1) A type `T` models and satisfies the concept `tuple-like` if std::remove_cvref_t <T> is a specialization of

- std::array,

- std::complex,

(since C++26)

- std::pair,
- std::tuple, or
- std::ranges::subrange.

2) `pair-like` objects are `tuple-like` objects with exactly 2 elements.

### Notes

`tuple-like` types implement the tuple protocol, i.e., such types can be used with `std::get`, `std::tuple_element` and `std::tuple_size`.

Elements of `tuple-like` types can be bound with structured binding.

### See also

`tuple-like` and `pair-like` are used in the following standard library components:

(constructor) | constructs a new `tuple` (public member function)
operator= | assigns the contents of one `tuple` to another (public member function)
operator==operator!=operator<operator<=operator>operator>=operator<=> (removed in C++20)(removed in C++20)(removed in C++20)(removed in C++20)(removed in C++20)(C++20) | lexicographically compares the values in the tuple (function template)
std::basic_common_reference<tuple-like> (C++23) | determines the common reference type of a `tuple` and a `tuple-like` type (class template specialization)
std::common_type<tuple-like> (C++23) | determines the common type of a `tuple` and a `tuple-like` type (class template specialization)
tuple_cat (C++11) | creates a `tuple` by concatenating any number of tuples (function template)
apply (C++17) | calls a function with a tuple of arguments (function template)
make_from_tuple (C++17) | construct an object with a tuple of arguments (function template)
(constructor) | constructs new `pair` (public member function of `std::pair<T1,T2>`)
operator= | assigns the contents (public member function of `std::pair<T1,T2>`)
operator PairLike | converts the `subrange` to a `pair-like` type (public member function of `std::ranges::subrange<I,S,K>`)
ranges::elements_viewviews::elements (C++20) | takes a `view` consisting of `tuple-like` values and a number N and produces a `view` of Nth element of each tuple (class template) (range adaptor object)

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