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std::pair

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pair

(C++11)

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std::pair

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pair::operator=

(C++11)

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operator==operator!=operator<operator<=operator>operator>=operator<=>

(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)

swap(std::pair)

(C++11)

(C++11)

tuple_size<std::pair>

(C++11)

tuple_element<std::pair>

(C++11)

basic_common_reference<std::pair>

(C++23)

common_type<std::pair>

(C++23)

formatter<std::pair>

(C++23)

piecewise_construct_t

(C++11)

Deduction guides (C++17)

Defined in header <utility>

template<

class T1,
class T2

> struct pair;

std::pair is a class template that provides a way to store two heterogeneous objects as a single unit. A pair is a specific case of a std::tuple with two elements.

If neither T1 nor T2 is a possibly cv-qualified class type with non-trivial destructor, or array thereof, the destructor of pair is trivial.

Contents

[edit] Template parameters

T1, T2 - the types of the elements that the pair stores.

[edit] Member types

Member type Definition

first_type T1

second_type T2

[edit] Member objects

Member name Type

first T1

second T2

[edit] Member functions

constructs new pair
(public member function) [edit]

assigns the contents
(public member function) [edit]

(C++11)

swaps the contents
(public member function) [edit]

[edit] Non-member functions

creates a pair object of type, determined by the argument types
(function template) [edit]

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 pair
(function template) [edit]

std::swap(std::pair)

(C++11)

specializes the std::swap algorithm
(function template) [edit]

(C++11)

accesses an element of a pair
(function template) [edit]

[edit] Helper classes

std::tuple_size<std::pair>

(C++11)

obtains the size of a pair
(class template specialization) [edit]

std::tuple_element<std::pair>

(C++11)

obtains the type of the elements of pair
(class template specialization) [edit]

std::basic_common_reference<std::pair>

(C++23)

determines the common reference type of two pairs
(class template specialization) [edit]

std::common_type<std::pair>

(C++23)

determines the common type of two pairs
(class template specialization) [edit]

std::formatter<std::pair>

(C++23)

formatting support for pair
(class template specialization) [edit]

[edit] Helper specializations

template< class T, class U >

constexpr bool enable_nonlocking_formatter_optimization<std::pair<T, U>> =
enable_nonlocking_formatter_optimization<T> &&

enable_nonlocking_formatter_optimization<U>;

(since C++23)

This specialization of std::enable_nonlocking_formatter_optimization enables efficient implementation of std::print and std::println for printing a pair object when both T and U enable it.

[edit] Deduction guides (since C++17)

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 2796	C++98	triviality of the destructor of `pair` was unspecified	specified

[edit] See also

(C++11)

implements fixed size container, which holds elements of possibly different types
(class template) [edit]

(C++11)

creates a tuple of lvalue references or unpacks a tuple into individual objects
(function template) [edit]

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