std::pair

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Utilities library

Language support

Type support (basic types, RTTI)

Library feature-test macros(C++20)

Program utilities

Variadic functions

initializer_list

(C++11)

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(C++20)

is_within_lifetime

(C++26)

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(C++20)

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Three-way comparison

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)

(C++20)

(C++20)

(C++20)

(C++20)

compare_strong_order_fallback

(C++20)

compare_weak_order_fallback

(C++20)

compare_partial_order_fallback

(C++20)

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

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

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rel_ops::operator<=rel_ops::operator>=

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cmp_equalcmp_lesscmp_less_than

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

cmp_not_equalcmp_greatercmp_greater_than

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

in_range

(C++20)

Swap andtype operations

swap
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Common vocabulary types

pair
tuple (C++11)
optional (C++17)
any (C++17)
variant (C++17)

tuple_size (C++11)
tuple_element (C++11)
apply (C++17)
make_from_tuple (C++17)
expected (C++23)

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std::pair

Member functions
pair::pair
pair::operator=
pair::swap (C++11)
Non-member functions
make_pair
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)
get(std::pair) (C++11)
Helper classes
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)

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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 astd::tuple with two elements.

If neitherT1 norT2 is a possibly cv-qualified class type with non-trivial destructor, or array thereof, the destructor ofpair is trivial.

[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

(constructor)	constructs new`pair` (public member function)[edit]
operator=	assigns the contents (public member function)[edit]
swap (C++11)	swaps the contents (public member function)[edit]

[edit]Non-member functions

make_pair	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 thestd::swap algorithm (function template)[edit]
get(std::pair) (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`pair`s (class template specialization)[edit]
std::common_type<std::pair> (C++23)	determines the common type of two`pair`s (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> constexprbool enable_nonlocking_formatter_optimization<std::pair<T, U>>= enable_nonlocking_formatter_optimization<T>&& enable_nonlocking_formatter_optimization<U>;		(since C++23)

This specialization ofstd::enable_nonlocking_formatter_optimization enables efficient implementation ofstd::print andstd::println for printing apair object when bothT andU 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

tuple (C++11)	implements fixed size container, which holds elements of possibly different types (class template)[edit]
tie (C++11)	creates atuple of lvalue references or unpacks a tuple into individual objects (function template)[edit]