std::pair - cppreference.com (original) (raw)
| | | | | -------------------------------------------- | | | | 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
- 1 Template parameters
- 2 Member types
- 3 Member objects
- 4 Member functions
- 5 Non-member functions
- 6 Helper classes
- 7 Helper specializations
- 8 Deduction guides(since C++17)
- 9 Defect reports
- 10 See also
[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
[edit] Non-member functions
[edit] Helper classes
[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
| | implements fixed size container, which holds elements of possibly different types (class template) [edit] | | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | creates a tuple of lvalue references or unpacks a tuple into individual objects (function template) [edit] |