NAME¶

std::get(std::pair) - std::get(std::pair)

Synopsis¶

Defined in header <utility>
template< std::size_t I, class T1, class T2
> (since
C++11)
typename std::tuple_element<I, (until
std::pair<T1,T2> >::type& C++14)

get( std::pair<T1, T2>& p ) noexcept;
template< std::size_t I, class T1, class T2
>
(since
constexpr std::tuple_element_t<I, C++14)
std::pair<T1,T2> >&

get( std::pair<T1, T2>& p ) noexcept;
template< std::size_t I, class T1, class T2
> (since
C++11)
const typename std::tuple_element<I, (until
std::pair<T1,T2> >::type& C++14)

get( const std::pair<T1,T2>& p ) noexcept;
template< std::size_t I, class T1, class T2
>
(since
constexpr const std::tuple_element_t<I, C++14)
std::pair<T1,T2> >&

get( const std::pair<T1,T2>& p ) noexcept;
template< std::size_t I, class T1, class T2
> (since
C++11)
typename std::tuple_element<I, (until
std::pair<T1,T2> >::type&& C++14)

get( std::pair<T1,T2>&& p ) noexcept;
template< std::size_t I, class T1, class T2
>
(since
constexpr std::tuple_element_t<I, C++14)
std::pair<T1,T2> >&& (1)

get( std::pair<T1,T2>&& p ) noexcept;
template< std::size_t I, class T1, class T2
> (since
C++11)
const typename std::tuple_element<I, (until
std::pair<T1,T2> >::type&& (2) C++14)

get( const std::pair<T1,T2>&& p ) noexcept;
template< std::size_t I, class T1, class T2
>
(since
constexpr const std::tuple_element_t<I, C++14)
std::pair<T1,T2> >&& (3)

get( const std::pair<T1,T2>&& p ) noexcept;
template <class T, class U> (since
constexpr T& get(std::pair<T, U>& p) (5) C++14)
noexcept;
template <class T, class U> (since
constexpr const T& get(const std::pair<T, (4) (6) C++14)
U>& p) noexcept;
template <class T, class U> (since
constexpr T&& get(std::pair<T, U>&& p) (7) C++14)
noexcept;
template <class T, class U> (since
constexpr const T&& get(const std::pair<T, (8) C++14)
U>&& p) noexcept;
template <class T, class U> (since
constexpr T& get(std::pair<U, T>& p) (9) C++14)
noexcept;
template <class T, class U> (since
constexpr const T& get(const std::pair<U, (10) C++14)
T>& p) noexcept;
template <class T, class U> (since
constexpr T&& get(std::pair<U, T>&& p) (11) C++14)
noexcept;
template <class T, class U> (since
constexpr const T&& get(const std::pair<U, (12) C++14)
T>&& p) noexcept;

Extracts an element from the pair using tuple-like interface.

The index-based overloads (1-4) fail to compile if the index I is neither 0 nor 1.

The type-based overloads (5-12) fail to compile if the types T and U are the same.

Parameters¶

p - pair whose contents to extract

Return value¶

1-4) Returns a reference to p.first if I==0 and a reference to p.second if I==1.
5-8) Returns a reference to p.first.
9-12) Returns a reference to p.second.

Example¶

// Run this code

#include <iostream>
#include <utility>

int main()
{
auto p = std::make_pair(1, 3.14);
std::cout << '(' << std::get<0>(p) << ", " << std::get<1>(p) << ")\n";
std::cout << '(' << std::get<int>(p) << ", " << std::get<double>(p) << ")\n";
}

Output:¶

(1, 3.14)
(1, 3.14)

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 2485 C++11 (by index) there are no overloads for const the overloads are added
C++14 (by type) pair&&

See also¶

Structured binding (C++17) binds the specified names to sub-objects or tuple
elements of the initializer
std::get(std::tuple) tuple accesses specified element
(C++11) (function template)
std::get(std::array) accesses an element of an array
(C++11) (function template)
std::get(std::variant) reads the value of the variant given the index or the
(C++17) type (if the type is unique), throws on error
(function template)
get(std::ranges::subrange) obtains iterator or sentinel from a std::ranges::subrange
(C++20) (function template)