std::get(std::pair)

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

 

Utilities library

Type support (basic types, RTTI, type traits)

Dynamic memory management

Error handling

Program utilities

Variadic functions

Date and time

Function objects

initializer_list (C++11)

bitset

hash (C++11)

Relational operators

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

optional, any and variant (C++17)

optional

any

variant

in_placein_place_typein_place_indexin_place_tin_place_type_tin_place_index_t

Pairs and tuples

pair

tuple (C++11)

apply (C++17)

make_from_tuple (C++17)

piecewise_construct_t (C++11)

piecewise_construct (C++11)

integer_sequence (C++14)

Swap, forward and move

swap

exchange (C++14)

forward (C++11)

move (C++11)

move_if_noexcept (C++11)

Elementary string conversions

to_chars (C++17)

from_chars (C++17)

chars_format (C++17)

Type operations

declval (C++11)

as_const (C++17)

 

std::pair

Member functions

pair::pair

pair::operator=

pair::swap

Non-member functions

make_pair

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

std::swap

get (C++11)

Helper classes

tuple_size (C++11)

tuple_element (C++11)

 

Defined in header <utility>
	(1)
template< size_t I, class T1, class T2 > typename std::tuple_element<I, std::pair<T1,T2> >::type&     get( pair<T1, T2>& p );		(1)	(since C++11) (until C++14)
template< size_t I, class T1, class T2 > constexpr std::tuple_element_t<I, std::pair<T1,T2> >&     get( pair<T1, T2>& p );		(1)	(since C++14)
		(2)
template< size_t I, class T1, class T2 > const typename std::tuple_element<I, std::pair<T1,T2> >::type&     get( const pair<T1,T2>& p );			(2)	(since C++11) (until C++14)
template< size_t I, class T1, class T2 > constexpr const std::tuple_element_t<I, std::pair<T1,T2> >&     get( const pair<T1,T2>& p );			(2)	(since C++14)
			(3)
template< size_t I, class T1, class T2 > typename std::tuple_element<I, std::pair<T1,T2> >::type&&     get( std::pair<T1,T2>&& p );				(3)	(since C++11) (until C++14)
template< size_t I, class T1, class T2 > constexpr std::tuple_element_t<I, std::pair<T1,T2> >&&     get( std::pair<T1,T2>&& p );				(3)	(since C++14)
template< size_t I, class T1, class T2 > constexpr const std::tuple_element_t<I, std::pair<T1,T2> >&&     get( const std::pair<T1,T2>&& p );				(4)	(since C++17)
template <class T, class U> constexpr T& get(std::pair<T, U>& p);				(5)	(since C++14)
template <class T, class U> constexpr const T& get(const std::pair<T, U>& p);				(6)	(since C++14)
template <class T, class U> constexpr T&& get(std::pair<T, U>&& p);				(7)	(since C++14)
template <class T, class U> constexpr const T&& get(const std::pair<T, U>&& p);				(8)	(since C++17)
template <class T, class U> constexpr T& get(std::pair<U, T>& p);				(9)	(since C++14)
template <class T, class U> constexpr const T& get(const std::pair<U, T>& p);				(10)	(since C++14)
template <class T, class U> constexpr T&& get(std::pair<U, T>&& p);				(11)	(since C++14)
template <class T, class U> constexpr const T&& get(const std::pair<U, T>&& p);				(12)	(since C++17)

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.

Exceptions

noexcept specification:  

noexcept

  

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)

See also

std::get(std::tuple)	tuple accesses specified element (function template)
std::get(std::array)	accesses an element of an array (function template)
std::get(std::variant) (C++17)	reads the value of the variant given the index or the type (if the type is unique), throws on error (function template)