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std::get(std::pair)

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< cpp‎ | utility‎ | pair
 
 
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Defined in header <utility>
(1)
template< std::size_t I, class T1, class T2 >

typename std::tuple_element<I, std::pair<T1,T2> >::type&

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

constexpr std::tuple_element_t<I, std::pair<T1,T2> >&

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

const typename std::tuple_element<I, std::pair<T1,T2> >::type&

    get( const std::pair<T1,T2>& p ) noexcept;
(since C++11)
(until C++14)
template< std::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 ) noexcept;
(since C++14)
(3)
template< std::size_t I, class T1, class T2 >

typename std::tuple_element<I, std::pair<T1,T2> >::type&&

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

constexpr std::tuple_element_t<I, std::pair<T1,T2> >&&

    get( std::pair<T1,T2>&& p ) noexcept;
(since C++14)
(4)
template< std::size_t I, class T1, class T2 >

const typename std::tuple_element<I, std::pair<T1,T2> >::type&&

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

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.

Contents

[edit] Parameters

p - pair whose contents to extract

[edit] 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.

[edit] Example

#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)

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

[edit] See also

tuple accesses specified element
(function template) [edit]
accesses an element of an array
(function template) [edit]
reads the value of the variant given the index or the type (if the type is unique), throws on error
(function template) [edit]