std::get(std::pair)

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std::pair

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pair::pair
pair::operator=
pair::swap (C++11)
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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)
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get(std::pair) (C++11)
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Defined in header`<utility>`
template<std::size_t I,class T1,class T2> typenamestd::tuple_element<I,std::pair<T1,T2>>::type& get(std::pair<T1, T2>& p)noexcept;	(1)	(since C++11) (constexpr since C++14)
template<std::size_t I,class T1,class T2> consttypenamestd::tuple_element<I,std::pair<T1,T2>>::type& get(conststd::pair<T1,T2>& p)noexcept;	(2)	(since C++11) (constexpr since C++14)
template<std::size_t I,class T1,class T2> typenamestd::tuple_element<I,std::pair<T1,T2>>::type&& get(std::pair<T1,T2>&& p)noexcept;	(3)	(since C++11) (constexpr since C++14)
template<std::size_t I,class T1,class T2> consttypenamestd::tuple_element<I,std::pair<T1,T2>>::type&& get(conststd::pair<T1,T2>&& p)noexcept;	(4)	(since C++11) (constexpr 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> constexprconst T& get(conststd::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> constexprconst T&& get(conststd::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> constexprconst T& get(conststd::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> constexprconst T&& get(conststd::pair<U, T>&& p)noexcept;	(12)	(since C++14)

Extracts an element from the pair usingtuple-like interface.

1-4) The index-based overloads fail to compile if the indexI is neither0 nor1.

5-12) The type-based overloads fail to compile if the typesT andU are the same.

[edit]Parameters

pair whose contents to extract

[edit]Return value

1-4) Returns a reference top.first ifI==0 and a reference top.second ifI==1.

5-8) Returns a reference top.first.

9-12) Returns a reference top.second.

[edit]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)

[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

Structured binding(C++17)	binds the specified names to sub-objects or tuple elements of the initializer[edit]
get(std::tuple) (C++11)	tuple accesses specified element (function template)[edit]
get(std::array) (C++11)	accesses an element of an`array` (function template)[edit]
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)[edit]
get(std::ranges::subrange) (C++20)	obtains iterator or sentinel from astd::ranges::subrange (function template)[edit]
get(std::complex) (C++26)	obtains a reference to real or imaginary part from astd::complex (function template)[edit]

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std::get(std::pair)

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