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Showing content from https://en.cppreference.com/w/cpp/language/../error/error_code/../../utility/tuple/get.html below:

std::get(std::tuple) - cppreference.com

(1) (since C++11)
(constexpr since C++14) (2) (since C++11)
(constexpr since C++14) (3) (since C++11)
(constexpr since C++14) (4) (since C++11)
(constexpr since C++14) template< class T, class... Types > constexpr T& get( std::tuple<Types...>& t ) noexcept; (5) (since C++14) template< class T, class... Types > constexpr T&& get( std::tuple<Types...>&& t ) noexcept; (6) (since C++14) template< class T, class... Types > constexpr const T& get( const std::tuple<Types...>& t ) noexcept; (7) (since C++14) template< class T, class... Types > constexpr const T&& get( const std::tuple<Types...>&& t ) noexcept; (8) (since C++14)

1-4) Extracts the I^th element from the tuple. I must be an integer value in [â0â, sizeof...(Types)).

5-8) Extracts the element of the tuple t whose type is T. Fails to compile unless the tuple has exactly one element of that type.

[edit] Parameters t - tuple whose contents to extract [edit] Return value

A reference to the selected element of t.

[edit] Notes [edit] Example

#include <cassert>
#include <iostream>
#include <string>
#include <tuple>
 
int main()
{
    auto x = std::make_tuple(1, "Foo", 3.14);
 
    // Index-based access
    std::cout << "( " << std::get<0>(x)
              << ", " << std::get<1>(x)
              << ", " << std::get<2>(x)
              << " )\n";
 
    // Type-based access (since C++14)
    std::cout << "( " << std::get<int>(x)
              << ", " << std::get<const char*>(x)
              << ", " << std::get<double>(x)
              << " )\n";
 
    const std::tuple<int, const int, double, double> y(1, 2, 6.9, 9.6);
    const int& i1 = std::get<int>(y); // OK: not ambiguous
    assert(i1 == 1);
    const int& i2 = std::get<const int>(y); // OK: not ambiguous
    assert(i2 == 2);
    // const double& d = std::get<double>(y); // Error: ill-formed (ambiguous)
 
    // Note: std::tie and structured binding can be
    // used to unpack a tuple into individual objects.
}

Output:

( 1, Foo, 3.14 )
( 1, Foo, 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 tuple&& added these overloads ((4) and (8)) [edit] See also

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