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

1-4) Extracts the Ith element from the tuple. I must be an integer value in [​0​, 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

[edit] Return value

A reference to the selected element of t.

[edit] Notes

[edit] Example

#include #include #include #include   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(x) << ", " << std::get<const char*>(x) << ", " << std::get(x) << " )\n";   const std::tuple<int, const int, double, double> y(1, 2, 6.9, 9.6); const int& i1 = std::get(y); // OK: not ambiguous assert(i1 == 1); const int& i2 = std::get(y); // OK: not ambiguous assert(i2 == 2); // const double& d = std::get(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.

[edit] See also