std::get(std::tuple) (3) - Linux Manuals

std::get(std::tuple): std::get(std::tuple)

NAME

std::get(std::tuple) - std::get(std::tuple)

Synopsis

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

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.

Parameters

t - tuple whose contents to extract

Return value

A reference to the selected element of t.

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 there are no overloads for const tuple&& the overloads are added

Example

// Run this code

  #include <iostream>
  #include <string>
  #include <tuple>

  int main()
  {
      auto t = std::make_tuple(1, "Foo", 3.14);
      // index-based access
      std::cout << "(" << std::get<0>(t) << ", " << std::get<1>(t)
                << ", " << std::get<2>(t) << ")\n";
      // type-based access
      std::cout << "(" << std::get<int>(t) << ", " << std::get<const char*>(t)
                << ", " << std::get<double>(t) << ")\n";
      // Note: std::tie and structured binding may also be used to decompose a tuple
  }

Output:

  (1, Foo, 3.14)
  (1, Foo, 3.14)