std::get(std::tuple)

Posted 2021-12-29 thefist11

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

eg.

#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 (C++14 or later)
    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)