NAME¶

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

Synopsis¶

Defined in header <tuple>
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 >

typename std::tuple_element<I, tuple<Types...> >::type (3) (since C++11)
const& (constexpr since C++14)

get( const tuple<Types...>& t ) noexcept;
template< std::size_t I, class... Types >

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

Notes¶

Feature-test macro: __cpp_lib_tuples_by_type (for type-based access)

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 (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)

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) there are no overloads for const the overloads are added
C++14 (by type) tuple&&

See also¶

Structured binding (C++17) binds the specified names to sub-objects or tuple
elements of the initializer
std::get(std::array) accesses an element of an array
(C++11) (function template)
std::get(std::pair) accesses an element of a pair
(C++11) (function template)
std::get(std::variant) reads the value of the variant given the index or the
(C++17) type (if the type is unique), throws on error
(function template)
get(std::ranges::subrange) obtains iterator or sentinel from a std::ranges::subrange
(C++20) (function template)