# std::get(std::tuple)

From cppreference.com
< cpp‎ | utility‎ | tuple

Defined in header `<tuple>` |  |
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)

1-4) Extracts the `I`th 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 | Value | Std | Comment
--- | --- | --- | ---
`__cpp_lib_tuples_by_type` | 201304L | (C++14) | 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) C++14 (by type) | there are no overloads for const tuple&& | the overloads are added

### See also

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

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/utility/tuple/get&oldid=151691"