# std::ranges::get(std::ranges::subrange)

From cppreference.com
< cpp‎ | ranges‎ | subrange

Defined in header `<ranges>` |  |
template< std::size_t N, class I, class S, ranges::subrange_kind K > requires ((N == 0 && std::copyable <I>) || N == 1) constexpr auto get( const ranges::subrange <I, S, K>& r ); | (1) | (since C++20)
template< std::size_t N, class I, class S, ranges::subrange_kind K > requires (N < 2) constexpr auto get( ranges::subrange <I, S, K>&& r ); | (2) | (since C++20)
namespace std { using ranges::get; } | (3) | (since C++20)

Provides structured binding support.

1) Obtains the iterator or sentinel from a `subrange` lvalue (or a const rvalue) when N == 0 or N == 1, respectively.
2) Same as (1), except that it takes a non-const `subrange` rvalue.
3) Overloads (1,2) are imported into namespace `std`, which simplifies their usage and makes every `subrange` with a copyable iterator a pair-like type.

### Parameters

r | - | a `subrange`

### Return value

1,2) If N is ​0​, returns r.begin(). Otherwise (N is 1), returns r.end().

### Example

Run this code

    #include <array>
    #include <iostream>
    #include <iterator>
    #include <ranges>

    int main()
    {
        std::array a{1, -2, 3, -4};

        std::ranges::subrange sub_a{std::next(a.begin()), std::prev(a.end())};
        std::cout << *std::ranges::get<0>(sub_a) << ' '   // == *(begin(a) + 1)
                  << *std::ranges::get<1>(sub_a) << '\n'; // == *(end(a) - 1)

        *std::get<0>(sub_a) = 42; // OK
    //  *std::get<2>(sub_a) = 13; // Error: index can only be 0 or 1
    }

Output:

    -2 -4

### 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 3589 | C++20 | overload (1) copies `begin_` if N is ​0​, but `I` might not model `copyable` | added constraints

### See also

Structured binding (C++17) | binds the specified names to sub-objects or tuple elements of the initializer
get(std::tuple) (C++11) | tuple accesses specified element (function template)
get(std::pair) (C++11) | accesses an element of a `pair` (function template)
get(std::array) (C++11) | accesses an element of an `array` (function template)
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::complex) (C++26) | obtains a reference to real or imaginary part from a std::complex (function template)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/ranges/subrange/get&oldid=176929"