# std::ranges::subrange<I,S,K>::size

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< cpp‎ | ranges‎ | subrange

constexpr /*make-unsigned-like-t*/< std::iter_difference_t <I>> size() const requires (K == ranges::subrange_kind::sized); |  | (since C++20)

Obtains the number of elements in the `subrange`:

- If `StoreSize` is true, returns `size_`.
- Otherwise, returns `to-unsigned-like`﻿(`end_``` -`` `begin_`﻿).

For the definition of /*make-unsigned-like-t*/, see `make-unsigned-like-t`﻿.

### Return value

As described above.

### Example

Run this code

    #include <functional>
    #include <iostream>
    #include <ranges>
    #include <utility>

    int main()
    {
        const auto v = {2, 2, 2, 7, 1, 1, 1, 1, 8, 2, 2, 2, 2, 2};

        // the value type of views::chunk_by is the ranges::subrange

        auto to_pair = [](auto sub) { return std::make_pair(sub[0], sub.size()); };
                                                                     /* ^^^^ */
        auto pairs = v | std::views::chunk_by(std::equal_to{})
                       | std::views::transform(to_pair);

        for (auto x : pairs bitor std::views::keys)
            std::cout << x << ' ';
        std::cout << '\n';
        for (auto x : pairs bitor std::views::values)
            std::cout << x << ' ';
        std::cout << '\n';
    }

Output:

    2 7 1 8 2
    3 1 4 1 5

### See also

empty | checks whether the `subrange` is empty (public member function)
sizessize (C++17)(C++20) | returns the size of a container or array (function template)
ranges::size (C++20) | returns an integer equal to the size of a range (customization point object)

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