# std::span<T,Extent>::first

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< cpp‎ | container‎ | span

template< std::size_t Count > constexpr std::span <element_type, Count> first() const; |  | (since C++20)
constexpr std::span <element_type, std::dynamic_extent > first( size_type Count ) const; |  | (since C++20)

Obtains a span that is a view over the first `Count` elements of this span. The program is ill-formed if Count > Extent. The behavior is undefined if Count > size().

### Return value

A span `r` that is a view over the first `Count` elements of *this, such that r.data() == this->data() && r.size() == Count.

### Example

Run this code

    #include <iostream>
    #include <ranges>
    #include <span>
    #include <string_view>

    void print(std::string_view const title,
               std::ranges::forward_range auto const& container)
    {
        auto size{std::size(container)};
        std::cout << title << '[' << size << "]{";
        for (auto const& elem : container)
            std::cout << elem << (--size ? ", " : "");
        std::cout << "};\n";
    }

    void run_game(std::span<const int> span)
    {
        print("span: ", span);

        std::span<const int, 5> span_first = span.first<5>();
        print("span.first<5>(): ", span_first);

        std::span<const int, std::dynamic_extent> span_first_dynamic = span.first(4);
        print("span.first(4): ", span_first_dynamic);
    }

    int main()
    {
        int a[8]{1, 2, 3, 4, 5, 6, 7, 8};
        print("int a", a);
        run_game(a);
    }

Output:

    int a[8]{1, 2, 3, 4, 5, 6, 7, 8};
    span: [8]{1, 2, 3, 4, 5, 6, 7, 8};
    span.first<5>(): [5]{1, 2, 3, 4, 5};
    span.first(4): [4]{1, 2, 3, 4};

### See also

last | obtains a subspan consisting of the last `N` elements of the sequence (public member function)
subspan | obtains a subspan (public member function)

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