C++: What is std::span (C++20)?

1#include <span>
2
3void process(std::span<int> data) {
4    for (int& val : data) {
5        val *= 2;
6    }
7}
8
9int arr[] = {1, 2, 3, 4, 5};
10std::vector<int> vec = {6, 7, 8, 9, 10};
11
12process(arr);   // Works with C array
13process(vec);   // Works with vector
14
15// Subspan
16std::span<int> s(arr);
17auto sub = s.subspan(1, 3);  // {2, 3, 4}
18auto first3 = s.first(3);     // {1, 2, 3}
19auto last3 = s.last(3);       // {3, 4, 5}
20
21// Check bounds
22std::cout << s.size();     // 5
23std::cout << s.empty();    // false
24std::cout << s.data();     // pointer to arr