C++: What is std::mdspan (C++23)?

1#include <mdspan>
2
3// Create 2D span
4std::vector<int> data(12);  // 3x4 matrix
5std::mdspan<int, std::extents<size_t, 3, 4>> matrix(data.data());
6
7// Access elements
8matrix(1, 2) = 42;
9std::cout << matrix(1, 2);  // 42
10
11// Dynamic extents
12std::mdspan<int, std::dextents<size_t, 2>> dyn(data.data(), 3, 4);
13
14// Iteration
15for (size_t i = 0; i < matrix.extent(0); i++) {
16    for (size_t j = 0; j < matrix.extent(1); j++) {
17        matrix(i, j) = i * 4 + j;
18    }
19}
20
21// Properties
22std::cout << matrix.rank();          // 2
23std::cout << matrix.extent(0);       // 3
24std::cout << matrix.total_extent();  // 12
25std::cout << matrix.data_handle();   // Raw pointer
26
27// 3D span
28std::vector<float> vol(24);  // 2x3x4
29std::mdspan<float, std::extents<size_t, 2, 3, 4>> volume(vol.data());
30volume(1, 2, 3) = 1.0f;