mdspan/mdspanstrideUB3.cpp

The following code example is taken from the book
C++23 - The Complete Guide by Nicolai M. Josuttis, Leanpub, 2026
The code is licensed under a Creative Commons Attribution 4.0 International License.

---

// raw code

#include <vector>
#include <mdspan>
#include "print2d.hpp"

int main()
{
  std::vector vec{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};

  // stride layout with overlaps => UNDEFINED BEHAVIOR:
  std::mdspan mds{vec.data(),
                  std::layout_stride::mapping{std::extents{3, 5},
                                              std::array{1, 2}}};
  print2D(mds);

  // multiply each element by 10:
  for (std::size_t i=0; i != mds.extent(0); i++) {
    for (std::size_t j=0; j != mds.extent(1); j++) {
      mds[i, j] *= 10;   // call *= 10 for each element
    }
  }
  print2D(mds);
}