std::linalg::compatible-static-extents(C++26)

namespace std::linalg {
  template<class MDS1, class MDS2>
    requires(is-mdspan<MDS1> && is-mdspan<MDS2>) 
  constexpr bool compatible-static-extents(size_t r1, size_t r2)
  {
    return MDS1::static_extent(r1) == dynamic_extent ||
           MDS2::static_extent(r2) == dynamic_extent || 
           MDS1::static_extent(r1) == MDS2::static_extent(r2);
  }
}