I am looking forward to the proposed mdspan, and was thinking of a toy example. What I thought of was game of life, which works on a binary 2d array. Naturally I would like to use an mdspan over a bitset or std::vector<bool>, both of which address individual bits via funky iterators. Now I was thinking I could do that by providing a suitable AccessPolicy, but as it turns out (in 26.7 here) AccessorPolicy has a decay member which returns a real pointer to an element type, which basically does not exist for std::vector<bool>. Furthermore I looked at the only Implementation I could find on github and while it defines this member for accessor_basic (the only required model) it actually never uses it in the mdspan implementation.
now I am bonked as to why they did that, thereby forbidding any proxy iterators, while not even needing this for mdspan? Is it for allowing use of memcpy in certain cases? If so, why not allow "opt-in"?