Endlich.
ND Arrays in std C++ wir kommen
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1161r3.html
Don't forget GCC -Werror=unused-value
array[x] // Ok array[(x,y)] // Ok, uses y as index/key array[x,y] // Deprecated, uses y as index/key