Does anybody know why boost::array does not support multiple dimensions?

From: Ivan Matek (libbooze_at_[hidden])
Date: 2022-01-01 10:42:08

I don't know much about library development, but with variadic templates
does not seem so hard, although every library development is much harder
than regular user code.

Sure boost::array probably wants to support ancient compilers, but variadic
version could exist only for "modern"(I do not consider >10y old standards
modern) C++.

I found this std:: proposal
http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2013/n3794.html#Ch05
from 9 y ago,
also author seemed to have some working impl on github
https://github.com/CTMacUser/ArrayMD/tree/master/include/boost/container

But I guess none of it ever progressed.

Does anybody knows more about this?
It is not trivial since there are probably a ton of edge cases, typdefs,
semantics(what should size return?, I would say array of dims) to deal
with, but I think it would be a nice extension since I find nested
std::array hideous (with current syntax), e.g.:

std::array<std::array<int,3>, 4> arr;

I would like to have this
boost::array<int,4,3> arr;

P.S. I know I can use Eigen or some other library, but I think if not std
then at least boost should support simple way to have multidim arrays.