Affine Space Types

I have this tagged as "math" because it is, but the math is really lightweight and easy to follow along.

Arguably this could have been tagged "c++" because these concepts are written up as C++ code in the article, but I didn't tag it that because I think the concept is really language agnostic. There's only a little bit of the article that is really C++ specific where it's related to C++'s iterators.

edit: also thanks to Dawn Ahukanna on mastodon for this link