Well defined semantics for positions and displacements.

Affine Space Types

by Adi Shavit

From the article:

I recently came across a geometric structure that deserves to be better known: The Affine Space. In fact, like many abstract mathematical concepts, it is so fundamental that we are all subconsciously familiar with it though may have never considered its mathematical underpinnings.
This post will introduce the Affine Space structure and focus mainly on its role in the C++ type system, the standard library and for creating new strong types.