Since there are not many computer software that handles units seriously, except possibly for Boost.Units and Mathematica`Units in my opinion, I just wanted to point out to this post: Automatic Physical Units in Mathematica http://blog.wolfram.com/2010/12/09/automatic-physical-units-in-mathematica/ Interesting discussion in terms of features. One of the reasons I hated Mathematica units handling so far was due to the lack of a typing system which C++ and boost.Units have naturally, the other reason was that the physical quantites didn't seem to play well with other parts of the system. Now it seems that Mathematica Units is discovering "types". One of the features that it mentions is the ability to perform automatic conversions upon arithmetic operations of mixed units. In fact I was working in a way to perform automatic conversion in Boost.Units inside arithmetic formulas, since Mathematica has unbounded precision arithmetic by default the automatic conversions are not a real problem. An exact matching of this feature can not be achieved with a limited precision representation (like double). I'll take the opportunity ask two broad general questions: Does any body have experience with using boost.units quantity with a underlying type that are not double, e.g. multiple precision, or vector (geometric) objects? Does it work well? Are there future planned developments for Boost.Units, in terms of external features (e.g. automatic conversion, better interaction with boost.phoenix) or internal implementation? Thank you, Alfredo