Hi,
Second, I would like to pick the attention of Boost.Geometry again in order to suggest them use boost.units as a way to make the Boost.Geometry library very general. (...) I think none of the two options makes general sense. The only point at which units make sense is at the "metric" of the space. Since in Boost.geometry library coordinate system an metric are tied together, we need a special type of coordinates system. For example one suggestion could be to extend the coordinate systems of Boost.Geometry to include the units and dimension of space. For example one way to specify points in space could be by means of a type like this
model::point<double, 3, cs::unit::cartesian<si::length> >
and then specialize all the template functions that use cartesian as coordinate system, for example distance. This makes sense because the only point at which units are useful is when we take distances, modulus or projections between vectors in that "space" with unit/dimension.
I will look at this usage soon. Thanks, Barend