On Fri, 5 Nov 2004 23:54:30 +0000, Val Samko <boost@digiways.com> wrote:
Once again, in geometry, vector and point are practically the same thing. Not really - you can only represent a point by its radius/position vector wrt a given coordinate system.
Radius vector and point are not the same thing, though. For instance, there is no meaning behind multiplying a point by a scalar. More formal, points are not members of any vector space, so you can't apply operations which are only defined on vectors on them.
RD> If you do point - point, then the resulting type is a size type that RD> represents the distance between the two points.
Just like size - size. The point (pun intended) is, that the resulting type is NOT a point. "point-point" has a different meaning than "vector-vector".
RD> So in a mathematical sense, the difference between size and position is RD> entirely relevant, it's just that some libraries (not mentioning names) RD> do not adhere to the above mathematical rules.
There are no mathematical rules, which say that a point in nD Cartesian coordinate system is not just a set of corresponding distances along each axe. A point can be *specified* by means of a vector, but it's not the same.
Another important.. point would be that o Cheers, Michael