When I write code using points, I actually seldom have to use
[snip] directly
those accessors. I am not talking about writing the point class, but using it. How often do we have to use something else than functions/operators (norm, +/-/*, etc.) on points in complex expressions?
The thing is, you can never have a one-size-fits-all point type. Some folks say they need heterogeneous dimension types. If you use arrays, then you can't have those. And how about legacy types, need for higher dimensions, Etc.
So, again, use concepts! And use them all the way! Don't generalize on concrete point types like above! You can't. Use concepts. An elegant concept hierarchy for points should satisfy all the needs for all users. And, there can be interoperability between different models of the unified point concept.
Regards, -- Joel de Guzman
I would add that these concepts should NOT require coordinates for PointConcept or SpatialVectorConcept, there should be a separate CoordinatesConcept and RuntimeIndexedCoordinatesConcept (names may be changed :) ). I suspect most of this dialog would fall under what I just called the CoordinatesConcept and RuntimeIndexedCoordinatesConcept. For instance one can not add, multiply, or take the norm/length of points (you need spatial vectors for that). You can also measure distance between points, but not vectors. You can translate a point, but not a vector, and you can not scale a point but you can scale a vector. Since coordinates are free from interpretation you can do whatever you want to with them, but the result is coordinates, not a point or a vector. I think the concepts for a point would require a typedef for the vector type, and likewise a vector would require a typedef for the corresponding point type. Coordinates should probably satisfy both concepts for a point and for a vector. Again I do not know if these concepts or equivalents are part of GTL. Is it appropriate/possible to try to flesh out details like this on the boost wiki? Would folks be interested in starting up or helping with a googlecode project to flesh out these concepts for a possible boost submission at a later date? -- John