"Leland Brown" wrote
I was under the impression that the vector<3, free_quantity> syntax was just one alternative to the lengthier one,
That was my understanding too. I see no reason to preclude the type parameter from being free_quantity, and this would automatically allow mixed vectors - and automatically ensure they're only used in ways that make sense.
FWIW the type T of allowable elements of a vector<N,T>, should be described in terms of a Concept. IOW in my limited understanding of Conceptgcc : http://www.generic-programming.org/software/ConceptGCC/ The vector definition would be something like: template <int N, Quantity Q> struct vector {/*...*/}; Current C++ cant enforce the Quantity Concept, so it will have to rely on external documentation. (Though I really ought to try to get Conceptgcc running) Working this way then assuming a PQS type is a model of Quantity then things should work. This would allow the Geometry library to be decoupled from PQS. BTW Leland Thanks for the post. There is a huge amount I would like to comment on , but for time reasons I'll just lay down my garbled notes in hope they make some sense: Yes free quantity, Must be able to switch this in and out for performance reasons, greatly affects how PQS might be used. Need various views. Apologies if that makes no sense ... regards Andy Little