Hi Luke,
The following does not compile (I wish it did):
const orientation_2d horizontal_constant;
template <orientation2d orient> coordinate get(const point& pt) { return coord_[orient.to_int()]; }
coordinate value = get<horizontal_constant>(my_point);
because orient has to be a built in type.
Acutally, that to_int() is getting back into runtime, so this wouldn't count as a compile-time access even if it compiled. OTOH, this could be made to compile if desired: struct horizontal{ static const int value = 0 ; } template <class orient> coordinate get(const point& pt) { return pt[orient::value]; } coordinate value = get<horizontal>(my_point); Having said that, if the library aims to educate users not to do something as terrible as if(condition) point.x() = value; else point.y() = value; then it should advocate higher level abstractions: vector delta = condition ? vector(value,0) : vector(0,value) {} translate modify (delta); point = modify(point); which, being essentially coordinate-free, hides the coordinate-access issue from the user pushing into the library implementation. Best -- Fernando Cacciola SciSoft http://scisoft-consulting.com http://fcacciola.50webs.com http://groups.google.com/group/cppba