>From: <[EMAIL PROTECTED]> Still on the subject of a quantity library.
> > There is DEFINITELY a need for this - and in the C++ Standard Library, > > but the relative merits of the two proposals mae so far are not yet > > clear to me. > > > > Perhaps we need more real user experience. (Or is the problem that the > > MSVC compiler can't/couldn't handle the SIUnits code?) > > real user experience... you asked for it ;-) > we use the int-based template approach for a couple of years now in > our AGV controller software. We actually sometimes reach the stage that > it works when succesfully compiled and linked. Since our control software > is physics throughout (field of robotics), the type safety is very > important. However, besides the basic SI units we also have 'angle' > as a dimension which allows us to distinguish 'velocity' and 'angular > velocity' for example. Hence, from out 'real user' experience (engineering > point of view) it would be a necessity to add 'angle' as a dimension > without breaking already defined quantities. Most (all?) units libraries > already define 'angle' to be dimensionless, which is true in scientifically > spoken, but pragmatically (engineering ;-) less handy. Regarding this angle dimension, should it be treated like the other SI-dimensions? That is, say that you represent an SI quantity/unit with an integer vector giving the exponents: template<int kg,int m,int s,int A,int K,int mol,int cd,int angle> class quantity; If you multiply two quantities, you multiply the value and add the exponents, so quantity<0,1,0,0,0,0,0,0>(10) * quantity<0,1,0,0,0,0,0,0>(10) = quantity<0,2,0,0,0,0,0,0>(100) (m * m = m^2) Would this hold for angle, as well? That is, does it make sense to say angle * angle = angle^2? I understand that e.g. angle/s (angular velocity) makes sense, but should a library allow any combination with angle and the other dimensions? How do you treat angle in your own library? Regards, Terje _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
