From: Andreas Harnack <ah.boost.02@justmail.de>
I might have been a bit imprecise here, so please consider:
const unsigned int Time = 2; const unsigned int Length = 3; const unsigned int Mass = 5; const unsigned int Current = 7; const unsigned int Temp = 11; const unsigned int Amount = 13; const unsigned int Intensity = 17;
template <unsigned int N, unsigned int D=1> struct Rational { ... };
typedef Rational<Time> time; typedef Rational<Length> length; typedef Rational<Mass*Length,Times*Times> force; typedef Rational<Mass*Length*Length,Times*Times> energy;
quantity<energy, double> e;
so the representation of energy would be just 5*3*3/2*2 = 45/4.
You're right, there is a computational limit, but I wouldn't expect to a see a dimension with the power of 31. Exponends of 4 are about the highest I've ever seen, and (2*3*5*7*11*13*17)^3 still fits in 57 bits, so we might want to use long or even long long unsigned ints, but that should be fine for most situations.
If exponents of 4 are the highest you've seen, shouldn't you consider the size of (2*3*5*7*11*13*17)^4, which requires 76 bits? Also, I may want to extend the list - some people have requested a "money" unit, for example, which would be assigned the value 19 in your system. Then I can't even represent all powers of 3. I suspect this idea, while clever, does not cover the problem domain sufficiently well to be superior to lists. - James Jones Administrative Data Mgmt. Webmaster 375 Raritan Center Pkwy, Suite A Data Architect Edison, NJ 08837