On 1/18/07, Matthias Schabel <boost@schabel-family.org> wrote:
... 3) implemented quantity_cast for three cases (see unit_example_5.cpp) : a) construction of quantities from raw value types b) conversion of value_types c) conversion of unit systems
It isn't clear to me what the semantics of these three are. I'd quantity_cast should be a dimensionally safe operation. Is that the semantics you have in mind? It seems like (a) should just be handled by multiplication. That is, double x = 42.0; quantity<SI::length> y = x * SI::meter; For (b), it might be better to have a static_quantity_cas, as in quantity<SI::length> x = 42.0 * SI::meter; quantity<SI::length, int> y = static_quantity_cast<quantity<SI::length, int> >(x); For (c), do you mean this: quantity<SI::length> x = 42.0 * SI::meter; quantity<CGS::length> y = quantity_cast<quantity<CGS::length> >(x); where y ends up being 4200 cm? —Ben PS I must say I'm thrilled to see someone putting serious effort into this. I've thought about it for years.