Matthias Schabel wrote:
std::cout << ((x + y) * user_selected_unit) << std::endl;
How is this different from/better than
std::cout << quantity<your_system::psi>(x+y) << std::endl;
or, if you prefer,
typedef quantity<your_system::psi> psi;
std::cout << psi(x+y) << std::endl;
??
Well, like I said earlier, this solution requires a system for every possible unit you're using. It also doesn't allow one to assign units since they are distinct types. In order to create a runtime unit quantity in with your plan is to use something akin to boost::any to wrap any unit "type" into something that can be assigned to/from. I started going that direction and realized quite quickly it's a big mess and there isn't much need for it except the desire to do everything in compile mode, which is unnecessary.