Hi Robert, Robert Ramey wrote:
it looks like I'm missing something; Here is the test program again - with all the headers.
#include <boost/units/systems/si/length.hpp> #include <boost/units/base_units/us/mile.hpp> #include <boost/units/quantity.hpp> int main(int argc, char * argv[]){ using namespace boost::units; using namespace boost::units::si; using namespace boost::units::us; quantity<length, float> l1; l1 = 1.0 * meters; quantity<length, float> l2; l2 = static_cast<quantity<length, float> >(1.0 * miles); quantity<length, float> l3 = l1 + l2; return 0; }
Just in case you haven't gotten this yet, here's something that compiles and runs (with g++): #include <boost/units/io.hpp> #include <boost/units/quantity.hpp> #include <boost/units/static_constant.hpp> #include <boost/units/systems/si/length.hpp> #include <boost/units/base_units/us/mile.hpp> #include <iostream> namespace boost { namespace units { namespace us { typedef boost::units::make_system<boost::units::us::mile_base_unit>::type mile_system; typedef boost::units::unit<boost::units::length_dimension,mile_system> mile_length; BOOST_UNITS_STATIC_CONSTANT(mile, mile_length); BOOST_UNITS_STATIC_CONSTANT(miles, mile_length); }}} int main(){ using namespace boost::units; using namespace boost::units::si; using namespace boost::units::us; quantity<length, float> l1; l1 = 1000.f * meters; quantity<length, float> l2; l2 = static_cast<quantity<length, float> >(1.f * miles); quantity<length, float> l3 = l1 + l2; std::cout << l3 << std::endl; } //Outputs 2609.34 m The key is that value times unit = quantity, but you can't create a unit from a base_unit without a system. (There doesn't appear to be a system which declares mile units definitions, as you already found, I think.) Unfortunately, any other base_units which aren't used in the systems folder will require similar boilerplate. HTH, Nate