Millimeters in boost::units

Question

I want to use boost::units for some SI metrics. However our code mostly deals with millimeters and instead of using

quantity value = 1*milli*m         


        

Answer 1

I am using the following approach:

// your namespace name for units
namespace outernamespace {
    namespace millimeter_system {
        typedef boost::units::scaled_base_unit>> millimeter_base_unit;

        typedef boost::units::make_system::type system;
        typedef boost::units::unit length;

        BOOST_UNITS_STATIC_CONSTANT(millimeter, length);
        BOOST_UNITS_STATIC_CONSTANT(millimeters, length);
    }

    typedef boost::units::quantity quantity_millimeter;
    using millimeter_system::millimeter;
    using millimeter_system::millimeters;
}

// demonstration of usage
void foo() {
    using namespace outernamespace;
    using namespace boost::units;
    using namespace boost::units::si;

    quantity_millimeter mm = 5 * millimeter;
    quantity m = 0.004 * meter;
    if (mm < static_cast(m)) {
        std::cout << 'lt ' << std::endl;
    }
    else {
        std::cout << 'geq ' << std::endl;
    }
}