Boost Units

One of the BoostLibraries

A brilliant example of the power of Static Typing. An extensible framework for compile-time dimensional analysis in C++ with no runtime overhead.

http://boost.org/libs/units

Example:


        /// the ideal gas law in si units

        template

        quantity 

        idealGasLaw(const quantity& P,

        const quantity& V,

        const quantity& T)

        {

        using namespace boost::units::si;


        #if BOOST_UNITS_HAS_TYPEOF 

        using namespace constants::codata;

        return (P*V/(R*T));

        #else

        return P*V/(8.314472*(joules/(kelvin*mole))*T);

        #endif // BOOST_UNITS_HAS_TYPEOF

        }

Which is used as follows:


        /// test ideal gas law

        quantity   T = (273.+37.)*kelvin;

        quantity      P = 1.01325e5*pascals;

        quantity        r = 0.5e-6*meters;

        quantity        V = (4.0/3.0)*3.141592*pow<3>(r);

        quantity        n(idealGasLaw(P,V,T));

Note that defining the base units is sufficient to use any plausible derived unit.