Using physical constants with boost

Question

I'd like to define some constants in a c++ program. The excellent boost library has them predefined, and I like to assign my constants these values, eg something like

#include <iostream>
#include <boost/units/systems/si/codata/electromagnetic_constants.hpp>

int main(int argc, const char * argv[]) {
    double electron_charge = boost::units::si::constants::codata::e;

    std::cout << electron_charge << std::endl;
    return 0;
}

But this does not work since boost's e is not of type double but of type value_type . How can I access the value in double precision?

Answer 1

您需要将电子的电荷除以电荷单位：库仑：

double electron_charge = boost::units::si::constants::codata::e / boost::units::si::coulomb;