TypeSI - Units of "Système international" Blended for C++

Header-only C++ library that provides type safety for handling physical values defined in the International System of Units regulated by the International Bureau of Weights and Measures (BIPM) and published in the SI brochure. Example:

#include "src/si_base.hpp"
#include "src/si_derived.hpp"
#include <iostream>

Si::Derived::Watt<double> calculatePower(Si::Derived::Joule<double> energy,
                                         Si::Base::Second<double> time) {
  return energy / time;
}

int main() {
  using namespace Si::Base::Literals;
  Si::Base::Second<double> time(1.5);
  auto speed = 29.4_m / time;
  auto acceleration = speed / 2.0_s;
  auto power = calculatePower(acceleration * 1.2_kg * 0.4_m, 3.2_s);
  std::cout << "With g = " << +acceleration << " power equals " << +power
            << std::endl;
}

If any of the explicitly specified types doesn't match with compile-time calculated one the program will just fail to compile.

auto power = calculatePower(acceleration * 1.2_kg, 3.2_s); // won't compile

You can also add prefixes to units at will. They will be checked and automatically converted on demand.

#include "src/si_base.hpp"
#include "src/si_derived.hpp"
#include "src/si_prefix.hpp"
#include <iostream>

template <typename T>
using minute = Si::Prefix<std::ratio<60>, Si::Base::Second<T>>;
template <typename T>
using kWth = Si::Prefix<std::ratio<3600000>, Si::Derived::Joule<T>>;

Si::Prefix<std::giga, Si::Derived::Watt<double>>
calculatePower(kWth<double> energy, minute<double> time) {
  return energy / time;
}

int main() {
  auto energy = kWth<double>(100833);
  auto time = minute<double>(5);
  std::cout << "If you've spent " << +energy << " kilowatt*hours in " << +time
            << " minutes your grid allows to draw "
            << +calculatePower(energy, time) << " gigawatts of power"
            << std::endl;
}

On top of that you are provided with compatible pow function

#include "src/si_base.hpp"
#include "src/si_derived.hpp"
#include "src/si_math.hpp"
#include <iostream>

void printPressure(Si::Prefix<std::kilo, Si::Derived::Pascal<double>> p) {
  std::cout << "Pressure is " << +p << " kPa" << std::endl;
}

int main() {
  using namespace Si::Base::Literals;
  using namespace Si::Derived::Literals;
  printPressure(1000.0_N / Si::Math::pow<std::ratio<2>>(0.1_m));
}