A C++20/23 library for descriptive units of measurements as drop-in replacements for fundamental types with minimal overhead.
- Static inheritance via C++20 concepts
- Implicit unit conversions
- Build any unit of arbitrary dimension
- Templated for arithmetic types
- Classes behave like fundamental types
- No memory overhead
- No performance overhead with
constexpr
- Nondescript, error-prone
constexpr auto IdealGas(int n, double V, double T) {
const auto R = 8.3145; // Units?
const auto P = n * R * T / V;
return P;
}
constexpr auto UseIG() {
const auto T = 300.0; // Units?
const auto V = 10.1; // Units?
return IdealGas(2, T, V); // No enforcement of incorrect parameter order
}- Self-documents, implicit unit correction
#include <csm_units/units.hpp>
using namespace csm_units;
using namespace csm_units::literals;
constexpr auto IdealGas(Kilomole n, Liter volume, Fahrenheit temperature) {
const auto R = 8.3145 * m3 * Pa / (K * mol);
static_assert(std::convertible_to<decltype(R), decltype(1_J / (mol * K))>);
static_assert(not std::convertible_to<decltype(R), decltype(1_J)>);
const Bar P = n * R * temperature / volume; // implicit conversion
return P;
};
constexpr auto UseIG() {
return IdealGas(2_mol, 10.1_m3,
100.0_degC); // implicit parameter conversions
};| ns/op | benchmark |
|---|---|
| 0.54 | Add doubles |
| 0.52 | Add csm_units |
| 0.53 | Subtract doubles |
| 0.53 | Subtract csm_units |
| 0.52 | Multiply doubles |
| 0.52 | Multiply csm_units |
| 1.04 | Divide doubles |
| 1.04 | Divide csm_units |