C++ library to handle metric type and conversion
Metrics library provides strongly typed types to make interfaces and API precise. It also provide implicit conversions on similar types, and explicit conversions on arithmetic.
This library provide types and conversion for:
- angular speed
- distance
- electric current
- energy
- force
- frequency
- mass
- power
- pressure
- speed
- voltage
- volume
- flowrate
The Metrics library is a header's only library. Just copy the necessary metrics (.hpp file) into your code.
An example of strongly typed signature.
#include <iostream>
#include <metrics.hpp>
void printSpeed(metric::metre distance, std::chrono::minutes duration) // Enforce type used.
{
metric::mph speed = distance / duration;
std::cout << "You're driving at " << speed.count() << " mph" << std::endl;
// Create a custom speed:
typedef metric::distance<long long, std::ratio<1852LL, 1LL>> nauticalmile;
typedef metric::speed<nauticalmile, std::chrono::hours> knot;
knot speed = distance / duration;
std::cout << "You're driving at " << speed.count() << " knots" << std::endl;
}
int main()
{
printSpeed(metric::metre(247530), std::chrono::minutes(128));
return 0;
}An example of unit conversion
#include <iostream>
#include <metrics.hpp>
using namespace metric::literals;
template<uint8_t Temperature>
struct waterDensity
{
static constexpr double temp = static_cast<double>(Temperature);
// (Air saturated) Formula source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4909168/
static constexpr double value = 999.84847 + (6.337563 * 0.01) * temp + (-8.523829 * 0.001) * temp * temp + (6.943248 * 0.00001) * temp * temp * temp + (-3.821216 * 0.0000001) * temp * temp * temp * temp;
};
template<int8_t Temperature>
struct mercuryDensity
{
// Formula source: https://www.techniques-ingenieur.fr/base-documentaire/sciences-fondamentales-th8/introduction-aux-constantes-physico-chimiques-42342210/corrections-barometriques-k64/masse-volumique-du-mercure-k64niv10002.html
static constexpr double value = 13595.1 / (1 + (1.818 * 0.0001 * (Temperature)));
};
template<typename Density, typename MassType, typename MassRatio>
metric::volume<double, MassRatio> operator/ (const metric::mass<MassType, MassRatio>& m, Density d)
{
return metric::volume<double, MassRatio>(m.count() / Density::value);
}
int main()
{
std::cout << "10kg of water at 25°C = " << metric::volume_cast<metric::millilitre>(10_kg / waterDensity<25>()).count() << " millilitre" << std::endl;
std::cout << " 1kg of mercury at 5°C = " << metric::volume_cast<metric::microlitre>( 1_kg / mercuryDensity< 5>()).count() << " microlitre" << std::endl;
return 0;
}| ratio | literal | ||
|---|---|---|---|
| angularspeed | degree / second | 10/1 | _degsec |
| turn / second | 3600/1 | _rps | |
| turn / minute | 60/1 | _rpm | |
| turn / hour | 1/1 | _rph | |
| distance | attometre | atto | _am |
| femtometre | femto | _fm | |
| picometre | pico | _pm | |
| nanometre | nano | _nm | |
| micrometre | micro | _um | |
| millimetre | milli | _mm | |
| centimetre | centi | _cm | |
| metre | 1/1 | _m | |
| kilometre | kilo | _km | |
| megametre | mega | _Mm | |
| gigametre | giga | _Gm | |
| terametre | tera | _Tm | |
| petametre | peta | _Pm | |
| exametre | exa | _Em | |
| yard | 9144/10000 | _yd | |
| inch | 254/10000 | _in | |
| nauticalmile | 1852/1 | _nmi | |
| foot | 3048/10000 | _ft | |
| electric current: | femtoampere | femto | _fA |
| picoampere | pico | _pA | |
| nanoampere | nano | _nA | |
| microampere | micro | _uA | |
| milliampere | milli | _mA | |
| ampere | 1/1 | _A | |
| kiloampere | kilo | _kA | |
| megaampere | mega | _MA | |
| energy: | microwatthour | _uWh | |
| milliwatthour | _mWh | ||
| watthour | _Wh | ||
| kilowatthour | _kWh | ||
| megawatthour | _MWh | ||
| gigawatthour | _GWh | ||
| terawatthour | _TWh | ||
| petawatthour | _PWh | ||
| joule | _j | ||
| calorie | _c | ||
| force: | millinewton | milli | _mN |
| newton | 1/1 | _N | |
| decanewton | deca | _dN | |
| gramforce | 980665/100000000 | _gf | |
| kilogramforce | 980665/100000 | _kgf | |
| frequency: | millihertz | milli | _mHz |
| hertz | 1/1 | _Hz | |
| kilohertz | kilo | _kHz | |
| megahertz | mega | _MHz | |
| gigahertz | giga | _GHz | |
| mass: | nanogram | nano | _ng |
| microgram | micro | _ug | |
| milligram | milli | _mg | |
| gram | 1/1 | _g | |
| kilogram | kilo | _kg | |
| ton | mega | _ton | |
| power: | nanowatt | nano | _nW |
| microwatt | micro | _uW | |
| milliwatt | milli | _mW | |
| watt | 1/1 | _W | |
| kilowatt | kilo | _kW | |
| megawatt | mega | _MW | |
| gigawatt | giga | _GW | |
| pressure: | millimetremercury | 1/760 | _mmHg |
| pascal | 1/101325 | _Pa | |
| hectopascal | 100/101325 | _hPa | |
| kilopascal | 1000/101325 | _kPa | |
| megapascal | 1000000/101325 | _MPa | |
| gigapascal | 1000000000/101325 | _GPa | |
| terapascal | 1000000000000/101325 | _TPa | |
| bar | 1000000/1013250 | _bar | |
| millibar | 1000/1013250 | _mbar | |
| microbar | 1/1013250 | _ubar | |
| speed: | micrometre/second | _um_sec | |
| micrometre/minute | _um_m | ||
| micrometre/hour | _um_h | ||
| millimetre/second | _mm_sec | ||
| millimetre/minute | _mm_m | ||
| millimetre/hour | _mm_h | ||
| millimetre/day | _mm_d | ||
| metre/second | _m_sec | ||
| metre/minute | _m_m | ||
| metre/hour | _m_h | ||
| metre/day | _m_d | ||
| voltage: | nanovolt | nano | _nV |
| microvolt | micro | _uV | |
| millivolt | milli | _mV | |
| volt | 1/1 | _V | |
| kilovolt | kilo | _kV | |
| megavolt | mega | _MV | |
| volume: | nanolitre | nano | _nl |
| microlitre | micro | _ul | |
| millilitre | milli | _ml | |
| litre | 1/1 | _l | |
| kilolitre | kilo | _kl | |
| megalitre | mega | _Ml | |
| flowrate: | microlitre/second | _ul_sec | |
| microlitre/minute | _ul_m | ||
| microlitre/hour | _ul_h | ||
| millilitre/second | _ml_sec | ||
| millilitre/minute | _ml_m | ||
| millilitre/hour | _ml_h | ||
| millilitre/day | _ml_d |