Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world.

libs/units/example/quantity.cpp

```// Boost.Units - A C++ library for zero-overhead dimensional analysis and
// unit/quantity manipulation and conversion
//
// Copyright (C) 2003-2008 Matthias Christian Schabel
// Copyright (C) 2008 Steven Watanabe
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at

/**
\file

\brief quantity.cpp

\details
Test quantity algebra.

Output:
@verbatim

//[quantity_output_double
L                                 = 2 m
L+L                               = 4 m
L-L                               = 0 m
L*L                               = 4 m^2
L/L                               = 1 dimensionless
L*meter                           = 2 m^2
kilograms*(L/seconds)*(L/seconds) = 4 m^2 kg s^-2
kilograms*(L/seconds)^2           = 4 m^2 kg s^-2
L^3                               = 8 m^3
L^(3/2)                           = 2.82843 m^(3/2)
2vL                               = 1.41421 m^(1/2)
(3/2)vL                           = 1.5874 m^(2/3)
//]

//[quantity_output_complex
L                                 = (3,4) m
L+L                               = (6,8) m
L-L                               = (0,0) m
L*L                               = (-7,24) m^2
L/L                               = (1,0) dimensionless
L*meter                           = (3,4) m^2
kilograms*(L/seconds)*(L/seconds) = (-7,24) m^2 kg s^-2
kilograms*(L/seconds)^2           = (-7,24) m^2 kg s^-2
L^3                               = (-117,44) m^3
L^(3/2)                           = (2,11) m^(3/2)
2vL                               = (2,1) m^(1/2)
(3/2)vL                           = (2.38285,1.69466) m^(2/3)
//]

@endverbatim
**/

#include <complex>
#include <iostream>

#include <boost/mpl/list.hpp>

#include <boost/typeof/std/complex.hpp>

#include <boost/units/pow.hpp>
#include <boost/units/quantity.hpp>
#include <boost/units/io.hpp>

#include "test_system.hpp"

int main(void)
{
using namespace boost::units;
using namespace boost::units::test;

{
//[quantity_snippet_1
quantity<length> L = 2.0*meters;                     // quantity of length
quantity<energy> E = kilograms*pow<2>(L/seconds);    // quantity of energy
//]

std::cout << "L                                 = " << L << std::endl
<< "L+L                               = " << L+L << std::endl
<< "L-L                               = " << L-L << std::endl
<< "L*L                               = " << L*L << std::endl
<< "L/L                               = " << L/L << std::endl
<< "L*meter                           = " << L*meter << std::endl
<< "kilograms*(L/seconds)*(L/seconds) = "
<< kilograms*(L/seconds)*(L/seconds) << std::endl
<< "kilograms*(L/seconds)^2           = "
<< kilograms*pow<2>(L/seconds) << std::endl
<< "L^3                               = "
<< pow<3>(L) << std::endl
<< "L^(3/2)                           = "
<< pow<static_rational<3,2> >(L) << std::endl
<< "2vL                               = "
<< root<2>(L) << std::endl
<< "(3/2)vL                           = "
<< root<static_rational<3,2> >(L) << std::endl
<< std::endl;
}

{
//[quantity_snippet_2
quantity<length,std::complex<double> > L(std::complex<double>(3.0,4.0)*meters);
quantity<energy,std::complex<double> > E(kilograms*pow<2>(L/seconds));
//]

std::cout << "L                                 = " << L << std::endl
<< "L+L                               = " << L+L << std::endl
<< "L-L                               = " << L-L << std::endl
<< "L*L                               = " << L*L << std::endl
<< "L/L                               = " << L/L << std::endl
<< "L*meter                           = " << L*meter << std::endl
<< "kilograms*(L/seconds)*(L/seconds) = "
<< kilograms*(L/seconds)*(L/seconds) << std::endl
<< "kilograms*(L/seconds)^2           = "
<< kilograms*pow<2>(L/seconds) << std::endl
<< "L^3                               = "
<< pow<3>(L) << std::endl
<< "L^(3/2)                           = "
<< pow<static_rational<3,2> >(L) << std::endl
<< "2vL                               = "
<< root<2>(L) << std::endl
<< "(3/2)vL                           = "
<< root<static_rational<3,2> >(L) << std::endl
<< std::endl;
}

return 0;
}
```