boost_1_45_0/libs/units/example/tutorial.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
// http://www.boost.org/LICENSE_1_0.txt)

/**
\file tutorial.cpp
    
\brief Basic tutorial using SI units.

\details
Tutorial 
Defines a function that computes the work, in joules,
done by exerting a force in newtons over a specified distance 
in meters and outputs the result to std::cout. 

Also code for computing the complex impedance
using std::complex<double> as the value type.

Output:
@verbatim
//[tutorial_output
F  = 2 N
dx = 2 m
E  = 4 J

V   = (12.5,0) V
I   = (3,4) A
Z   = (1.5,-2) Ohm
I*Z = (12.5,0) V
I*Z == V? true
//]
@endverbatim
*/

//[tutorial_code
#include <complex>
#include <iostream>

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

#include <boost/units/systems/si/energy.hpp>
#include <boost/units/systems/si/force.hpp>
#include <boost/units/systems/si/length.hpp>
#include <boost/units/systems/si/electric_potential.hpp>
#include <boost/units/systems/si/current.hpp>
#include <boost/units/systems/si/resistance.hpp>
#include <boost/units/systems/si/io.hpp>

using namespace boost::units;
using namespace boost::units::si;

quantity<energy> 
work(const quantity<force>& F, const quantity<length>& dx)
{
    return F * dx; // Defines the relation: work = force * distance.
}

int main()
{   
    /// Test calculation of work.
    quantity<force>     F(2.0 * newton); // Define a quantity of force.
    quantity<length>    dx(2.0 * meter); // and a distance,
    quantity<energy>    E(work(F,dx));  // and calculate the work done.
    
    std::cout << "F  = " << F << std::endl
              << "dx = " << dx << std::endl
              << "E  = " << E << std::endl
              << std::endl;

    /// Test and check complex quantities.
    typedef std::complex<double> complex_type; // double real and imaginary parts.
    
    // Define some complex electrical quantities.
    quantity<electric_potential, complex_type> v = complex_type(12.5, 0.0) * volts;
    quantity<current, complex_type>            i = complex_type(3.0, 4.0) * amperes;
    quantity<resistance, complex_type>         z = complex_type(1.5, -2.0) * ohms;
    
    std::cout << "V   = " << v << std::endl
              << "I   = " << i << std::endl
              << "Z   = " << z << std::endl 
              // Calculate from Ohm's law voltage = current * resistance.
              << "I * Z = " << i * z << std::endl
              // Check defined V is equal to calculated.
              << "I * Z == V? " << std::boolalpha << (i * z == v) << std::endl
              << std::endl;
    return 0;
}
//]