units/example/tutorial.cpp
Steven Watanabe bf2c4d2586 A few fixes before merging this PR
* Revert most of the changes to examples, because ugly macros don't belong
  in examples.  Just use constexpr as appropriate.
* Revert Lambda changes as they're wrong and Boost.Lambda doesn't support
  constexpr.
* Remove include of broken math_fwd.hpp.
2018-01-10 12:07:09 -07:00

96 lines
2.8 KiB
C++

// 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;
constexpr
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;
}
//]