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<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <title>Examples</title> <link rel="stylesheet" href="../../../doc/src/boostbook.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.78.1"> <link rel="home" href="../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> <link rel="up" href="../boost_units.html" title="Chapter 36. Boost.Units 1.1.0"> <link rel="prev" href="Quantities.html" title="Quantities"> <link rel="next" href="Utilities.html" title="Utilities"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table cellpadding="2" width="100%"><tr> <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../boost.png"></td> <td align="center"><a href="../../../index.html">Home</a></td> <td align="center"><a href="../../../libs/libraries.htm">Libraries</a></td> <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> <td align="center"><a href="../../../more/index.htm">More</a></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="Quantities.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../boost_units.html"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="Utilities.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> </div> <div class="section"> <div class="titlepage"><div><div><h2 class="title" style="clear: both"> <a name="boost_units.Examples"></a><a class="link" href="Examples.html" title="Examples">Examples</a> </h2></div></div></div> <div class="toc"><dl class="toc"> <dt><a href="Examples.html#boost_units.Examples.DimensionExample">Dimension Example</a></dt> <dt><a href="Examples.html#boost_units.Examples.UnitExample">Unit Example</a></dt> <dt><a href="Examples.html#boost_units.Examples.QuantityExample">Quantity Example</a></dt> <dt><a href="Examples.html#boost_units.Examples.KitchenSinkExample">Kitchen Sink Example using SI units</a></dt> <dt><a href="Examples.html#boost_units.Examples.ConversionExample">Conversion Example</a></dt> <dt><a href="Examples.html#boost_units.Examples.UDTExample">User Defined Types</a></dt> <dt><a href="Examples.html#boost_units.Examples.ComplexExample">Complex Example</a></dt> <dt><a href="Examples.html#boost_units.Examples.PerformanceExample">Performance Example</a></dt> <dt><a href="Examples.html#boost_units.Examples.RadarBeamHeightExample">Radar Beam Height</a></dt> <dt><a href="Examples.html#boost_units.Examples.HeterogeneousUnitExample">Heterogeneous Unit Example</a></dt> <dt><a href="Examples.html#boost_units.Examples.AbsoluteRelativeTemperatureExample">Absolute and Relative Temperature Example</a></dt> <dt><a href="Examples.html#boost_units.Examples.RuntimeConversionFactorExample">Runtime Conversion Factor Example</a></dt> <dt><a href="Examples.html#boost_units.Examples.UnitsWithNonbaseDimensions">Units with Non-base Dimensions</a></dt> <dt><a href="Examples.html#boost_units.Examples.OutputForCompositeUnits">Output for Composite Units</a></dt> <dt><a href="Examples.html#boost_units.Examples.autoscale">Automatically Scaled Units</a></dt> <dt><a href="Examples.html#boost_units.Examples.ConversionFactor">Conversion Factor</a></dt> <dt><a href="Examples.html#boost_units.Examples.RuntimeUnits">Runtime Units</a></dt> <dt><a href="Examples.html#boost_units.Examples.lambda">Interoperability with Boost.Lambda</a></dt> </dl></div> <div class="section"> <div class="titlepage"><div><div><h3 class="title"> <a name="boost_units.Examples.DimensionExample"></a><a class="link" href="Examples.html#boost_units.Examples.DimensionExample" title="Dimension Example">Dimension Example</a> </h3></div></div></div> (<a href="../../../libs/units/example/dimension.cpp" target="_top">dimension.cpp</a>) By using MPL metafunctions and the template specializations for operations on composite dimensions (defined in <code class="computeroutput"><a class="link" href="Reference.html#header.boost.units.dimension_hpp" title="Header <boost/units/dimension.hpp>">boost/units/dimension.hpp</a></code>) it is possible to perform compile time arithmetic according to the dimensional analysis rules described <a class="link" href="Dimensional_Analysis.html" title="Dimensional Analysis">above</a> to produce new composite dimensions : <pre class="programlisting">typedef mpl::times<length_dimension,mass_dimension>::type LM_type; typedef mpl::divides<length_dimension,time_dimension>::type L_T_type; typedef static_root< mpl::divides<energy_dimension,mass_dimension>::type, static_rational<2> >::type V_type; </pre> outputting (with symbol demangling, implemented in <a href="../../../boost/units/detail/utility.hpp" target="_top">utility.hpp</a>) <pre class="programlisting">length_dimension = list<dim<length_base_dimension, static_rational<1l, 1l> >, dimensionless_type> mass_dimension = list<dim<mass_base_dimension, static_rational<1l, 1l> >, dimensionless_type> time_dimension = list<dim<time_base_dimension, static_rational<1l, 1l> >, dimensionless_type> energy_dimension = list<dim<length_base_dimension, static_rational<2l, 1l> >, list<dim<mass_base_dimension, static_rational<1l, 1l> >, list<dim<time_base_dimension, static_rational<-2l, 1l> >, dimensionless_type> > > LM_type = list<dim<length_base_dimension, static_rational<1l, 1l> >, list<dim<mass_base_dimension, static_rational<1l, 1l> >, dimensionless_type> > L_T_type = list<dim<length_base_dimension, static_rational<1l, 1l> >, list<dim<time_base_dimension, static_rational<-1l, 1l> >, dimensionless_type> > V_type = list<dim<length_base_dimension, static_rational<1l, 1l> >, list<dim<time_base_dimension, static_rational<-1l, 1l> >, dimensionless_type> > </pre> </div> <div class="section"> <div class="titlepage"><div><div><h3 class="title"> <a name="boost_units.Examples.UnitExample"></a><a class="link" href="Examples.html#boost_units.Examples.UnitExample" title="Unit Example">Unit Example</a> </h3></div></div></div> (<a href="../../../libs/units/example/unit.cpp" target="_top">unit.cpp</a>) This example demonstrates the use of the simple but functional unit system implemented in <a href="../../../libs/units/example/test_system.hpp" target="_top">test_system.hpp</a> <pre class="programlisting">const length L; const mass M; // needs to be namespace-qualified because of global time definition const boost::units::test::time T; const energy E; </pre> We can perform various algebraic operations on these units, resulting in the following output: <pre class="programlisting">L = m L+L = m L-L = m L/L = dimensionless meter*meter = m^2 M*(L/T)*(L/T) = m^2 kg s^-2 M*(L/T)^2 = m^2 kg s^-2 L^3 = m^3 L^(3/2) = m^(3/2) 2vM = kg^(1/2) (3/2)vM = kg^(2/3) </pre> </div> <div class="section"> <div class="titlepage"><div><div><h3 class="title"> <a name="boost_units.Examples.QuantityExample"></a><a class="link" href="Examples.html#boost_units.Examples.QuantityExample" title="Quantity Example">Quantity Example</a> </h3></div></div></div> (<a href="../../../libs/units/example/quantity.cpp" target="_top">quantity.cpp</a>) This example demonstrates how to use quantities of our toy unit system : <pre class="programlisting">quantity<length> L = 2.0*meters; // quantity of length quantity<energy> E = kilograms*pow<2>(L/seconds); // quantity of energy </pre> giving us the basic quantity functionality : <pre class="programlisting">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) </pre> As a further demonstration of the flexibility of the system, we replace the <code class="computeroutput">double</code> value type with a <code class="computeroutput">std::complex<double></code> value type (ignoring the question of the meaningfulness of complex lengths and energies) : <pre class="programlisting">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)); </pre> and find that the code functions exactly as expected with no additional work, delegating operations to <code class="computeroutput">std::complex<double></code> and performing the appropriate dimensional analysis : <pre class="programlisting">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) </pre> </div> <div class="section"> <div class="titlepage"><div><div><h3 class="title"> <a name="boost_units.Examples.KitchenSinkExample"></a><a class="link" href="Examples.html#boost_units.Examples.KitchenSinkExample" title="Kitchen Sink Example using SI units">Kitchen Sink Example using SI units</a> </h3></div></div></div> <div class="toc"><dl class="toc"><dt><a href="Examples.html#boost_units.Examples.KitchenSinkExample.UDT_Quantities">User-defined value types</a></dt></dl></div> (<a href="../../../libs/units/example/kitchen_sink.cpp" target="_top">kitchen_sink.cpp</a>) This example provides a fairly extensive set of tests covering most of the <code class="computeroutput"><a class="link" href="../boost/units/quantity.html" title="Class template quantity">quantity</a></code> functionality. It uses the SI unit system defined in <code class="computeroutput"><a class="link" href="Reference.html#header.boost.units.systems.si_hpp" title="Header <boost/units/systems/si.hpp>">boost/units/systems/si.hpp</a></code>. If we define a few units and associated quantities, <pre class="programlisting">/// scalar const double s1 = 2; const long x1 = 2; const static_rational<4,3> x2; /// define some units force u1 = newton; energy u2 = joule; /// define some quantities quantity<force> q1(1.0*u1); quantity<energy> q2(2.0*u2); </pre> the various algebraic operations between scalars, units, and quantities give <pre class="programlisting">S1 : 2 X1 : 2 X2 : (4/3) U1 : N U2 : J Q1 : 1 N Q2 : 2 J </pre> Scalar/unit operations : <pre class="programlisting">U1*S1 : 2 N S1*U1 : 2 N U1/S1 : 0.5 N S1/U1 : 2 m^-1 kg^-1 s^2 </pre> Unit/unit operations and integral/rational powers of units : <pre class="programlisting">U1+U1 : N U1-U1 : N U1*U1 : m^2 kg^2 s^-4 U1/U1 : dimensionless U1*U2 : m^3 kg^2 s^-4 U1/U2 : m^-1 U1^X : m^2 kg^2 s^-4 X1vU1 : m^(1/2) kg^(1/2) s^-1 U1^X2 : m^(4/3) kg^(4/3) s^(-8/3) X2vU1 : m^(3/4) kg^(3/4) s^(-3/2) </pre> Scalar/quantity operations : <pre class="programlisting">Q1*S1 : 2 N S1*Q1 : 2 N Q1/S1 : 0.5 N S1/Q1 : 2 m^-1 kg^-1 s^2 </pre> Unit/quantity operations : <pre class="programlisting">U1*Q1 : 1 m^2 kg^2 s^-4 Q1*U1 : 1 m^2 kg^2 s^-4 U1/Q1 : 1 dimensionless Q1/U1 : 1 dimensionless </pre> Quantity/quantity operations and integral/rational powers of quantities : <pre class="programlisting">+Q1 : 1 N -Q1 : -1 N Q1+Q1 : 2 N Q1-Q1 : 0 N Q1*Q1 : 1 m^2 kg^2 s^-4 Q1/Q1 : 1 dimensionless Q1*Q2 : 2 m^3 kg^2 s^-4 Q1/Q2 : 0.5 m^-1 Q1^X1 : 1 m^2 kg^2 s^-4 X1vQ1 : 1 m^(1/2) kg^(1/2) s^-1 Q1^X2 : 1 m^(4/3) kg^(4/3) s^(-8/3) X2vQ1 : 1 m^(3/4) kg^(3/4) s^(-3/2) </pre> Logical comparison operators are also defined between quantities : <pre class="programlisting">/// check comparison tests quantity<length> l1(1.0*meter), l2</spa