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| <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> |
| <dt><span class="section"><a href="Examples.html#boost_units.Examples.DimensionExample">Dimension Example</a></span></dt> |
| <dt><span class="section"><a href="Examples.html#boost_units.Examples.UnitExample">Unit Example</a></span></dt> |
| <dt><span class="section"><a href="Examples.html#boost_units.Examples.QuantityExample">Quantity Example</a></span></dt> |
| <dt><span class="section"><a href="Examples.html#boost_units.Examples.KitchenSinkExample">Kitchen Sink |
| Example using SI units</a></span></dt> |
| <dt><span class="section"><a href="Examples.html#boost_units.Examples.ConversionExample">Conversion Example</a></span></dt> |
| <dt><span class="section"><a href="Examples.html#boost_units.Examples.UDTExample">User Defined Types</a></span></dt> |
| <dt><span class="section"><a href="Examples.html#boost_units.Examples.ComplexExample">Complex Example</a></span></dt> |
| <dt><span class="section"><a href="Examples.html#boost_units.Examples.PerformanceExample">Performance |
| Example</a></span></dt> |
| <dt><span class="section"><a href="Examples.html#boost_units.Examples.RadarBeamHeightExample">Radar Beam |
| Height</a></span></dt> |
| <dt><span class="section"><a href="Examples.html#boost_units.Examples.HeterogeneousUnitExample">Heterogeneous |
| Unit Example</a></span></dt> |
| <dt><span class="section"><a href="Examples.html#boost_units.Examples.AbsoluteRelativeTemperatureExample">Absolute |
| and Relative Temperature Example</a></span></dt> |
| <dt><span class="section"><a href="Examples.html#boost_units.Examples.RuntimeConversionFactorExample">Runtime |
| Conversion Factor Example</a></span></dt> |
| <dt><span class="section"><a href="Examples.html#boost_units.Examples.UnitsWithNonbaseDimensions">Units |
| with Non-base Dimensions</a></span></dt> |
| <dt><span class="section"><a href="Examples.html#boost_units.Examples.OutputForCompositeUnits">Output |
| for Composite Units</a></span></dt> |
| <dt><span class="section"><a href="Examples.html#boost_units.Examples.autoscale">Automatically Scaled |
| Units</a></span></dt> |
| <dt><span class="section"><a href="Examples.html#boost_units.Examples.ConversionFactor">Conversion Factor</a></span></dt> |
| <dt><span class="section"><a href="Examples.html#boost_units.Examples.RuntimeUnits">Runtime Units</a></span></dt> |
| <dt><span class="section"><a href="Examples.html#boost_units.Examples.lambda">Interoperability with Boost.Lambda</a></span></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> |
| <p> |
| (<a href="../../../libs/units/example/dimension.cpp" target="_top">dimension.cpp</a>) |
| </p> |
| <p> |
| 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 : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">times</span><span class="special"><</span><span class="identifier">length_dimension</span><span class="special">,</span><span class="identifier">mass_dimension</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">LM_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">divides</span><span class="special"><</span><span class="identifier">length_dimension</span><span class="special">,</span><span class="identifier">time_dimension</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">L_T_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">static_root</span><span class="special"><</span> |
| <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">divides</span><span class="special"><</span><span class="identifier">energy_dimension</span><span class="special">,</span><span class="identifier">mass_dimension</span><span class="special">>::</span><span class="identifier">type</span><span class="special">,</span> |
| <span class="identifier">static_rational</span><span class="special"><</span><span class="number">2</span><span class="special">></span> |
| <span class="special">>::</span><span class="identifier">type</span> <span class="identifier">V_type</span><span class="special">;</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| outputting (with symbol demangling, implemented in <a href="../../../boost/units/detail/utility.hpp" target="_top">utility.hpp</a>) |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">length_dimension</span> <span class="special">=</span> <span class="identifier">list</span><span class="special"><</span><span class="identifier">dim</span><span class="special"><</span><span class="identifier">length_base_dimension</span><span class="special">,</span> <span class="identifier">static_rational</span><span class="special"><</span><span class="number">1l</span><span class="special">,</span> <span class="number">1l</span><span class="special">></span> <span class="special">>,</span> <span class="identifier">dimensionless_type</span><span class="special">></span> |
| <span class="identifier">mass_dimension</span> <span class="special">=</span> <span class="identifier">list</span><span class="special"><</span><span class="identifier">dim</span><span class="special"><</span><span class="identifier">mass_base_dimension</span><span class="special">,</span> <span class="identifier">static_rational</span><span class="special"><</span><span class="number">1l</span><span class="special">,</span> <span class="number">1l</span><span class="special">></span> <span class="special">>,</span> <span class="identifier">dimensionless_type</span><span class="special">></span> |
| <span class="identifier">time_dimension</span> <span class="special">=</span> <span class="identifier">list</span><span class="special"><</span><span class="identifier">dim</span><span class="special"><</span><span class="identifier">time_base_dimension</span><span class="special">,</span> <span class="identifier">static_rational</span><span class="special"><</span><span class="number">1l</span><span class="special">,</span> <span class="number">1l</span><span class="special">></span> <span class="special">>,</span> <span class="identifier">dimensionless_type</span><span class="special">></span> |
| <span class="identifier">energy_dimension</span> <span class="special">=</span> <span class="identifier">list</span><span class="special"><</span><span class="identifier">dim</span><span class="special"><</span><span class="identifier">length_base_dimension</span><span class="special">,</span> <span class="identifier">static_rational</span><span class="special"><</span><span class="number">2l</span><span class="special">,</span> <span class="number">1l</span><span class="special">></span> <span class="special">>,</span> <span class="identifier">list</span><span class="special"><</span><span class="identifier">dim</span><span class="special"><</span><span class="identifier">mass_base_dimension</span><span class="special">,</span> <span class="identifier">static_rational</span><span class="special"><</span><span class="number">1l</span><span class="special">,</span> <span class="number">1l</span><span class="special">></span> <span class="special">>,</span> <span class="identifier">list</span><span class="special"><</span><span class="identifier">dim</span><span class="special"><</span><span class="identifier">time_base_dimension</span><span class="special">,</span> <span class="identifier">static_rational</span><span class="special"><-</span><span class="number">2l</span><span class="special">,</span> <span class="number">1l</span><span class="special">></span> <span class="special">>,</span> <span class="identifier">dimensionless_type</span><span class="special">></span> <span class="special">></span> <span class="special">></span> |
| <span class="identifier">LM_type</span> <span class="special">=</span> <span class="identifier">list</span><span class="special"><</span><span class="identifier">dim</span><span class="special"><</span><span class="identifier">length_base_dimension</span><span class="special">,</span> <span class="identifier">static_rational</span><span class="special"><</span><span class="number">1l</span><span class="special">,</span> <span class="number">1l</span><span class="special">></span> <span class="special">>,</span> <span class="identifier">list</span><span class="special"><</span><span class="identifier">dim</span><span class="special"><</span><span class="identifier">mass_base_dimension</span><span class="special">,</span> <span class="identifier">static_rational</span><span class="special"><</span><span class="number">1l</span><span class="special">,</span> <span class="number">1l</span><span class="special">></span> <span class="special">>,</span> <span class="identifier">dimensionless_type</span><span class="special">></span> <span class="special">></span> |
| <span class="identifier">L_T_type</span> <span class="special">=</span> <span class="identifier">list</span><span class="special"><</span><span class="identifier">dim</span><span class="special"><</span><span class="identifier">length_base_dimension</span><span class="special">,</span> <span class="identifier">static_rational</span><span class="special"><</span><span class="number">1l</span><span class="special">,</span> <span class="number">1l</span><span class="special">></span> <span class="special">>,</span> <span class="identifier">list</span><span class="special"><</span><span class="identifier">dim</span><span class="special"><</span><span class="identifier">time_base_dimension</span><span class="special">,</span> <span class="identifier">static_rational</span><span class="special"><-</span><span class="number">1l</span><span class="special">,</span> <span class="number">1l</span><span class="special">></span> <span class="special">>,</span> <span class="identifier">dimensionless_type</span><span class="special">></span> <span class="special">></span> |
| <span class="identifier">V_type</span> <span class="special">=</span> <span class="identifier">list</span><span class="special"><</span><span class="identifier">dim</span><span class="special"><</span><span class="identifier">length_base_dimension</span><span class="special">,</span> <span class="identifier">static_rational</span><span class="special"><</span><span class="number">1l</span><span class="special">,</span> <span class="number">1l</span><span class="special">></span> <span class="special">>,</span> <span class="identifier">list</span><span class="special"><</span><span class="identifier">dim</span><span class="special"><</span><span class="identifier">time_base_dimension</span><span class="special">,</span> <span class="identifier">static_rational</span><span class="special"><-</span><span class="number">1l</span><span class="special">,</span> <span class="number">1l</span><span class="special">></span> <span class="special">>,</span> <span class="identifier">dimensionless_type</span><span class="special">></span> <span class="special">></span> |
| </pre> |
| <p> |
| </p> |
| </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> |
| <p> |
| (<a href="../../../libs/units/example/unit.cpp" target="_top">unit.cpp</a>) |
| </p> |
| <p> |
| 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> |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">const</span> <span class="identifier">length</span> <span class="identifier">L</span><span class="special">;</span> |
| <span class="keyword">const</span> <span class="identifier">mass</span> <span class="identifier">M</span><span class="special">;</span> |
| <span class="comment">// needs to be namespace-qualified because of global time definition |
| </span><span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">test</span><span class="special">::</span><span class="identifier">time</span> <span class="identifier">T</span><span class="special">;</span> |
| <span class="keyword">const</span> <span class="identifier">energy</span> <span class="identifier">E</span><span class="special">;</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| We can perform various algebraic operations on these units, resulting in |
| the following output: |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">L</span> <span class="special">=</span> <span class="identifier">m</span> |
| <span class="identifier">L</span><span class="special">+</span><span class="identifier">L</span> <span class="special">=</span> <span class="identifier">m</span> |
| <span class="identifier">L</span><span class="special">-</span><span class="identifier">L</span> <span class="special">=</span> <span class="identifier">m</span> |
| <span class="identifier">L</span><span class="special">/</span><span class="identifier">L</span> <span class="special">=</span> <span class="identifier">dimensionless</span> |
| <span class="identifier">meter</span><span class="special">*</span><span class="identifier">meter</span> <span class="special">=</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> |
| <span class="identifier">M</span><span class="special">*(</span><span class="identifier">L</span><span class="special">/</span><span class="identifier">T</span><span class="special">)*(</span><span class="identifier">L</span><span class="special">/</span><span class="identifier">T</span><span class="special">)</span> <span class="special">=</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> <span class="identifier">kg</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">2</span> |
| <span class="identifier">M</span><span class="special">*(</span><span class="identifier">L</span><span class="special">/</span><span class="identifier">T</span><span class="special">)^</span><span class="number">2</span> <span class="special">=</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> <span class="identifier">kg</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">2</span> |
| <span class="identifier">L</span><span class="special">^</span><span class="number">3</span> <span class="special">=</span> <span class="identifier">m</span><span class="special">^</span><span class="number">3</span> |
| <span class="identifier">L</span><span class="special">^(</span><span class="number">3</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> <span class="special">=</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">3</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> |
| <span class="number">2</span><span class="identifier">vM</span> <span class="special">=</span> <span class="identifier">kg</span><span class="special">^(</span><span class="number">1</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> |
| <span class="special">(</span><span class="number">3</span><span class="special">/</span><span class="number">2</span><span class="special">)</span><span class="identifier">vM</span> <span class="special">=</span> <span class="identifier">kg</span><span class="special">^(</span><span class="number">2</span><span class="special">/</span><span class="number">3</span><span class="special">)</span> |
| </pre> |
| <p> |
| </p> |
| </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> |
| <p> |
| (<a href="../../../libs/units/example/quantity.cpp" target="_top">quantity.cpp</a>) |
| </p> |
| <p> |
| This example demonstrates how to use quantities of our toy unit system : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">length</span><span class="special">></span> <span class="identifier">L</span> <span class="special">=</span> <span class="number">2.0</span><span class="special">*</span><span class="identifier">meters</span><span class="special">;</span> <span class="comment">// quantity of length |
| </span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">energy</span><span class="special">></span> <span class="identifier">E</span> <span class="special">=</span> <span class="identifier">kilograms</span><span class="special">*</span><span class="identifier">pow</span><span class="special"><</span><span class="number">2</span><span class="special">>(</span><span class="identifier">L</span><span class="special">/</span><span class="identifier">seconds</span><span class="special">);</span> <span class="comment">// quantity of energy |
| </span></pre> |
| <p> |
| </p> |
| <p> |
| giving us the basic quantity functionality : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">L</span> <span class="special">=</span> <span class="number">2</span> <span class="identifier">m</span> |
| <span class="identifier">L</span><span class="special">+</span><span class="identifier">L</span> <span class="special">=</span> <span class="number">4</span> <span class="identifier">m</span> |
| <span class="identifier">L</span><span class="special">-</span><span class="identifier">L</span> <span class="special">=</span> <span class="number">0</span> <span class="identifier">m</span> |
| <span class="identifier">L</span><span class="special">*</span><span class="identifier">L</span> <span class="special">=</span> <span class="number">4</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> |
| <span class="identifier">L</span><span class="special">/</span><span class="identifier">L</span> <span class="special">=</span> <span class="number">1</span> <span class="identifier">dimensionless</span> |
| <span class="identifier">L</span><span class="special">*</span><span class="identifier">meter</span> <span class="special">=</span> <span class="number">2</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> |
| <span class="identifier">kilograms</span><span class="special">*(</span><span class="identifier">L</span><span class="special">/</span><span class="identifier">seconds</span><span class="special">)*(</span><span class="identifier">L</span><span class="special">/</span><span class="identifier">seconds</span><span class="special">)</span> <span class="special">=</span> <span class="number">4</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> <span class="identifier">kg</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">2</span> |
| <span class="identifier">kilograms</span><span class="special">*(</span><span class="identifier">L</span><span class="special">/</span><span class="identifier">seconds</span><span class="special">)^</span><span class="number">2</span> <span class="special">=</span> <span class="number">4</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> <span class="identifier">kg</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">2</span> |
| <span class="identifier">L</span><span class="special">^</span><span class="number">3</span> <span class="special">=</span> <span class="number">8</span> <span class="identifier">m</span><span class="special">^</span><span class="number">3</span> |
| <span class="identifier">L</span><span class="special">^(</span><span class="number">3</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> <span class="special">=</span> <span class="number">2.82843</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">3</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> |
| <span class="number">2</span><span class="identifier">vL</span> <span class="special">=</span> <span class="number">1.41421</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">1</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> |
| <span class="special">(</span><span class="number">3</span><span class="special">/</span><span class="number">2</span><span class="special">)</span><span class="identifier">vL</span> <span class="special">=</span> <span class="number">1.5874</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">2</span><span class="special">/</span><span class="number">3</span><span class="special">)</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| As a further demonstration of the flexibility of the system, we replace the |
| <code class="computeroutput"><span class="keyword">double</span></code> value type with a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">complex</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span></code> value type (ignoring the question of |
| the meaningfulness of complex lengths and energies) : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">length</span><span class="special">,</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">complex</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="special">></span> <span class="identifier">L</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">complex</span><span class="special"><</span><span class="keyword">double</span><span class="special">>(</span><span class="number">3.0</span><span class="special">,</span><span class="number">4.0</span><span class="special">)*</span><span class="identifier">meters</span><span class="special">);</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">energy</span><span class="special">,</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">complex</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="special">></span> <span class="identifier">E</span><span class="special">(</span><span class="identifier">kilograms</span><span class="special">*</span><span class="identifier">pow</span><span class="special"><</span><span class="number">2</span><span class="special">>(</span><span class="identifier">L</span><span class="special">/</span><span class="identifier">seconds</span><span class="special">));</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| and find that the code functions exactly as expected with no additional work, |
| delegating operations to <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">complex</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span></code> and performing the appropriate dimensional |
| analysis : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">L</span> <span class="special">=</span> <span class="special">(</span><span class="number">3</span><span class="special">,</span><span class="number">4</span><span class="special">)</span> <span class="identifier">m</span> |
| <span class="identifier">L</span><span class="special">+</span><span class="identifier">L</span> <span class="special">=</span> <span class="special">(</span><span class="number">6</span><span class="special">,</span><span class="number">8</span><span class="special">)</span> <span class="identifier">m</span> |
| <span class="identifier">L</span><span class="special">-</span><span class="identifier">L</span> <span class="special">=</span> <span class="special">(</span><span class="number">0</span><span class="special">,</span><span class="number">0</span><span class="special">)</span> <span class="identifier">m</span> |
| <span class="identifier">L</span><span class="special">*</span><span class="identifier">L</span> <span class="special">=</span> <span class="special">(-</span><span class="number">7</span><span class="special">,</span><span class="number">24</span><span class="special">)</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> |
| <span class="identifier">L</span><span class="special">/</span><span class="identifier">L</span> <span class="special">=</span> <span class="special">(</span><span class="number">1</span><span class="special">,</span><span class="number">0</span><span class="special">)</span> <span class="identifier">dimensionless</span> |
| <span class="identifier">L</span><span class="special">*</span><span class="identifier">meter</span> <span class="special">=</span> <span class="special">(</span><span class="number">3</span><span class="special">,</span><span class="number">4</span><span class="special">)</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> |
| <span class="identifier">kilograms</span><span class="special">*(</span><span class="identifier">L</span><span class="special">/</span><span class="identifier">seconds</span><span class="special">)*(</span><span class="identifier">L</span><span class="special">/</span><span class="identifier">seconds</span><span class="special">)</span> <span class="special">=</span> <span class="special">(-</span><span class="number">7</span><span class="special">,</span><span class="number">24</span><span class="special">)</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> <span class="identifier">kg</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">2</span> |
| <span class="identifier">kilograms</span><span class="special">*(</span><span class="identifier">L</span><span class="special">/</span><span class="identifier">seconds</span><span class="special">)^</span><span class="number">2</span> <span class="special">=</span> <span class="special">(-</span><span class="number">7</span><span class="special">,</span><span class="number">24</span><span class="special">)</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> <span class="identifier">kg</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">2</span> |
| <span class="identifier">L</span><span class="special">^</span><span class="number">3</span> <span class="special">=</span> <span class="special">(-</span><span class="number">117</span><span class="special">,</span><span class="number">44</span><span class="special">)</span> <span class="identifier">m</span><span class="special">^</span><span class="number">3</span> |
| <span class="identifier">L</span><span class="special">^(</span><span class="number">3</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> <span class="special">=</span> <span class="special">(</span><span class="number">2</span><span class="special">,</span><span class="number">11</span><span class="special">)</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">3</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> |
| <span class="number">2</span><span class="identifier">vL</span> <span class="special">=</span> <span class="special">(</span><span class="number">2</span><span class="special">,</span><span class="number">1</span><span class="special">)</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">1</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> |
| <span class="special">(</span><span class="number">3</span><span class="special">/</span><span class="number">2</span><span class="special">)</span><span class="identifier">vL</span> <span class="special">=</span> <span class="special">(</span><span class="number">2.38285</span><span class="special">,</span><span class="number">1.69466</span><span class="special">)</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">2</span><span class="special">/</span><span class="number">3</span><span class="special">)</span> |
| </pre> |
| <p> |
| </p> |
| </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><dt><span class="section"><a href="Examples.html#boost_units.Examples.KitchenSinkExample.UDT_Quantities">User-defined |
| value types</a></span></dt></dl></div> |
| <p> |
| (<a href="../../../libs/units/example/kitchen_sink.cpp" target="_top">kitchen_sink.cpp</a>) |
| </p> |
| <p> |
| This example provides a fairly extensive set of tests covering most of the |
| <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/quantity.html" title="Class template quantity">quantity</a></code></span> |
| 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>. |
| </p> |
| <p> |
| If we define a few units and associated quantities, |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="comment">/// scalar |
| </span><span class="keyword">const</span> <span class="keyword">double</span> <span class="identifier">s1</span> <span class="special">=</span> <span class="number">2</span><span class="special">;</span> |
| |
| <span class="keyword">const</span> <span class="keyword">long</span> <span class="identifier">x1</span> <span class="special">=</span> <span class="number">2</span><span class="special">;</span> |
| <span class="keyword">const</span> <span class="identifier">static_rational</span><span class="special"><</span><span class="number">4</span><span class="special">,</span><span class="number">3</span><span class="special">></span> <span class="identifier">x2</span><span class="special">;</span> |
| |
| <span class="comment">/// define some units |
| </span><span class="identifier">force</span> <span class="identifier">u1</span> <span class="special">=</span> <span class="identifier">newton</span><span class="special">;</span> |
| <span class="identifier">energy</span> <span class="identifier">u2</span> <span class="special">=</span> <span class="identifier">joule</span><span class="special">;</span> |
| |
| <span class="comment">/// define some quantities |
| </span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">force</span><span class="special">></span> <span class="identifier">q1</span><span class="special">(</span><span class="number">1.0</span><span class="special">*</span><span class="identifier">u1</span><span class="special">);</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">energy</span><span class="special">></span> <span class="identifier">q2</span><span class="special">(</span><span class="number">2.0</span><span class="special">*</span><span class="identifier">u2</span><span class="special">);</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| the various algebraic operations between scalars, units, and quantities give |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">S1</span> <span class="special">:</span> <span class="number">2</span> |
| <span class="identifier">X1</span> <span class="special">:</span> <span class="number">2</span> |
| <span class="identifier">X2</span> <span class="special">:</span> <span class="special">(</span><span class="number">4</span><span class="special">/</span><span class="number">3</span><span class="special">)</span> |
| <span class="identifier">U1</span> <span class="special">:</span> <span class="identifier">N</span> |
| <span class="identifier">U2</span> <span class="special">:</span> <span class="identifier">J</span> |
| <span class="identifier">Q1</span> <span class="special">:</span> <span class="number">1</span> <span class="identifier">N</span> |
| <span class="identifier">Q2</span> <span class="special">:</span> <span class="number">2</span> <span class="identifier">J</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| Scalar/unit operations : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">U1</span><span class="special">*</span><span class="identifier">S1</span> <span class="special">:</span> <span class="number">2</span> <span class="identifier">N</span> |
| <span class="identifier">S1</span><span class="special">*</span><span class="identifier">U1</span> <span class="special">:</span> <span class="number">2</span> <span class="identifier">N</span> |
| <span class="identifier">U1</span><span class="special">/</span><span class="identifier">S1</span> <span class="special">:</span> <span class="number">0.5</span> <span class="identifier">N</span> |
| <span class="identifier">S1</span><span class="special">/</span><span class="identifier">U1</span> <span class="special">:</span> <span class="number">2</span> <span class="identifier">m</span><span class="special">^-</span><span class="number">1</span> <span class="identifier">kg</span><span class="special">^-</span><span class="number">1</span> <span class="identifier">s</span><span class="special">^</span><span class="number">2</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| Unit/unit operations and integral/rational powers of units : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">U1</span><span class="special">+</span><span class="identifier">U1</span> <span class="special">:</span> <span class="identifier">N</span> |
| <span class="identifier">U1</span><span class="special">-</span><span class="identifier">U1</span> <span class="special">:</span> <span class="identifier">N</span> |
| <span class="identifier">U1</span><span class="special">*</span><span class="identifier">U1</span> <span class="special">:</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> <span class="identifier">kg</span><span class="special">^</span><span class="number">2</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">4</span> |
| <span class="identifier">U1</span><span class="special">/</span><span class="identifier">U1</span> <span class="special">:</span> <span class="identifier">dimensionless</span> |
| <span class="identifier">U1</span><span class="special">*</span><span class="identifier">U2</span> <span class="special">:</span> <span class="identifier">m</span><span class="special">^</span><span class="number">3</span> <span class="identifier">kg</span><span class="special">^</span><span class="number">2</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">4</span> |
| <span class="identifier">U1</span><span class="special">/</span><span class="identifier">U2</span> <span class="special">:</span> <span class="identifier">m</span><span class="special">^-</span><span class="number">1</span> |
| <span class="identifier">U1</span><span class="special">^</span><span class="identifier">X</span> <span class="special">:</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> <span class="identifier">kg</span><span class="special">^</span><span class="number">2</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">4</span> |
| <span class="identifier">X1vU1</span> <span class="special">:</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">1</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> <span class="identifier">kg</span><span class="special">^(</span><span class="number">1</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">1</span> |
| <span class="identifier">U1</span><span class="special">^</span><span class="identifier">X2</span> <span class="special">:</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">4</span><span class="special">/</span><span class="number">3</span><span class="special">)</span> <span class="identifier">kg</span><span class="special">^(</span><span class="number">4</span><span class="special">/</span><span class="number">3</span><span class="special">)</span> <span class="identifier">s</span><span class="special">^(-</span><span class="number">8</span><span class="special">/</span><span class="number">3</span><span class="special">)</span> |
| <span class="identifier">X2vU1</span> <span class="special">:</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">3</span><span class="special">/</span><span class="number">4</span><span class="special">)</span> <span class="identifier">kg</span><span class="special">^(</span><span class="number">3</span><span class="special">/</span><span class="number">4</span><span class="special">)</span> <span class="identifier">s</span><span class="special">^(-</span><span class="number">3</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| Scalar/quantity operations : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">Q1</span><span class="special">*</span><span class="identifier">S1</span> <span class="special">:</span> <span class="number">2</span> <span class="identifier">N</span> |
| <span class="identifier">S1</span><span class="special">*</span><span class="identifier">Q1</span> <span class="special">:</span> <span class="number">2</span> <span class="identifier">N</span> |
| <span class="identifier">Q1</span><span class="special">/</span><span class="identifier">S1</span> <span class="special">:</span> <span class="number">0.5</span> <span class="identifier">N</span> |
| <span class="identifier">S1</span><span class="special">/</span><span class="identifier">Q1</span> <span class="special">:</span> <span class="number">2</span> <span class="identifier">m</span><span class="special">^-</span><span class="number">1</span> <span class="identifier">kg</span><span class="special">^-</span><span class="number">1</span> <span class="identifier">s</span><span class="special">^</span><span class="number">2</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| Unit/quantity operations : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">U1</span><span class="special">*</span><span class="identifier">Q1</span> <span class="special">:</span> <span class="number">1</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> <span class="identifier">kg</span><span class="special">^</span><span class="number">2</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">4</span> |
| <span class="identifier">Q1</span><span class="special">*</span><span class="identifier">U1</span> <span class="special">:</span> <span class="number">1</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> <span class="identifier">kg</span><span class="special">^</span><span class="number">2</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">4</span> |
| <span class="identifier">U1</span><span class="special">/</span><span class="identifier">Q1</span> <span class="special">:</span> <span class="number">1</span> <span class="identifier">dimensionless</span> |
| <span class="identifier">Q1</span><span class="special">/</span><span class="identifier">U1</span> <span class="special">:</span> <span class="number">1</span> <span class="identifier">dimensionless</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| Quantity/quantity operations and integral/rational powers of quantities : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="special">+</span><span class="identifier">Q1</span> <span class="special">:</span> <span class="number">1</span> <span class="identifier">N</span> |
| <span class="special">-</span><span class="identifier">Q1</span> <span class="special">:</span> <span class="special">-</span><span class="number">1</span> <span class="identifier">N</span> |
| <span class="identifier">Q1</span><span class="special">+</span><span class="identifier">Q1</span> <span class="special">:</span> <span class="number">2</span> <span class="identifier">N</span> |
| <span class="identifier">Q1</span><span class="special">-</span><span class="identifier">Q1</span> <span class="special">:</span> <span class="number">0</span> <span class="identifier">N</span> |
| <span class="identifier">Q1</span><span class="special">*</span><span class="identifier">Q1</span> <span class="special">:</span> <span class="number">1</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> <span class="identifier">kg</span><span class="special">^</span><span class="number">2</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">4</span> |
| <span class="identifier">Q1</span><span class="special">/</span><span class="identifier">Q1</span> <span class="special">:</span> <span class="number">1</span> <span class="identifier">dimensionless</span> |
| <span class="identifier">Q1</span><span class="special">*</span><span class="identifier">Q2</span> <span class="special">:</span> <span class="number">2</span> <span class="identifier">m</span><span class="special">^</span><span class="number">3</span> <span class="identifier">kg</span><span class="special">^</span><span class="number">2</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">4</span> |
| <span class="identifier">Q1</span><span class="special">/</span><span class="identifier">Q2</span> <span class="special">:</span> <span class="number">0.5</span> <span class="identifier">m</span><span class="special">^-</span><span class="number">1</span> |
| <span class="identifier">Q1</span><span class="special">^</span><span class="identifier">X1</span> <span class="special">:</span> <span class="number">1</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> <span class="identifier">kg</span><span class="special">^</span><span class="number">2</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">4</span> |
| <span class="identifier">X1vQ1</span> <span class="special">:</span> <span class="number">1</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">1</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> <span class="identifier">kg</span><span class="special">^(</span><span class="number">1</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">1</span> |
| <span class="identifier">Q1</span><span class="special">^</span><span class="identifier">X2</span> <span class="special">:</span> <span class="number">1</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">4</span><span class="special">/</span><span class="number">3</span><span class="special">)</span> <span class="identifier">kg</span><span class="special">^(</span><span class="number">4</span><span class="special">/</span><span class="number">3</span><span class="special">)</span> <span class="identifier">s</span><span class="special">^(-</span><span class="number">8</span><span class="special">/</span><span class="number">3</span><span class="special">)</span> |
| <span class="identifier">X2vQ1</span> <span class="special">:</span> <span class="number">1</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">3</span><span class="special">/</span><span class="number">4</span><span class="special">)</span> <span class="identifier">kg</span><span class="special">^(</span><span class="number">3</span><span class="special">/</span><span class="number">4</span><span class="special">)</span> <span class="identifier">s</span><span class="special">^(-</span><span class="number">3</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| Logical comparison operators are also defined between quantities : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="comment">/// check comparison tests |
| </span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">length</span><span class="special">></span> <span class="identifier">l1</span><span class="special">(</span><span class="number">1.0</span><span class="special">*</span><span class="identifier">meter</span><span class="special">),</span> |
| <span class="identifier">l2</span><span class="special">(</span><span class="number">2.0</span><span class="special">*</span><span class="identifier">meters</span><span class="special">);</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| giving |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">l1</span> <span class="special">==</span> <span class="identifier">l2</span> <span class="keyword">false</span> |
| <span class="identifier">l1</span> <span class="special">!=</span> <span class="identifier">l2</span> <span class="keyword">true</span> |
| <span class="identifier">l1</span> <span class="special"><=</span> <span class="identifier">l2</span> <span class="keyword">true</span> |
| <span class="identifier">l1</span> <span class="special"><</span> <span class="identifier">l2</span> <span class="keyword">true</span> |
| <span class="identifier">l1</span> <span class="special">>=</span> <span class="identifier">l2</span> <span class="keyword">false</span> |
| <span class="identifier">l1</span> <span class="special">></span> <span class="identifier">l2</span> <span class="keyword">false</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| Implicit conversion is allowed between dimensionless quantities and their |
| corresponding value types : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="comment">/// check implicit unit conversion from dimensionless to value_type |
| </span><span class="keyword">const</span> <span class="keyword">double</span> <span class="identifier">dimless</span> <span class="special">=</span> <span class="special">(</span><span class="identifier">q1</span><span class="special">/</span><span class="identifier">q1</span><span class="special">);</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| A generic function for computing mechanical work can be defined that takes |
| force and distance arguments in an arbitrary unit system and returns energy |
| in the same system: |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="comment">/// the physical definition of work - computed for an arbitrary unit system |
| </span><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">System</span><span class="special">,</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">></span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">unit</span><span class="special"><</span><span class="identifier">energy_dimension</span><span class="special">,</span><span class="identifier">System</span><span class="special">>,</span><span class="identifier">Y</span><span class="special">></span> |
| <span class="identifier">work</span><span class="special">(</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">unit</span><span class="special"><</span><span class="identifier">force_dimension</span><span class="special">,</span><span class="identifier">System</span><span class="special">>,</span><span class="identifier">Y</span><span class="special">></span> <span class="identifier">F</span><span class="special">,</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">unit</span><span class="special"><</span><span class="identifier">length_dimension</span><span class="special">,</span><span class="identifier">System</span><span class="special">>,</span><span class="identifier">Y</span><span class="special">></span> <span class="identifier">dx</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="identifier">F</span><span class="special">*</span><span class="identifier">dx</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="comment">/// test calcuation of work |
| </span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">force</span><span class="special">></span> <span class="identifier">F</span><span class="special">(</span><span class="number">1.0</span><span class="special">*</span><span class="identifier">newton</span><span class="special">);</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">length</span><span class="special">></span> <span class="identifier">dx</span><span class="special">(</span><span class="number">1.0</span><span class="special">*</span><span class="identifier">meter</span><span class="special">);</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">energy</span><span class="special">></span> <span class="identifier">E</span><span class="special">(</span><span class="identifier">work</span><span class="special">(</span><span class="identifier">F</span><span class="special">,</span><span class="identifier">dx</span><span class="special">));</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| which functions as expected for SI quantities : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">F</span> <span class="special">=</span> <span class="number">1</span> <span class="identifier">N</span> |
| <span class="identifier">dx</span> <span class="special">=</span> <span class="number">1</span> <span class="identifier">m</span> |
| <span class="identifier">E</span> <span class="special">=</span> <span class="number">1</span> <span class="identifier">J</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| The ideal gas law can also be implemented in SI units : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="comment">/// the ideal gas law in si units |
| </span><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">></span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">amount</span><span class="special">,</span><span class="identifier">Y</span><span class="special">></span> |
| <span class="identifier">idealGasLaw</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">pressure</span><span class="special">,</span><span class="identifier">Y</span><span class="special">>&</span> <span class="identifier">P</span><span class="special">,</span> |
| <span class="keyword">const</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">volume</span><span class="special">,</span><span class="identifier">Y</span><span class="special">>&</span> <span class="identifier">V</span><span class="special">,</span> |
| <span class="keyword">const</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">temperature</span><span class="special">,</span><span class="identifier">Y</span><span class="special">>&</span> <span class="identifier">T</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">si</span><span class="special">;</span> |
| |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">constants</span><span class="special">::</span><span class="identifier">codata</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="special">(</span><span class="identifier">P</span><span class="special">*</span><span class="identifier">V</span><span class="special">/(</span><span class="identifier">R</span><span class="special">*</span><span class="identifier">T</span><span class="special">));</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="comment">/// test ideal gas law |
| </span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">temperature</span><span class="special">></span> <span class="identifier">T</span> <span class="special">=</span> <span class="special">(</span><span class="number">273.</span><span class="special">+</span><span class="number">37.</span><span class="special">)*</span><span class="identifier">kelvin</span><span class="special">;</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">pressure</span><span class="special">></span> <span class="identifier">P</span> <span class="special">=</span> <span class="number">1.01325e5</span><span class="special">*</span><span class="identifier">pascals</span><span class="special">;</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">length</span><span class="special">></span> <span class="identifier">r</span> <span class="special">=</span> <span class="number">0.5e-6</span><span class="special">*</span><span class="identifier">meters</span><span class="special">;</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">volume</span><span class="special">></span> <span class="identifier">V</span> <span class="special">=</span> <span class="special">(</span><span class="number">4.0</span><span class="special">/</span><span class="number">3.0</span><span class="special">)*</span><span class="number">3.141592</span><span class="special">*</span><span class="identifier">pow</span><span class="special"><</span><span class="number">3</span><span class="special">>(</span><span class="identifier">r</span><span class="special">);</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">amount</span><span class="special">></span> <span class="identifier">n</span><span class="special">(</span><span class="identifier">idealGasLaw</span><span class="special">(</span><span class="identifier">P</span><span class="special">,</span><span class="identifier">V</span><span class="special">,</span><span class="identifier">T</span><span class="special">));</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| with the resulting output : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">r</span> <span class="special">=</span> <span class="number">5e-07</span> <span class="identifier">m</span> |
| <span class="identifier">P</span> <span class="special">=</span> <span class="number">101325</span> <span class="identifier">Pa</span> |
| <span class="identifier">V</span> <span class="special">=</span> <span class="number">5.23599e-19</span> <span class="identifier">m</span><span class="special">^</span><span class="number">3</span> |
| <span class="identifier">T</span> <span class="special">=</span> <span class="number">310</span> <span class="identifier">K</span> |
| <span class="identifier">n</span> <span class="special">=</span> <span class="number">2.05835e-17</span> <span class="identifier">mol</span> |
| <span class="identifier">R</span> <span class="special">=</span> <span class="number">8.314472</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> <span class="identifier">kg</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">2</span> <span class="identifier">K</span><span class="special">^-</span><span class="number">1</span> <span class="identifier">mol</span><span class="special">^-</span><span class="number">1</span> <span class="special">(</span><span class="identifier">rel</span><span class="special">.</span> <span class="identifier">unc</span><span class="special">.</span> <span class="special">=</span> <span class="number">1.8e-06</span><span class="special">)</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| Trigonometric and inverse trigonometric functions can be implemented for |
| any unit system that provides an angular base dimension. For radians, these |
| functions are found in <code class="computeroutput"><a class="link" href="Reference.html#header.boost.units.cmath_hpp" title="Header <boost/units/cmath.hpp>">boost/units/cmath.hpp</a></code> |
| These behave as one expects, with trigonometric functions taking an angular |
| quantity and returning a dimensionless quantity, while the inverse trigonometric |
| functions take a dimensionless quantity and return an angular quantity : |
| </p> |
| <p> |
| Defining a few angular quantities, |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="comment">/// test trig stuff |
| </span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">plane_angle</span><span class="special">></span> <span class="identifier">theta</span> <span class="special">=</span> <span class="number">0.375</span><span class="special">*</span><span class="identifier">radians</span><span class="special">;</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">dimensionless</span><span class="special">></span> <span class="identifier">sin_theta</span> <span class="special">=</span> <span class="identifier">sin</span><span class="special">(</span><span class="identifier">theta</span><span class="special">);</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">plane_angle</span><span class="special">></span> <span class="identifier">thetap</span> <span class="special">=</span> <span class="identifier">asin</span><span class="special">(</span><span class="identifier">sin_theta</span><span class="special">);</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| yields |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">theta</span> <span class="special">=</span> <span class="number">0.375</span> <span class="identifier">rd</span> |
| <span class="identifier">sin</span><span class="special">(</span><span class="identifier">theta</span><span class="special">)</span> <span class="special">=</span> <span class="number">0.366273</span> <span class="identifier">dimensionless</span> |
| <span class="identifier">asin</span><span class="special">(</span><span class="identifier">sin</span><span class="special">(</span><span class="identifier">theta</span><span class="special">))</span> <span class="special">=</span> <span class="number">0.375</span> <span class="identifier">rd</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| Dealing with complex quantities is trivial. Here is the calculation of complex |
| impedance : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">electric_potential</span><span class="special">,</span><span class="identifier">complex_type</span><span class="special">></span> <span class="identifier">v</span> <span class="special">=</span> <span class="identifier">complex_type</span><span class="special">(</span><span class="number">12.5</span><span class="special">,</span><span class="number">0.0</span><span class="special">)*</span><span class="identifier">volts</span><span class="special">;</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">current</span><span class="special">,</span><span class="identifier">complex_type</span><span class="special">></span> <span class="identifier">i</span> <span class="special">=</span> <span class="identifier">complex_type</span><span class="special">(</span><span class="number">3.0</span><span class="special">,</span><span class="number">4.0</span><span class="special">)*</span><span class="identifier">amperes</span><span class="special">;</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">resistance</span><span class="special">,</span><span class="identifier">complex_type</span><span class="special">></span> <span class="identifier">z</span> <span class="special">=</span> <span class="identifier">complex_type</span><span class="special">(</span><span class="number">1.5</span><span class="special">,-</span><span class="number">2.0</span><span class="special">)*</span><span class="identifier">ohms</span><span class="special">;</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| giving |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">V</span> <span class="special">=</span> <span class="special">(</span><span class="number">12.5</span><span class="special">,</span><span class="number">0</span><span class="special">)</span> <span class="identifier">V</span> |
| <span class="identifier">I</span> <span class="special">=</span> <span class="special">(</span><span class="number">3</span><span class="special">,</span><span class="number">4</span><span class="special">)</span> <span class="identifier">A</span> |
| <span class="identifier">Z</span> <span class="special">=</span> <span class="special">(</span><span class="number">1.5</span><span class="special">,-</span><span class="number">2</span><span class="special">)</span> <span class="identifier">Ohm</span> |
| <span class="identifier">I</span><span class="special">*</span><span class="identifier">Z</span> <span class="special">=</span> <span class="special">(</span><span class="number">12.5</span><span class="special">,</span><span class="number">0</span><span class="special">)</span> <span class="identifier">V</span> |
| </pre> |
| <p> |
| </p> |
| <div class="section"> |
| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="boost_units.Examples.KitchenSinkExample.UDT_Quantities"></a><a class="link" href="Examples.html#boost_units.Examples.KitchenSinkExample.UDT_Quantities" title="User-defined value types">User-defined |
| value types</a> |
| </h4></div></div></div> |
| <p> |
| User-defined value types that support the appropriate arithmetic operations |
| are automatically supported as quantity value types. The operators that |
| are supported by default for quantity value types are unary plus, unary |
| minus, addition, subtraction, multiplication, division, equal-to, not-equal-to, |
| less-than, less-or-equal-to, greater-than, and greater-or-equal-to. Support |
| for rational powers and roots can be added by overloading the <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/power_typeof_helper.html" title="Struct template power_typeof_helper">power_typeof_helper</a></code></span> |
| and <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/root_typeof_helper.html" title="Struct template root_typeof_helper">root_typeof_helper</a></code></span> |
| classes. Here we implement a user-defined <code class="computeroutput"><span class="identifier">measurement</span></code> |
| class that models a numerical measurement with an associated measurement |
| error and the appropriate algebra and demonstrates its use as a quantity |
| value type; the full code is found in <a href="../../../libs/units/example/measurement.hpp" target="_top">measurement.hpp</a>. |
| </p> |
| <p> |
| Then, defining some <code class="computeroutput"><span class="identifier">measurement</span></code> |
| <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/quantity.html" title="Class template quantity">quantity</a></code></span> |
| variables |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">length</span><span class="special">,</span><span class="identifier">measurement</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="special">></span> |
| <span class="identifier">u</span><span class="special">(</span><span class="identifier">measurement</span><span class="special"><</span><span class="keyword">double</span><span class="special">>(</span><span class="number">1.0</span><span class="special">,</span><span class="number">0.0</span><span class="special">)*</span><span class="identifier">meters</span><span class="special">),</span> |
| <span class="identifier">w</span><span class="special">(</span><span class="identifier">measurement</span><span class="special"><</span><span class="keyword">double</span><span class="special">>(</span><span class="number">4.52</span><span class="special">,</span><span class="number">0.02</span><span class="special">)*</span><span class="identifier">meters</span><span class="special">),</span> |
| <span class="identifier">x</span><span class="special">(</span><span class="identifier">measurement</span><span class="special"><</span><span class="keyword">double</span><span class="special">>(</span><span class="number">2.0</span><span class="special">,</span><span class="number">0.2</span><span class="special">)*</span><span class="identifier">meters</span><span class="special">),</span> |
| <span class="identifier">y</span><span class="special">(</span><span class="identifier">measurement</span><span class="special"><</span><span class="keyword">double</span><span class="special">>(</span><span class="number">3.0</span><span class="special">,</span><span class="number">0.6</span><span class="special">)*</span><span class="identifier">meters</span><span class="special">);</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| gives |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">x</span><span class="special">+</span><span class="identifier">y</span><span class="special">-</span><span class="identifier">w</span> <span class="special">=</span> <span class="number">0.48</span><span class="special">(+/-</span><span class="number">0.632772</span><span class="special">)</span> <span class="identifier">m</span> |
| <span class="identifier">w</span><span class="special">*</span><span class="identifier">x</span> <span class="special">=</span> <span class="number">9.04</span><span class="special">(+/-</span><span class="number">0.904885</span><span class="special">)</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> |
| <span class="identifier">x</span><span class="special">/</span><span class="identifier">y</span> <span class="special">=</span> <span class="number">0.666667</span><span class="special">(+/-</span><span class="number">0.149071</span><span class="special">)</span> <span class="identifier">dimensionless</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| If we implement the overloaded helper classes for rational powers and roots |
| then we can also compute rational powers of measurement quantities : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">w</span><span class="special">*</span><span class="identifier">y</span><span class="special">^</span><span class="number">2</span><span class="special">/(</span><span class="identifier">u</span><span class="special">*</span><span class="identifier">x</span><span class="special">)^</span><span class="number">2</span> <span class="special">=</span> <span class="number">10.17</span><span class="special">(+/-</span><span class="number">3.52328</span><span class="special">)</span> <span class="identifier">m</span><span class="special">^-</span><span class="number">1</span> |
| <span class="identifier">w</span><span class="special">/(</span><span class="identifier">u</span><span class="special">*</span><span class="identifier">x</span><span class="special">)^(</span><span class="number">1</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> <span class="special">=</span> <span class="number">3.19612</span><span class="special">(+/-</span><span class="number">0.160431</span><span class="special">)</span> <span class="identifier">dimensionless</span> |
| </pre> |
| <p> |
| </p> |
| </div> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_units.Examples.ConversionExample"></a><a class="link" href="Examples.html#boost_units.Examples.ConversionExample" title="Conversion Example">Conversion Example</a> |
| </h3></div></div></div> |
| <p> |
| (<a href="../../../libs/units/example/conversion.cpp" target="_top">conversion.cpp</a>) |
| </p> |
| <p> |
| This example demonstrates the various allowed conversions between SI and |
| CGS units. Defining some quantities |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">length</span><span class="special">></span> <span class="identifier">L1</span> <span class="special">=</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">length</span><span class="special">,</span><span class="keyword">int</span><span class="special">>(</span><span class="keyword">int</span><span class="special">(</span><span class="number">2.5</span><span class="special">)*</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">meters</span><span class="special">);</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">length</span><span class="special">,</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">L2</span><span class="special">(</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">length</span><span class="special">,</span><span class="keyword">double</span><span class="special">>(</span><span class="number">2.5</span><span class="special">*</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">meters</span><span class="special">));</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| illustrates implicit conversion of quantities of different value types where |
| implicit conversion of the value types themselves is allowed. N.B. The conversion |
| from double to int is treated as an explicit conversion because there is |
| no way to emulate the exact behavior of the built-in conversion. Explicit |
| constructors allow conversions for two cases: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> |
| explicit casting of a <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/quantity.html" title="Class template quantity">quantity</a></code></span> |
| to a different <code class="computeroutput"><span class="identifier">value_type</span></code> |
| : |
| </li></ul></div> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">length</span><span class="special">,</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">L3</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">length</span><span class="special">,</span><span class="keyword">int</span><span class="special">></span> <span class="special">>(</span><span class="identifier">L1</span><span class="special">);</span> |
| </pre> |
| <p> |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> |
| and explicit casting of a <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/quantity.html" title="Class template quantity">quantity</a></code></span> |
| to a different unit : |
| </li></ul></div> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">cgs</span><span class="special">::</span><span class="identifier">length</span><span class="special">></span> <span class="identifier">L4</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">cgs</span><span class="special">::</span><span class="identifier">length</span><span class="special">></span> <span class="special">>(</span><span class="identifier">L1</span><span class="special">);</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| giving the following output : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">L1</span> <span class="special">=</span> <span class="number">2</span> <span class="identifier">m</span> |
| <span class="identifier">L2</span> <span class="special">=</span> <span class="number">2</span> <span class="identifier">m</span> |
| <span class="identifier">L3</span> <span class="special">=</span> <span class="number">2</span> <span class="identifier">m</span> |
| <span class="identifier">L4</span> <span class="special">=</span> <span class="number">200</span> <span class="identifier">cm</span> |
| <span class="identifier">L5</span> <span class="special">=</span> <span class="number">5</span> <span class="identifier">m</span> |
| <span class="identifier">L6</span> <span class="special">=</span> <span class="number">4</span> <span class="identifier">m</span> |
| <span class="identifier">L7</span> <span class="special">=</span> <span class="number">200</span> <span class="identifier">cm</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| A few more explicit unit system conversions : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">volume</span><span class="special">></span> <span class="identifier">vs</span><span class="special">(</span><span class="number">1.0</span><span class="special">*</span><span class="identifier">pow</span><span class="special"><</span><span class="number">3</span><span class="special">>(</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">meter</span><span class="special">));</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">cgs</span><span class="special">::</span><span class="identifier">volume</span><span class="special">></span> <span class="identifier">vc</span><span class="special">(</span><span class="identifier">vs</span><span class="special">);</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">volume</span><span class="special">></span> <span class="identifier">vs2</span><span class="special">(</span><span class="identifier">vc</span><span class="special">);</span> |
| |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">energy</span><span class="special">></span> <span class="identifier">es</span><span class="special">(</span><span class="number">1.0</span><span class="special">*</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">joule</span><span class="special">);</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">cgs</span><span class="special">::</span><span class="identifier">energy</span><span class="special">></span> <span class="identifier">ec</span><span class="special">(</span><span class="identifier">es</span><span class="special">);</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">energy</span><span class="special">></span> <span class="identifier">es2</span><span class="special">(</span><span class="identifier">ec</span><span class="special">);</span> |
| |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">velocity</span><span class="special">></span> <span class="identifier">v1</span> <span class="special">=</span> <span class="number">2.0</span><span class="special">*</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">meters</span><span class="special">/</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">second</span><span class="special">,</span> |
| <span class="identifier">v2</span><span class="special">(</span><span class="number">2.0</span><span class="special">*</span><span class="identifier">cgs</span><span class="special">::</span><span class="identifier">centimeters</span><span class="special">/</span><span class="identifier">cgs</span><span class="special">::</span><span class="identifier">second</span><span class="special">);</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| which produces the following output: |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">volume</span> <span class="special">(</span><span class="identifier">m</span><span class="special">^</span><span class="number">3</span><span class="special">)</span> <span class="special">=</span> <span class="number">1</span> <span class="identifier">m</span><span class="special">^</span><span class="number">3</span> |
| <span class="identifier">volume</span> <span class="special">(</span><span class="identifier">cm</span><span class="special">^</span><span class="number">3</span><span class="special">)</span> <span class="special">=</span> <span class="number">1e+06</span> <span class="identifier">cm</span><span class="special">^</span><span class="number">3</span> |
| <span class="identifier">volume</span> <span class="special">(</span><span class="identifier">m</span><span class="special">^</span><span class="number">3</span><span class="special">)</span> <span class="special">=</span> <span class="number">1</span> <span class="identifier">m</span><span class="special">^</span><span class="number">3</span> |
| |
| <span class="identifier">energy</span> <span class="special">(</span><span class="identifier">joules</span><span class="special">)</span> <span class="special">=</span> <span class="number">1</span> <span class="identifier">J</span> |
| <span class="identifier">energy</span> <span class="special">(</span><span class="identifier">ergs</span><span class="special">)</span> <span class="special">=</span> <span class="number">1e+07</span> <span class="identifier">erg</span> |
| <span class="identifier">energy</span> <span class="special">(</span><span class="identifier">joules</span><span class="special">)</span> <span class="special">=</span> <span class="number">1</span> <span class="identifier">J</span> |
| |
| <span class="identifier">velocity</span> <span class="special">(</span><span class="number">2</span> <span class="identifier">m</span><span class="special">/</span><span class="identifier">s</span><span class="special">)</span> <span class="special">=</span> <span class="number">2</span> <span class="identifier">m</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">1</span> |
| <span class="identifier">velocity</span> <span class="special">(</span><span class="number">2</span> <span class="identifier">cm</span><span class="special">/</span><span class="identifier">s</span><span class="special">)</span> <span class="special">=</span> <span class="number">0.02</span> <span class="identifier">m</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">1</span> |
| </pre> |
| <p> |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_units.Examples.UDTExample"></a><a class="link" href="Examples.html#boost_units.Examples.UDTExample" title="User Defined Types">User Defined Types</a> |
| </h3></div></div></div> |
| <p> |
| (<a href="../../../libs/units/example/quaternion.cpp" target="_top">quaternion.cpp</a>) |
| </p> |
| <p> |
| This example demonstrates the use of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">quaternion</span></code> |
| as a value type for <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/quantity.html" title="Class template quantity">quantity</a></code></span> |
| and the converse. For the first case, we first define specializations of |
| <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/power_typeof_helper.html" title="Struct template power_typeof_helper">power_typeof_helper</a></code></span> |
| and <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/root_typeof_helper.html" title="Struct template root_typeof_helper">root_typeof_helper</a></code></span> |
| for powers and roots, respectively: |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="comment">/// specialize power typeof helper |
| </span><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">,</span><span class="keyword">long</span> <span class="identifier">N</span><span class="special">,</span><span class="keyword">long</span> <span class="identifier">D</span><span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">power_typeof_helper</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">quaternion</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>,</span><span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="special">></span> |
| <span class="special">{</span> |
| <span class="comment">// boost::math::quaternion only supports integer powers |
| </span> <span class="identifier">BOOST_STATIC_ASSERT</span><span class="special">(</span><span class="identifier">D</span><span class="special">==</span><span class="number">1</span><span class="special">);</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">quaternion</span><span class="special"><</span> |
| <span class="keyword">typename</span> <span class="identifier">power_typeof_helper</span><span class="special"><</span><span class="identifier">Y</span><span class="special">,</span><span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="special">>::</span><span class="identifier">type</span> |
| <span class="special">></span> <span class="identifier">type</span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="identifier">type</span> <span class="identifier">value</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">quaternion</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>&</span> <span class="identifier">x</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">pow</span><span class="special">(</span><span class="identifier">x</span><span class="special">,</span><span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">int</span><span class="special">>(</span><span class="identifier">N</span><span class="special">));</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="comment">/// specialize root typeof helper |
| </span><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">,</span><span class="keyword">long</span> <span class="identifier">N</span><span class="special">,</span><span class="keyword">long</span> <span class="identifier">D</span><span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">root_typeof_helper</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">quaternion</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>,</span><span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="special">></span> |
| <span class="special">{</span> |
| <span class="comment">// boost::math::quaternion only supports integer powers |
| </span> <span class="identifier">BOOST_STATIC_ASSERT</span><span class="special">(</span><span class="identifier">N</span><span class="special">==</span><span class="number">1</span><span class="special">);</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">quaternion</span><span class="special"><</span> |
| <span class="keyword">typename</span> <span class="identifier">root_typeof_helper</span><span class="special"><</span><span class="identifier">Y</span><span class="special">,</span><span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="special">>::</span><span class="identifier">type</span> |
| <span class="special">></span> <span class="identifier">type</span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="identifier">type</span> <span class="identifier">value</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">quaternion</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>&</span> <span class="identifier">x</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">pow</span><span class="special">(</span><span class="identifier">x</span><span class="special">,</span><span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">int</span><span class="special">>(</span><span class="identifier">D</span><span class="special">));</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| We can now declare a <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/quantity.html" title="Class template quantity">quantity</a></code></span> |
| of a <code class="computeroutput"><span class="identifier">quaternion</span></code> : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">length</span><span class="special">,</span><span class="identifier">quaternion</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="special">></span> <span class="identifier">length_dimension</span><span class="special">;</span> |
| |
| <span class="identifier">length_dimension</span> <span class="identifier">L</span><span class="special">(</span><span class="identifier">quaternion</span><span class="special"><</span><span class="keyword">double</span><span class="special">>(</span><span class="number">4.0</span><span class="special">,</span><span class="number">3.0</span><span class="special">,</span><span class="number">2.0</span><span class="special">,</span><span class="number">1.0</span><span class="special">)*</span><span class="identifier">meters</span><span class="special">);</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| so that all operations that are defined in the <code class="computeroutput"><span class="identifier">quaternion</span></code> |
| class behave correctly. If rational powers were defined for this class, it |
| would be possible to compute rational powers and roots with no additional |
| changes. |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="special">+</span><span class="identifier">L</span> <span class="special">=</span> <span class="special">(</span><span class="number">4</span><span class="special">,</span><span class="number">3</span><span class="special">,</span><span class="number">2</span><span class="special">,</span><span class="number">1</span><span class="special">)</span> <span class="identifier">m</span> |
| <span class="special">-</span><span class="identifier">L</span> <span class="special">=</span> <span class="special">(-</span><span class="number">4</span><span class="special">,-</span><span class="number">3</span><span class="special">,-</span><span class="number">2</span><span class="special">,-</span><span class="number">1</span><span class="special">)</span> <span class="identifier">m</span> |
| <span class="identifier">L</span><span class="special">+</span><span class="identifier">L</span> <span class="special">=</span> <span class="special">(</span><span class="number">8</span><span class="special">,</span><span class="number">6</span><span class="special">,</span><span class="number">4</span><span class="special">,</span><span class="number">2</span><span class="special">)</span> <span class="identifier">m</span> |
| <span class="identifier">L</span><span class="special">-</span><span class="identifier">L</span> <span class="special">=</span> <span class="special">(</span><span class="number">0</span><span class="special">,</span><span class="number">0</span><span class="special">,</span><span class="number">0</span><span class="special">,</span><span class="number">0</span><span class="special">)</span> <span class="identifier">m</span> |
| <span class="identifier">L</span><span class="special">*</span><span class="identifier">L</span> <span class="special">=</span> <span class="special">(</span><span class="number">2</span><span class="special">,</span><span class="number">24</span><span class="special">,</span><span class="number">16</span><span class="special">,</span><span class="number">8</span><span class="special">)</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> |
| <span class="identifier">L</span><span class="special">/</span><span class="identifier">L</span> <span class="special">=</span> <span class="special">(</span><span class="number">1</span><span class="special">,</span><span class="number">0</span><span class="special">,</span><span class="number">0</span><span class="special">,</span><span class="number">0</span><span class="special">)</span> <span class="identifier">dimensionless</span> |
| <span class="identifier">L</span><span class="special">^</span><span class="number">3</span> <span class="special">=</span> <span class="special">(-</span><span class="number">104</span><span class="special">,</span><span class="number">102</span><span class="special">,</span><span class="number">68</span><span class="special">,</span><span class="number">34</span><span class="special">)</span> <span class="identifier">m</span><span class="special">^</span><span class="number">3</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| Now, if for some reason we preferred the <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/quantity.html" title="Class template quantity">quantity</a></code></span> to be the value |
| type of the <code class="computeroutput"><span class="identifier">quaternion</span></code> class |
| we would have : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">quaternion</span><span class="special"><</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">length</span><span class="special">></span> <span class="special">></span> <span class="identifier">length_dimension</span><span class="special">;</span> |
| |
| <span class="identifier">length_dimension</span> <span class="identifier">L</span><span class="special">(</span><span class="number">4.0</span><span class="special">*</span><span class="identifier">meters</span><span class="special">,</span><span class="number">3.0</span><span class="special">*</span><span class="identifier">meters</span><span class="special">,</span><span class="number">2.0</span><span class="special">*</span><span class="identifier">meters</span><span class="special">,</span><span class="number">1.0</span><span class="special">*</span><span class="identifier">meters</span><span class="special">);</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| Here, the unary plus and minus and addition and subtraction operators function |
| correctly. Unfortunately, the multiplication and division operations fail |
| because <code class="computeroutput"><span class="identifier">quaternion</span></code> implements |
| them in terms of the <code class="computeroutput"><span class="special">*=</span></code> and |
| <code class="computeroutput"><span class="special">/=</span></code> operators, respectively, |
| which are incapable of representing the heterogeneous unit algebra needed |
| for quantities (an identical problem occurs with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">complex</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code>, |
| for the same reason). In order to compute rational powers and roots, we need |
| to specialize <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/power_typeof_helper.html" title="Struct template power_typeof_helper">power_typeof_helper</a></code></span> |
| and <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/root_typeof_helper.html" title="Struct template root_typeof_helper">root_typeof_helper</a></code></span> |
| as follows: |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="comment">/// specialize power typeof helper for quaternion<quantity<Unit,Y> > |
| </span><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Unit</span><span class="special">,</span><span class="keyword">long</span> <span class="identifier">N</span><span class="special">,</span><span class="keyword">long</span> <span class="identifier">D</span><span class="special">,</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">power_typeof_helper</span><span class="special"><</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">quaternion</span><span class="special"><</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">Unit</span><span class="special">,</span><span class="identifier">Y</span><span class="special">></span> <span class="special">>,</span> |
| <span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="special">></span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">power_typeof_helper</span><span class="special"><</span> |
| <span class="identifier">Y</span><span class="special">,</span> |
| <span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> |
| <span class="special">>::</span><span class="identifier">type</span> <span class="identifier">value_type</span><span class="special">;</span> |
| |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">power_typeof_helper</span><span class="special"><</span> |
| <span class="identifier">Unit</span><span class="special">,</span> |
| <span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> |
| <span class="special">>::</span><span class="identifier">type</span> <span class="identifier">unit_type</span><span class="special">;</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">unit_type</span><span class="special">,</span><span class="identifier">value_type</span><span class="special">></span> <span class="identifier">quantity_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">quaternion</span><span class="special"><</span><span class="identifier">quantity_type</span><span class="special">></span> <span class="identifier">type</span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="identifier">type</span> <span class="identifier">value</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">quaternion</span><span class="special"><</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">Unit</span><span class="special">,</span><span class="identifier">Y</span><span class="special">></span> <span class="special">>&</span> <span class="identifier">x</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">quaternion</span><span class="special"><</span><span class="identifier">value_type</span><span class="special">></span> <span class="identifier">tmp</span> <span class="special">=</span> |
| <span class="identifier">pow</span><span class="special"><</span><span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="special">>(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">quaternion</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>(</span> |
| <span class="identifier">x</span><span class="special">.</span><span class="identifier">R_component_1</span><span class="special">().</span><span class="identifier">value</span><span class="special">(),</span> |
| <span class="identifier">x</span><span class="special">.</span><span class="identifier">R_component_2</span><span class="special">().</span><span class="identifier">value</span><span class="special">(),</span> |
| <span class="identifier">x</span><span class="special">.</span><span class="identifier">R_component_3</span><span class="special">().</span><span class="identifier">value</span><span class="special">(),</span> |
| <span class="identifier">x</span><span class="special">.</span><span class="identifier">R_component_4</span><span class="special">().</span><span class="identifier">value</span><span class="special">()));</span> |
| |
| <span class="keyword">return</span> <span class="identifier">type</span><span class="special">(</span><span class="identifier">quantity_type</span><span class="special">::</span><span class="identifier">from_value</span><span class="special">(</span><span class="identifier">tmp</span><span class="special">.</span><span class="identifier">R_component_1</span><span class="special">()),</span> |
| <span class="identifier">quantity_type</span><span class="special">::</span><span class="identifier">from_value</span><span class="special">(</span><span class="identifier">tmp</span><span class="special">.</span><span class="identifier">R_component_2</span><span class="special">()),</span> |
| <span class="identifier">quantity_type</span><span class="special">::</span><span class="identifier">from_value</span><span class="special">(</span><span class="identifier">tmp</span><span class="special">.</span><span class="identifier">R_component_3</span><span class="special">()),</span> |
| <span class="identifier">quantity_type</span><span class="special">::</span><span class="identifier">from_value</span><span class="special">(</span><span class="identifier">tmp</span><span class="special">.</span><span class="identifier">R_component_4</span><span class="special">()));</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="comment">/// specialize root typeof helper for quaternion<quantity<Unit,Y> > |
| </span><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Unit</span><span class="special">,</span><span class="keyword">long</span> <span class="identifier">N</span><span class="special">,</span><span class="keyword">long</span> <span class="identifier">D</span><span class="special">,</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">root_typeof_helper</span><span class="special"><</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">quaternion</span><span class="special"><</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">Unit</span><span class="special">,</span><span class="identifier">Y</span><span class="special">></span> <span class="special">>,</span> |
| <span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="special">></span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">root_typeof_helper</span><span class="special"><</span> |
| <span class="identifier">Y</span><span class="special">,</span> |
| <span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> |
| <span class="special">>::</span><span class="identifier">type</span> <span class="identifier">value_type</span><span class="special">;</span> |
| |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">root_typeof_helper</span><span class="special"><</span> |
| <span class="identifier">Unit</span><span class="special">,</span> |
| <span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> |
| <span class="special">>::</span><span class="identifier">type</span> <span class="identifier">unit_type</span><span class="special">;</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">unit_type</span><span class="special">,</span><span class="identifier">value_type</span><span class="special">></span> <span class="identifier">quantity_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">quaternion</span><span class="special"><</span><span class="identifier">quantity_type</span><span class="special">></span> <span class="identifier">type</span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="identifier">type</span> <span class="identifier">value</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">quaternion</span><span class="special"><</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">Unit</span><span class="special">,</span><span class="identifier">Y</span><span class="special">></span> <span class="special">>&</span> <span class="identifier">x</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">quaternion</span><span class="special"><</span><span class="identifier">value_type</span><span class="special">></span> <span class="identifier">tmp</span> <span class="special">=</span> |
| <span class="identifier">root</span><span class="special"><</span><span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="special">>(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">quaternion</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>(</span> |
| <span class="identifier">x</span><span class="special">.</span><span class="identifier">R_component_1</span><span class="special">().</span><span class="identifier">value</span><span class="special">(),</span> |
| <span class="identifier">x</span><span class="special">.</span><span class="identifier">R_component_2</span><span class="special">().</span><span class="identifier">value</span><span class="special">(),</span> |
| <span class="identifier">x</span><span class="special">.</span><span class="identifier">R_component_3</span><span class="special">().</span><span class="identifier">value</span><span class="special">(),</span> |
| <span class="identifier">x</span><span class="special">.</span><span class="identifier">R_component_4</span><span class="special">().</span><span class="identifier">value</span><span class="special">()));</span> |
| |
| <span class="keyword">return</span> <span class="identifier">type</span><span class="special">(</span><span class="identifier">quantity_type</span><span class="special">::</span><span class="identifier">from_value</span><span class="special">(</span><span class="identifier">tmp</span><span class="special">.</span><span class="identifier">R_component_1</span><span class="special">()),</span> |
| <span class="identifier">quantity_type</span><span class="special">::</span><span class="identifier">from_value</span><span class="special">(</span><span class="identifier">tmp</span><span class="special">.</span><span class="identifier">R_component_2</span><span class="special">()),</span> |
| <span class="identifier">quantity_type</span><span class="special">::</span><span class="identifier">from_value</span><span class="special">(</span><span class="identifier">tmp</span><span class="special">.</span><span class="identifier">R_component_3</span><span class="special">()),</span> |
| <span class="identifier">quantity_type</span><span class="special">::</span><span class="identifier">from_value</span><span class="special">(</span><span class="identifier">tmp</span><span class="special">.</span><span class="identifier">R_component_4</span><span class="special">()));</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| giving: |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="special">+</span><span class="identifier">L</span> <span class="special">=</span> <span class="special">(</span><span class="number">4</span> <span class="identifier">m</span><span class="special">,</span><span class="number">3</span> <span class="identifier">m</span><span class="special">,</span><span class="number">2</span> <span class="identifier">m</span><span class="special">,</span><span class="number">1</span> <span class="identifier">m</span><span class="special">)</span> |
| <span class="special">-</span><span class="identifier">L</span> <span class="special">=</span> <span class="special">(-</span><span class="number">4</span> <span class="identifier">m</span><span class="special">,-</span><span class="number">3</span> <span class="identifier">m</span><span class="special">,-</span><span class="number">2</span> <span class="identifier">m</span><span class="special">,-</span><span class="number">1</span> <span class="identifier">m</span><span class="special">)</span> |
| <span class="identifier">L</span><span class="special">+</span><span class="identifier">L</span> <span class="special">=</span> <span class="special">(</span><span class="number">8</span> <span class="identifier">m</span><span class="special">,</span><span class="number">6</span> <span class="identifier">m</span><span class="special">,</span><span class="number">4</span> <span class="identifier">m</span><span class="special">,</span><span class="number">2</span> <span class="identifier">m</span><span class="special">)</span> |
| <span class="identifier">L</span><span class="special">-</span><span class="identifier">L</span> <span class="special">=</span> <span class="special">(</span><span class="number">0</span> <span class="identifier">m</span><span class="special">,</span><span class="number">0</span> <span class="identifier">m</span><span class="special">,</span><span class="number">0</span> <span class="identifier">m</span><span class="special">,</span><span class="number">0</span> <span class="identifier">m</span><span class="special">)</span> |
| <span class="identifier">L</span><span class="special">^</span><span class="number">3</span> <span class="special">=</span> <span class="special">(-</span><span class="number">104</span> <span class="identifier">m</span><span class="special">^</span><span class="number">3</span><span class="special">,</span><span class="number">102</span> <span class="identifier">m</span><span class="special">^</span><span class="number">3</span><span class="special">,</span><span class="number">68</span> <span class="identifier">m</span><span class="special">^</span><span class="number">3</span><span class="special">,</span><span class="number">34</span> <span class="identifier">m</span><span class="special">^</span><span class="number">3</span><span class="special">)</span> |
| </pre> |
| <p> |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_units.Examples.ComplexExample"></a><a class="link" href="Examples.html#boost_units.Examples.ComplexExample" title="Complex Example">Complex Example</a> |
| </h3></div></div></div> |
| <p> |
| (<a href="../../../libs/units/example/complex.cpp" target="_top">complex.cpp</a>) |
| </p> |
| <p> |
| This example demonstrates how to implement a replacement <code class="computeroutput"><span class="identifier">complex</span></code> |
| class that functions correctly both as a quantity value type and as a quantity |
| container class, including heterogeneous multiplication and division operations |
| and rational powers and roots. Naturally, heterogeneous operations are only |
| supported on compilers that implement <code class="computeroutput"><span class="identifier">typeof</span></code>. |
| The primary differences are that binary operations are not implemented using |
| the <code class="computeroutput"><span class="identifier">op</span><span class="special">=</span></code> |
| operators and use the utility classes <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/add_typeof_helper.html" title="Struct template add_typeof_helper">add_typeof_helper</a></code></span>, |
| <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/subtract_typeof_helper.html" title="Struct template subtract_typeof_helper">subtract_typeof_helper</a></code></span>, |
| <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/multiply_typeof_helper.html" title="Struct template multiply_typeof_helper">multiply_typeof_helper</a></code></span>, |
| and <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/divide_typeof_helper.html" title="Struct template divide_typeof_helper">divide_typeof_helper</a></code></span>. |
| In addition, <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/power_typeof_helper.html" title="Struct template power_typeof_helper">power_typeof_helper</a></code></span> |
| and <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/root_typeof_helper.html" title="Struct template root_typeof_helper">root_typeof_helper</a></code></span> |
| are defined for both cases : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> |
| |
| <span class="keyword">namespace</span> <span class="identifier">units</span> <span class="special">{</span> |
| |
| <span class="comment">/// replacement complex class |
| </span><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> |
| <span class="keyword">class</span> <span class="identifier">complex</span> |
| <span class="special">{</span> |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="keyword">typedef</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">this_type</span><span class="special">;</span> |
| |
| <span class="identifier">complex</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">r</span> <span class="special">=</span> <span class="number">0</span><span class="special">,</span><span class="keyword">const</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">)</span> <span class="special">:</span> <span class="identifier">r_</span><span class="special">(</span><span class="identifier">r</span><span class="special">),</span><span class="identifier">i_</span><span class="special">(</span><span class="identifier">i</span><span class="special">)</span> <span class="special">{</span> <span class="special">}</span> |
| <span class="identifier">complex</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">this_type</span><span class="special">&</span> <span class="identifier">source</span><span class="special">)</span> <span class="special">:</span> <span class="identifier">r_</span><span class="special">(</span><span class="identifier">source</span><span class="special">.</span><span class="identifier">r_</span><span class="special">),</span><span class="identifier">i_</span><span class="special">(</span><span class="identifier">source</span><span class="special">.</span><span class="identifier">i_</span><span class="special">)</span> <span class="special">{</span> <span class="special">}</span> |
| |
| <span class="identifier">this_type</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">=(</span><span class="keyword">const</span> <span class="identifier">this_type</span><span class="special">&</span> <span class="identifier">source</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="keyword">this</span> <span class="special">==</span> <span class="special">&</span><span class="identifier">source</span><span class="special">)</span> <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;</span> |
| |
| <span class="identifier">r_</span> <span class="special">=</span> <span class="identifier">source</span><span class="special">.</span><span class="identifier">r_</span><span class="special">;</span> |
| <span class="identifier">i_</span> <span class="special">=</span> <span class="identifier">source</span><span class="special">.</span><span class="identifier">i_</span><span class="special">;</span> |
| |
| <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">T</span><span class="special">&</span> <span class="identifier">real</span><span class="special">()</span> <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">r_</span><span class="special">;</span> <span class="special">}</span> |
| <span class="identifier">T</span><span class="special">&</span> <span class="identifier">imag</span><span class="special">()</span> <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">i_</span><span class="special">;</span> <span class="special">}</span> |
| |
| <span class="keyword">const</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">real</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">r_</span><span class="special">;</span> <span class="special">}</span> |
| <span class="keyword">const</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">imag</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">i_</span><span class="special">;</span> <span class="special">}</span> |
| |
| <span class="identifier">this_type</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">+=(</span><span class="keyword">const</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">val</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">r_</span> <span class="special">+=</span> <span class="identifier">val</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">this_type</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">-=(</span><span class="keyword">const</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">val</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">r_</span> <span class="special">-=</span> <span class="identifier">val</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">this_type</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">*=(</span><span class="keyword">const</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">val</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">r_</span> <span class="special">*=</span> <span class="identifier">val</span><span class="special">;</span> |
| <span class="identifier">i_</span> <span class="special">*=</span> <span class="identifier">val</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">this_type</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">/=(</span><span class="keyword">const</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">val</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">r_</span> <span class="special">/=</span> <span class="identifier">val</span><span class="special">;</span> |
| <span class="identifier">i_</span> <span class="special">/=</span> <span class="identifier">val</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">this_type</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">+=(</span><span class="keyword">const</span> <span class="identifier">this_type</span><span class="special">&</span> <span class="identifier">source</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">r_</span> <span class="special">+=</span> <span class="identifier">source</span><span class="special">.</span><span class="identifier">r_</span><span class="special">;</span> |
| <span class="identifier">i_</span> <span class="special">+=</span> <span class="identifier">source</span><span class="special">.</span><span class="identifier">i_</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">this_type</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">-=(</span><span class="keyword">const</span> <span class="identifier">this_type</span><span class="special">&</span> <span class="identifier">source</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">r_</span> <span class="special">-=</span> <span class="identifier">source</span><span class="special">.</span><span class="identifier">r_</span><span class="special">;</span> |
| <span class="identifier">i_</span> <span class="special">-=</span> <span class="identifier">source</span><span class="special">.</span><span class="identifier">i_</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">this_type</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">*=(</span><span class="keyword">const</span> <span class="identifier">this_type</span><span class="special">&</span> <span class="identifier">source</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="special">*</span><span class="keyword">this</span> <span class="special">=</span> <span class="special">*</span><span class="keyword">this</span> <span class="special">*</span> <span class="identifier">source</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">this_type</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">/=(</span><span class="keyword">const</span> <span class="identifier">this_type</span><span class="special">&</span> <span class="identifier">source</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="special">*</span><span class="keyword">this</span> <span class="special">=</span> <span class="special">*</span><span class="keyword">this</span> <span class="special">/</span> <span class="identifier">source</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">private</span><span class="special">:</span> |
| <span class="identifier">T</span> <span class="identifier">r_</span><span class="special">,</span><span class="identifier">i_</span><span class="special">;</span> |
| <span class="special">};</span> |
| |
| <span class="special">}</span> |
| |
| <span class="special">}</span> |
| |
| <span class="preprocessor">#if</span> <span class="identifier">BOOST_UNITS_HAS_BOOST_TYPEOF</span> |
| |
| <span class="preprocessor">#include</span> <span class="identifier">BOOST_TYPEOF_INCREMENT_REGISTRATION_GROUP</span><span class="special">()</span> |
| |
| <span class="identifier">BOOST_TYPEOF_REGISTER_TEMPLATE</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">complex</span><span class="special">,</span> <span class="number">1</span><span class="special">)</span> |
| |
| <span class="preprocessor">#endif</span> |
| |
| <span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> |
| |
| <span class="keyword">namespace</span> <span class="identifier">units</span> <span class="special">{</span> |
| |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">X</span><span class="special">></span> |
| <span class="identifier">complex</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">unary_plus_typeof_helper</span><span class="special"><</span><span class="identifier">X</span><span class="special">>::</span><span class="identifier">type</span><span class="special">></span> |
| <span class="keyword">operator</span><span class="special">+(</span><span class="keyword">const</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">X</span><span class="special">>&</span> <span class="identifier">x</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">unary_plus_typeof_helper</span><span class="special"><</span><span class="identifier">X</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">type</span><span class="special">;</span> |
| |
| <span class="keyword">return</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">type</span><span class="special">>(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">real</span><span class="special">(),</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">imag</span><span class="special">());</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">X</span><span class="special">></span> |
| <span class="identifier">complex</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">unary_minus_typeof_helper</span><span class="special"><</span><span class="identifier">X</span><span class="special">>::</span><span class="identifier">type</span><span class="special">></span> |
| <span class="keyword">operator</span><span class="special">-(</span><span class="keyword">const</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">X</span><span class="special">>&</span> <span class="identifier">x</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">unary_minus_typeof_helper</span><span class="special"><</span><span class="identifier">X</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">type</span><span class="special">;</span> |
| |
| <span class="keyword">return</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">type</span><span class="special">>(-</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">real</span><span class="special">(),-</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">imag</span><span class="special">());</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">X</span><span class="special">,</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">></span> |
| <span class="identifier">complex</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">add_typeof_helper</span><span class="special"><</span><span class="identifier">X</span><span class="special">,</span><span class="identifier">Y</span><span class="special">>::</span><span class="identifier">type</span><span class="special">></span> |
| <span class="keyword">operator</span><span class="special">+(</span><span class="keyword">const</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">X</span><span class="special">>&</span> <span class="identifier">x</span><span class="special">,</span><span class="keyword">const</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>&</span> <span class="identifier">y</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">add_typeof_helper</span><span class="special"><</span><span class="identifier">X</span><span class="special">,</span><span class="identifier">Y</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">type</span><span class="special">;</span> |
| |
| <span class="keyword">return</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">type</span><span class="special">>(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">real</span><span class="special">()+</span><span class="identifier">y</span><span class="special">.</span><span class="identifier">real</span><span class="special">(),</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">imag</span><span class="special">()+</span><span class="identifier">y</span><span class="special">.</span><span class="identifier">imag</span><span class="special">());</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">X</span><span class="special">,</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">></span> |
| <span class="identifier">complex</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">subtract_typeof_helper</span><span class="special"><</span><span class="identifier">X</span><span class="special">,</span><span class="identifier">Y</span><span class="special">>::</span><span class="identifier">type</span><span class="special">></span> |
| <span class="keyword">operator</span><span class="special">-(</span><span class="keyword">const</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">X</span><span class="special">>&</span> <span class="identifier">x</span><span class="special">,</span><span class="keyword">const</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>&</span> <span class="identifier">y</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">subtract_typeof_helper</span><span class="special"><</span><span class="identifier">X</span><span class="special">,</span><span class="identifier">Y</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">type</span><span class="special">;</span> |
| |
| <span class="keyword">return</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">type</span><span class="special">>(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">real</span><span class="special">()-</span><span class="identifier">y</span><span class="special">.</span><span class="identifier">real</span><span class="special">(),</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">imag</span><span class="special">()-</span><span class="identifier">y</span><span class="special">.</span><span class="identifier">imag</span><span class="special">());</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">X</span><span class="special">,</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">></span> |
| <span class="identifier">complex</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">multiply_typeof_helper</span><span class="special"><</span><span class="identifier">X</span><span class="special">,</span><span class="identifier">Y</span><span class="special">>::</span><span class="identifier">type</span><span class="special">></span> |
| <span class="keyword">operator</span><span class="special">*(</span><span class="keyword">const</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">X</span><span class="special">>&</span> <span class="identifier">x</span><span class="special">,</span><span class="keyword">const</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>&</span> <span class="identifier">y</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">multiply_typeof_helper</span><span class="special"><</span><span class="identifier">X</span><span class="special">,</span><span class="identifier">Y</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">type</span><span class="special">;</span> |
| |
| <span class="keyword">return</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">type</span><span class="special">>(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">real</span><span class="special">()*</span><span class="identifier">y</span><span class="special">.</span><span class="identifier">real</span><span class="special">()</span> <span class="special">-</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">imag</span><span class="special">()*</span><span class="identifier">y</span><span class="special">.</span><span class="identifier">imag</span><span class="special">(),</span> |
| <span class="identifier">x</span><span class="special">.</span><span class="identifier">real</span><span class="special">()*</span><span class="identifier">y</span><span class="special">.</span><span class="identifier">imag</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">imag</span><span class="special">()*</span><span class="identifier">y</span><span class="special">.</span><span class="identifier">real</span><span class="special">());</span> |
| |
| <span class="comment">// fully correct implementation has more complex return type |
| </span><span class="comment">// |
| </span><span class="comment">// typedef typename boost::units::multiply_typeof_helper<X,Y>::type xy_type; |
| </span><span class="comment">// |
| </span><span class="comment">// typedef typename boost::units::add_typeof_helper< |
| </span><span class="comment">// xy_type,xy_type>::type xy_plus_xy_type; |
| </span><span class="comment">// typedef typename |
| </span><span class="comment">// boost::units::subtract_typeof_helper<xy_type,xy_type>::type |
| </span><span class="comment">// xy_minus_xy_type; |
| </span><span class="comment">// |
| </span><span class="comment">// BOOST_STATIC_ASSERT((boost::is_same<xy_plus_xy_type, |
| </span><span class="comment">// xy_minus_xy_type>::value == true)); |
| </span><span class="comment">// |
| </span><span class="comment">// return complex<xy_plus_xy_type>(x.real()*y.real()-x.imag()*y.imag(), |
| </span><span class="comment">// x.real()*y.imag()+x.imag()*y.real()); |
| </span><span class="special">}</span> |
| |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">X</span><span class="special">,</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">></span> |
| <span class="identifier">complex</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">divide_typeof_helper</span><span class="special"><</span><span class="identifier">X</span><span class="special">,</span><span class="identifier">Y</span><span class="special">>::</span><span class="identifier">type</span><span class="special">></span> |
| <span class="keyword">operator</span><span class="special">/(</span><span class="keyword">const</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">X</span><span class="special">>&</span> <span class="identifier">x</span><span class="special">,</span><span class="keyword">const</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>&</span> <span class="identifier">y</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="comment">// naive implementation of complex division |
| </span> <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">divide_typeof_helper</span><span class="special"><</span><span class="identifier">X</span><span class="special">,</span><span class="identifier">Y</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">type</span><span class="special">;</span> |
| |
| <span class="keyword">return</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">type</span><span class="special">>((</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">real</span><span class="special">()*</span><span class="identifier">y</span><span class="special">.</span><span class="identifier">real</span><span class="special">()+</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">imag</span><span class="special">()*</span><span class="identifier">y</span><span class="special">.</span><span class="identifier">imag</span><span class="special">())/</span> |
| <span class="special">(</span><span class="identifier">y</span><span class="special">.</span><span class="identifier">real</span><span class="special">()*</span><span class="identifier">y</span><span class="special">.</span><span class="identifier">real</span><span class="special">()+</span><span class="identifier">y</span><span class="special">.</span><span class="identifier">imag</span><span class="special">()*</span><span class="identifier">y</span><span class="special">.</span><span class="identifier">imag</span><span class="special">()),</span> |
| <span class="special">(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">imag</span><span class="special">()*</span><span class="identifier">y</span><span class="special">.</span><span class="identifier">real</span><span class="special">()-</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">real</span><span class="special">()*</span><span class="identifier">y</span><span class="special">.</span><span class="identifier">imag</span><span class="special">())/</span> |
| <span class="special">(</span><span class="identifier">y</span><span class="special">.</span><span class="identifier">real</span><span class="special">()*</span><span class="identifier">y</span><span class="special">.</span><span class="identifier">real</span><span class="special">()+</span><span class="identifier">y</span><span class="special">.</span><span class="identifier">imag</span><span class="special">()*</span><span class="identifier">y</span><span class="special">.</span><span class="identifier">imag</span><span class="special">()));</span> |
| |
| <span class="comment">// fully correct implementation has more complex return type |
| </span><span class="comment">// |
| </span><span class="comment">// typedef typename boost::units::multiply_typeof_helper<X,Y>::type xy_type; |
| </span><span class="comment">// typedef typename boost::units::multiply_typeof_helper<Y,Y>::type yy_type; |
| </span><span class="comment">// |
| </span><span class="comment">// typedef typename boost::units::add_typeof_helper<xy_type, xy_type>::type |
| </span><span class="comment">// xy_plus_xy_type; |
| </span><span class="comment">// typedef typename boost::units::subtract_typeof_helper< |
| </span><span class="comment">// xy_type,xy_type>::type xy_minus_xy_type; |
| </span><span class="comment">// |
| </span><span class="comment">// typedef typename boost::units::divide_typeof_helper< |
| </span><span class="comment">// xy_plus_xy_type,yy_type>::type xy_plus_xy_over_yy_type; |
| </span><span class="comment">// typedef typename boost::units::divide_typeof_helper< |
| </span><span class="comment">// xy_minus_xy_type,yy_type>::type xy_minus_xy_over_yy_type; |
| </span><span class="comment">// |
| </span><span class="comment">// BOOST_STATIC_ASSERT((boost::is_same<xy_plus_xy_over_yy_type, |
| </span><span class="comment">// xy_minus_xy_over_yy_type>::value == true)); |
| </span><span class="comment">// |
| </span><span class="comment">// return complex<xy_plus_xy_over_yy_type>( |
| </span><span class="comment">// (x.real()*y.real()+x.imag()*y.imag())/ |
| </span><span class="comment">// (y.real()*y.real()+y.imag()*y.imag()), |
| </span><span class="comment">// (x.imag()*y.real()-x.real()*y.imag())/ |
| </span><span class="comment">// (y.real()*y.real()+y.imag()*y.imag())); |
| </span><span class="special">}</span> |
| |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">></span> |
| <span class="identifier">complex</span><span class="special"><</span><span class="identifier">Y</span><span class="special">></span> |
| <span class="identifier">pow</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>&</span> <span class="identifier">x</span><span class="special">,</span><span class="keyword">const</span> <span class="identifier">Y</span><span class="special">&</span> <span class="identifier">y</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">complex</span><span class="special"><</span><span class="identifier">Y</span><span class="special">></span> <span class="identifier">tmp</span><span class="special">(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">real</span><span class="special">(),</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">imag</span><span class="special">());</span> |
| |
| <span class="identifier">tmp</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">pow</span><span class="special">(</span><span class="identifier">tmp</span><span class="special">,</span><span class="identifier">y</span><span class="special">);</span> |
| |
| <span class="keyword">return</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>(</span><span class="identifier">tmp</span><span class="special">.</span><span class="identifier">real</span><span class="special">(),</span><span class="identifier">tmp</span><span class="special">.</span><span class="identifier">imag</span><span class="special">());</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">></span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span><span class="special">&</span> <span class="keyword">operator</span><span class="special"><<(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span><span class="special">&</span> <span class="identifier">os</span><span class="special">,</span><span class="keyword">const</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>&</span> <span class="identifier">val</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">os</span> <span class="special"><<</span> <span class="identifier">val</span><span class="special">.</span><span class="identifier">real</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" + "</span> <span class="special"><<</span> <span class="identifier">val</span><span class="special">.</span><span class="identifier">imag</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" i"</span><span class="special">;</span> |
| |
| <span class="keyword">return</span> <span class="identifier">os</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="comment">/// specialize power typeof helper for complex<Y> |
| </span><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">,</span><span class="keyword">long</span> <span class="identifier">N</span><span class="special">,</span><span class="keyword">long</span> <span class="identifier">D</span><span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">power_typeof_helper</span><span class="special"><</span><span class="identifier">complex</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>,</span><span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="special">></span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="identifier">complex</span><span class="special"><</span> |
| <span class="keyword">typename</span> <span class="identifier">power_typeof_helper</span><span class="special"><</span><span class="identifier">Y</span><span class="special">,</span><span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="special">>::</span><span class="identifier">type</span> |
| <span class="special">></span> <span class="identifier">type</span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="identifier">type</span> <span class="identifier">value</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>&</span> <span class="identifier">x</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">const</span> <span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="identifier">rat</span><span class="special">;</span> |
| |
| <span class="keyword">const</span> <span class="identifier">Y</span> <span class="identifier">m</span> <span class="special">=</span> <span class="identifier">Y</span><span class="special">(</span><span class="identifier">rat</span><span class="special">.</span><span class="identifier">numerator</span><span class="special">())/</span><span class="identifier">Y</span><span class="special">(</span><span class="identifier">rat</span><span class="special">.</span><span class="identifier">denominator</span><span class="special">());</span> |
| |
| <span class="keyword">return</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">pow</span><span class="special">(</span><span class="identifier">x</span><span class="special">,</span><span class="identifier">m</span><span class="special">);</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| |
| <span class="comment">/// specialize root typeof helper for complex<Y> |
| </span><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">,</span><span class="keyword">long</span> <span class="identifier">N</span><span class="special">,</span><span class="keyword">long</span> <span class="identifier">D</span><span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">root_typeof_helper</span><span class="special"><</span><span class="identifier">complex</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>,</span><span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="special">></span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="identifier">complex</span><span class="special"><</span> |
| <span class="keyword">typename</span> <span class="identifier">root_typeof_helper</span><span class="special"><</span><span class="identifier">Y</span><span class="special">,</span><span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="special">>::</span><span class="identifier">type</span> |
| <span class="special">></span> <span class="identifier">type</span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="identifier">type</span> <span class="identifier">value</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>&</span> <span class="identifier">x</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">const</span> <span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="identifier">rat</span><span class="special">;</span> |
| |
| <span class="keyword">const</span> <span class="identifier">Y</span> <span class="identifier">m</span> <span class="special">=</span> <span class="identifier">Y</span><span class="special">(</span><span class="identifier">rat</span><span class="special">.</span><span class="identifier">denominator</span><span class="special">())/</span><span class="identifier">Y</span><span class="special">(</span><span class="identifier">rat</span><span class="special">.</span><span class="identifier">numerator</span><span class="special">());</span> |
| |
| <span class="keyword">return</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">pow</span><span class="special">(</span><span class="identifier">x</span><span class="special">,</span><span class="identifier">m</span><span class="special">);</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| |
| <span class="comment">/// specialize power typeof helper for complex<quantity<Unit,Y> > |
| </span><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">,</span><span class="keyword">class</span> <span class="identifier">Unit</span><span class="special">,</span><span class="keyword">long</span> <span class="identifier">N</span><span class="special">,</span><span class="keyword">long</span> <span class="identifier">D</span><span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">power_typeof_helper</span><span class="special"><</span><span class="identifier">complex</span><span class="special"><</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">Unit</span><span class="special">,</span><span class="identifier">Y</span><span class="special">></span> <span class="special">>,</span><span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="special">></span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> |
| <span class="identifier">power_typeof_helper</span><span class="special"><</span><span class="identifier">Y</span><span class="special">,</span><span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="special">>::</span><span class="identifier">type</span> <span class="identifier">value_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> |
| <span class="identifier">power_typeof_helper</span><span class="special"><</span><span class="identifier">Unit</span><span class="special">,</span><span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="special">>::</span><span class="identifier">type</span> <span class="identifier">unit_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">unit_type</span><span class="special">,</span><span class="identifier">value_type</span><span class="special">></span> <span class="identifier">quantity_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">quantity_type</span><span class="special">></span> <span class="identifier">type</span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="identifier">type</span> <span class="identifier">value</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">Unit</span><span class="special">,</span><span class="identifier">Y</span><span class="special">></span> <span class="special">>&</span> <span class="identifier">x</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">const</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">value_type</span><span class="special">></span> <span class="identifier">tmp</span> <span class="special">=</span> |
| <span class="identifier">pow</span><span class="special"><</span><span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="special">>(</span><span class="identifier">complex</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">real</span><span class="special">().</span><span class="identifier">value</span><span class="special">(),</span> |
| <span class="identifier">x</span><span class="special">.</span><span class="identifier">imag</span><span class="special">().</span><span class="identifier">value</span><span class="special">()));</span> |
| |
| <span class="keyword">return</span> <span class="identifier">type</span><span class="special">(</span><span class="identifier">quantity_type</span><span class="special">::</span><span class="identifier">from_value</span><span class="special">(</span><span class="identifier">tmp</span><span class="special">.</span><span class="identifier">real</span><span class="special">()),</span> |
| <span class="identifier">quantity_type</span><span class="special">::</span><span class="identifier">from_value</span><span class="special">(</span><span class="identifier">tmp</span><span class="special">.</span><span class="identifier">imag</span><span class="special">()));</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| |
| <span class="comment">/// specialize root typeof helper for complex<quantity<Unit,Y> > |
| </span><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">,</span><span class="keyword">class</span> <span class="identifier">Unit</span><span class="special">,</span><span class="keyword">long</span> <span class="identifier">N</span><span class="special">,</span><span class="keyword">long</span> <span class="identifier">D</span><span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">root_typeof_helper</span><span class="special"><</span><span class="identifier">complex</span><span class="special"><</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">Unit</span><span class="special">,</span><span class="identifier">Y</span><span class="special">></span> <span class="special">>,</span><span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="special">></span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> |
| <span class="identifier">root_typeof_helper</span><span class="special"><</span><span class="identifier">Y</span><span class="special">,</span><span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="special">>::</span><span class="identifier">type</span> <span class="identifier">value_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> |
| <span class="identifier">root_typeof_helper</span><span class="special"><</span><span class="identifier">Unit</span><span class="special">,</span><span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="special">>::</span><span class="identifier">type</span> <span class="identifier">unit_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">unit_type</span><span class="special">,</span><span class="identifier">value_type</span><span class="special">></span> <span class="identifier">quantity_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">quantity_type</span><span class="special">></span> <span class="identifier">type</span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="identifier">type</span> <span class="identifier">value</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">Unit</span><span class="special">,</span><span class="identifier">Y</span><span class="special">></span> <span class="special">>&</span> <span class="identifier">x</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">const</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">value_type</span><span class="special">></span> <span class="identifier">tmp</span> <span class="special">=</span> |
| <span class="identifier">root</span><span class="special"><</span><span class="identifier">static_rational</span><span class="special"><</span><span class="identifier">N</span><span class="special">,</span><span class="identifier">D</span><span class="special">></span> <span class="special">>(</span><span class="identifier">complex</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">real</span><span class="special">().</span><span class="identifier">value</span><span class="special">(),</span> |
| <span class="identifier">x</span><span class="special">.</span><span class="identifier">imag</span><span class="special">().</span><span class="identifier">value</span><span class="special">()));</span> |
| |
| <span class="keyword">return</span> <span class="identifier">type</span><span class="special">(</span><span class="identifier">quantity_type</span><span class="special">::</span><span class="identifier">from_value</span><span class="special">(</span><span class="identifier">tmp</span><span class="special">.</span><span class="identifier">real</span><span class="special">()),</span> |
| <span class="identifier">quantity_type</span><span class="special">::</span><span class="identifier">from_value</span><span class="special">(</span><span class="identifier">tmp</span><span class="special">.</span><span class="identifier">imag</span><span class="special">()));</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| |
| <span class="special">}</span> <span class="comment">// namespace units |
| </span> |
| <span class="special">}</span> <span class="comment">// namespace boost |
| </span></pre> |
| <p> |
| </p> |
| <p> |
| With this replacement <code class="computeroutput"><span class="identifier">complex</span></code> |
| class, we can declare a complex variable : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">length</span><span class="special">,</span><span class="identifier">complex</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="special">></span> <span class="identifier">length_dimension</span><span class="special">;</span> |
| |
| <span class="identifier">length_dimension</span> <span class="identifier">L</span><span class="special">(</span><span class="identifier">complex</span><span class="special"><</span><span class="keyword">double</span><span class="special">>(</span><span class="number">2.0</span><span class="special">,</span><span class="number">1.0</span><span class="special">)*</span><span class="identifier">meters</span><span class="special">);</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| to get the correct behavior for all cases supported by <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/quantity.html" title="Class template quantity">quantity</a></code></span> with a <code class="computeroutput"><span class="identifier">complex</span></code> value type : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="special">+</span><span class="identifier">L</span> <span class="special">=</span> <span class="number">2</span> <span class="special">+</span> <span class="number">1</span> <span class="identifier">i</span> <span class="identifier">m</span> |
| <span class="special">-</span><span class="identifier">L</span> <span class="special">=</span> <span class="special">-</span><span class="number">2</span> <span class="special">+</span> <span class="special">-</span><span class="number">1</span> <span class="identifier">i</span> <span class="identifier">m</span> |
| <span class="identifier">L</span><span class="special">+</span><span class="identifier">L</span> <span class="special">=</span> <span class="number">4</span> <span class="special">+</span> <span class="number">2</span> <span class="identifier">i</span> <span class="identifier">m</span> |
| <span class="identifier">L</span><span class="special">-</span><span class="identifier">L</span> <span class="special">=</span> <span class="number">0</span> <span class="special">+</span> <span class="number">0</span> <span class="identifier">i</span> <span class="identifier">m</span> |
| <span class="identifier">L</span><span class="special">*</span><span class="identifier">L</span> <span class="special">=</span> <span class="number">3</span> <span class="special">+</span> <span class="number">4</span> <span class="identifier">i</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> |
| <span class="identifier">L</span><span class="special">/</span><span class="identifier">L</span> <span class="special">=</span> <span class="number">1</span> <span class="special">+</span> <span class="number">0</span> <span class="identifier">i</span> <span class="identifier">dimensionless</span> |
| <span class="identifier">L</span><span class="special">^</span><span class="number">3</span> <span class="special">=</span> <span class="number">2</span> <span class="special">+</span> <span class="number">11</span> <span class="identifier">i</span> <span class="identifier">m</span><span class="special">^</span><span class="number">3</span> |
| <span class="identifier">L</span><span class="special">^(</span><span class="number">3</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> <span class="special">=</span> <span class="number">2.56713</span> <span class="special">+</span> <span class="number">2.14247</span> <span class="identifier">i</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">3</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> |
| <span class="number">3</span><span class="identifier">vL</span> <span class="special">=</span> <span class="number">1.29207</span> <span class="special">+</span> <span class="number">0.201294</span> <span class="identifier">i</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">1</span><span class="special">/</span><span class="number">3</span><span class="special">)</span> |
| <span class="special">(</span><span class="number">3</span><span class="special">/</span><span class="number">2</span><span class="special">)</span><span class="identifier">vL</span> <span class="special">=</span> <span class="number">1.62894</span> <span class="special">+</span> <span class="number">0.520175</span> <span class="identifier">i</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">2</span><span class="special">/</span><span class="number">3</span><span class="special">)</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| and, similarly, <code class="computeroutput"><span class="identifier">complex</span></code> with |
| a <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/quantity.html" title="Class template quantity">quantity</a></code></span> |
| value type |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">complex</span><span class="special"><</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">length</span><span class="special">></span> <span class="special">></span> <span class="identifier">length_dimension</span><span class="special">;</span> |
| |
| <span class="identifier">length_dimension</span> <span class="identifier">L</span><span class="special">(</span><span class="number">2.0</span><span class="special">*</span><span class="identifier">meters</span><span class="special">,</span><span class="number">1.0</span><span class="special">*</span><span class="identifier">meters</span><span class="special">);</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| gives |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="special">+</span><span class="identifier">L</span> <span class="special">=</span> <span class="number">2</span> <span class="identifier">m</span> <span class="special">+</span> <span class="number">1</span> <span class="identifier">m</span> <span class="identifier">i</span> |
| <span class="special">-</span><span class="identifier">L</span> <span class="special">=</span> <span class="special">-</span><span class="number">2</span> <span class="identifier">m</span> <span class="special">+</span> <span class="special">-</span><span class="number">1</span> <span class="identifier">m</span> <span class="identifier">i</span> |
| <span class="identifier">L</span><span class="special">+</span><span class="identifier">L</span> <span class="special">=</span> <span class="number">4</span> <span class="identifier">m</span> <span class="special">+</span> <span class="number">2</span> <span class="identifier">m</span> <span class="identifier">i</span> |
| <span class="identifier">L</span><span class="special">-</span><span class="identifier">L</span> <span class="special">=</span> <span class="number">0</span> <span class="identifier">m</span> <span class="special">+</span> <span class="number">0</span> <span class="identifier">m</span> <span class="identifier">i</span> |
| <span class="identifier">L</span><span class="special">*</span><span class="identifier">L</span> <span class="special">=</span> <span class="number">3</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> <span class="special">+</span> <span class="number">4</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> <span class="identifier">i</span> |
| <span class="identifier">L</span><span class="special">/</span><span class="identifier">L</span> <span class="special">=</span> <span class="number">1</span> <span class="identifier">dimensionless</span> <span class="special">+</span> <span class="number">0</span> <span class="identifier">dimensionless</span> <span class="identifier">i</span> |
| <span class="identifier">L</span><span class="special">^</span><span class="number">3</span> <span class="special">=</span> <span class="number">2</span> <span class="identifier">m</span><span class="special">^</span><span class="number">3</span> <span class="special">+</span> <span class="number">11</span> <span class="identifier">m</span><span class="special">^</span><span class="number">3</span> <span class="identifier">i</span> |
| <span class="identifier">L</span><span class="special">^(</span><span class="number">3</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> <span class="special">=</span> <span class="number">2.56713</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">3</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> <span class="special">+</span> <span class="number">2.14247</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">3</span><span class="special">/</span><span class="number">2</span><span class="special">)</span> <span class="identifier">i</span> |
| <span class="number">3</span><span class="identifier">vL</span> <span class="special">=</span> <span class="number">1.29207</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">1</span><span class="special">/</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="number">0.201294</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">1</span><span class="special">/</span><span class="number">3</span><span class="special">)</span> <span class="identifier">i</span> |
| <span class="special">(</span><span class="number">3</span><span class="special">/</span><span class="number">2</span><span class="special">)</span><span class="identifier">vL</span> <span class="special">=</span> <span class="number">1.62894</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">2</span><span class="special">/</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="number">0.520175</span> <span class="identifier">m</span><span class="special">^(</span><span class="number">2</span><span class="special">/</span><span class="number">3</span><span class="special">)</span> <span class="identifier">i</span> |
| </pre> |
| <p> |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_units.Examples.PerformanceExample"></a><a class="link" href="Examples.html#boost_units.Examples.PerformanceExample" title="Performance Example">Performance |
| Example</a> |
| </h3></div></div></div> |
| <p> |
| (<a href="../../../libs/units/example/performance.cpp" target="_top">performance.cpp</a>) |
| </p> |
| <p> |
| This example provides an ad hoc performance test to verify that zero runtime |
| overhead is incurred when using <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/quantity.html" title="Class template quantity">quantity</a></code></span> |
| in place of <code class="computeroutput"><span class="keyword">double</span></code>. Note that |
| performance optimization and testing is not trivial, so some care must be |
| taken in profiling. It is also critical to have a compiler capable of optimizing |
| the many template instantiations and inline calls effectively to achieve |
| maximal performance. Zero overhead for this test has been verified using |
| gcc 4.0.1, and icc 9.0, 10.0, and 10.1 on Mac OS 10.4 and 10.5, and using |
| msvc 8.0 on Windows XP. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_units.Examples.RadarBeamHeightExample"></a><a class="link" href="Examples.html#boost_units.Examples.RadarBeamHeightExample" title="Radar Beam Height">Radar Beam |
| Height</a> |
| </h3></div></div></div> |
| <p> |
| (<a href="../../../libs/units/example/radar_beam_height.cpp" target="_top">radar_beam_height.cpp</a>) |
| </p> |
| <p> |
| This example demonstrates the implementation of two non-SI units of length, |
| the nautical mile : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">nautical</span> <span class="special">{</span> |
| |
| <span class="keyword">struct</span> <span class="identifier">length_base_unit</span> <span class="special">:</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">base_unit</span><span class="special"><</span><span class="identifier">length_base_unit</span><span class="special">,</span> <span class="identifier">length_dimension</span><span class="special">,</span> <span class="number">1</span><span class="special">></span> |
| <span class="special">{</span> |
| <span class="keyword">static</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">name</span><span class="special">()</span> <span class="special">{</span> <span class="keyword">return</span> <span class="string">"nautical mile"</span><span class="special">;</span> <span class="special">}</span> |
| <span class="keyword">static</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">symbol</span><span class="special">()</span> <span class="special">{</span> <span class="keyword">return</span> <span class="string">"nmi"</span><span class="special">;</span> <span class="special">}</span> |
| <span class="special">};</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">make_system</span><span class="special"><</span><span class="identifier">length_base_unit</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">system</span><span class="special">;</span> |
| |
| <span class="comment">/// unit typedefs |
| </span><span class="keyword">typedef</span> <span class="identifier">unit</span><span class="special"><</span><span class="identifier">length_dimension</span><span class="special">,</span><span class="identifier">system</span><span class="special">></span> <span class="identifier">length</span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="keyword">const</span> <span class="identifier">length</span> <span class="identifier">mile</span><span class="special">,</span><span class="identifier">miles</span><span class="special">;</span> |
| |
| <span class="special">}</span> <span class="comment">// namespace nautical |
| </span> |
| <span class="comment">// helper for conversions between nautical length and si length |
| </span><span class="identifier">BOOST_UNITS_DEFINE_CONVERSION_FACTOR</span><span class="special">(</span><span class="identifier">nautical</span><span class="special">::</span><span class="identifier">length_base_unit</span><span class="special">,</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">meter_base_unit</span><span class="special">,</span> |
| <span class="keyword">double</span><span class="special">,</span> <span class="number">1.852e3</span><span class="special">);</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| and the imperial foot : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">imperial</span> <span class="special">{</span> |
| |
| <span class="keyword">struct</span> <span class="identifier">length_base_unit</span> <span class="special">:</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">base_unit</span><span class="special"><</span><span class="identifier">length_base_unit</span><span class="special">,</span> <span class="identifier">length_dimension</span><span class="special">,</span> <span class="number">2</span><span class="special">></span> |
| <span class="special">{</span> |
| <span class="keyword">static</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">name</span><span class="special">()</span> <span class="special">{</span> <span class="keyword">return</span> <span class="string">"foot"</span><span class="special">;</span> <span class="special">}</span> |
| <span class="keyword">static</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">symbol</span><span class="special">()</span> <span class="special">{</span> <span class="keyword">return</span> <span class="string">"ft"</span><span class="special">;</span> <span class="special">}</span> |
| <span class="special">};</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">make_system</span><span class="special"><</span><span class="identifier">length_base_unit</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">system</span><span class="special">;</span> |
| |
| <span class="comment">/// unit typedefs |
| </span><span class="keyword">typedef</span> <span class="identifier">unit</span><span class="special"><</span><span class="identifier">length_dimension</span><span class="special">,</span><span class="identifier">system</span><span class="special">></span> <span class="identifier">length</span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="keyword">const</span> <span class="identifier">length</span> <span class="identifier">foot</span><span class="special">,</span><span class="identifier">feet</span><span class="special">;</span> |
| |
| <span class="special">}</span> <span class="comment">// imperial |
| </span> |
| <span class="comment">// helper for conversions between imperial length and si length |
| </span><span class="identifier">BOOST_UNITS_DEFINE_CONVERSION_FACTOR</span><span class="special">(</span><span class="identifier">imperial</span><span class="special">::</span><span class="identifier">length_base_unit</span><span class="special">,</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">meter_base_unit</span><span class="special">,</span> |
| <span class="keyword">double</span><span class="special">,</span> <span class="number">1.0</span><span class="special">/</span><span class="number">3.28083989501312</span><span class="special">);</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| These units include conversions between themselves and the meter. Three functions |
| for computing radar beam height from radar range and the local earth radius |
| are defined. The first takes arguments in one system and returns a value |
| in the same system : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">System</span><span class="special">,</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">></span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">unit</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">length_dimension</span><span class="special">,</span><span class="identifier">System</span><span class="special">>,</span><span class="identifier">T</span><span class="special">></span> |
| <span class="identifier">radar_beam_height</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">unit</span><span class="special"><</span><span class="identifier">length_dimension</span><span class="special">,</span><span class="identifier">System</span><span class="special">>,</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">radar_range</span><span class="special">,</span> |
| <span class="keyword">const</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">unit</span><span class="special"><</span><span class="identifier">length_dimension</span><span class="special">,</span><span class="identifier">System</span><span class="special">>,</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">earth_radius</span><span class="special">,</span> |
| <span class="identifier">T</span> <span class="identifier">k</span> <span class="special">=</span> <span class="number">4.0</span><span class="special">/</span><span class="number">3.0</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">unit</span><span class="special"><</span><span class="identifier">length_dimension</span><span class="special">,</span><span class="identifier">System</span><span class="special">>,</span><span class="identifier">T</span><span class="special">></span> |
| <span class="special">(</span><span class="identifier">pow</span><span class="special"><</span><span class="number">2</span><span class="special">>(</span><span class="identifier">radar_range</span><span class="special">)/(</span><span class="number">2.0</span><span class="special">*</span><span class="identifier">k</span><span class="special">*</span><span class="identifier">earth_radius</span><span class="special">));</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| The second is similar, but is templated on return type, so that the arguments |
| are converted to the return unit system internally : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">return_type</span><span class="special">,</span><span class="keyword">class</span> <span class="identifier">System1</span><span class="special">,</span><span class="keyword">class</span> <span class="identifier">System2</span><span class="special">,</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">></span> |
| <span class="identifier">return_type</span> |
| <span class="identifier">radar_beam_height</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">unit</span><span class="special"><</span><span class="identifier">length_dimension</span><span class="special">,</span><span class="identifier">System1</span><span class="special">>,</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">radar_range</span><span class="special">,</span> |
| <span class="keyword">const</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">unit</span><span class="special"><</span><span class="identifier">length_dimension</span><span class="special">,</span><span class="identifier">System2</span><span class="special">>,</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">earth_radius</span><span class="special">,</span> |
| <span class="identifier">T</span> <span class="identifier">k</span> <span class="special">=</span> <span class="number">4.0</span><span class="special">/</span><span class="number">3.0</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="comment">// need to decide which system to use for calculation |
| </span> <span class="keyword">const</span> <span class="identifier">return_type</span> <span class="identifier">rr</span><span class="special">(</span><span class="identifier">radar_range</span><span class="special">),</span> |
| <span class="identifier">er</span><span class="special">(</span><span class="identifier">earth_radius</span><span class="special">);</span> |
| |
| <span class="keyword">return</span> <span class="identifier">return_type</span><span class="special">(</span><span class="identifier">pow</span><span class="special"><</span><span class="number">2</span><span class="special">>(</span><span class="identifier">rr</span><span class="special">)/(</span><span class="number">2.0</span><span class="special">*</span><span class="identifier">k</span><span class="special">*</span><span class="identifier">er</span><span class="special">));</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| Finally, the third function is an empirical approximation that is only valid |
| for radar ranges specified in nautical miles, returning beam height in feet. |
| This function uses the heterogeneous unit of nautical miles per square root |
| of feet to ensure dimensional correctness : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">imperial</span><span class="special">::</span><span class="identifier">length</span><span class="special">></span> |
| <span class="identifier">radar_beam_height</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">nautical</span><span class="special">::</span><span class="identifier">length</span><span class="special">>&</span> <span class="identifier">range</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">imperial</span><span class="special">::</span><span class="identifier">length</span><span class="special">></span> |
| <span class="special">(</span><span class="identifier">pow</span><span class="special"><</span><span class="number">2</span><span class="special">>(</span><span class="identifier">range</span><span class="special">/(</span><span class="number">1.23</span><span class="special">*</span><span class="identifier">nautical</span><span class="special">::</span><span class="identifier">miles</span><span class="special">/</span><span class="identifier">root</span><span class="special"><</span><span class="number">2</span><span class="special">>(</span><span class="identifier">imperial</span><span class="special">::</span><span class="identifier">feet</span><span class="special">))));</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| With these, we can compute radar beam height in various unit systems : |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">const</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">nautical</span><span class="special">::</span><span class="identifier">length</span><span class="special">></span> <span class="identifier">radar_range</span><span class="special">(</span><span class="number">300.0</span><span class="special">*</span><span class="identifier">miles</span><span class="special">);</span> |
| <span class="keyword">const</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">length</span><span class="special">></span> <span class="identifier">earth_radius</span><span class="special">(</span><span class="number">6371.0087714</span><span class="special">*</span><span class="identifier">kilo</span><span class="special">*</span><span class="identifier">meters</span><span class="special">);</span> |
| |
| <span class="keyword">const</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">length</span><span class="special">></span> <span class="identifier">beam_height_1</span><span class="special">(</span><span class="identifier">radar_beam_height</span><span class="special">(</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">length</span><span class="special">>(</span><span class="identifier">radar_range</span><span class="special">),</span><span class="identifier">earth_radius</span><span class="special">));</span> |
| <span class="keyword">const</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">nautical</span><span class="special">::</span><span class="identifier">length</span><span class="special">></span> <span class="identifier">beam_height_2</span><span class="special">(</span><span class="identifier">radar_beam_height</span><span class="special">(</span><span class="identifier">radar_range</span><span class="special">,</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">nautical</span><span class="special">::</span><span class="identifier">length</span><span class="special">>(</span><span class="identifier">earth_radius</span><span class="special">)));</span> |
| <span class="keyword">const</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">length</span><span class="special">></span> <span class="identifier">beam_height_3</span><span class="special">(</span><span class="identifier">radar_beam_height</span><span class="special"><</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">length</span><span class="special">></span> <span class="special">>(</span><span class="identifier">radar_range</span><span class="special">,</span><span class="identifier">earth_radius</span><span class="special">));</span> |
| <span class="keyword">const</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">nautical</span><span class="special">::</span><span class="identifier">length</span><span class="special">></span> <span class="identifier">beam_height_4</span><span class="special">(</span><span class="identifier">radar_beam_height</span><span class="special"><</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">nautical</span><span class="special">::</span><span class="identifier">length</span><span class="special">></span> <span class="special">>(</span><span class="identifier">radar_range</span><span class="special">,</span><span class="identifier">earth_radius</span><span class="special">));</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| giving |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">radar</span> <span class="identifier">range</span> <span class="special">:</span> <span class="number">300</span> <span class="identifier">nmi</span> |
| <span class="identifier">earth</span> <span class="identifier">radius</span> <span class="special">:</span> <span class="number">6.37101e+06</span> <span class="identifier">m</span> |
| <span class="identifier">beam</span> <span class="identifier">height</span> <span class="number">1</span> <span class="special">:</span> <span class="number">18169.7</span> <span class="identifier">m</span> |
| <span class="identifier">beam</span> <span class="identifier">height</span> <span class="number">2</span> <span class="special">:</span> <span class="number">9.81085</span> <span class="identifier">nmi</span> |
| <span class="identifier">beam</span> <span class="identifier">height</span> <span class="number">3</span> <span class="special">:</span> <span class="number">18169.7</span> <span class="identifier">m</span> |
| <span class="identifier">beam</span> <span class="identifier">height</span> <span class="number">4</span> <span class="special">:</span> <span class="number">9.81085</span> <span class="identifier">nmi</span> |
| <span class="identifier">beam</span> <span class="identifier">height</span> <span class="identifier">approx</span> <span class="special">:</span> <span class="number">59488.4</span> <span class="identifier">ft</span> |
| <span class="identifier">beam</span> <span class="identifier">height</span> <span class="identifier">approx</span> <span class="special">:</span> <span class="number">18132.1</span> <span class="identifier">m</span> |
| </pre> |
| <p> |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_units.Examples.HeterogeneousUnitExample"></a><a class="link" href="Examples.html#boost_units.Examples.HeterogeneousUnitExample" title="Heterogeneous Unit Example">Heterogeneous |
| Unit Example</a> |
| </h3></div></div></div> |
| <p> |
| (<a href="../../../libs/units/example/heterogeneous_unit.cpp" target="_top">heterogeneous_unit.cpp</a>) |
| </p> |
| <p> |
| Mixed units and mixed unit conversions. |
| </p> |
| <p> |
| This code: |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">length</span><span class="special">></span> <span class="identifier">L</span><span class="special">(</span><span class="number">1.5</span><span class="special">*</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">meter</span><span class="special">);</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">cgs</span><span class="special">::</span><span class="identifier">mass</span><span class="special">></span> <span class="identifier">M</span><span class="special">(</span><span class="number">1.0</span><span class="special">*</span><span class="identifier">cgs</span><span class="special">::</span><span class="identifier">gram</span><span class="special">);</span> |
| |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">L</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span> |
| <span class="special"><<</span> <span class="identifier">M</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span> |
| <span class="special"><<</span> <span class="identifier">L</span><span class="special">*</span><span class="identifier">M</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span> |
| <span class="special"><<</span> <span class="identifier">L</span><span class="special">/</span><span class="identifier">M</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span> |
| <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="number">1.0</span><span class="special">*</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">meter</span><span class="special">*</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">kilogram</span><span class="special">/</span><span class="identifier">pow</span><span class="special"><</span><span class="number">2</span><span class="special">>(</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">second</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span> |
| <span class="special"><<</span> <span class="number">1.0</span><span class="special">*</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">meter</span><span class="special">*</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">kilogram</span><span class="special">/</span><span class="identifier">pow</span><span class="special"><</span><span class="number">2</span><span class="special">>(</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">second</span><span class="special">)/</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">meter</span> |
| <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="number">1.0</span><span class="special">*</span><span class="identifier">cgs</span><span class="special">::</span><span class="identifier">centimeter</span><span class="special">*</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">kilogram</span><span class="special">/</span><span class="identifier">pow</span><span class="special"><</span><span class="number">2</span><span class="special">>(</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">second</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span> |
| <span class="special"><<</span> <span class="number">1.0</span><span class="special">*</span><span class="identifier">cgs</span><span class="special">::</span><span class="identifier">centimeter</span><span class="special">*</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">kilogram</span><span class="special">/</span><span class="identifier">pow</span><span class="special"><</span><span class="number">2</span><span class="special">>(</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">second</span><span class="special">)/</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">meter</span> |
| <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| gives |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="number">1.5</span> <span class="identifier">m</span> |
| <span class="number">1</span> <span class="identifier">g</span> |
| <span class="number">1.5</span> <span class="identifier">m</span> <span class="identifier">g</span> |
| <span class="number">1.5</span> <span class="identifier">m</span> <span class="identifier">g</span><span class="special">^-</span><span class="number">1</span> |
| |
| <span class="number">1</span> <span class="identifier">N</span> |
| <span class="number">1</span> <span class="identifier">kg</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">2</span> |
| |
| <span class="number">1</span> <span class="identifier">cm</span> <span class="identifier">kg</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">2</span> |
| <span class="number">1</span> <span class="identifier">cm</span> <span class="identifier">m</span><span class="special">^-</span><span class="number">1</span> <span class="identifier">kg</span> <span class="identifier">s</span><span class="special">^-</span><span class="number">2</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| Arbitrary conversions also work: |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">area</span><span class="special">></span> <span class="identifier">A</span><span class="special">(</span><span class="number">1.5</span><span class="special">*</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">meter</span><span class="special">*</span><span class="identifier">cgs</span><span class="special">::</span><span class="identifier">centimeter</span><span class="special">);</span> |
| |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="number">1.5</span><span class="special">*</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">meter</span><span class="special">*</span><span class="identifier">cgs</span><span class="special">::</span><span class="identifier">centimeter</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span> |
| <span class="special"><<</span> <span class="identifier">A</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span> |
| <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| yielding |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="number">1.5</span> <span class="identifier">cm</span> <span class="identifier">m</span> |
| <span class="number">0.015</span> <span class="identifier">m</span><span class="special">^</span><span class="number">2</span> |
| </pre> |
| <p> |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_units.Examples.AbsoluteRelativeTemperatureExample"></a><a class="link" href="Examples.html#boost_units.Examples.AbsoluteRelativeTemperatureExample" title="Absolute and Relative Temperature Example">Absolute |
| and Relative Temperature Example</a> |
| </h3></div></div></div> |
| <p> |
| (<a href="../../../libs/units/example/temperature.cpp" target="_top">temperature.cpp</a>) |
| </p> |
| <p> |
| This example demonstrates using of absolute temperatures and relative temperature |
| differences in Fahrenheit and converting between these and the Kelvin temperature |
| scale. This issue touches on some surprisingly deep mathematical concepts |
| (see <a href="http://en.wikipedia.org/wiki/Affine_space" target="_top">Wikipedia</a> |
| for a basic review), but for our purposes here, we will simply observe that |
| it is important to be able to differentiate between an absolute temperature |
| measurement and a measurement of temperature difference. This is accomplished |
| by using the <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/absolute.html" title="Class template absolute">absolute</a></code></span> |
| wrapper class. |
| </p> |
| <p> |
| First we define a system using the predefined fahrenheit base unit: |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">temperature</span><span class="special">::</span><span class="identifier">fahrenheit_base_unit</span><span class="special">::</span><span class="identifier">unit_type</span> <span class="identifier">temperature</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">get_system</span><span class="special"><</span><span class="identifier">temperature</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">system</span><span class="special">;</span> |
| |
| <span class="identifier">BOOST_UNITS_STATIC_CONSTANT</span><span class="special">(</span><span class="identifier">degree</span><span class="special">,</span><span class="identifier">temperature</span><span class="special">);</span> |
| <span class="identifier">BOOST_UNITS_STATIC_CONSTANT</span><span class="special">(</span><span class="identifier">degrees</span><span class="special">,</span><span class="identifier">temperature</span><span class="special">);</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| Now we can create some quantities: |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">absolute</span><span class="special"><</span><span class="identifier">fahrenheit</span><span class="special">::</span><span class="identifier">temperature</span><span class="special">></span> <span class="special">></span> <span class="identifier">T1p</span><span class="special">(</span> |
| <span class="number">32.0</span><span class="special">*</span><span class="identifier">absolute</span><span class="special"><</span><span class="identifier">fahrenheit</span><span class="special">::</span><span class="identifier">temperature</span><span class="special">>());</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">fahrenheit</span><span class="special">::</span><span class="identifier">temperature</span><span class="special">></span> <span class="identifier">T1v</span><span class="special">(</span> |
| <span class="number">32.0</span><span class="special">*</span><span class="identifier">fahrenheit</span><span class="special">::</span><span class="identifier">degrees</span><span class="special">);</span> |
| |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">absolute</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">temperature</span><span class="special">></span> <span class="special">></span> <span class="identifier">T2p</span><span class="special">(</span><span class="identifier">T1p</span><span class="special">);</span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">temperature</span><span class="special">></span> <span class="identifier">T2v</span><span class="special">(</span><span class="identifier">T1v</span><span class="special">);</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| Note the use of <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/absolute.html" title="Class template absolute">absolute</a></code></span> |
| to wrap a unit. The resulting output is: |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="special">{</span> <span class="number">32</span> <span class="special">}</span> <span class="identifier">F</span> |
| <span class="special">{</span> <span class="number">273.15</span> <span class="special">}</span> <span class="identifier">K</span> |
| <span class="special">{</span> <span class="number">273.15</span> <span class="special">}</span> <span class="identifier">K</span> |
| <span class="special">[</span> <span class="number">32</span> <span class="special">]</span> <span class="identifier">F</span> |
| <span class="special">[</span> <span class="number">17.7778</span> <span class="special">]</span> <span class="identifier">K</span> |
| <span class="special">[</span> <span class="number">17.7778</span> <span class="special">]</span> <span class="identifier">K</span> |
| </pre> |
| <p> |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_units.Examples.RuntimeConversionFactorExample"></a><a class="link" href="Examples.html#boost_units.Examples.RuntimeConversionFactorExample" title="Runtime Conversion Factor Example">Runtime |
| Conversion Factor Example</a> |
| </h3></div></div></div> |
| <p> |
| (<a href="../../../libs/units/example/runtime_conversion_factor.cpp" target="_top">runtime_conversion_factor.cpp</a>) |
| </p> |
| <p> |
| The Boost.Units library does not require that the conversion factors be compile |
| time constants, as is demonstrated in this example: |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">base_dimension</span><span class="special">;</span> |
| <span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">base_unit</span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="keyword">const</span> <span class="keyword">long</span> <span class="identifier">currency_base</span> <span class="special">=</span> <span class="number">1</span><span class="special">;</span> |
| |
| <span class="keyword">struct</span> <span class="identifier">currency_base_dimension</span> <span class="special">:</span> <span class="identifier">base_dimension</span><span class="special"><</span><span class="identifier">currency_base_dimension</span><span class="special">,</span> <span class="number">1</span><span class="special">></span> <span class="special">{};</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">currency_base_dimension</span><span class="special">::</span><span class="identifier">dimension_type</span> <span class="identifier">currency_type</span><span class="special">;</span> |
| |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">long</span> <span class="identifier">N</span><span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">currency_base_unit</span> <span class="special">:</span> |
| <span class="identifier">base_unit</span><span class="special"><</span><span class="identifier">currency_base_unit</span><span class="special"><</span><span class="identifier">N</span><span class="special">>,</span> <span class="identifier">currency_type</span><span class="special">,</span> <span class="identifier">currency_base</span> <span class="special">+</span> <span class="identifier">N</span><span class="special">></span> <span class="special">{};</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">currency_base_unit</span><span class="special"><</span><span class="number">0</span><span class="special">></span> <span class="identifier">us_dollar_base_unit</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">currency_base_unit</span><span class="special"><</span><span class="number">1</span><span class="special">></span> <span class="identifier">euro_base_unit</span><span class="special">;</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">us_dollar_base_unit</span><span class="special">::</span><span class="identifier">unit_type</span> <span class="identifier">us_dollar</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">euro_base_unit</span><span class="special">::</span><span class="identifier">unit_type</span> <span class="identifier">euro</span><span class="special">;</span> |
| |
| <span class="comment">// an array of all possible conversions |
| </span><span class="keyword">double</span> <span class="identifier">conversion_factors</span><span class="special">[</span><span class="number">2</span><span class="special">][</span><span class="number">2</span><span class="special">]</span> <span class="special">=</span> <span class="special">{</span> |
| <span class="special">{</span><span class="number">1.0</span><span class="special">,</span> <span class="number">1.0</span><span class="special">},</span> |
| <span class="special">{</span><span class="number">1.0</span><span class="special">,</span> <span class="number">1.0</span><span class="special">}</span> |
| <span class="special">};</span> |
| |
| <span class="keyword">double</span> <span class="identifier">get_conversion_factor</span><span class="special">(</span><span class="keyword">long</span> <span class="identifier">from</span><span class="special">,</span> <span class="keyword">long</span> <span class="identifier">to</span><span class="special">)</span> <span class="special">{</span> |
| <span class="keyword">return</span><span class="special">(</span><span class="identifier">conversion_factors</span><span class="special">[</span><span class="identifier">from</span><span class="special">][</span><span class="identifier">to</span><span class="special">]);</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">void</span> <span class="identifier">set_conversion_factor</span><span class="special">(</span><span class="keyword">long</span> <span class="identifier">from</span><span class="special">,</span> <span class="keyword">long</span> <span class="identifier">to</span><span class="special">,</span> <span class="keyword">double</span> <span class="identifier">value</span><span class="special">)</span> <span class="special">{</span> |
| <span class="identifier">conversion_factors</span><span class="special">[</span><span class="identifier">from</span><span class="special">][</span><span class="identifier">to</span><span class="special">]</span> <span class="special">=</span> <span class="identifier">value</span><span class="special">;</span> |
| <span class="identifier">conversion_factors</span><span class="special">[</span><span class="identifier">to</span><span class="special">][</span><span class="identifier">from</span><span class="special">]</span> <span class="special">=</span> <span class="number">1.0</span> <span class="special">/</span> <span class="identifier">value</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">BOOST_UNITS_DEFINE_CONVERSION_FACTOR_TEMPLATE</span><span class="special">((</span><span class="keyword">long</span> <span class="identifier">N1</span><span class="special">)(</span><span class="keyword">long</span> <span class="identifier">N2</span><span class="special">),</span> |
| <span class="identifier">currency_base_unit</span><span class="special"><</span><span class="identifier">N1</span><span class="special">>,</span> |
| <span class="identifier">currency_base_unit</span><span class="special"><</span><span class="identifier">N2</span><span class="special">>,</span> |
| <span class="keyword">double</span><span class="special">,</span> <span class="identifier">get_conversion_factor</span><span class="special">(</span><span class="identifier">N1</span><span class="special">,</span> <span class="identifier">N2</span><span class="special">));</span> |
| |
| </pre> |
| <p> |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_units.Examples.UnitsWithNonbaseDimensions"></a><a class="link" href="Examples.html#boost_units.Examples.UnitsWithNonbaseDimensions" title="Units with Non-base Dimensions">Units |
| with Non-base Dimensions</a> |
| </h3></div></div></div> |
| <p> |
| (<a href="../../../libs/units/example/non_base_dimension.cpp" target="_top">non_base_dimension.cpp</a>) |
| </p> |
| <p> |
| It is also possible to define base units that have derived rather than base |
| dimensions: |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">imperial_gallon_tag</span> <span class="special">:</span> |
| <span class="identifier">base_unit</span><span class="special"><</span><span class="identifier">imperial_gallon_tag</span><span class="special">,</span> <span class="identifier">volume_dimension</span><span class="special">,</span> <span class="number">1</span><span class="special">></span> <span class="special">{</span> <span class="special">};</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">make_system</span><span class="special"><</span><span class="identifier">imperial_gallon_tag</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">imperial</span><span class="special">;</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">unit</span><span class="special"><</span><span class="identifier">volume_dimension</span><span class="special">,</span><span class="identifier">imperial</span><span class="special">></span> <span class="identifier">imperial_gallon</span><span class="special">;</span> |
| |
| <span class="keyword">struct</span> <span class="identifier">us_gallon_tag</span> <span class="special">:</span> <span class="identifier">base_unit</span><span class="special"><</span><span class="identifier">us_gallon_tag</span><span class="special">,</span> <span class="identifier">volume_dimension</span><span class="special">,</span> <span class="number">2</span><span class="special">></span> <span class="special">{</span> <span class="special">};</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">make_system</span><span class="special"><</span><span class="identifier">us_gallon_tag</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">us</span><span class="special">;</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">unit</span><span class="special"><</span><span class="identifier">volume_dimension</span><span class="special">,</span><span class="identifier">us</span><span class="special">></span> <span class="identifier">us_gallon</span><span class="special">;</span> |
| |
| </pre> |
| <p> |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_units.Examples.OutputForCompositeUnits"></a><a class="link" href="Examples.html#boost_units.Examples.OutputForCompositeUnits" title="Output for Composite Units">Output |
| for Composite Units</a> |
| </h3></div></div></div> |
| <p> |
| (<a href="../../../libs/units/example/composite_output.cpp" target="_top">composite_output.cpp</a>) |
| </p> |
| <p> |
| If a unit has a special name and/or symbol, the free functions <code class="computeroutput"><span class="identifier">name_string</span></code> and <code class="computeroutput"><span class="identifier">symbol_string</span></code> |
| can be overloaded directly. |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">name_string</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">cgs</span><span class="special">::</span><span class="identifier">force</span><span class="special">&)</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="string">"dyne"</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">symbol_string</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">cgs</span><span class="special">::</span><span class="identifier">force</span><span class="special">&)</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="string">"dyn"</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| </pre> |
| <p> |
| </p> |
| <p> |
| In this case, any unit that reduces to the overloaded unit will be output |
| with the replacement symbol. |
| </p> |
| <p> |
| Special names and symbols for the SI and CGS unit systems are found in <code class="computeroutput"><a class="link" href="Reference.html#header.boost.units.systems.si.io_hpp" title="Header <boost/units/systems/si/io.hpp>">boost/units/systems/si/io.hpp</a></code> |
| and <code class="computeroutput"><a class="link" href="Reference.html#header.boost.units.systems.cgs.io_hpp" title="Header <boost/units/systems/cgs/io.hpp>">boost/units/systems/cgs/io.hpp</a></code>, |
| respectively. If these headers are not included, the output will simply follow |
| default rules using the appropriate fundamental dimensions. Note that neither |
| of these functions is defined for quantities because doing so would require |
| making assumptions on how the corresponding value type should be formatted. |
| </p> |
| <p> |
| Three <code class="computeroutput"><span class="identifier">ostream</span></code> formatters, |
| <code class="computeroutput"><span class="identifier">symbol_format</span></code>, <code class="computeroutput"><span class="identifier">name_format</span></code>, and <code class="computeroutput"><span class="identifier">typename_format</span></code> |
| are provided for convenience. These select the textual representation of |
| units provided by <code class="computeroutput"><span class="identifier">symbol_string</span></code> |
| or <code class="computeroutput"><span class="identifier">name_string</span></code> in the first |
| two cases, while the latter returns a demangled typename for debugging purposes. |
| Formatting of scaled unit is also done correctly. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_units.Examples.autoscale"></a><a class="link" href="Examples.html#boost_units.Examples.autoscale" title="Automatically Scaled Units">Automatically Scaled |
| Units</a> |
| </h3></div></div></div> |
| <p> |
| It is often desirable to scale a <span class="underline"><code class="computeroutput"><a class="link" href="../boost/units/unit.html" title="Class template unit">unit</a></code></span> |
| automatically, depending on its value, to keep the integral part in a limited |
| range, usually between 1 and 999. |
| </p> |
| <p> |
| For example, using <a href="http://en.wikipedia.org/wiki/Engineering_notation" target="_top">engineering |
| notation prefixes</a>, |
| </p> |
| <pre class="programlisting"><span class="string">"1234.5 m"</span> <span class="identifier">is</span> <span class="identifier">more</span> <span class="identifier">helpfully</span> <span class="identifier">displayed</span> <span class="identifier">as</span> <span class="string">"1.234 km"</span> |
| <span class="string">"0.000000001234 m"</span> <span class="identifier">is</span> <span class="identifier">more</span> <span class="identifier">clearly</span> <span class="identifier">displayed</span> <span class="identifier">as</span> <span class="string">"1.2345 nanometer"</span><span class="special">.</span> |
| </pre> |
| <p> |
| The iostream manipulators <code class="computeroutput"><span class="identifier">engineering_prefixes</span></code> |
| or <code class="computeroutput"><span class="identifier">binary_prefixes</span></code> make this |
| easy. |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">binary_prefix</span><span class="special">;</span> |
| <span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">engineering_prefix</span><span class="special">;</span> |
| <span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">no_prefix</span><span class="special">;</span> |
| |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">length</span><span class="special">></span> <span class="identifier">l</span> <span class="special">=</span> <span class="number">2.345</span> <span class="special">*</span> <span class="identifier">meters</span><span class="special">;</span> <span class="comment">// A quantity of length, in units of meters. |
| </span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">engineering_prefix</span> <span class="special"><<</span> <span class="identifier">l</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> <span class="comment">// Outputs "2.345 m". |
| </span><span class="identifier">l</span> <span class="special">=</span> <span class="number">1000.0</span> <span class="special">*</span> <span class="identifier">l</span><span class="special">;</span> <span class="comment">// Increase it by 1000, so expect a k prefix. |
| </span><span class="comment">// Note that a double 1000.0 is required - an integer will fail to compile. |
| </span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">engineering_prefix</span> <span class="special"><<</span> <span class="identifier">l</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> <span class="comment">// Output autoprefixed with k to "2.345 km". |
| </span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">energy</span><span class="special">></span> <span class="identifier">e</span> <span class="special">=</span> <span class="identifier">kilograms</span> <span class="special">*</span> <span class="identifier">pow</span><span class="special"><</span><span class="number">2</span><span class="special">>(</span><span class="identifier">l</span> <span class="special">/</span> <span class="identifier">seconds</span><span class="special">);</span> <span class="comment">// A quantity of energy. |
| </span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">engineering_prefix</span> <span class="special"><<</span> <span class="identifier">e</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> <span class="comment">// 5.49902 MJ |
| </span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">name_format</span> <span class="special"><<</span> <span class="identifier">engineering_prefix</span> <span class="special"><<</span> <span class="identifier">e</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> <span class="comment">// 5.49902 megaJoule |
| </span></pre> |
| <p> |
| </p> |
| <p> |
| (The complete set of <a href="http://physics.nist.gov/cuu/Units/prefixes.html" target="_top">engineering |
| and scientific multiples</a> is not used (not centi or deci for example), |
| but only powers of ten that are multiples of three, 10^3). |
| </p> |
| <p> |
| Similarly, the equivalent <a href="http://en.wikipedia.org/wiki/Binary_prefixes" target="_top">binary |
| prefixes</a> used for displaying computing kilobytes, megabytes, gigabytes... |
| </p> |
| <p> |
| These are the 2^10 = 1024, 2^20 = 1 048 576, 2^30 ... multiples. |
| </p> |
| <p> |
| (See also <a href="http://physics.nist.gov/cuu/Units/binary.html" target="_top">Prefixes |
| for binary multiples</a> |
| </p> |
| <p> |
| This scale is specified in IEC 60027-2, Second edition, 2000-11, Letter symbols |
| to be used in electrical technology - Part 2: Telecommunications and electronics). |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="comment">// Don't forget that the units name or symbol format specification is persistent. |
| </span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">symbol_format</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> <span class="comment">// Resets the format to the default symbol format. |
| </span> |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">byte_base_unit</span><span class="special">::</span><span class="identifier">unit_type</span><span class="special">></span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2048.</span> <span class="special">*</span> <span class="identifier">byte_base_unit</span><span class="special">::</span><span class="identifier">unit_type</span><span class="special">();</span> |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">engineering_prefix</span> <span class="special"><<</span> <span class="identifier">b</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> <span class="comment">// 2.048 kb |
| </span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">symbol_format</span> <span class="special"><<</span> <span class="identifier">binary_prefix</span> <span class="special"><<</span> <span class="identifier">b</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> <span class="comment">// "2 Kib" |
| </span></pre> |
| <p> |
| </p> |
| <p> |
| But note that scalar dimensionless values, like int, float and double, are |
| <span class="bold"><strong>not</strong></span> prefixed automatically by the engineering_prefix |
| or binary_prefix iostream manipulators. |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">const</span> <span class="keyword">double</span> <span class="identifier">s1</span> <span class="special">=</span> <span class="number">2345.6</span><span class="special">;</span> |
| <span class="keyword">const</span> <span class="keyword">long</span> <span class="identifier">x1</span> <span class="special">=</span> <span class="number">23456</span><span class="special">;</span> |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">engineering_prefix</span> <span class="special"><<</span> <span class="identifier">s1</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> <span class="comment">// 2345.6 |
| </span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">engineering_prefix</span> <span class="special"><<</span> <span class="identifier">x1</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> <span class="comment">// 23456 |
| </span> |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">binary_prefix</span> <span class="special"><<</span> <span class="identifier">s1</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> <span class="comment">// 2345.6 |
| </span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">binary_prefix</span> <span class="special"><<</span> <span class="identifier">x1</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> <span class="comment">// 23456 |
| </span></pre> |
| <p> |
| </p> |
| <p> |
| You can output the name or symbol of a unit (rather than the most common |
| quantity of a unit). |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">const</span> <span class="identifier">length</span> <span class="identifier">L</span><span class="special">;</span> <span class="comment">// A unit of length (but not a quantity of length). |
| </span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">L</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> <span class="comment">// Default length unit is meter, |
| </span><span class="comment">// but default is symbol format so output is just "m". |
| </span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">name_format</span> <span class="special"><<</span> <span class="identifier">L</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> <span class="comment">// default length name is "meter". |
| </span></pre> |
| <p> |
| </p> |
| <p> |
| Note too that all the formatting flags are persistent, so that if you set |
| engineering_prefix, then it applies to all future outputs, until you select |
| binary_prefix, or explicitly switch autoprefix off. You can specify no prefix |
| (the default of course) in two ways: |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">no_prefix</span><span class="special">(</span><span class="identifier">cout</span><span class="special">);</span> <span class="comment">// Clear any prefix flag. |
| </span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">no_prefix</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> <span class="comment">// Clear any prefix flag using `no_prefix` manipulator. |
| </span></pre> |
| <p> |
| </p> |
| <p> |
| And you can get the format flags for diagnosing problems. |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">get_autoprefix</span><span class="special">(</span><span class="identifier">cout</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> <span class="comment">// 8 is `autoprefix_binary` from `enum autoprefix_mode`. |
| </span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">get_format</span><span class="special">(</span><span class="identifier">cout</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> <span class="comment">// 1 is `name_fmt` from `enum format_mode`. |
| </span></pre> |
| <p> |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_units.Examples.ConversionFactor"></a><a class="link" href="Examples.html#boost_units.Examples.ConversionFactor" title="Conversion Factor">Conversion Factor</a> |
| </h3></div></div></div> |
| <p> |
| This code demonstrates the use of the <code class="computeroutput"><span class="identifier">conversion_factor</span></code> |
| free function to determine the scale factor between two units. |
| </p> |
| <p> |
| (<a href="../../../libs/units/example/conversion_factor.cpp" target="_top">conversion_factor.cpp</a>) |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">double</span> <span class="identifier">dyne_to_newton</span> <span class="special">=</span> |
| <span class="identifier">conversion_factor</span><span class="special">(</span><span class="identifier">cgs</span><span class="special">::</span><span class="identifier">dyne</span><span class="special">,</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">newton</span><span class="special">);</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">dyne_to_newton</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| |
| <span class="keyword">double</span> <span class="identifier">force_over_mass_conversion</span> <span class="special">=</span> |
| <span class="identifier">conversion_factor</span><span class="special">(</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">newton</span><span class="special">/</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">kilogram</span><span class="special">,</span><span class="identifier">cgs</span><span class="special">::</span><span class="identifier">dyne</span><span class="special">/</span><span class="identifier">cgs</span><span class="special">::</span><span class="identifier">gram</span><span class="special">);</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">force_over_mass_conversion</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| |
| <span class="keyword">double</span> <span class="identifier">momentum_conversion</span> <span class="special">=</span> |
| <span class="identifier">conversion_factor</span><span class="special">(</span><span class="identifier">cgs</span><span class="special">::</span><span class="identifier">momentum</span><span class="special">(),</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">momentum</span><span class="special">());</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">momentum_conversion</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| |
| <span class="keyword">double</span> <span class="identifier">momentum_over_mass_conversion</span> <span class="special">=</span> |
| <span class="identifier">conversion_factor</span><span class="special">(</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">momentum</span><span class="special">()/</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">mass</span><span class="special">(),</span><span class="identifier">cgs</span><span class="special">::</span><span class="identifier">momentum</span><span class="special">()/</span><span class="identifier">cgs</span><span class="special">::</span><span class="identifier">gram</span><span class="special">);</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">momentum_over_mass_conversion</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| |
| <span class="keyword">double</span> <span class="identifier">acceleration_conversion</span> <span class="special">=</span> |
| <span class="identifier">conversion_factor</span><span class="special">(</span><span class="identifier">cgs</span><span class="special">::</span><span class="identifier">gal</span><span class="special">,</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">meter_per_second_squared</span><span class="special">);</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">acceleration_conversion</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| |
| </pre> |
| <p> |
| </p> |
| <p> |
| Produces |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="number">1e-005</span> |
| <span class="number">100</span> |
| <span class="number">1e-005</span> |
| <span class="number">100</span> |
| <span class="number">0.01</span> |
| </pre> |
| <p> |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_units.Examples.RuntimeUnits"></a><a class="link" href="Examples.html#boost_units.Examples.RuntimeUnits" title="Runtime Units">Runtime Units</a> |
| </h3></div></div></div> |
| <p> |
| (<a href="../../../libs/units/example/runtime_unit.cpp" target="_top">runtime_unit.cpp</a>) |
| </p> |
| <p> |
| This example shows how to implement an interface that allow different units |
| at runtime while still maintaining type safety for internal calculations. |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">namespace</span> <span class="special">{</span> |
| |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">;</span> |
| <span class="keyword">using</span> <span class="identifier">imperial</span><span class="special">::</span><span class="identifier">foot_base_unit</span><span class="special">;</span> |
| |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">map</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">,</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">length</span><span class="special">></span> <span class="special">></span> <span class="identifier">known_units</span><span class="special">;</span> |
| |
| <span class="special">}</span> |
| |
| <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">length</span><span class="special">></span> <span class="identifier">calculate</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">length</span><span class="special">>&</span> <span class="identifier">t</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">hypot</span><span class="special">(</span><span class="identifier">t</span><span class="special">,</span> <span class="number">2.0</span> <span class="special">*</span> <span class="identifier">si</span><span class="special">::</span><span class="identifier">meters</span><span class="special">));</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="identifier">known_units</span><span class="special">[</span><span class="string">"meter"</span><span class="special">]</span> <span class="special">=</span> <span class="number">1.0</span> <span class="special">*</span> <span class="identifier">si</span><span class="special">::</span><span class="identifier">meters</span><span class="special">;</span> |
| <span class="identifier">known_units</span><span class="special">[</span><span class="string">"centimeter"</span><span class="special">]</span> <span class="special">=</span> <span class="special">.</span><span class="number">01</span> <span class="special">*</span> <span class="identifier">si</span><span class="special">::</span><span class="identifier">meters</span><span class="special">;</span> |
| <span class="identifier">known_units</span><span class="special">[</span><span class="string">"foot"</span><span class="special">]</span> <span class="special">=</span> |
| <span class="identifier">conversion_factor</span><span class="special">(</span><span class="identifier">foot_base_unit</span><span class="special">::</span><span class="identifier">unit_type</span><span class="special">(),</span> <span class="identifier">si</span><span class="special">::</span><span class="identifier">meter</span><span class="special">)</span> <span class="special">*</span> <span class="identifier">si</span><span class="special">::</span><span class="identifier">meter</span><span class="special">;</span> |
| |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">output_type</span><span class="special">(</span><span class="string">"meter"</span><span class="special">);</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">input</span><span class="special">;</span> |
| |
| <span class="keyword">while</span><span class="special">((</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"> "</span><span class="special">)</span> <span class="special">&&</span> <span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">cin</span> <span class="special">>></span> <span class="identifier">input</span><span class="special">))</span> |
| <span class="special">{</span> |
| <span class="keyword">if</span><span class="special">(!</span><span class="identifier">input</span><span class="special">.</span><span class="identifier">empty</span><span class="special">()</span> <span class="special">&&</span> <span class="identifier">input</span><span class="special">[</span><span class="number">0</span><span class="special">]</span> <span class="special">==</span> <span class="char">'#'</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">getline</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">cin</span><span class="special">,</span> <span class="identifier">input</span><span class="special">);</span> |
| <span class="special">}</span> |
| <span class="keyword">else</span> <span class="keyword">if</span><span class="special">(</span><span class="identifier">input</span> <span class="special">==</span> <span class="string">"exit"</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">break</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="keyword">else</span> <span class="keyword">if</span><span class="special">(</span><span class="identifier">input</span> <span class="special">==</span> <span class="string">"help"</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"type \"exit\" to exit\n"</span> |
| <span class="string">"type \"return 'unit'\" to set the return units\n"</span> |
| <span class="string">"type \"'number' 'unit'\" to do a simple calculation"</span> |
| <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="keyword">else</span> <span class="keyword">if</span><span class="special">(</span><span class="identifier">input</span> <span class="special">==</span> <span class="string">"return"</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">if</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">cin</span> <span class="special">>></span> <span class="identifier">input</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">if</span><span class="special">(</span><span class="identifier">known_units</span><span class="special">.</span><span class="identifier">find</span><span class="special">(</span><span class="identifier">input</span><span class="special">)</span> <span class="special">!=</span> <span class="identifier">known_units</span><span class="special">.</span><span class="identifier">end</span><span class="special">())</span> |
| <span class="special">{</span> |
| <span class="identifier">output_type</span> <span class="special">=</span> <span class="identifier">input</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Done."</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="keyword">else</span> |
| <span class="special">{</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Unknown unit \""</span> <span class="special"><<</span> <span class="identifier">input</span> <span class="special"><<</span> <span class="string">"\""</span> |
| <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="special">}</span> |
| <span class="keyword">else</span> |
| <span class="special">{</span> |
| <span class="keyword">break</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="special">}</span> |
| <span class="keyword">else</span> |
| <span class="special">{</span> |
| <span class="keyword">try</span> |
| <span class="special">{</span> |
| <span class="keyword">double</span> <span class="identifier">value</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">lexical_cast</span><span class="special"><</span><span class="keyword">double</span><span class="special">>(</span><span class="identifier">input</span><span class="special">);</span> |
| |
| <span class="keyword">if</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">cin</span> <span class="special">>></span> <span class="identifier">input</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">if</span><span class="special">(</span><span class="identifier">known_units</span><span class="special">.</span><span class="identifier">find</span><span class="special">(</span><span class="identifier">input</span><span class="special">)</span> <span class="special">!=</span> <span class="identifier">known_units</span><span class="special">.</span><span class="identifier">end</span><span class="special">())</span> |
| <span class="special">{</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">double</span><span class="special">>(</span> |
| <span class="identifier">calculate</span><span class="special">(</span><span class="identifier">value</span> <span class="special">*</span> <span class="identifier">known_units</span><span class="special">[</span><span class="identifier">input</span><span class="special">])</span> <span class="special">/</span> |
| <span class="identifier">known_units</span><span class="special">[</span><span class="identifier">output_type</span><span class="special">])</span> |
| <span class="special"><<</span> <span class="char">' '</span> <span class="special"><<</span> <span class="identifier">output_type</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="keyword">else</span> |
| <span class="special">{</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Unknown unit \""</span> <span class="special"><<</span> <span class="identifier">input</span> <span class="special"><<</span> <span class="string">"\""</span> |
| <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="special">}</span> |
| <span class="keyword">else</span> |
| <span class="special">{</span> |
| <span class="keyword">break</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="special">}</span> |
| <span class="keyword">catch</span><span class="special">(...)</span> |
| <span class="special">{</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Input error"</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="special">}</span> |
| <span class="special">}</span> |
| <span class="special">}</span> |
| |
| </pre> |
| <p> |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_units.Examples.lambda"></a><a class="link" href="Examples.html#boost_units.Examples.lambda" title="Interoperability with Boost.Lambda">Interoperability with Boost.Lambda</a> |
| </h3></div></div></div> |
| <p> |
| (<a href="../../../libs/units/example/lambda.cpp" target="_top">lambda.cpp</a>) |
| </p> |
| <p> |
| The header <code class="computeroutput"><a class="link" href="Reference.html#header.boost.units.lambda_hpp" title="Header <boost/units/lambda.hpp>">boost/units/lambda.hpp</a></code> |
| provides overloads and specializations needed to make Boost.Units usable |
| with the Boost.Lambda library. |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">argc</span><span class="special">,</span> <span class="keyword">char</span> <span class="special">**</span><span class="identifier">argv</span><span class="special">)</span> <span class="special">{</span> |
| |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span class="special">;</span> |
| <span class="keyword">namespace</span> <span class="identifier">bl</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">lambda</span><span class="special">;</span> |
| <span class="keyword">namespace</span> <span class="identifier">bu</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">;</span> |
| <span class="keyword">namespace</span> <span class="identifier">si</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">units</span><span class="special">::</span><span class="identifier">si</span><span class="special">;</span> |
| |
| |
| <span class="comment">//////////////////////////////////////////////////////////////////////// |
| </span> <span class="comment">// Mechanical example: linear accelerated movement |
| </span> <span class="comment">//////////////////////////////////////////////////////////////////////// |
| </span> |
| <span class="comment">// Initial condition variables for acceleration, speed, and displacement |
| </span> <span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">acceleration</span><span class="special">></span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">2.0</span> <span class="special">*</span> <span class="identifier">si</span><span class="special">::</span><span class="identifier">meters_per_second_squared</span><span class="special">;</span> |
| <span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">velocity</span><span class="special">></span> <span class="identifier">v</span> <span class="special">=</span> <span class="number">1.0</span> <span class="special">*</span> <span class="identifier">si</span><span class="special">::</span><span class="identifier">meters_per_second</span><span class="special">;</span> |
| <span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">length</span><span class="special">></span> <span class="identifier">s0</span> <span class="special">=</span> <span class="number">0.5</span> <span class="special">*</span> <span class="identifier">si</span><span class="special">::</span><span class="identifier">meter</span><span class="special">;</span> |
| |
| <span class="comment">// Displacement over time |
| </span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">function</span><span class="special"><</span><span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">length</span><span class="special">></span> <span class="special">(</span><span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">time</span><span class="special">>)</span> <span class="special">></span> |
| <span class="identifier">s</span> <span class="special">=</span> <span class="number">0.5</span> <span class="special">*</span> <span class="identifier">bl</span><span class="special">::</span><span class="identifier">var</span><span class="special">(</span><span class="identifier">a</span><span class="special">)</span> <span class="special">*</span> <span class="identifier">bl</span><span class="special">::</span><span class="identifier">_1</span> <span class="special">*</span> <span class="identifier">bl</span><span class="special">::</span><span class="identifier">_1</span> |
| <span class="special">+</span> <span class="identifier">bl</span><span class="special">::</span><span class="identifier">var</span><span class="special">(</span><span class="identifier">v</span><span class="special">)</span> <span class="special">*</span> <span class="identifier">bl</span><span class="special">::</span><span class="identifier">_1</span> |
| <span class="special">+</span> <span class="identifier">bl</span><span class="special">::</span><span class="identifier">var</span><span class="special">(</span><span class="identifier">s0</span><span class="special">);</span> |
| |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Linear accelerated movement:"</span> <span class="special"><<</span> <span class="identifier">endl</span> |
| <span class="special"><<</span> <span class="string">"a = "</span> <span class="special"><<</span> <span class="identifier">a</span> <span class="special"><<</span> <span class="string">", v = "</span> <span class="special"><<</span> <span class="identifier">v</span> <span class="special"><<</span> <span class="string">", s0 = "</span> <span class="special"><<</span> <span class="identifier">s0</span> <span class="special"><<</span> <span class="identifier">endl</span> |
| <span class="special"><<</span> <span class="string">"s(1.0 * si::second) = "</span> <span class="special"><<</span> <span class="identifier">s</span><span class="special">(</span><span class="number">1.0</span> <span class="special">*</span> <span class="identifier">si</span><span class="special">::</span><span class="identifier">second</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">endl</span> |
| <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> |
| |
| <span class="comment">// Change initial conditions |
| </span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1.0</span> <span class="special">*</span> <span class="identifier">si</span><span class="special">::</span><span class="identifier">meters_per_second_squared</span><span class="special">;</span> |
| <span class="identifier">v</span> <span class="special">=</span> <span class="number">2.0</span> <span class="special">*</span> <span class="identifier">si</span><span class="special">::</span><span class="identifier">meters_per_second</span><span class="special">;</span> |
| <span class="identifier">s0</span> <span class="special">=</span> <span class="special">-</span><span class="number">1.5</span> <span class="special">*</span> <span class="identifier">si</span><span class="special">::</span><span class="identifier">meter</span><span class="special">;</span> |
| |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"a = "</span> <span class="special"><<</span> <span class="identifier">a</span> <span class="special"><<</span> <span class="string">", v = "</span> <span class="special"><<</span> <span class="identifier">v</span> <span class="special"><<</span> <span class="string">", s0 = "</span> <span class="special"><<</span> <span class="identifier">s0</span> <span class="special"><<</span> <span class="identifier">endl</span> |
| <span class="special"><<</span> <span class="string">"s(1.0 * si::second) = "</span> <span class="special"><<</span> <span class="identifier">s</span><span class="special">(</span><span class="number">1.0</span> <span class="special">*</span> <span class="identifier">si</span><span class="special">::</span><span class="identifier">second</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">endl</span> |
| <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> |
| |
| |
| <span class="comment">//////////////////////////////////////////////////////////////////////// |
| </span> <span class="comment">// Electrical example: oscillating current |
| </span> <span class="comment">//////////////////////////////////////////////////////////////////////// |
| </span> |
| <span class="comment">// Constants for the current amplitude, frequency, and offset current |
| </span> <span class="keyword">const</span> <span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">current</span><span class="special">></span> <span class="identifier">iamp</span> <span class="special">=</span> <span class="number">1.5</span> <span class="special">*</span> <span class="identifier">si</span><span class="special">::</span><span class="identifier">ampere</span><span class="special">;</span> |
| <span class="keyword">const</span> <span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">frequency</span><span class="special">></span> <span class="identifier">f</span> <span class="special">=</span> <span class="number">1.0e3</span> <span class="special">*</span> <span class="identifier">si</span><span class="special">::</span><span class="identifier">hertz</span><span class="special">;</span> |
| <span class="keyword">const</span> <span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">current</span><span class="special">></span> <span class="identifier">i0</span> <span class="special">=</span> <span class="number">0.5</span> <span class="special">*</span> <span class="identifier">si</span><span class="special">::</span><span class="identifier">ampere</span><span class="special">;</span> |
| |
| <span class="comment">// The invocation of the sin function needs to be postponed using |
| </span> <span class="comment">// bind to specify the oscillation function. A lengthy static_cast |
| </span> <span class="comment">// to the function pointer referencing boost::units::sin() is needed |
| </span> <span class="comment">// to avoid an "unresolved overloaded function type" error. |
| </span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">function</span><span class="special"><</span><span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">current</span><span class="special">></span> <span class="special">(</span><span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">time</span><span class="special">>)</span> <span class="special">></span> |
| <span class="identifier">i</span> <span class="special">=</span> <span class="identifier">iamp</span> |
| <span class="special">*</span> <span class="identifier">bl</span><span class="special">::</span><span class="identifier">bind</span><span class="special">(</span><span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">bu</span><span class="special">::</span><span class="identifier">dimensionless_quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">system</span><span class="special">,</span> <span class="keyword">double</span><span class="special">>::</span><span class="identifier">type</span> <span class="special">(*)(</span><span class="keyword">const</span> <span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">plane_angle</span><span class="special">>&)>(</span><span class="identifier">bu</span><span class="special">::</span><span class="identifier">sin</span><span class="special">),</span> |
| <span class="number">2.0</span> <span class="special">*</span> <span class="identifier">pi</span> <span class="special">*</span> <span class="identifier">si</span><span class="special">::</span><span class="identifier">radian</span> <span class="special">*</span> <span class="identifier">f</span> <span class="special">*</span> <span class="identifier">bl</span><span class="special">::</span><span class="identifier">_1</span><span class="special">)</span> |
| <span class="special">+</span> <span class="identifier">i0</span><span class="special">;</span> |
| |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Oscillating current:"</span> <span class="special"><<</span> <span class="identifier">endl</span> |
| <span class="special"><<</span> <span class="string">"iamp = "</span> <span class="special"><<</span> <span class="identifier">iamp</span> <span class="special"><<</span> <span class="string">", f = "</span> <span class="special"><<</span> <span class="identifier">f</span> <span class="special"><<</span> <span class="string">", i0 = "</span> <span class="special"><<</span> <span class="identifier">i0</span> <span class="special"><<</span> <span class="identifier">endl</span> |
| <span class="special"><<</span> <span class="string">"i(1.25e-3 * si::second) = "</span> <span class="special"><<</span> <span class="identifier">i</span><span class="special">(</span><span class="number">1.25e-3</span> <span class="special">*</span> <span class="identifier">si</span><span class="special">::</span><span class="identifier">second</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">endl</span> |
| <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> |
| |
| |
| <span class="comment">//////////////////////////////////////////////////////////////////////// |
| </span> <span class="comment">// Geometric example: area calculation for a square |
| </span> <span class="comment">//////////////////////////////////////////////////////////////////////// |
| </span> |
| <span class="comment">// Length constant |
| </span> <span class="keyword">const</span> <span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">length</span><span class="special">></span> <span class="identifier">l</span> <span class="special">=</span> <span class="number">1.5</span> <span class="special">*</span> <span class="identifier">si</span><span class="special">::</span><span class="identifier">meter</span><span class="special">;</span> |
| |
| <span class="comment">// Again an ugly static_cast is needed to bind pow<2> to the first |
| </span> <span class="comment">// function argument. |
| </span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">function</span><span class="special"><</span><span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">area</span><span class="special">></span> <span class="special">(</span><span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">length</span><span class="special">>)</span> <span class="special">></span> |
| <span class="identifier">A</span> <span class="special">=</span> <span class="identifier">bl</span><span class="special">::</span><span class="identifier">bind</span><span class="special">(</span><span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">area</span><span class="special">></span> <span class="special">(*)(</span><span class="keyword">const</span> <span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">length</span><span class="special">>&)>(</span><span class="identifier">bu</span><span class="special">::</span><span class="identifier">pow</span><span class="special"><</span><span class="number">2</span><span class="special">>),</span> |
| <span class="identifier">bl</span><span class="special">::</span><span class="identifier">_1</span><span class="special">);</span> |
| |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Area of a square:"</span> <span class="special"><<</span> <span class="identifier">endl</span> |
| <span class="special"><<</span> <span class="string">"A("</span> <span class="special"><<</span> <span class="identifier">l</span> <span class="special"><<</span><span class="string">") = "</span> <span class="special"><<</span> <span class="identifier">A</span><span class="special">(</span><span class="identifier">l</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">endl</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> |
| |
| |
| <span class="comment">//////////////////////////////////////////////////////////////////////// |
| </span> <span class="comment">// Thermal example: temperature difference of two absolute temperatures |
| </span> <span class="comment">//////////////////////////////////////////////////////////////////////// |
| </span> |
| <span class="comment">// Absolute temperature constants |
| </span> <span class="keyword">const</span> <span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">bu</span><span class="special">::</span><span class="identifier">absolute</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">temperature</span><span class="special">></span> <span class="special">></span> |
| <span class="identifier">Tref</span> <span class="special">=</span> <span class="number">273.15</span> <span class="special">*</span> <span class="identifier">bu</span><span class="special">::</span><span class="identifier">absolute</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">temperature</span><span class="special">>();</span> |
| <span class="keyword">const</span> <span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">bu</span><span class="special">::</span><span class="identifier">absolute</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">temperature</span><span class="special">></span> <span class="special">></span> |
| <span class="identifier">Tamb</span> <span class="special">=</span> <span class="number">300.00</span> <span class="special">*</span> <span class="identifier">bu</span><span class="special">::</span><span class="identifier">absolute</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">temperature</span><span class="special">>();</span> |
| |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">function</span><span class="special"><</span><span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">temperature</span><span class="special">></span> <span class="special">(</span><span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">bu</span><span class="special">::</span><span class="identifier">absolute</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">temperature</span><span class="special">></span> <span class="special">>,</span> |
| <span class="identifier">bu</span><span class="special">::</span><span class="identifier">quantity</span><span class="special"><</span><span class="identifier">bu</span><span class="special">::</span><span class="identifier">absolute</span><span class="special"><</span><span class="identifier">si</span><span class="special">::</span><span class="identifier">temperature</span><span class="special">></span> <span class="special">>)></span> |
| <span class="identifier">dT</span> <span class="special">=</span> <span class="identifier">bl</span><span class="special">::</span><span class="identifier">_2</span> <span class="special">-</span> <span class="identifier">bl</span><span class="special">::</span><span class="identifier">_1</span><span class="special">;</span> |
| |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Temperature difference of two absolute temperatures:"</span> <span class="special"><<</span> <span class="identifier">endl</span> |
| <span class="special"><<</span> <span class="string">"dT("</span> <span class="special"><<</span> <span class="identifier">Tref</span> <span class="special"><<</span> <span class="string">", "</span> <span class="special"><<</span> <span class="identifier">Tamb</span> <span class="special"><<</span> <span class="string">") = "</span> <span class="special"><<</span> <span class="identifier">dT</span><span class="special">(</span><span class="identifier">Tref</span><span class="special">,</span> <span class="identifier">Tamb</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">endl</span> |
| <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> |
| |
| |
| <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| </p> |
| </div> |
| </div> |
| <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> |
| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2003 -2008 Matthias Christian Schabel, 2007-2010 Steven |
| Watanabe<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) |
| </p> |
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