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| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="geometry.reference.algorithms.distance.comparable_distance"></a><a class="link" href="comparable_distance.html" title="comparable_distance">comparable_distance</a> |
| </h5></div></div></div> |
| <p> |
| <a class="indexterm" name="id852133"></a> |
| Calculate the comparable distance measurement of two geometries. |
| </p> |
| <a name="geometry.reference.algorithms.distance.comparable_distance.description"></a><h6> |
| <a name="geometry.reference.algorithms.distance.comparable_distance.description-heading"></a> |
| <a class="link" href="comparable_distance.html#geometry.reference.algorithms.distance.comparable_distance.description">Description</a> |
| </h6> |
| <p> |
| The free function comparable_distance does not necessarily calculate |
| the distance, but it calculates a distance measure such that two distances |
| are comparable to each other. For example: for the Cartesian coordinate |
| system, Pythagoras is used but the square root is not taken, which makes |
| it faster and the results of two point pairs can still be compared to |
| each other. |
| </p> |
| <a name="geometry.reference.algorithms.distance.comparable_distance.synopsis"></a><h6> |
| <a name="geometry.reference.algorithms.distance.comparable_distance.synopsis-heading"></a> |
| <a class="link" href="comparable_distance.html#geometry.reference.algorithms.distance.comparable_distance.synopsis">Synopsis</a> |
| </h6> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Geometry1</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Geometry2</span><span class="special">></span> |
| <span class="identifier">default_distance_result</span><span class="special"><</span><span class="identifier">Geometry1</span><span class="special">,</span> <span class="identifier">Geometry2</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">comparable_distance</span><span class="special">(</span><span class="identifier">Geometry1</span> <span class="keyword">const</span> <span class="special">&</span> <span class="identifier">geometry1</span><span class="special">,</span> <span class="identifier">Geometry2</span> <span class="keyword">const</span> <span class="special">&</span> <span class="identifier">geometry2</span><span class="special">)</span></pre> |
| <p> |
| </p> |
| <a name="geometry.reference.algorithms.distance.comparable_distance.parameters"></a><h6> |
| <a name="geometry.reference.algorithms.distance.comparable_distance.parameters-heading"></a> |
| <a class="link" href="comparable_distance.html#geometry.reference.algorithms.distance.comparable_distance.parameters">Parameters</a> |
| </h6> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| Type |
| </p> |
| </th> |
| <th> |
| <p> |
| Concept |
| </p> |
| </th> |
| <th> |
| <p> |
| Name |
| </p> |
| </th> |
| <th> |
| <p> |
| Description |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| Geometry1 const & |
| </p> |
| </td> |
| <td> |
| <p> |
| first geometry type |
| </p> |
| </td> |
| <td> |
| <p> |
| geometry1 |
| </p> |
| </td> |
| <td> |
| <p> |
| A model of the specified concept |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| Geometry2 const & |
| </p> |
| </td> |
| <td> |
| <p> |
| second geometry type |
| </p> |
| </td> |
| <td> |
| <p> |
| geometry2 |
| </p> |
| </td> |
| <td> |
| <p> |
| A model of the specified concept |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| <a name="geometry.reference.algorithms.distance.comparable_distance.returns"></a><h6> |
| <a name="geometry.reference.algorithms.distance.comparable_distance.returns-heading"></a> |
| <a class="link" href="comparable_distance.html#geometry.reference.algorithms.distance.comparable_distance.returns">Returns</a> |
| </h6> |
| <p> |
| The calculated comparable distance |
| </p> |
| <a name="geometry.reference.algorithms.distance.comparable_distance.header"></a><h6> |
| <a name="geometry.reference.algorithms.distance.comparable_distance.header-heading"></a> |
| <a class="link" href="comparable_distance.html#geometry.reference.algorithms.distance.comparable_distance.header">Header</a> |
| </h6> |
| <p> |
| Either |
| </p> |
| <p> |
| <code class="computeroutput"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code> |
| </p> |
| <p> |
| Or |
| </p> |
| <p> |
| <code class="computeroutput"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">/</span><span class="identifier">algorithms</span><span class="special">/</span><span class="identifier">comparable_distance</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code> |
| </p> |
| <a name="geometry.reference.algorithms.distance.comparable_distance.behaviour"></a><h6> |
| <a name="geometry.reference.algorithms.distance.comparable_distance.behaviour-heading"></a> |
| <a class="link" href="comparable_distance.html#geometry.reference.algorithms.distance.comparable_distance.behaviour">Behaviour</a> |
| </h6> |
| <p> |
| There is no (not yet) version with a strategy. |
| </p> |
| <p> |
| It depends on the coordinate system of the geometry's point type if there |
| is a strategy available which can determine (more efficient than the |
| standard strategy) a measure of comparable distance. |
| </p> |
| <a name="geometry.reference.algorithms.distance.comparable_distance.complexity"></a><h6> |
| <a name="geometry.reference.algorithms.distance.comparable_distance.complexity-heading"></a> |
| <a class="link" href="comparable_distance.html#geometry.reference.algorithms.distance.comparable_distance.complexity">Complexity</a> |
| </h6> |
| <p> |
| Linear |
| </p> |
| <a name="geometry.reference.algorithms.distance.comparable_distance.example"></a><h6> |
| <a name="geometry.reference.algorithms.distance.comparable_distance.example-heading"></a> |
| <a class="link" href="comparable_distance.html#geometry.reference.algorithms.distance.comparable_distance.example">Example</a> |
| </h6> |
| <p> |
| Shows how to efficiently get the closest point |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> |
| |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">/</span><span class="identifier">geometries</span><span class="special">/</span><span class="identifier">point_xy</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">numeric</span><span class="special">/</span><span class="identifier">conversion</span><span class="special">/</span><span class="identifier">bounds</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">foreach</span><span class="special">.</span><span class="identifier">hpp</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="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">model</span><span class="special">::</span><span class="identifier">d2</span><span class="special">::</span><span class="identifier">point_xy</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">point_type</span><span class="special">;</span> |
| |
| <span class="identifier">point_type</span> <span class="identifier">p</span><span class="special">(</span><span class="number">1.4</span><span class="special">,</span> <span class="number">2.6</span><span class="special">);</span> |
| |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="identifier">point_type</span><span class="special">></span> <span class="identifier">v</span><span class="special">;</span> |
| <span class="keyword">for</span> <span class="special">(</span><span class="keyword">double</span> <span class="identifier">x</span> <span class="special">=</span> <span class="number">0.0</span><span class="special">;</span> <span class="identifier">x</span> <span class="special"><=</span> <span class="number">4.0</span><span class="special">;</span> <span class="identifier">x</span><span class="special">++)</span> |
| <span class="special">{</span> |
| <span class="keyword">for</span> <span class="special">(</span><span class="keyword">double</span> <span class="identifier">y</span> <span class="special">=</span> <span class="number">0.0</span><span class="special">;</span> <span class="identifier">y</span> <span class="special"><=</span> <span class="number">4.0</span><span class="special">;</span> <span class="identifier">y</span><span class="special">++)</span> |
| <span class="special">{</span> |
| <span class="identifier">v</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="identifier">point_type</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="special">}</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">point_type</span> <span class="identifier">min_p</span><span class="special">;</span> |
| <span class="keyword">double</span> <span class="identifier">min_d</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">numeric</span><span class="special">::</span><span class="identifier">bounds</span><span class="special"><</span><span class="keyword">double</span><span class="special">>::</span><span class="identifier">highest</span><span class="special">();</span> |
| <span class="identifier">BOOST_FOREACH</span><span class="special">(</span><span class="identifier">point_type</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">pv</span><span class="special">,</span> <span class="identifier">v</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">double</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">comparable_distance</span><span class="special">(</span><span class="identifier">p</span><span class="special">,</span> <span class="identifier">pv</span><span class="special">);</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">d</span> <span class="special"><</span> <span class="identifier">min_d</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">min_d</span> <span class="special">=</span> <span class="identifier">d</span><span class="special">;</span> |
| <span class="identifier">min_p</span> <span class="special">=</span> <span class="identifier">pv</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">cout</span> |
| <span class="special"><<</span> <span class="string">"Closest: "</span> <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">dsv</span><span class="special">(</span><span class="identifier">min_p</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="string">"At: "</span> <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">distance</span><span class="special">(</span><span class="identifier">p</span><span class="special">,</span> <span class="identifier">min_p</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="keyword">return</span> <span class="number">0</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| </pre> |
| <p> |
| </p> |
| <p> |
| Output: |
| </p> |
| <pre class="programlisting">Closest: (1, 3) |
| At: 0.565685 |
| </pre> |
| </div> |
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| <td align="right"><div class="copyright-footer">Copyright © 2011 Barend Gehrels, Bruno Lalande, Mateusz Loskot<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>) |
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