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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">&lt;</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">&gt;</span>
<span class="identifier">default_distance_result</span><span class="special">&lt;</span><span class="identifier">Geometry1</span><span class="special">,</span> <span class="identifier">Geometry2</span><span class="special">&gt;::</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">&amp;</span> <span class="identifier">geometry1</span><span class="special">,</span> <span class="identifier">Geometry2</span> <span class="keyword">const</span> <span class="special">&amp;</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 &amp;
</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 &amp;
</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">&lt;</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">&gt;</span></code>
</p>
<p>
Or
</p>
<p>
<code class="computeroutput"><span class="preprocessor">#include</span> <span class="special">&lt;</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">&gt;</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">&lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</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">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</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">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</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">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</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">&gt;</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">&lt;</span><span class="keyword">double</span><span class="special">&gt;</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">&lt;</span><span class="identifier">point_type</span><span class="special">&gt;</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">&lt;=</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">&lt;=</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">&lt;</span><span class="keyword">double</span><span class="special">&gt;::</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">&amp;</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">&lt;</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">&lt;&lt;</span> <span class="string">"Closest: "</span> <span class="special">&lt;&lt;</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">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span>
<span class="special">&lt;&lt;</span> <span class="string">"At: "</span> <span class="special">&lt;&lt;</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">&lt;&lt;</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>
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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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