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<title>for_each_segment (const version)</title>
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<a name="geometry.reference.algorithms.for_each.for_each_segment_2_const_version"></a><a class="link" href="for_each_segment_2_const_version.html" title="for_each_segment (const version)">for_each_segment
(const version)</a>
</h5></div></div></div>
<p>
<a class="indexterm" name="id868461"></a>
Applies function <span class="bold"><strong>f</strong></span> to each segment.
</p>
<a name="geometry.reference.algorithms.for_each.for_each_segment_2_const_version.description"></a><h6>
<a name="geometry.reference.algorithms.for_each.for_each_segment_2_const_version.description-heading"></a>
<a class="link" href="for_each_segment_2_const_version.html#geometry.reference.algorithms.for_each.for_each_segment_2_const_version.description">Description</a>
</h6>
<p>
Applies a function <span class="bold"><strong>f</strong></span> (functor, having
operator() defined) to each segment making up the geometry
</p>
<a name="geometry.reference.algorithms.for_each.for_each_segment_2_const_version.synopsis"></a><h6>
<a name="geometry.reference.algorithms.for_each.for_each_segment_2_const_version.synopsis-heading"></a>
<a class="link" href="for_each_segment_2_const_version.html#geometry.reference.algorithms.for_each.for_each_segment_2_const_version.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">Geometry</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Functor</span><span class="special">&gt;</span>
<span class="identifier">Functor</span> <span class="identifier">for_each_segment</span><span class="special">(</span><span class="identifier">Geometry</span> <span class="keyword">const</span> <span class="special">&amp;</span> <span class="identifier">geometry</span><span class="special">,</span> <span class="identifier">Functor</span> <span class="identifier">f</span><span class="special">)</span></pre>
<p>
</p>
<a name="geometry.reference.algorithms.for_each.for_each_segment_2_const_version.parameters"></a><h6>
<a name="geometry.reference.algorithms.for_each.for_each_segment_2_const_version.parameters-heading"></a>
<a class="link" href="for_each_segment_2_const_version.html#geometry.reference.algorithms.for_each.for_each_segment_2_const_version.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>
Geometry const &amp;
</p>
</td>
<td>
<p>
Any type fulfilling a Geometry Concept
</p>
</td>
<td>
<p>
geometry
</p>
</td>
<td>
<p>
A model of the specified concept
</p>
</td>
</tr>
<tr>
<td>
<p>
Functor
</p>
</td>
<td>
<p>
Function or class with operator()
</p>
</td>
<td>
<p>
f
</p>
</td>
<td>
<p>
Unary function, taking a const segment as argument
</p>
</td>
</tr>
</tbody>
</table></div>
<a name="geometry.reference.algorithms.for_each.for_each_segment_2_const_version.header"></a><h6>
<a name="geometry.reference.algorithms.for_each.for_each_segment_2_const_version.header-heading"></a>
<a class="link" href="for_each_segment_2_const_version.html#geometry.reference.algorithms.for_each.for_each_segment_2_const_version.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">for_each</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
</p>
<a name="geometry.reference.algorithms.for_each.for_each_segment_2_const_version.example"></a><h6>
<a name="geometry.reference.algorithms.for_each.for_each_segment_2_const_version.example-heading"></a>
<a class="link" href="for_each_segment_2_const_version.html#geometry.reference.algorithms.for_each.for_each_segment_2_const_version.example">Example</a>
</h6>
<p>
Sample using for_each_segment, using a functor to get the minimum and
maximum length of a segment in a linestring
</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">linestring</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">assign</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
<span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Segment</span><span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">gather_segment_statistics</span>
<span class="special">{</span>
<span class="comment">// Remember that if coordinates are integer, the length might be floating point</span>
<span class="comment">// So use "double" for integers. In other cases, use coordinate type</span>
<span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">select_most_precise</span>
<span class="special">&lt;</span>
<span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">coordinate_type</span><span class="special">&lt;</span><span class="identifier">Segment</span><span class="special">&gt;::</span><span class="identifier">type</span><span class="special">,</span>
<span class="keyword">double</span>
<span class="special">&gt;::</span><span class="identifier">type</span> <span class="identifier">type</span><span class="special">;</span>
<span class="identifier">type</span> <span class="identifier">min_length</span><span class="special">,</span> <span class="identifier">max_length</span><span class="special">;</span>
<span class="comment">// Initialize min and max</span>
<span class="identifier">gather_segment_statistics</span><span class="special">()</span>
<span class="special">:</span> <span class="identifier">min_length</span><span class="special">(</span><span class="number">1e38</span><span class="special">)</span>
<span class="special">,</span> <span class="identifier">max_length</span><span class="special">(-</span><span class="number">1</span><span class="special">)</span>
<span class="special">{}</span>
<span class="comment">// This operator is called for each segment</span>
<span class="keyword">inline</span> <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()(</span><span class="identifier">Segment</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">s</span><span class="special">)</span>
<span class="special">{</span>
<span class="identifier">type</span> <span class="identifier">length</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">length</span><span class="special">(</span><span class="identifier">s</span><span class="special">);</span>
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">length</span> <span class="special">&lt;</span> <span class="identifier">min_length</span><span class="special">)</span> <span class="identifier">min_length</span> <span class="special">=</span> <span class="identifier">length</span><span class="special">;</span>
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">length</span> <span class="special">&gt;</span> <span class="identifier">max_length</span><span class="special">)</span> <span class="identifier">max_length</span> <span class="special">=</span> <span class="identifier">length</span><span class="special">;</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="comment">// Bring "+=" for a vector into scope</span>
<span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">assign</span><span class="special">;</span>
<span class="comment">// Define a type</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</span><span class="special">;</span>
<span class="comment">// Declare a linestring</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">linestring</span><span class="special">&lt;</span><span class="identifier">point</span><span class="special">&gt;</span> <span class="identifier">polyline</span><span class="special">;</span>
<span class="comment">// Use Boost.Assign to initialize a linestring</span>
<span class="identifier">polyline</span> <span class="special">+=</span> <span class="identifier">point</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">point</span><span class="special">(</span><span class="number">3</span><span class="special">,</span> <span class="number">3</span><span class="special">),</span> <span class="identifier">point</span><span class="special">(</span><span class="number">5</span><span class="special">,</span> <span class="number">1</span><span class="special">),</span> <span class="identifier">point</span><span class="special">(</span><span class="number">6</span><span class="special">,</span> <span class="number">2</span><span class="special">),</span>
<span class="identifier">point</span><span class="special">(</span><span class="number">8</span><span class="special">,</span> <span class="number">0</span><span class="special">),</span> <span class="identifier">point</span><span class="special">(</span><span class="number">4</span><span class="special">,</span> <span class="special">-</span><span class="number">4</span><span class="special">),</span> <span class="identifier">point</span><span class="special">(</span><span class="number">1</span><span class="special">,</span> <span class="special">-</span><span class="number">1</span><span class="special">),</span> <span class="identifier">point</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="comment">// Declare the gathering class...</span>
<span class="identifier">gather_segment_statistics</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">model</span><span class="special">::</span><span class="identifier">referring_segment</span><span class="special">&lt;</span><span class="identifier">point</span><span class="special">&gt;</span>
<span class="special">&gt;</span> <span class="identifier">functor</span><span class="special">;</span>
<span class="comment">// ... and use it, the essention.</span>
<span class="comment">// As also in std::for_each it is a const value, so retrieve it as a return value.</span>
<span class="identifier">functor</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">for_each_segment</span><span class="special">(</span><span class="identifier">polyline</span><span class="special">,</span> <span class="identifier">functor</span><span class="special">);</span>
<span class="comment">// Output the results</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span>
<span class="special">&lt;&lt;</span> <span class="string">"Min segment length: "</span> <span class="special">&lt;&lt;</span> <span class="identifier">functor</span><span class="special">.</span><span class="identifier">min_length</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">"Max segment length: "</span> <span class="special">&lt;&lt;</span> <span class="identifier">functor</span><span class="special">.</span><span class="identifier">max_length</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">Min segment length: 1.41421
Max segment length: 5.65685
</pre>
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<td align="right"><div class="copyright-footer">Copyright &#169; 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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