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POboost::geometry: How to do for_each_segment?
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  1. POboost::geometry: How to do for_each_segment?
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    copied!<p>I try to figure out <code>how boost::geometry</code>'s <code>for_each_segment</code> ist working. The documentation tells me, that <code>for_each_segment</code> expects a geometry and a Functor. This functor is called <code>polylength_helper</code> in my example, as long as this snippet is not compiling I just increment a number there to keep things simple until it compiles.</p> <pre><code>// foo.h typedef boost::geometry::model::point&lt;double, 2, bg::cs::cartesian&gt; GeographicPoint; typedef boost::geometry::model::linestring&lt;GeographicPoint&gt; GeographicPolyLine; typedef boost::geometry::model::segment&lt;GeographicPoint&gt; GeographicSegment; double poly_length(const GeographicPolyLine&amp;); template&lt;typename Segment&gt; struct polylength_helper{ polylength_helper() : length(0){}; inline void operator()(Segment s){ length += 1; }; double length; }; // foo.cpp double poly_length(GeographicPolyLine &amp;poly){ polylength_helper&lt;GeographicSegment&gt; helper; bg::for_each_segment(poly, helper); return helper.length; } </code></pre> <p>Well, this does not compile. I used <code>clang</code> for a more understandable output, it says:</p> <pre><code>note: candidate function not viable: no known conversion from 'model::referring_segment&lt;point_type&gt;' to 'boost::geometry::model::segment&lt;boost::geometry::model::point&lt;double, 2, boost::geometry::cs::cartesian&gt; &gt;' for 1st argument inline void operator()(Segment s){ ^ </code></pre> <p>Can anyone help me out? Especially I have no idea where the <code>referring_segment</code> in the message comes from.</p> <p>Here is an example from the docs:</p> <p><a href="http://www.boost.org/doc/libs/1_48_0/libs/geometry/doc/html/geometry/reference/algorithms/for_each/for_each_segment_2_const_version.html" rel="nofollow">http://www.boost.org/doc/libs/1_48_0/libs/geometry/doc/html/geometry/reference/algorithms/for_each/for_each_segment_2_const_version.html</a></p> <p>But I cannot figure out how this differs from my version, except for the <code>typedef</code>s.</p>
 

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