title: Iterate over vertices of CGAL polygon and get int coordinates
body: <p>My first problem is, that vertex iterators and points are "unknown" in CLION.
  When I declare a point and want to access its member functions, there is no auto completion (unlike polygons, etc.).</p>
  
  <p>My second question is, how can I iterate over the vertices of a polygon and get the coordinates of the vertices as int values?</p>
  
  <p>The idea was as follows, but the return type of p.x() isn't an int or a double.</p>
  
  <pre><code>#include &lt;CGAL/Exact_predicates_exact_constructions_kernel.h&gt;
  #include &lt;CGAL/Polygon_2.h&gt;
  
  typedef CGAL::Exact_predicates_exact_constructions_kernel Kernel;
  typedef Kernel::Point_2 Point;
  typedef CGAL::Polygon_2&lt;Kernel&gt; Polygon_2;
  
  int main() {
      std::vector&lt;Point&gt; points;
  
      points.emplace_back(Point(10, 10));
      points.emplace_back(Point(20, 10));
      points.emplace_back(Point(20, 20));
      points.emplace_back(Point(10, 20));
  
      Polygon_2 poly(points.begin(), points.end());
  
      for (auto vi = poly.vertices_begin(); vi != poly.vertices_end(); ++vi)
      {
          int x = (*vi).x();
          int y = (*vi).y();
      }
  
      return 0;
  }
  </code></pre>
  
  <p>Compiler Error:</p>
  
  <pre><code>main.cpp:20:13: error: no viable conversion from 'typename cpp11::result_of&lt;typename R::Compute_x_2 (Point_2&lt;Epeck&gt;)&gt;::type' (aka 'Lazy_exact_nt&lt;CGAL::Gmpq&gt;') to 'int'
      int x = (*vi).x();
          ^   ~~~~~~~~~
  </code></pre>
  
  <p>Thanks for help!</p>