CGAL users discussion list

[Philipp Moeller <>]

Alessandro Attanasi 
<>
 writes:

> anyhow I found another strange behaviour, I computed lower and upper hull,
> but I obtained the same results. Points are the same I described in the
> previous email, and the code I used to compute the lower and upper
> hull are

You call lower_hull_points_2 twice.

>
>   std::vector<K::Point_2>lower_hull;
>
>   CGAL::lower_hull_points_2( points_vect.begin(), points_vect.end(),
> std::back_inserter(lower_hull) );
>
>   ch_points = lower_hull.size();
>
>   std::cout << "6) Points on the lower hull = " << ch_points << std::endl;
>
>   for(int i = 0; i < ch_points; i++)
>
>   {
>
>     std::cout << lower_hull[i] << std::endl;
>
>   }
>
>
>   std::vector<K::Point_2>upper_hull;
>
>   CGAL::lower_hull_points_2( points_vect.begin(), points_vect.end(),
>                              std::back_inserter(upper_hull) );
          ^^^^^^^^^^^^^^^^^^^^

This should be upper_hull_points_2.

>
>   ch_points = upper_hull.size();
>
>   std::cout << "7) Points on the upper hull = " << ch_points << std::endl;
>
>   for(int i = 0; i < ch_points; i++)
>
>   {
>
>     std::cout << upper_hull[i] << std::endl;
>
>   }
>
> obtaining in both cases the same result:
>
> 6) Points on the lower hull = 2
> 0 0
> 4 0
>
> 7) Points on the upper hull = 2
> 0 0
> 4 0