CGAL users discussion list

["Liyang" <>]

Hi experts,

 

I'm reading the code of HalfedgeDS_decorator<HDS>::join_vertex , the question is, after the loop(while(h!=gprev)...), all halfedges previously pointed to get_vertex(gprev) but gprev have pointed to get_vertex(hprev), don't we need to make gprev point to get_vertex(hprev)?

 

Thank you for your attention and sorry for my poor English.

 

Best regards.

 

 

/*                            The codes are as follow                       */

Halfedge_handle join_vertex( Halfedge_handle h) {

        // joins the two vertices incident to h. The vertex denoted by

        // `h->opposite()' gets removed by `hds'. Returns the predecessor

        // of h around the vertex. The invariant `join_vertex(

        // split_vertex( h, g))' returns h and keeps the polyhedron

        // unchanged. The time is proportional to the degree of the vertex

        // removed and the time to compute `h->prev()'. Precondition:

        // `Supports_removal' == `Tag_true'.

        Assert_compile_time_tag( Tag_true(), Supports_removal());

        Halfedge_handle hprev = find_prev( h->opposite());

        Halfedge_handle gprev = find_prev( h);

        remove_halfedge( hprev);

        remove_halfedge( gprev);

        hds->edges_erase( h);

        vertices_erase( get_vertex( gprev));

        // 'half' of the halfedges have their correct vertex.

        // Here we do the remaining halfedges.

        h = hprev;

        CGAL_assertion_code( std::size_t termination_count = 0;)

        while ( h != gprev) {

            CGAL_assertion( ++termination_count != 0);

            h = h->next()->opposite();

            set_vertex( h, get_vertex( hprev));

        }

        set_vertex_halfedge( hprev);

        if ( ! hprev->is_border())

            set_face_halfedge(  hprev);

        if ( ! gprev->is_border())

            set_face_halfedge(  gprev);

        return hprev;

    }

2012-08-14

---

Liyang