class boost::graph_traits< DGtal::DigitalSurface< TDigitalSurfaceContainer > >::edge_iterator
Iterator for visiting all edges of the graph. We use an iterator facade to create a STL-compliant iterator with as little effort as possible.
- The difficulty is that DGtal graphs do not provide iterators for visiting edges or adjacent vertices, but merely provide a method that outputs them. Therefore, this iterator mixes a vertex_iterator (to visit all vertices) and a local out_edge_iterator (to visit all out edges of each vertex). This is for instance used by function edges, which returns a pair of edge_iterator. A potential problem is that the user may have called twice edges, and may wish to compare iterators obtained by two different calls. Here, edges are constructed on the fly, hence iterators may not point on the same container even if the values are the same.
typedef typename DigitalSurface<...> G;
std::pair<edge_iterator,edge_iterator> vp1 = boost::edges
( g );
std::pair<edge_iterator,edge_iterator> vp2 = boost::edges
( g );
In this case, vp1 and vp2 are not pointing on the same structure, hence the address pointed by vp1 is different from the address pointed by vp2. They are then not comparable a priori. The edge_iterator is written so that vp1 (.first or .second) and vp2 (.first or .second) are comparable, using value comparison and out-of-range check.
Definition at line 329 of file DigitalSurfaceBoostGraphInterface.h.