In this case, The site P is a util::vertex which means this iterator can automatically converts towards this type. More...
#include <neighb_niter_impl.hh>
In this case, The site P is a util::vertex which means this iterator can automatically converts towards this type.
There would be an ambiguity between util::edge members and the one declared in neighb_niter_impl_graph_window<P,E> if this specialization did not exist.