null_visitor
A no-op event visitor that does nothing. Useful as a placeholder or default when an algorithm requires a visitor but no action is needed, or to fill an unused slot when combining event visitors.
Defined in: <boost/graph/visitors.hpp>
Models: EventVisitor
Synopsis
struct null_visitor {
typedef on_no_event event_filter;
template <class T, class Graph>
void operator()(T x, Graph& g);
};