Event Visitor List
An EventVisitorList is how you pass multiple event visitors to an algorithm.
It is either a single EventVisitor, or several EventVisitors combined with
std::make_pair.
Combining two event visitors
auto vis = make_bfs_visitor(
std::make_pair(
record_predecessors(pred.data(), on_tree_edge()),
record_distances(dist.data(), on_tree_edge())
)
);Combining three or more
Nest the pairs:
auto vis = make_dfs_visitor(
std::make_pair(
stamp_times(dtime.data(), on_discover_vertex()),
std::make_pair(
stamp_times(ftime.data(), on_finish_vertex()),
put_property(back_map, true, on_back_edge())
)
)
);A single event visitor
No pairing needed:
auto vis = make_bfs_visitor(
record_predecessors(pred.data(), on_tree_edge())
);Writing custom event visitors
A custom event visitor is a struct with an event_filter typedef and an
operator():
struct print_vertex : public boost::base_visitor<print_vertex> {
using event_filter = boost::on_discover_vertex;
template <typename Vertex, typename Graph>
void operator()(Vertex v, const Graph&) const {
std::cout << v << " ";
}
};Custom event visitors can be combined with pre-built ones in the same list.