Dear Jeremiah Willcock,

Thanks for your explanations.

I think I am starting to walk out of the chaos...

For the adjacency_list, there isn't an edge_index property.

That means the edge_index property is not used by the

graph internally, but could be used by user just like the edge_weight or edge_name, and these property should be assgined by user manually.

So in the examples "exterior_properties.cpp", I could replace all the strings "edge_index" with "edge_weight", and doing this will not affect the result.

The property map works in this case beacuse the edge_index property is type of int, and the value of the edge_index property

is the offset to the beginning of the underlying property containers (int capacity[] and int flow[]).

And the whole mapping process when calling the "boost::get(capacity, *out)" includes two mappings:

Frist mapping: KEY=*out (edge descriptor)-->VALUE = offset value (int)

Second mapping: KEY=offset value (int) --> VALUE= the corresponding property value

Am I right?

Thanks.

Zhiyu LI

"exterior_properties.cpp":

typedef boost::adjacency_list<boost::vecS, boost::vecS,

boost::bidirectionalS, boost::no_property,

boost::property<boost::edge_index_t, std::size_t> > Graph;

int capacity[] = { 10, 20, 20, 20, 40, 40, 20, 20, 20, 10 };

int flow[] = { 8, 12, 12, 12, 12, 12, 16, 16, 16, 8 };

boost::add_edge(0, 1, 0, G);

boost::add_edge(1, 4, 1, G);

...

typedef boost::property_map<Graph, boost::edge_index_t>::type EdgeIndexMap;

EdgeIndexMap edge_id = boost::get(boost::edge_index, G);

boost::iterator_property_map <int*, EdgeIndexMap, int, int&>

capacity_array(capacity, edge_id), flow_array(flow, edge_id);

print_network(G, capacity_array, flow_array);

inside the function print_network:

boost::get(capacity, *out) ...