Hate to keep peppering the list with these, but I am stuck: In the Kevin Bacon sample, there appears this fragment: // Convenience function template <typename DistanceMap> bacon_number_recorder<DistanceMap> record_bacon_number(DistanceMap d) { return bacon_number_recorder<DistanceMap>(d); } Which is used thus: std::vector<int> bacon_number(num_vertices(g)); breadth_first_search(g, src, visitor(record_bacon_number(&bacon_number[0]))); I am puzzled about the convenience function ... why use it at all? But when I take it out: vector<int> numbers(num_vertices(g)); numbers[s] = 0; breadth_first_search(g, s, visitor(my_distance_recorder

(numbers)));

All entries for vector<int> numbers are zero. I changed the declaration for the recorder's ctor to look like this: my_distance_recorder(Map& _m):m(_m){}; Making it get a reference to that vector, because I assumed I was recording into a local copy that was being thrown away. No dice, still zeroes. My "graph" is a straight line of v---v---v---v---v---etc. for simplicity, so I should be seeing a bfs count of 0, 1, 2, 3, etc. The visitor function is being called and is writing incremented values into the vector - but when it comes back, all are zero. What's going on? The convenience function must be related to this problem but I don't see the connection. Eric Also noticed that: breadth_first_search(g, s, visitor(my_distance_recorder

(&numbers[0])));

for breadth_first_search(g, s, visitor(my_distance_recorder

(numbers)));

gets a compile time error.