What's the point of boost::multi_index_container::index<Tag>::type ?
If you have a boost::multi_index_container< > with multiple indices, there are obviously multiple ways to iterate over it - each index defines a way. For instance, if you have an index with tag T, you can iterate from container.get<T>().begin() to container.get<T>().end(). If you try to do so in a for-loop (and do not have C++0x auto),...