gchen wrote:
What is the difference of this library from hash_map in some STL extention libraries? Is it just a new name for hash_map/hash_set?
Hash containers were not standardized so there are different implementations with different guarantees and features (some used incremental hashing or bidirectional iterators) and C++ unordered containers have been standardized to support a broad range of implementations adding new features, like bucket iterators. You shouldn't use hash_map and other similar containers if you want to write portable code just because they are not standard. Unordered aims to be the Boost implementation of standard C++ hash containers. For more information about the rationale and the evolution of unordered containers design see Matthew Austern's proposal: A Proposal to Add Hash Tables to the Standard Library (revision 4) http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2003/n1456.html Regards, Ion