[Boost-users] [boost-users][hash] adding hash_value to boost namespace(s)?

Hi, I'd like to define hash_value() for some types defined in Boost, in order to use those types in hashed containers. It seems that the only way to do this is to define hash_value() in namespace boost, or the inner namespaces (where the desired type is defined) - isn't it? Is this legal? Thank you, Igor'.