hash_set and hash_multiset define a host of nested types similar to standard containers. Several noteworthy points:
- key_type and value_type are the same type and represent the type of element stored.
- key_hasher and value_hasher are the same type and represent the hash function.
- key_compare and value_compare are the same type and represent the comparison function.
- iterator and const_iterator are the same type and have semantics common to a forward const_iterator.