Hash Confusion

[Paulo Matos]

Hi all,

I'm somewhat confused. What's the difference in g++4.1.1 between
ext/hash_map, ext/hashtable and tr1/hashtable?

Moreover, when I try ext/hash_map, the second third template argument
is hash<T> type, where is this defined? In which namespace?

Are there any documents where can I find info on these? It seems the
g++ manual doesn't have a description for these.

Thanks in advance,

Paulo Matos