views/stored procedures

The previous thread regarding stored procedures made me wonder: what is
the difference between a stored procedure and a view? I understand
postgres uses query rewriting for views, is there a performance hit with

that compared to stored procedures? Will postgres be adding stored
procedures?

Thanks,
Jeff Davis

[PS: I tried sending a similar message to the list yesterday evening,
but it never appeared. I apologize if this is a re-post]