clean up Atom code some, switch to IntMap for reverse lookup
clean up Atom code some, switch to IntMap for reverse lookup

darcs-hash:20061104042935-1a7c6-84483aac3495be04ea4c755cbc2c0e4f9268e13b

kirbyfan64/jhc,kirbyfan64/jhc,kirbyfan64/jhc,kirbyfan64/jhc