--- /dev/null
+module Network.DNS.RBL ( lookup_simple )
+where
+
+-- | Look up the given @host@ on all of the white/blacklists contained
+-- in @rbls@. If the results, multiplied by their weights, add up to
+-- (at least) @threshold@, then @True@ is returned; that is, the
+-- @host@ is \"listed\". Otherwise, @False@ is returned.
+--
+lookup_simple :: String -> Int -> String -> Bool
+lookup_simple rbls threshold host = undefined