+import Network.DNS (
+ Domain,
+ Resolver,
+ lookupMX,
+ lookupNS )
+
+type LookupResult = (Domain, Maybe [Domain])
+
+lookupMX' :: Resolver -> Domain -> IO LookupResult
+lookupMX' resolver domain =
+ lookupMX resolver domain >>= return . pair_em . drop_priority
+ where
+ drop_priority :: Maybe [(Domain, Int)] -> Maybe [Domain]
+ drop_priority = fmap (map fst)
+
+ pair_em :: a -> (Domain, a)
+ pair_em = (,) domain
+
+-- This function keeps the domain matches with its NS records.
+lookupNS' :: Resolver -> Domain -> IO LookupResult
+lookupNS' resolver domain =
+ lookupNS resolver domain >>= return . pair_em
+ where
+ pair_em :: a -> (Domain, a)
+ pair_em = (,) domain