getCommonSupers :: CS.Sign f e -> [SORT] -> Set.Set SORT
getCommonSupers csig s = let supers t = Set.insert t $ supersortsOf t csig in
   if null s then Set.empty else foldr1 Set.intersection $ map supers s
getCommonSupers :: CS.Sign f e -> [SORT] -> Set.Set SORT
getCommonSupers csig s = let supers t = Set.insert t $ supersortsOf t csig in
   if null s then Set.empty else foldr1 Set.intersection $ map supers s
getCommonSupers csig s = let supers t = Set.insert t $ supersortsOf t csig in
   if null s then Set.empty else foldr1 Set.intersection $ map supers s