updEqualities :: [Equality] -> NO [HAtom]
updEqualities eqs
  = do known   <- equalities <$> get
       let eqs' = [e | e <- eqs, (lhs e, rhs e) `S.notElem` known] 
       mapM addEq eqs'
updEqualities :: [Equality] -> NO [HAtom]
updEqualities eqs
  = do known   <- equalities <$> get
       let eqs' = [e | e <- eqs, (lhs e, rhs e) `S.notElem` known] 
       mapM addEq eqs'
updEqualities eqs
  = do known   <- equalities <$> get
       let eqs' = [e | e <- eqs, (lhs e, rhs e) `S.notElem` known] 
       mapM addEq eqs'