prd_term :: TERM -> Set.Set NAME
prd_term t =
  case t of
    Name_term n -> prd_name n
    Funct_term ft tseqs _ -> prd_add_term ft `Set.union` prd_termSeqs tseqs
    Comment_term ct _ _ -> prd_term ct
prd_term :: TERM -> Set.Set NAME
prd_term t =
  case t of
    Name_term n -> prd_name n
    Funct_term ft tseqs _ -> prd_add_term ft `Set.union` prd_termSeqs tseqs
    Comment_term ct _ _ -> prd_term ct
prd_term t =
  case t of
    Name_term n -> prd_name n
    Funct_term ft tseqs _ -> prd_add_term ft `Set.union` prd_termSeqs tseqs
    Comment_term ct _ _ -> prd_term ct