added helper -- cf. SET616^5
(* Classical Higher-order Logic -- batteries included *)
use_thys ["Library", "List_Prefix", "List_lexord", "Sublist_Order",
"Product_Lattice",
"Code_Char_chr", "Code_Char_ord", "Code_Integer", "Efficient_Nat"(*, "Code_Prolog"*),
"Code_Real_Approx_By_Float", "Target_Numeral"];