proposition: Fact half_tile_length l : length (half_tile l) = length l.
proof: Proof. induction l; simpl; f_equal; auto. Qed.
imports: List Arith Lia Bool Undecidability.Shared.Libs.DLW(utils list_bool pos vec subcode sss) Undecidability.StackMachines.BSM(tiles_solvable bsm_defs)