RosettaCodeData/Task/Order-two-numerical-lists/Mercury/order-two-numerical-lists-2.mercury

:- pred lt(list(T)::in, list(T)::in) is semidet <= comparable(T).
lt([], [_|_]).
lt([H1|T1], [H2|T2]) :- H1 =< H2, T1 `lt` T2.