%% background knowledge

% Note: We can use SWI-Prolog's built-in definition!
% succ(A,B) :-
%    integer(A), % ground(B),
%    B is A+1.

% % Too easy
% % lt(A,B) :-
% %         A @< B.

% % le(A,B) :-
% %         A @=< B.


% gt(A,B) :-
%         A @> B.

% ge(A,B) :-
%         A @>= B.