mylength([], 0).
mylength(X, Len) :- X = [_|T], mylength(T, TLen), Len is TLen + 1.  % (A) (Prompts after "N = 0")
%mylength([_|T], Len) :- mylength(T, TLen), Len is TLen + 1.        % (B) (Says "N = 0." and stops.)
% gprolog behaves in the same way as swipl
