% P08 (**): Eliminate consecutive duplicates of list elements.

% compress(L1,L2) :- the list L2 is obtained from the list L1 by
%    compressing repeated occurrences of elements into a single copy
%    of the element.
%    (list,list) (+,?)

compress([],[]).
compress([X],[X]).
compress([X,X|Xs],Zs) :- compress([X|Xs],Zs).
compress([X,Y|Ys],[X|Zs]) :- X \= Y, compress([Y|Ys],Zs).