/*
	append(Xs,Ys,XsYs) :-
		XsYs is the result of concatening the lists Xs and Ys.
*/

	append([],Ys,Ys).
	append([X|Xs],Ys,[X|Zs]) :- append(Xs,Ys,Zs).

%	Program 3.15: Appending two lists