Subset of a set - back to content

		SUBSET verifies if a set is a subset of another set.

		?- subset([a,b],[a,c,d,b]).
	   	true.
		?-include([],[a,b]).
	  	true.

		subset([],L).
		subset([X|T],L):- member(X,L),subset(T,L).

		We verify if a set is included in all the sets of a list. 
 

        	?- all_subset([a,b],[[1,a],[c,b]).
          	false.	
		?- all_subset([a,c,b],[[a,b,c,d],[m,a,b,c]])
	  	true.

		subset([],L).
		subset([H|T],L):- member(H,L),subset(T,L).
	
		all_subset(X,[Y]):-   subset(X,Y).
		all_subset(X,[H|T]):- subset(X,H), all_subset(X,T).