====== List member 4 ======
{{tag>lists}}
===== Description =====
Testing for a subset

**Source**:  The Art of Prolog
===== Download =====
Program source code: {{list_member_4.pl}}
===== Listing =====
<code prolog>
/*
   members(Xs,Ys) :- Each element of the list Xs is an element of the list Ys.
*/
     members([X|Xs],Ys) :- member(X,Ys), members(Xs,Ys).
     members([],Ys).

%  Program 7.6    Testing for a subset
</code>
===== Comments =====