check if all members of one list are members of the other
Major Section:  PROGRAMMING

(Subsetp-equal x y) returns t if every member of x is a member of y, where membership is tested using member-equal.

The guard for subsetp-equal requires both arguments to be true lists. Subsetp-equal has the same functionality as the Common Lisp function subsetp, except that it uses the equal function to test membership rather than eql.