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.
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.