Subsetp is defined in Common Lisp. See any Common Lisp
documentation for more information.
member of one list is a member of the other
Major Section: PROGRAMMING
(Subsetp x y) is true if and only if every member of the list
x is a member of the list y.
Membership is tested using the function member. Thus, the guard
for subsetp requires that its arguments are true lists, and
moreover, at least one satisfies eqlable-listp. This guard
ensures that the guard for member will be met for each call
generated by subsetp.
Subsetp is defined in Common Lisp. See any Common Lisp
documentation for more information.