eq
Major Section: PROGRAMMING
(remove1-eq x l) is l if x is not a member of l as tested with
member-eq, else is the result of removing all occurrences of x from
l.
The guard for (remove1-eq x l) requires l to be a true list and
moreover, either x is a symbolp or all elements of l are
symbols (i.e., l is a symbol-listp).
Also see remove-eq, see remove1, and see remove1-equal.