- (let ((list1 (copy-sequence list1)))
- (while list2
- (setq list1 (delq (car list2) list1))
- (setq list2 (cdr list2)))
- list1))
+ (let ((hash2 (make-hash-table :test 'eq))
+ (result nil))
+ (dolist (elt list2) (puthash elt t hash2))
+ (dolist (elt list1)
+ (unless (gethash elt hash2)
+ (setq result (cons elt result))))
+ (nreverse result)))