1 665c255d 2023-08-04 jrmu (defun has-loop? (x)
 2 665c255d 2023-08-04 jrmu   (let ((pairs-table (make-hash-table :test #'eq)))
 3 665c255d 2023-08-04 jrmu     (labels (
 4 665c255d 2023-08-04 jrmu 	     (traverse-list (x)
 5 665c255d 2023-08-04 jrmu 	       (cond
 6 665c255d 2023-08-04 jrmu 		 ((null x) nil)
 7 665c255d 2023-08-04 jrmu 		 ((gethash x pairs-table) t)
 8 665c255d 2023-08-04 jrmu 		 (t
 9 665c255d 2023-08-04 jrmu 		  (setf (gethash x pairs-table) 1)
10 665c255d 2023-08-04 jrmu 		  (traverse-list (cdr x))))))
11 665c255d 2023-08-04 jrmu       (traverse-list x))))