+;; imported from Emacs 20.3.
+(defun-maybe last (x &optional n)
+ "Return the last link of the list X. Its car is the last element.
+If X is nil, return nil.
+If N is non-nil, return the Nth-to-last link of X.
+If N is bigger than the length of X, return X."
+ (if n
+ (let ((m 0) (p x))
+ (while (consp p)
+ (setq m (1+ m) p (cdr p)))
+ (if (<= n 0) p
+ (if (< n m) (nthcdr (- m n) x) x)))
+ (while (cdr x)
+ (setq x (cdr x)))
+ x))
+