1 (defun fold-right (op init seq)
2   (if (null seq)
3       init
4       (funcall op
5 	       (car seq)
6 	       (fold-right op init (cdr seq)))))
7 (defun fold-left (op init seq)
8   (labels (
9 	   (iter (result rest)
10 	     (if (null rest)
11 		 result
12 		 (iter (funcall op result (car rest))
13 		       (cdr rest)))))
14     (iter init seq)))
15 (fold-right #'* 1 '(1 2 3 4 5))
16 (fold-left #'* 1 '(1 2 3 4 5))