Arithmetic on linked lists

gistfile1.cl

(defun plus1. (lst)
  (cond ((null. lst) (cons '1 '()))
	((eq (car lst) '1)
	 (cons '0 (plus1. (cdr lst))))
	('t (cons '1 (cdr lst)))))

(defun minus1. (lst)
  (cond ((null. lst) '())
	((and. (null. (cdr lst)) (eq (car lst) '1)) '())
	((eq (car lst) '0)
	 (cons '1 (minus1. (cdr lst))))
	((eq (car lst) '1) (cons '0 (cdr lst)))))

(defun +. (lst1 lst2)
  (cond ((null. lst2) lst1)
	('t (+. (plus1.   lst1) (minus1. lst2)))))

(defun -. (lst1 lst2)
  (cond ((null. lst2) lst1)
	('t (-. (minus1. lst1) (minus1. lst2)))))

(defun ash+. (lst1 lst2)
  (cond ((null. lst2) lst1)
	('t (ash+. (cons '0 lst1) (minus1. lst2)))))

(defun >. (lst1 lst2)
  (cond ((and. (null. lst2) (null. lst1)) '())
	((null. lst2) 't)
	((null. lst1) '())
	('t (>. (minus1. lst1) (minus1. lst2)))))

(defun eqnum. (lst1 lst2)
  (cond ((and. (null. lst1) (null. lst2)) 't)
	((eq (car lst1) (car lst2))
	 (eqnum. (cdr lst1) (cdr lst2)))
	('t '())))