LISP

(defun my-nand (a b)
        (cond ((null a) t) ((null b) t) (t nil))
)


(defun my-not (a)
        (my-nand a a)
)


(defun my-and (a b)
        (my-not (my-nand a b))
)

(defun my-or (a b)
        (my-not (my-and (my-not a) (my-not b)))
)

(defun my-nor (a b)
        (my-and (my-not a) (my-not b))
)

(defun my-xor (a b)
        (my-or
                (my-and a (my-not b))
                (my-and (my-not a) b)
        )
)