Matching with Bindings in an Assoc. List

(defun match4 (p s)

(cond

((and (null p)(null s)) '((:yes . :yes)))

((or (atom p)(atom s)) nil)

((equalp (car p) (car s))

(match4 (cdr p)(cdr s)) )

((and (= (length (car p)) 2)

(eql (caar p) '?)

(let ((rest-match

(match4 (cdr p)(cdr s))))

(if rest-match

(acons (cadar p)

(car s) rest-match) ) ) ) )

(t nil) ) )