Ex-1.12

;; Find Pascal element
;; row = row number in the pascal triangle,
;;   row >= 1
;; elt = elt'th element of the row,
;;   1 <= elt <= row
(define (pascal row elt)
  (if (or (= elt 1) (= elt row)) 1
      (+ (pascal (- row 1) (- elt 1))
         (pascal (- row 1) elt))))