(define (make-point x y)
  (list x y))

(define (get-x p)
  (car p))

(define (get-y p)
  (cadr p))

(define (make-segment p1 p2)
  (list p1 p2))

(define (segment-start seg)
  (car seg))

(define (segment-end seg)
  (cadr seg))