define min-point points define min-point-iter ps if null ps let car ps

(define (min-point points)
  (define (min-point-iter p ps)
    (if (null? ps)
      p
      (let ((q (car ps)))
        (min-point-iter (cond ((< (point-y q) (point-y p)) q)
                              ((= (point-y q) (point-y p))
                               (if (< (point-x q) (point-x p))
                                 q))
                              (else p))
                        (cdr ps)))))
  min-point-iter (car points) (cdr points))