SICP_2.52-2.53

;;;;;;;;;;;;;;;;;2.52
(define (corner-split painter n)
  (if (= n 0)
      painter
      (let ((up (up-split painter (- n 1)))
            (right (right-split painter (- n 1)))
            (corner (corner-split painter (- n 1))))
        (beside (below painter up)
                (below right corner)))))

;;;;;;;;;;;;;;;;2.53
(define (square-limit painter n)
  (let ((combine (square-of-four identity flip-horiz
                                 flip-vect rotate180))
        (combine (corner-split painter n)))))