2.44.rkt

#lang sicp
;; Exercise 2.44: Define the procedure up-split used by corner-split.
;; It is similar to right-split, except that it switches the roles of below and beside.

(#%require sicp-pict)

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

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

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