sicp 2.52

Exercise 2.52.  Make changes to the square limit of wave shown in figure 2.9 by working at each of the levels described above. In particular:

a.  Add some segments to the primitive wave painter of exercise  2.49 (to add a smile, for example).

b.  Change the pattern constructed by corner-split (for example, by using only one copy of the up-split and right-split images instead of two).

c.  Modify the version of square-limit that uses square-of-four so as to assemble the corners in a different pattern. (For example, you might make the big Mr. Rogers look outward from each corner of the square.)

 

 

(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 up)
             (bottom-right right)
             (corner (corner-split painter (- n 1))))
	(beside (below painter top-left)
		(below bottom-right corner))))))

(define (square-limit painter n)
  (let ((combine4 (square-of-four identity flip-horiz
                                  flip-vert rotate180)))
    (combine (corner-split painter n))))