問題2-50 (2.2.4 Example: A Picture Language)

kiririmodeを逆にする。

(define (transform-painter painter origin corner1 corner2)
  (lambda (frame)
    (let ((m (frame-coord-map frame)))
      (let ((new-origin (m origin)))
        (painter
         (make-frame new-origin
                     (sub-vect (m corner1) new-origin)
                     (sub-vect (m corner2) new-origin)))))))

(define (flip-horiz painter)
  (transform-painter painter
		     (make-vect 1.0 0.0)
		     (make-vect 0.0 0.0)
		     (make-vect 1.0 1.0)))

180度回転させる。

(define (rotate180 painter)
  (transform-painter painter
		     (make-vect 1.0 1.0)
		     (make-vect 0.0 1.0)
		     (make-vect 1.0 0.0)))

270度回転させる。

(define (rotate270 painter)
  (rotate90 (rotate180 painter)))