sicp 2.50

Exercise 2.50.  Define the transformation flip-horiz, which flips painters horizontally, and transformations that rotate painters counterclockwise by 180 degrees and 270 degrees.

 

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

(define (flip-cc-180 painter)
  (transform-painter painter
                     (make-vect 1.0 1.0)
                     (make-vect 1.0 0.0)
                     (make-vect 0.0 1.0)))

(define (flip-cc-270 painter)
  (transform-painter painter
                     (make-vect 0.0 1.0)
                     (make-vect 1.0 1.0)
                     (make-vect 0.0 0.0)))