SICP 問題 2.50
(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))) (define (rotate180 painter) (transform-painter painter (make-vect 1.0 1.0) (make-vect 0.0 1.0) (make-vect 1.0 0.0))) (define (rotate270 paitner) (transform-painter painter (make-vect 0.0 1.0) (make-vect 0.0 0.0) (make-vect 1.0 1.0)))