(define wave2 (beside wave (flip-vert wave)))
(define wave4 (below wave2 wave2))

(define (flipped-pairs painter)
  (let ((painter2 (beside painter (flip-vert painter))))
    (below painter2 painter2)))

(define wave4 (flipped-pairs wave))

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

(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))))))

(define (square-limit painter n)
  (let ((quarter (corner-split painter n)))
    (let ((half (beside (flip-horiz quarter) quarter)))
      (below (flip-vert half) half))))

(define (square-of-four tl tr bl br)
  (lambda (painter)
    (let ((top (beside (tl painter) (tr painter)))
        (bottom (beside (bl painter) (br painter))))
      (below bottom top))))

(define (flipped-pairs painter)
  (let ((combine4 (square-of-four identity flip-vert
                                  identity flip-vert)))
    (combine4 painter)))

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

(define (frame-coord-map frame)
  (lambda (v)
    (add-vect
      (origin-frame frame)
    (add-vect (scale-vect (xcor-vect v) (edge1-frame frame))
              (scale-vect (ycor-vect v) (edge2-frame frame))))))

(define (segments->painter segment-list)
  (lambda (frame)
    (for-each
      (lambda (segment)
        (draw-line
          ((frame-coord-map frame)
           (start-segment segment))
          ((frame-coord-map frame)
           (end-segment segment))))
    segment-list)))

(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-vert painter)
  (transform-painter painter
                     (make-vect 0.0 1.0) ; new origin
                     (make-vect 1.0 1.0) ; new end of edge1
                     (make-vect 0.0 0.0))) ; new end of edge2

(define (shrink-to-upper-right painter)
  (transform-painter painter
                     (make-vect 0.5 0.5)
                     (make-vect 1.0 0.5)
                     (make-vect 0.5 1.0)))

(define (rotate90 painter)
  (transform-painter painter
                     (make-vect 1.0 0.0)
                     (make-vect 1.0 1.0)
                     (make-vect 0.0 0.0)))

(define (squash-inwards painter)
  (transform-painter painter
                     (make-vect 0.0 0.0)
                     (make-vect 0.65 0.35)
                     (make-vect 0.35 0.65)))

(define (beside painter1 painter2)
  (let ((split-point (make-vect 0.5 0.0)))
    (let ((paint-left
           (transform-painter painter1
                              (make-vect 0.0 0.0)
                              split-point
                              (make-vect 0.0 1.0)))
          (paint-right
           (transform-painter painter2
                              split-point
                              (make-vect 1.0 0.0)
                              (make-vect 0.5 1.0))))
      (lambda (frame)
        (paint-left frame)
        (paint-right frame)))))