2.52.tex

\documentclass[a4paper,12pt]{article}
\usepackage{listings}
\lstset{language=Lisp}

\begin{document}
\begin{lstlisting}
(define wave
  (segments->painter
   (list
    (make-segment (make-vector 5/12 2/3)
                  (make-vector 1/3 5/6))
    (make-segment (make-vector 1/3 5/6)
                  (make-vector 5/12 1))
    (make-segment (make-vector 7/12 1)
                  (make-vector 2/3 5/6))
    (make-segment (make-vector 2/3 5/6)
                  (make-vector 7/12 3/3))
    (make-segment (make-vector 7/12 2/3)
                  (make-vector 2/3 2/3))
    (make-segment (make-vector 2/3 2/3)
                  (make-vector 1 1/2))
    (make-segment (make-vector 1 1/3)
                  (make-vector 7/12 1/2))
    (make-segment (make-vector 7/12 1/2)
                  (make-vector 0 2/3))
    (make-segment (make-vector 0 5/9)
                  (make-vector 1/2 1/3))
    (make-segment (make-vector 1/2 1/3)
                  (make-vector 0 4/9))
    (make-segment (make-vector 0 1/3)
                  (make-vector 5/12 1/2))
    (make-segment (make-vector 5/12 1/2)
                  (make-vector 1/3 7/12))
    (make-segment (make-vector 1/3 7/12)
                  (make-vector 1/6 1/2))
    (make-segment (make-vector 1/6 1/2)
                  (make-vector 0 2/3))
    (make-segment (make-vector 0 5/6)
                  (make-vector 1/6 7/12))
    (make-segment (make-vector 1/6 7/12)
                  (make-vector 1/3 2/3))
    (make-segment (make-vector 1/3 2/3)
                  (make-vector 5/12 2/3))
    ;; Adding a smile
    (make-segment (make-vector 5/12 5/6)
                  (make-vector 11/24 3/4))
    (make-segment (make-vector 11/24 3/4)
                  (make-vector 13/24 3/4))
    (make-segment (make-vector 13/24 3/4)
                  (make-vector 7/12 5/6)))))

(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 painter up))
              (bottom-right (below painter 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 quarter (flip-horiz quarter))))
      (below half (flip-vert half)))))
\end{lstlisting}
\end{document}