2.51.tex

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

\begin{document}
\begin{lstlisting}
(define (below painter1 painter2)
  (let ((split-point (make-vect 0.0 0.5)))
    (let ((paint-bottom
           (transform-painter painter1
                              (make-vect 0.0 0.0)
                              split-point
                              (make-vect 1.0 0.0)))
          (paint-top
           (transform-painter painter2
                              split-point
                              (make-vect 0.0 1.0)
                              (make-vect 1.0 0.5))))
      (lambda (frame)
        (paint-bottom frame)
        (paint-top frame))))))

(define (below painter1 painter2)
  (rotat270 (beside painter2 painter1)))
\end{lstlisting}
\end{document}