\begin{flushleft}
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\vspace*{-4mm}

\begin{alltt}
STk> (define g (graph '(1 2 3) '((1 2) (1 3) (3 1)))){\em{
\#[undefined]} }
\end{alltt}
\begin{alltt}
STk> (define v (vertices g)){\em{
\#[undefined]} }
\end{alltt}
\begin{alltt}
STk> (describe v){\em{
\#[\(<\)set\(<\)vertex*\(>\)\(>\) \#p50c1b4] is an instance of class \(<\)set\(<\)vertex*\(>\)\(>\)
Slots are: 
     val = \{1 2 3\}
\#f} }
\end{alltt}
\begin{alltt}
STk> (define n (neighbors (ref v 0))){\em{
\#[undefined]} }
\end{alltt}
\begin{alltt}
STk> (describe n){\em{
\#[\(<\)set\(<\)vertex*\(>\)\(>\) \#p4fb45c] is an instance of class \(<\)set\(<\)vertex*\(>\)\(>\)
Slots are: 
     val = \{2 3\}
\#f} }
\end{alltt}

\vspace*{-5mm}

\hrulefill
\end{flushleft}