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

\begin{alltt}
STk> (define g (graph)){\em{
\#[undefined]} }
\end{alltt}
\begin{alltt}
STk> (do ((i 1 (+ i 1))) 
     ((= i 4) g)
     (add-vertex! i g)){\em{
\#[\(<\)ubingraph*\(>\) \#p4fdbbc]} }
\end{alltt}
\begin{alltt}
STk> (describe g){\em{
\#[\(<\)ubingraph*\(>\) \#p4fdbbc] is an instance of class \(<\)ubingraph*\(>\)
Slots are: 
     val = \{[1 2 3]  \{\}\}
\#f} }
\end{alltt}

\vspace*{-5mm}

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