Binary file slides/slides04.pdf has changed

--- a/slides/slides04.tex	Mon Oct 20 22:18:21 2025 +0200
+++ b/slides/slides04.tex	Tue Oct 21 08:41:46 2025 +0200
@@ -444,8 +444,37 @@
 
 \end{frame}
 
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
 
+% {
+% \setbeamercolor{background canvas}{bg=cream}
+% \begin{frame}[c]
+% \small
 
+% \begin{lstlisting}[language=Scala,numbers=none]
+% enum Rexp {
+%   case ZERO
+%   case ONE
+%   case CHAR(c: Char)
+%   case ALT(r1: Rexp, r2: Rexp)
+%   case SEQ(r1: Rexp, r2: Rexp)
+%   case STAR(r: Rexp)
+% }
+% \end{lstlisting}
+
+% \begin{lstlisting}[language=Scala,numbers=none]
+% enum Val {
+%   case Empty
+%   case Chr(c: Char)
+%   case Sequ(v1: Val, v2: Val)
+%   case Left(v: Val)
+%   case Right(v: Val)
+%   case Stars(vs: List[Val])
+% }
+% \end{lstlisting}
+
+% \end{frame}
+% }
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \begin{frame}[c]