--- a/slides/slides01.tex	Mon Nov 09 14:36:35 2020 +0000
+++ b/slides/slides01.tex	Mon Nov 09 17:49:12 2020 +0000
@@ -606,6 +606,7 @@
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \begin{frame}[c, fragile]
+%%\frametitle{General Scheme of}  
 
  \small
 \begin{lstlisting}[language=Scala,numbers=none]
@@ -620,6 +621,23 @@
 \end{frame}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
+\begin{frame}[c, fragile]
+
+\begin{lstlisting}[language=Scala,numbers=none]
+def average(xs: List[Int]) : Int = {
+  val s = xs.sum
+  val n = xs.length
+  s / n
+}
+\end{lstlisting}
+
+  
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+ 
+
+
+
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %\begin{frame}[c]