--- a/slides/slides06.tex	Wed Oct 30 03:36:10 2013 +0000
+++ b/slides/slides06.tex	Wed Oct 30 03:44:40 2013 +0000
@@ -152,6 +152,21 @@
 
 \end{frame}}
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\mode<presentation>{
+\begin{frame}[c]
+\frametitle{\begin{tabular}{c}Regular Languages\end{tabular}}
+
+While regular expressions are very useful for lexing, 
+there is no regular expression that can recognise the language \bl{$a^nb^n$}.\bigskip
+
+\begin{center}
+\bl{$(((()()))())$} \;\;vs.\;\; \bl{$(((()()))()))$}
+\end{center}
+
+
+\end{frame}}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
 
 
 \newcommand{\qq}{\mbox{\texttt{"}}}
@@ -649,7 +664,7 @@
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \mode<presentation>{
 \begin{frame}[c]
-\frametitle{Abstract Parsers}
+\frametitle{Abstract Parser Class}
 
 \mbox{\lstset{language=Scala}\fontsize{10}{12}\selectfont
 \texttt{\lstinputlisting{../progs/app7.scala}}}