--- a/slides/slides04.tex	Tue Oct 16 00:42:10 2018 +0100
+++ b/slides/slides04.tex	Tue Oct 16 08:28:12 2018 +0100
@@ -60,12 +60,17 @@
 \includegraphics[scale=0.2]{../pics/s2.png}
 \end{textblock}}
 
-\only<4>{
+\only<4->{
 \begin{textblock}{6}(0.6,8.5)
 \includegraphics[scale=0.2]{../pics/s3.png}
 \end{textblock}
 \begin{textblock}{6}(8,8.5)
 \includegraphics[scale=0.2]{../pics/s4.png}
+\end{textblock}}
+
+\only<5>{
+\begin{textblock}{6}(1.5,14.5)  
+  room too hot, 3h lecture
 \end{textblock}}  
 
 % \begin{itemize}
@@ -123,7 +128,7 @@
 \begin{textblock}{6}(1,0.8)
 \begin{bubble}[6.7cm]
 \begin{tabular}{r@ {\hspace{1mm}}c@ {\hspace{1mm}}l}
-\multicolumn{3}{@{}l}{substitute \bl{$\mbox{Q}_1$} into \bl{$\mbox{Q}_0$} + \bl{$\mbox{Q}_2$}:}\\    
+\multicolumn{3}{@{}l}{substitute \bl{$\mbox{Q}_1$} into \bl{$\mbox{Q}_0$} \& \bl{$\mbox{Q}_2$}:}\\    
 \bl{$\mbox{Q}_0$} & \bl{$=$} & \bl{$\ONE + \mbox{Q}_0\,b + \mbox{Q}_0\,a\,b +  \mbox{Q}_2\,b$}\\
 \bl{$\mbox{Q}_2$} & \bl{$=$} & \bl{$\mbox{Q}_0\,a\,a + \mbox{Q}_2\,a$}
 \end{tabular}
@@ -238,7 +243,8 @@
 \end{axis}
 \end{tikzpicture}
 
-The punchline is that existing libraries do depth-first search in NFAs.
+The punchline is that many existing libraries do depth-first search
+in NFAs (backtracking).
 
 \end{frame}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
@@ -469,7 +475,14 @@
   \end{center}
   
 Today a lexer.  
-  
+
+\only<2>{
+\begin{textblock}{1}(6,9.8)
+\begin{tabular}{c}
+\includegraphics[scale=0.13]{../pics/rosetta.jpg}\\[-2mm]
+\footnotesize lexing $\Rightarrow$ recognising words (Stone of Rosetta)
+\end{tabular}
+\end{textblock}}
 \end{frame}
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
@@ -767,7 +780,7 @@
   \bl{$inj\,(r_1 \cdot r_2)\,c\,(Seq(v_1,v_2))$} & \bl{$\dn$}  & \bl{$Seq(inj\,r_1\,c\,v_1,v_2)$}\\
   \bl{$inj\,(r_1 \cdot r_2)\,c\,(Left(Seq(v_1,v_2)))$} & \bl{$\dn$}  & \bl{$Seq(inj\,r_1\,c\,v_1,v_2)$}\\
   \bl{$inj\,(r_1 \cdot r_2)\,c\,(Right(v))$} & \bl{$\dn$}  & \bl{$Seq(mkeps(r_1),inj\,r_2\,c\,v)$}\\
-  \bl{$inj\,(r^*)\,c\,(Seq(v,vs))$} & \bl{$\dn$}  & \bl{$Stars\,(inj\,r\,c\,v\,::\,vs)$}\\
+  \bl{$inj\,(r^*)\,c\,(Seq(v,Stars\,vs))$} & \bl{$\dn$}  & \bl{$Stars\,(inj\,r\,c\,v\,::\,vs)$}\\
 \end{tabular}
 \end{center}\bigskip