--- a/slides/slides04.tex	Fri Oct 16 08:42:21 2015 +0100
+++ b/slides/slides04.tex	Fri Oct 16 08:56:25 2015 +0100
@@ -454,9 +454,16 @@
 
 \[
 \bl{(ab + a) \cdot (c + bc)}
-\]\bigskip
+\]\medskip
+
+and the string $\bl{abc}$.\pause\pause\bigskip
 
-and the string $\bl{abc}$
+Or, keywords are \pcode{if} and identifiers are 
+letters followed by ``letters + numbers + \_''$^*$
+
+\[
+\bl{iffoo}
+\]
 
 \end{frame}
 
@@ -478,7 +485,11 @@
 \small
 \hfill most posix matchers are buggy\\
 \footnotesize
-\hfill \url{http://www.haskell.org/haskellwiki/Regex_Posix}
+\hfill 
+\url{http://www.haskell.org/haskellwiki/Regex_Posix}
+\smallskip\pause
+
+\hfill \small traditional lexers are fast, but hairy
 
 %\url{http://www.technologyreview.com/tr10/?year=2011}  
 %finite deterministic automata/ nondeterministic automaton