--- a/slides/slides09.tex	Thu Nov 27 17:52:17 2014 +0000
+++ b/slides/slides09.tex	Fri Nov 28 12:22:50 2014 +0000
@@ -3,16 +3,7 @@
 \usepackage{../langs}
 \usepackage{../graphics}
 \usepackage{../grammar}
-
-%\usepackage{soul}
-
-%\newcommand\hl[1]{%
-%    \tikz[baseline,%
-%      outer sep=-15pt, inner sep = 0pt%
-%    ]%
-%   \node[decorate,rectangle,fill=yellow,anchor=text]{#1};%
-%}%
-\newcommand{\hl}[1]{#1}
+\usepackage{soul}
 
 % beamer stuff 
 \renewcommand{\slidecaption}{APP 09, King's College London}
@@ -1140,7 +1131,7 @@
 
 Replace all constants and variables by either 
 \pcode{+}, \pcode{-} or \pcode{0}. What we want to find out
-is what the sign of \texttt{a} and \texttt{n} is (they are 
+is what the sign of \texttt{a} and \texttt{n} is (they should 
 always positive).
 
 \end{frame}