diff -r a359976a6f3e -r 975d34506e88 cws/cw04.tex
--- a/cws/cw04.tex	Mon Dec 10 02:23:30 2018 +0000
+++ b/cws/cw04.tex	Fri Dec 14 14:41:54 2018 +0000
@@ -126,11 +126,11 @@
 Since some tasks are time sensitive, you can check the reference
 implementation as follows: if you want to know, for example, how long it takes
 to match strings of $a$'s using the regular expression $(a^*)^*\cdot b$
-you can querry as follows:
+you can query as follows:
 
 
 
-\begin{lstlisting}[language={},xleftmargin=1mm,numbers=none,basicstyle=\ttfamily\small]
+\begin{lstlisting}[xleftmargin=1mm,numbers=none,basicstyle=\ttfamily\small]
 $ scala -cp re.jar
 scala> import CW9a._  
 scala> for (i <- 0 to 5000000 by 500000) {
@@ -231,7 +231,7 @@
 
 \item[(2)] Implement a function, called \textit{der}, by recursion over
   regular expressions. It takes a character and a regular expression
-  as arguments and calculates the derivative regular expression according
+  as arguments and calculates the derivative of a xregular expression according
   to the rules:
 
 \begin{center}
@@ -308,11 +308,11 @@
 
   simplifies to just $r_1$. \textbf{Hint:} Regular expressions can be
   seen as trees and there are several methods for traversing
-  trees. One of them corresponds to the inside-out traversal, which is
-  sometimes also called post-order traversal: you traverse inside the
+  trees. One of them corresponds to the inside-out traversal, which is also
+  sometimes called post-order tra\-versal: you traverse inside the
   tree and on the way up you apply simplification rules.
-  Furthermore,
-  remember numerical expressions from school times: there you had expressions
+  \textbf{Another Hint:}
+  Remember numerical expressions from school times---there you had expressions
   like $u + \ldots + (1 \cdot x) - \ldots (z + (y \cdot 0)) \ldots$
   and simplification rules that looked very similar to rules
   above. You would simplify such numerical expressions by replacing
@@ -378,7 +378,7 @@
   \]  
 
   \noindent correctly to just \texttt{ONE}, where \texttt{SEQ} is nested
-  50 or more times.\\
+  50 or more times?\\
   \mbox{}\hfill[1 Mark]
 \end{itemize}