diff -r 1af5ec39d006 -r a6aa52ecc1c5 handouts/ho02.tex
--- a/handouts/ho02.tex	Thu Sep 28 19:07:37 2017 +0100
+++ b/handouts/ho02.tex	Tue Oct 03 23:01:06 2017 +0100
@@ -497,9 +497,9 @@
   \lstinputlisting[numbers=left,linebackgroundcolor=
                   {\ifodd\value{lstnumber}\color{capri!3}\fi}]
                   {../progs/app5.scala}
-\caption{A Scala implementation of the \textit{nullable} and 
-  derivative functions. These functions are easy to
-  implement in functional languages. This is because pattern 
+\caption{A Scala implementation of \textit{nullable} and 
+  derivative function. These functions are easy to
+  implement in functional programming languages. This is because pattern 
   matching and recursion allow us to mimic the mathematical
   definitions very closely. Nearly all functional
   programming languages support pattern matching and
@@ -844,7 +844,7 @@
 
 \begin{center}
 \begin{tabular}{r@{\hspace{1mm}}r@{\hspace{1mm}}l@{\hspace{13mm}}l}
-  $r$ & $::=$ &   $\ZERO$         & null language\\
+  $r$ & $::=$ &   $\ZERO$         & nothing\\
         & $\mid$ & $\ONE$           & empty string / \texttt{""} / []\\
         & $\mid$ & $c$                  & single character\\
         & $\mid$ & $r_1 + r_2$          & alternative / choice\\