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--- a/handouts/ho04.tex	Fri Apr 10 16:30:52 2020 +0100
+++ b/handouts/ho04.tex	Thu Apr 16 19:15:46 2020 +0100
@@ -884,15 +884,25 @@
   (top\_level:\texttt{ac.uk})]$
 \end{center}
 
-Recall that we want to lex a little programming language,
-called the \emph{While}-language. A simple program in this
-language is shown in Figure~\ref{while}. The main keywords in
-this language are \pcode{while}, \pcode{if}, \pcode{then} and
-\pcode{else}. As usual we have syntactic categories for
-identifiers, operators, numbers and so on. For this we would
-need to design the corresponding regular expressions to
-recognise these syntactic categories. I let you do this design
-task. Having these regular expressions at our disposal, we can
+Recall that we want to lex a little programming language, called the
+\emph{While}-language. A simple program in this language is shown in
+Figure~\ref{while}. The main keywords in this language are
+\pcode{while}, \pcode{if}, \pcode{then} and
+\pcode{else}.\footnote{Contrast this with the COBOL programming
+  language, which was developed around 1960 and thought to be dead for
+  many decades---even your friendly lecturer is not old enough to have
+  been taught this language. Anyway, this language had over 600
+  keywords (or what they called \emph{reserved words}). Interestingly
+  though this language is still used in 2020: during the height of
+  Corona crisis the State of New Jewrsey in the US was looking for
+  COBOL programers who could fix the state's national insurance
+  webpage. You were probably paid in gold and diamonds, if you were
+  able to program in COBOL. If you fixed their webpage, surely you
+  were allowed to marry the governer's son/daughter. } As usual we
+have syntactic categories for identifiers, operators, numbers and so
+on. For this we would need to design the corresponding regular
+expressions to recognise these syntactic categories. I let you do this
+design task. Having these regular expressions at our disposal, we can
 form the regular expression
 
 \begin{figure}[t]

--- a/hws/hw06.tex	Fri Apr 10 16:30:52 2020 +0100
+++ b/hws/hw06.tex	Thu Apr 16 19:15:46 2020 +0100
@@ -70,13 +70,21 @@
 recognise the strings (for 1) $ab$ and (for 2) $aaa$. Give in each case
 \emph{all} the values and indicate which one is the POSIX value.
 
+\item Given the regular expression $(a + b)^* \cdot b \cdot (a + b)^*$,
+  which of the following regular expressions are equyivalent
+
+\begin{center}
+\begin{tabular}{ll}    
+  1) & $(ab + bb)^* \cdot (a + b)^*$\\                     % no
+  2) & $(a + b)^* \cdot (ba + bb + b) \cdot (a + b)^*$\\   % yes
+  3) & $(a + b)^* \cdot (a + b) \cdot (a + b)^*$           % no
+\end{tabular}
+\end{center}
+
 \item Parsing combinators consist of atomic parsers, alternative
   parsers, sequence parsers and semantic actions.  What is the purpose
   of (1) atomic parsers and of (2) semantic actions?
 
-
-
-
 \item \POSTSCRIPT        
 \end{enumerate}
 

--- a/slides/slides01.tex	Fri Apr 10 16:30:52 2020 +0100
+++ b/slides/slides01.tex	Thu Apr 16 19:15:46 2020 +0100
@@ -18,6 +18,9 @@
 % beamer stuff 
 \renewcommand{\slidecaption}{CFL 01, King's College London}
 
+%% https://cs.rit.edu/~hh/teaching/_media/cc18/lectures/lect1/main.pdf
+%% https://cs.rit.edu/~hh/teaching/_media/cc18/lectures/lect2/main.pdf
+%% https://cs.rit.edu/~hh/teaching/_media/cc18/lectures/lect3/main.pdf
 
 \begin{document}