
diff -r e7e7fe274f5c -r 3aebe5505a80 cws/cw01.tex
--- a/cws/cw01.tex	Tue Apr 04 22:31:09 2023 +0100
+++ b/cws/cw01.tex	Thu May 25 21:22:23 2023 +0100
@@ -57,6 +57,7 @@
   $[c_1,c_2,\ldots,c_n]$ & a set of characters---for character ranges\\
   $r^+$ & one or more times $r$\\
   $r^?$ & optional $r$\\
+  $r_1 \,\&\, r_2$ & intersection (matched by both $r_1$ and $r_2$)\\
   $r^{\{n\}}$ & exactly $n$-times\\
   $r^{\{..m\}}$ & zero or more times $r$ but no more than $m$-times\\
   $r^{\{n..\}}$ & at least $n$-times $r$\\
@@ -72,7 +73,7 @@
 case classes  for the basic regular expressions, but also explicit case
 classes for
 the extended regular expressions.\footnote{Please call them
-  \code{RANGE}, \code{PLUS}, \code{OPTIONAL}, \code{NTIMES},
+  \code{RANGE}, \code{PLUS}, \code{OPTIONAL}, \code{AND}, \code{NTIMES},
   \code{UPTO}, \code{FROM} and \code{BETWEEN}.} 
   That means do not treat the extended regular expressions
 by just translating them into the basic ones. See also Question 3,
@@ -92,6 +93,7 @@
   $L([c_1,c_2,\ldots,c_n])$ & $\dn$ & $\{[c_1], [c_2], \ldots, [c_n]\}$\\ 
   $L(r^+)$                  & $\dn$ & $\bigcup_{1\le i}.\;L(r)^i$\\
   $L(r^?)$                  & $\dn$ & $L(r) \cup \{[]\}$\\
+  $L(r_1 \,\&\, r_2)$       & $\dn$ & $L(r_1) \cap L(r_2)$\\
   $L(r^{\{n\}})$             & $\dn$ & $L(r)^n$\\
   $L(r^{\{..m\}})$           & $\dn$ & $\bigcup_{0\le i \le m}.\;L(r)^i$\\
   $L(r^{\{n..\}})$           & $\dn$ & $\bigcup_{n\le i}.\;L(r)^i$\\
@@ -121,8 +123,9 @@
 \subsection*{Question 1 (Unmarked)}
 
 What is your King's email address (you will need it in
-Question 5)? Also could you please let me know from where you will be mainly
-studying? (online / in-person, in London / somewhere else) Thanks!
+Question 5)? Also could you please let me know whether you are
+a BSc / MSci and the year you are in (in case of MSci). Thanks!
+
 
 \subsection*{Question 2 (Unmarked)}
 
@@ -136,7 +139,7 @@
 From the
 lectures you have seen the definitions for the functions
 \textit{nullable} and \textit{der} for the basic regular
-expressions. Implement and write down the rules for the extended
+expressions. Implement and \underline{write down} the rules for the extended
 regular expressions:
 
 \begin{center}
@@ -144,6 +147,7 @@
   $\textit{nullable}([c_1,c_2,\ldots,c_n])$  & $\dn$ & $?$\\
   $\textit{nullable}(r^+)$                   & $\dn$ & $?$\\
   $\textit{nullable}(r^?)$                   & $\dn$ & $?$\\
+  $\textit{nullable}(r_1 \,\&\, r_2)$        & $\dn$ & $?$\\
   $\textit{nullable}(r^{\{n\}})$              & $\dn$ & $?$\\
   $\textit{nullable}(r^{\{..m\}})$            & $\dn$ & $?$\\
   $\textit{nullable}(r^{\{n..\}})$            & $\dn$ & $?$\\
@@ -157,6 +161,7 @@
   $der\, c\, ([c_1,c_2,\ldots,c_n])$  & $\dn$ & $?$\\
   $der\, c\, (r^+)$                   & $\dn$ & $?$\\
   $der\, c\, (r^?)$                   & $\dn$ & $?$\\
+  $der\, c\, (r_1 \,\&\, r_2)$        & $\dn$ & $?$\\
   $der\, c\, (r^{\{n\}})$              & $\dn$ & $?$\\
   $der\, c\, (r^{\{..m\}})$           & $\dn$ & $?$\\
   $der\, c\, (r^{\{n..\}})$           & $\dn$ & $?$\\
@@ -176,7 +181,7 @@
 \noindent
 Given the definitions of \textit{nullable} and \textit{der}, it is
 easy to implement a regular expression matcher.  Test your regular
-expression matcher with (at least) the examples:
+expression matcher with (\underline{at least}) the examples:
 
 
 \begin{center}




