--- a/hws/hw03.tex Mon Sep 22 13:42:14 2014 +0100
+++ b/hws/hw03.tex Fri Sep 26 14:06:55 2014 +0100
@@ -11,34 +11,41 @@
\begin{enumerate}
\item What is a regular language?
-\item Assume you have an alphabet consisting of the letters $a$, $b$ and $c$ only.
-(1) Find a regular expression that recognises the two strings $ab$ and $ac$. (2)
-Find a regular expression that matches all strings \emph{except} these two strings.
-Note, you can only use regular expressions of the form
+\item Assume you have an alphabet consisting of the letters
+ $a$, $b$ and $c$ only. (1) Find a regular expression
+ that recognises the two strings $ab$ and $ac$. (2) Find
+ a regular expression that matches all strings
+ \emph{except} these two strings. Note, you can only use
+ regular expressions of the form
+
+ \begin{center} $r ::=
+ \varnothing \;|\; \epsilon \;|\; c \;|\; r_1 + r_2 \;|\;
+ r_1 \cdot r_2 \;|\; r^*$
+ \end{center}
+
+\item Define the function \textit{zeroable} which takes a
+ regular expression as argument and returns a boolean.
+ The function should satisfy the following property:
+
\begin{center}
-$r ::= \varnothing \;|\; \epsilon \;|\; c \;|\; r_1 + r_2 \;|\; r_1 \cdot r_2 \;|\; r^*$
-\end{center}
-
-\item Define the function $zeroable$ which takes a regular expression as argument
-and returns a boolean. The
-function should satisfy the following property:
-\begin{center}
-$zeroable(r)$ \;if and only if\; $L(r) = \varnothing$
+$\textit{zeroable(r)} \;\text{if and only if}\; L(r) = \varnothing$
\end{center}
\item Define the tokens and regular expressions for a language
-consisting of numbers, left-parenthesis (, right-parenthesis ),
-identifiers and the operations $+$, $-$ and $*$. Can the following strings
-in this language be lexed?
+ consisting of numbers, left-parenthesis $($,
+ right-parenthesis $)$, identifiers and the operations $+$,
+ $-$ and $*$. Can the following strings in this language
+ be lexed?
\begin{itemize}
-\item \texttt{"}$(a + 3) * b$\texttt{"}
-\item \texttt{"}$)()++ -33$\texttt{"}
-\item \texttt{"}$(a / 3) * 3$\texttt{"}
+ \item $(a + 3) * b$
+ \item $)()++ -33$
+ \item $(a / 3) * 3$
\end{itemize}
+In case they can, can you give the corresponding token
+sequences.
-In case they can, can you give the corresponding token sequences.
\end{enumerate}