# HG changeset patch
# User Christian Urban <christian dot urban at kcl dot ac dot uk>
# Date 1380189954 -3600
# Node ID ffde837b1db1a923381428e142828e2531b5339f
# Parent  bea2dd1c7e73f7fe52c14e4bb8e04db550e8457d
updated

diff -r bea2dd1c7e73 -r ffde837b1db1 hws/hw01.pdf
Binary file hws/hw01.pdf has changed
diff -r bea2dd1c7e73 -r ffde837b1db1 hws/hw01.tex
--- a/hws/hw01.tex	Thu Sep 26 10:52:54 2013 +0100
+++ b/hws/hw01.tex	Thu Sep 26 11:05:54 2013 +0100
@@ -18,6 +18,9 @@
 \item {\bf (Optional)} Have a look at the crawler programs. 
 Can you find a usage for them in your daily programming life?
 
+\item Read the handout of the first lecture and make sure you
+understand the concepts of strings and languages. 
+
 \item In the context of the AFL-course, what is meant by the term \emph{language}?
 
 \item Give the definition for regular expressions. What is the meaning of a 
@@ -29,8 +32,6 @@
 \item How is the power of a language defined? (Hint: There are two rules, one for $\_\!\_^0$ and
 one for $\_\!\_^{n+1}$.)
 
-\item Given the regular expressions $r_1 = \epsilon$ and $r_2 = \varnothing$ and $r_3 = a$.
-How many strings can the regular expressions $r_1^*$, $r_2^*$ and $r_3^*$ each match?
 
 \end{enumerate}
 
diff -r bea2dd1c7e73 -r ffde837b1db1 hws/hw02.pdf
Binary file hws/hw02.pdf has changed
diff -r bea2dd1c7e73 -r ffde837b1db1 hws/hw02.tex
--- a/hws/hw02.tex	Thu Sep 26 10:52:54 2013 +0100
+++ b/hws/hw02.tex	Thu Sep 26 11:05:54 2013 +0100
@@ -9,6 +9,12 @@
 \section*{Homework 2}
 
 \begin{enumerate}
+\item What is the meaning of a regular expression? Give an inductive definition.
+
+\item Given the regular expressions $r_1 = \epsilon$ and $r_2 = \varnothing$ and $r_3 = a$.
+How many strings can the regular expressions $r_1^*$, $r_2^*$ and $r_3^*$ each match?
+
+
 \item Give regular expressions for (a) decimal numbers and for (b) binary numbers. 
 (Hint: Observe that the empty string is not a number. Also observe that leading 0s 
 are normally not written.)