--- a/handouts/ho01.tex	Mon Sep 28 23:47:34 2015 +0100
+++ b/handouts/ho01.tex	Thu Oct 01 21:22:03 2015 +0100
@@ -272,6 +272,23 @@
 A^* \dn \bigcup_{0\le n} A^n
 \]
 
+\noindent 
+Note that this expands to
+
+\[
+A^* \dn A^0 \cup A^1 \cup A^2 \cup A^3 \cup A^4 \cup \ldots
+\]
+
+\noindent which is equivalent to
+
+\[
+A^* \dn \{[]\} \cup A \cup A@A \cup A@A@A \cup A@A@A@A \cup \ldots
+\]
+
+\noindent 
+Remember that $A^0$ is always the set containing the empty 
+string.
+
 We will use parentheses to disambiguate regular expressions.
 Parentheses are not really part of a regular expression, and
 indeed we do not need them in our code because there the tree