
diff -r a5fade10c207 -r baf41b05210f handouts/notation.tex
--- a/handouts/notation.tex	Sun Sep 14 23:32:22 2014 +0100
+++ b/handouts/notation.tex	Mon Sep 15 03:49:07 2014 +0100
@@ -106,12 +106,12 @@
 stands for the string of $n$ repeated $a$s. So $a^{n}b^{n}$ is
 a string that has as many $a$s as $b$s.
 
-While for us strings are just lists of characters, programming
-languages often differentiate between the two concepts. In
-Scala, for example, there is the type of \code{String} and the
-type of lists of characters,  \code{List[Char]}. They are not
-the same and we need to explicitly coerce elements between the
-two types, for example
+Note however that while for us strings are just lists of
+characters, programming languages often differentiate between
+the two concepts. In Scala, for example, there is the type of
+\code{String} and the type of lists of characters,
+\code{List[Char]}. They are not the same and we need to
+explicitly coerce elements between the two types, for example
 
 \begin{lstlisting}[numbers=none]
 scala> "abc".toList
@@ -284,11 +284,11 @@
 $\Sigma = \{a, b\}$, then $\Sigma^*$ is
 
 \[
-\{[], a, b, ab, ba, aaa, aab, aba, abb, baa, bab, \ldots\}
+\{[], a, b, aa, ab, ba, bb, aaa, aab, aba, abb, baa, bab, \ldots\}
 \]
 
-\noindent or in other words all strings containing $a$s and 
-$b$s only.
+\noindent or in other words all strings containing $a$s and
+$b$s only, plus the empty string.
 
 \end{document}
 




