
diff -r ca349cfe3474 -r c29853b672fb hws/hw04.tex
--- a/hws/hw04.tex	Sat Nov 01 15:06:41 2014 +0000
+++ b/hws/hw04.tex	Sat Nov 01 16:19:05 2014 +0000
@@ -67,7 +67,11 @@
   that can recognise any character, and a regular expression \texttt{NOT} that recognises
   the complement of a regular expression.)
 
-
+\item How many basic regular expressions are there to match the string
+  $abcd$? (ii) How many if they cannot include $\epsilon$ and
+  $\varnothing$? (iii) How many if they are also not allowed to
+  contain stars? (iv) How many if they are also not allowed to contain
+  $\_ + \_$?
 
 %\item (Optional) The tokenizer in \texttt{regexp3.scala} takes as
 %argument a string and a list of rules. The result is a list of tokens. Improve this tokenizer so 




