diff -r f2d7b885b3e3 -r 5dc452d7c08e hws/hw04.tex
--- a/hws/hw04.tex	Tue Sep 26 14:07:29 2017 +0100
+++ b/hws/hw04.tex	Tue Sep 26 14:08:49 2017 +0100
@@ -97,7 +97,13 @@
 
 \item What is the purpose of the record regular expression in
       the Sulzmann \& Lu algorithm?
-  
+
+\item Recall the functions \textit{nullable} and \textit{zeroable}.
+  Define recursive functions \textit{atmostempty} (for regular expressions
+  that match no string or only the empty string), \textit{somechars} (for regular
+  expressions that match some non-empty string), \textit{infinitestrings} (for regular
+  expressions that can match infinitely many strings). 
+      
   
 %\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