diff -r c498cb53a9a8 -r ea47c3b8f35f hws/hw04.tex
--- a/hws/hw04.tex	Wed Jun 28 12:46:23 2017 +0100
+++ b/hws/hw04.tex	Thu Aug 03 01:21:19 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