--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/app5.scala	Thu Sep 27 11:59:41 2012 +0100
@@ -0,0 +1,8 @@
+def nullable (r: Rexp) : Boolean = r match {
+  case NULL => false
+  case EMPTY => true
+  case CHAR(_) => false
+  case ALT(r1, r2) => nullable(r1) || nullable(r2)
+  case SEQ(r1, r2) => nullable(r1) && nullable(r2)
+  case STAR(_) => true
+}