--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/progs/app51.scala	Sat Jun 15 09:23:18 2013 -0400
@@ -0,0 +1,8 @@
+abstract class Rexp
+
+case object NULL extends Rexp
+case object EMPTY extends Rexp
+case class CHAR(c: Char) extends Rexp
+case class ALT(r1: Rexp, r2: Rexp) extends Rexp
+case class SEQ(r1: Rexp, r2: Rexp) extends Rexp
+case class STAR(r: Rexp) extends Rexp