--- a/progs/re3.scala	Wed Oct 18 11:02:44 2017 +0100
+++ b/progs/re3.scala	Wed Oct 18 12:33:00 2017 +0100
@@ -11,6 +11,12 @@
 case class SEQ(r1: Rexp, r2: Rexp) extends Rexp 
 case class STAR(r: Rexp) extends Rexp 
 case class NTIMES(r: Rexp, n: Int) extends Rexp 
+case class CSET(cs: Set[Char]) extends Rexp
+case class CFUN(f: Char => Bool) extends Rexp
+
+CSET(('a' to 'z').toSet)
+
+val CSET2(cs: Set[Char]) = CFUN((c:Char) => cs.contains(c))
 
 
 // nullable function: tests whether the regular