--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/progs/app60.scala	Mon Oct 03 00:24:45 2016 +0100
@@ -0,0 +1,4 @@
+def ders(s: List[Char], r: Rexp) : Rexp = s match {
+  case Nil => r
+  case c::s => ders(s, simp(der(c, r)))          
+}