diff -r 8bdc44963c0c -r 2151c77e1e24 progs/re.scala
--- a/progs/re.scala	Thu Nov 17 16:21:56 2016 +0000
+++ b/progs/re.scala	Fri Nov 18 18:47:02 2016 +0000
@@ -6,8 +6,6 @@
 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 
-case class NTIMES(r: Rexp, n: Int) extends Rexp 
-case class UPNTIMES(r: Rexp, n: Int) extends Rexp 
 
 // nullable function: tests whether the regular 
 // expression can recognise the empty string
@@ -18,8 +16,6 @@
   case ALT(r1, r2) => nullable(r1) || nullable(r2)
   case SEQ(r1, r2) => nullable(r1) && nullable(r2)
   case STAR(_) => true
-  case NTIMES(r, i) => if (i == 0) true else nullable(r)
-  case UPNTIMES(r: Rexp, n: Int) => true
 }
 
 // derivative of a regular expression w.r.t. a character
@@ -32,13 +28,6 @@
     if (nullable(r1)) ALT(SEQ(der(c, r1), r2), der(c, r2))
     else SEQ(der(c, r1), r2)
   case STAR(r1) => SEQ(der(c, r1), STAR(r1))
-  case NTIMES(r1, i) => 
-    if (i == 0) ZERO else
-    if (nullable(r1)) SEQ(der(c, r1), UPNTIMES(r1, i - 1))
-    else SEQ(der(c, r1), NTIMES(r1, i - 1))
-  case UPNTIMES(r1, i) => 
-    if (i == 0) ZERO
-    else SEQ(der(c, r1), UPNTIMES(r1, i - 1)) 
 }
 
 def simp(r: Rexp) : Rexp = r match {