diff -r 8b432cef3805 -r 81c85f2746f5 progs/scala/re-ext.scala
--- a/progs/scala/re-ext.scala	Thu Mar 02 12:39:27 2017 +0000
+++ b/progs/scala/re-ext.scala	Sat Mar 04 21:35:12 2017 +0000
@@ -6,12 +6,11 @@
 abstract class Rexp 
 case object ZERO extends Rexp
 case object ONE extends Rexp
-case class CHAR(c: Char) extends Rexp
+case class CHARS(f: Char => Boolean) 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 
 case class RECD(x: String, r: Rexp) extends Rexp
-case class CRANGE(cs: String) extends Rexp
 case class PLUS(r: Rexp) extends Rexp
 case class OPT(r: Rexp) extends Rexp
 case class NTIMES(r: Rexp, n: Int) extends Rexp
@@ -28,8 +27,8 @@
 // some convenience for typing in regular expressions
 def charlist2rexp(s : List[Char]): Rexp = s match {
   case Nil => ONE
-  case c::Nil => CHAR(c)
-  case c::s => SEQ(CHAR(c), charlist2rexp(s))
+  case c::Nil => CHARS(_ == c)
+  case c::s => SEQ(CHARS(_ == c), charlist2rexp(s))
 }
 implicit def string2rexp(s : String) : Rexp = charlist2rexp(s.toList)
 
@@ -68,12 +67,11 @@
 def nullable (r: Rexp) : Boolean = r match {
   case ZERO => false
   case ONE => true
-  case CHAR(_) => false
+  case CHARS(_) => false
   case ALT(r1, r2) => nullable(r1) || nullable(r2)
   case SEQ(r1, r2) => nullable(r1) && nullable(r2)
   case STAR(_) => true
   case RECD(_, r1) => nullable(r1)
-  case CRANGE(_) => false
   case PLUS(r) => nullable(r)
   case OPT(_) => true
   case NTIMES(r, n) => if (n == 0) true else nullable(r)
@@ -83,17 +81,16 @@
 def der (c: Char, r: Rexp) : Rexp = r match {
   case ZERO => ZERO
   case ONE => ZERO
-  case CHAR(d) => if (c == d) ONE else ZERO
+  case CHARS(f) => if (f(c)) ONE else ZERO
   case ALT(r1, r2) => ALT(der(c, r1), der(c, r2))
   case SEQ(r1, r2) => 
     if (nullable(r1)) ALT(SEQ(der(c, r1), r2), der(c, r2))
     else SEQ(der(c, r1), r2)
   case STAR(r) => SEQ(der(c, r), STAR(r))
   case RECD(_, r1) => der(c, r1)
-  case CRANGE(cs) => if (cs.contains(c)) ONE else ZERO
   case PLUS(r) => SEQ(der(c, r), STAR(r))
   case OPT(r) => ALT(der(c, r), ZERO)
-  case NTIMES(r, n) => if (n == 0) ZERO else der(c, SEQ(r, NTIMES(r, n - 1)))
+  case NTIMES(r, n) => if (n == 0) ZERO else SEQ(der(c, r), NTIMES(r, n - 1))
 }
 
 // derivative w.r.t. a string (iterates der)
@@ -136,7 +133,7 @@
   case RECD(x, r) => Rec(x, mkeps(r))
   case PLUS(r) => Stars(List(mkeps(r)))
   case OPT(_) => Right(Empty)
-  case NTIMES(r, n) => if (n == 0) Stars(Nil) else Stars(Nil.padTo(n, mkeps(r)))
+  case NTIMES(r, n) => Stars(List.fill(n)(mkeps(r)))
 }
 
 
@@ -147,14 +144,11 @@
   case (SEQ(r1, r2), Right(v2)) => Sequ(mkeps(r1), inj(r2, c, v2))
   case (ALT(r1, r2), Left(v1)) => Left(inj(r1, c, v1))
   case (ALT(r1, r2), Right(v2)) => Right(inj(r2, c, v2))
-  case (CHAR(d), Empty) => Chr(c) 
+  case (CHARS(_), Empty) => Chr(c) 
   case (RECD(x, r1), _) => Rec(x, inj(r1, c, v))
-  case (CRANGE(_), Empty) => Chr(c) 
   case (PLUS(r), Sequ(v1, Stars(vs))) => Stars(inj(r, c, v1)::vs)
   case (OPT(r), Left(v1)) => Left(inj(r, c, v1))
   case (NTIMES(r, n), Sequ(v1, Stars(vs))) => Stars(inj(r, c, v1)::vs)
-  case (NTIMES(r, n), Left(Sequ(v1, Stars(vs)))) => Stars(inj(r, c, v1)::vs)
-  case (NTIMES(r, n), Right(Stars(v::vs))) => Stars(mkeps(r)::inj(r, c, v)::vs)
 }
 
 // main unsimplified lexing function (produces a value)
@@ -368,7 +362,7 @@
 // first benchmark regex 
 //=======================
 
-val reWord = CRANGE("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")
+val reWord = CHARS("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789" contains _)
 
 val reWordStar = STAR(reWord)
 val reWordPlus = reWord ~ reWordStar