diff -r e74c696821a2 -r 5deefcc8cffa progs/re5.scala
--- a/progs/re5.scala	Tue Aug 23 23:12:55 2016 +0200
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,118 +0,0 @@
-import scala.annotation.tailrec    
-import scala.language.implicitConversions
-    
-abstract class Rexp {
-  def simp : Rexp = this
-}
-
-case object ZERO extends Rexp
-case object ONE extends Rexp
-case class CHAR(c: Char) extends Rexp
-case class ALT(r1: Rexp, r2: Rexp) extends Rexp {
-  override def simp = (r1.simp, r2.simp) match {
-    case (ZERO, r) => r
-    case (r, ZERO) => r
-    case (r, ONE) => if (nullable(r)) r else ALT(r, ONE)
-    case (ONE, r) => if (nullable(r)) r else ALT(r, ONE)
-    case (r1, r2) => if (r1 == r2) r1 else ALT(r1, r2)
-  }
-}
-case class SEQ(r1: Rexp, r2: Rexp) extends Rexp {
-  override def simp = (r1.simp, r2.simp) match {
-    case (ZERO, _) => ZERO
-    case (_, ZERO) => ZERO
-    case (ONE, r) => r
-    case (r, ONE) => r
-    case (r1, r2) => SEQ(r1, r2)
-  }
-}
-case class STAR(r: Rexp) extends Rexp {
-  override def simp = r.simp match {
-    case ZERO => ONE
-    case ONE => ONE
-    case r => STAR(r)
-  }
-}
-case class NTIMES(r: Rexp, n: Int) extends Rexp {
-  override def simp = if (n == 0) ONE else 
-    r.simp match {
-      case ZERO => ZERO
-      case ONE => ONE
-      case r => NTIMES(r, n)
-    }
-}
-
-// 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))
-}
-implicit def string2rexp(s : String) : Rexp = charlist2rexp(s.toList)
-
-
-// nullable function: tests whether the regular 
-// expression can recognise the empty string
-def nullable (r: Rexp) : Boolean = r match {
-  case ZERO => false
-  case ONE => true
-  case CHAR(_) => false
-  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)
-}
-
-// derivative of a regular expression w.r.t. a character
-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 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 NTIMES(r, i) => 
-    if (i == 0) ZERO else SEQ(der(c, r), NTIMES(r, i - 1))
-}
-
-// derivative w.r.t. a string (iterates der)
-def ders2(s: List[Char], r: Rexp) : Rexp = (s, r) match {
-  case (Nil, r) => r
-  case (s, ZERO) => ZERO
-  case (s, ONE) => if (s == Nil) ONE else ZERO
-  case (s, CHAR(c)) => if (s == List(c)) ONE else 
-                       if (s == Nil) CHAR(c) else ZERO
-  case (s, ALT(r1, r2)) => ALT(ders2(s, r2), ders2(s, r2))
-  case (c::s, r) => ders2(s, der(c, r).simp)
-}
-
-// main matcher function
-def matcher(r: Rexp, s: String) : Boolean = nullable(ders2(s.toList, r))
-
-
-//one or zero
-def OPT(r: Rexp) = ALT(r, ONE)
-
-def EVIL1(n: Int) = SEQ(NTIMES(OPT("a"), n), NTIMES("a", n))
-val EVIL2 = SEQ(STAR("a"), "b")
-
-def time_needed[T](i: Int, code: => T) = {
-  val start = System.nanoTime()
-  for (j <- 1 to i) code
-  val end = System.nanoTime()
-  (end - start)/(i * 1.0e9)
-}
-
-val i = 5000
-println(i + " " + "%.5f".format(time_needed(10, matcher(EVIL1(i), "a" * i))))
-
-for (i <- 1 to 7000001 by 1000000) {
-  println(i + " " + "%.5f".format(time_needed(2, matcher(EVIL1(i), "a" * i))))
-}
-
-for (i <- 1 to 7500001 by 500000) {
-  println(i + " " + "%.5f".format(time_needed(2, matcher(EVIL2, "a" * i))))
-}
-