diff -r 47f86885d481 -r e85600529ca5 re2.scala
--- a/re2.scala	Sun Dec 23 00:38:56 2012 +0000
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,100 +0,0 @@
-    
-abstract class Rexp {
-  def simp : Rexp = this
-}
-
-case object NULL extends Rexp
-case object EMPTY 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 (NULL, r) => r
-    case (r, NULL) => r
-    case (r, EMPTY) => if (nullable(r)) r else ALT(r, EMPTY)
-    case (EMPTY, r) => if (nullable(r)) r else ALT(r, EMPTY)
-    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 (NULL, _) => NULL
-    case (_, NULL) => NULL
-    case (EMPTY, r) => r
-    case (r, EMPTY) => r
-    case (r1, r2) => SEQ(r1, r2)
-  }
-}
-case class STAR(r: Rexp) extends Rexp {
-  override def simp = r.simp match {
-    case NULL => EMPTY
-    case EMPTY => EMPTY
-    case r => STAR(r)
-  }
-}
-
-// some convenience for typing in regular expressions
-def charlist2rexp(s : List[Char]) : Rexp = s match {
-  case Nil => EMPTY
-  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 NULL => false
-  case EMPTY => true
-  case CHAR(_) => false
-  case ALT(r1, r2) => nullable(r1) || nullable(r2)
-  case SEQ(r1, r2) => nullable(r1) && nullable(r2)
-  case STAR(_) => true
-}
-
-// derivative of a regular expression w.r.t. a character
-def der (c: Char, r: Rexp) : Rexp = r match {
-  case NULL => NULL
-  case EMPTY => NULL
-  case CHAR(d) => if (c == d) EMPTY else NULL
-  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))
-}
-
-// derivative w.r.t. a string (iterates der)
-def ders (s: List[Char], r: Rexp) : Rexp = s match {
-  case Nil => r
-  case c::s => ders(s, der(c, r).simp)
-}
-
-// main matcher function
-def matcher(r: Rexp, s: String) : Boolean = nullable(ders(s.toList, r))
-
-
-//one or zero
-def OPT(r: Rexp) = ALT(r, EMPTY)
-
-//n-times
-def NTIMES(r: Rexp, n: Int) : Rexp = n match {
-  case 0 => EMPTY
-  case 1 => r
-  case n => SEQ(r, NTIMES(r, n - 1))
-}
-
-def RTEST(n: Int) = SEQ(NTIMES(OPT("a"), n), NTIMES("a", n))
-
-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)
-}
-
-for (i <- 1 to 100) {
-  println(i + ": " + "%.5f".format(time_needed(1, matcher(RTEST(i), "a" * i))))
-}
-
-