--- a/progs/re3ext.scala	Mon Jul 27 11:02:48 2020 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,151 +0,0 @@
-abstract class Rexp 
-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
-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 
-
-def simp(r: Rexp): Rexp = r match {
-  case ALT(r1, r2) => {
-    (simp(r1), simp(r2)) match {
-      case (ZERO, r2s) => r2s
-      case (r1s, ZERO) => r1s
-      case (r1s, r2s) => if (r1s == r2s) r1s else ALT(r1s, r2s)
-    }
-  }
-  case SEQ(r1, r2) => {
-    (simp(r1), simp(r2)) match {
-      case (ZERO, _) => ZERO
-      case (_, ZERO) => ZERO
-      case (ONE, r2s) => r2s
-      case (r1s, ONE) => r1s
-      case (r1s, r2s) => SEQ(r1s, r2s)
-    }
-  }
-  case NTIMES(r, n) => NTIMES(simp(r), n)    
-  case r => r
-}
-
-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)
-}
-
-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))
-}
-
-def ders (s: List[Char], r: Rexp) : Rexp = s match {
-  case Nil => r
-  case c::s => ders(s, simp(der(c, r)))
-}
-
-def matches(r: Rexp, s: String) : Boolean = nullable(ders(s.toList, r))
-
-
-//one or zero
-def OPT(r: Rexp) = ALT(r, ONE)
-
-def EVIL(n: Int) = SEQ(NTIMES(OPT(CHAR('a')), n), NTIMES(CHAR('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 9001 by 1000) {
-  println(i + " " + "%.5f".format(time_needed(1, matches(EVIL(i), "a" * i))))
-}
-*/
-
-// some convenience for typing in regular expressions
-import scala.language.implicitConversions    
-import scala.language.reflectiveCalls 
-
-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)
-
-implicit def RexpOps (r: Rexp) = new {
-  def | (s: Rexp) = ALT(r, s)
-  def % = STAR(r)
-  def ~ (s: Rexp) = SEQ(r, s)
-}
-
-implicit def stringOps (s: String) = new {
-  def | (r: Rexp) = ALT(s, r)
-  def | (r: String) = ALT(s, r)
-  def % = STAR(s)
-  def ~ (r: Rexp) = SEQ(s, r)
-  def ~ (r: String) = SEQ(s, r)
-}
-
-
-def PLUS(r: Rexp) = SEQ(r, STAR(r))
-def RANGE(s: List[Char]) : Rexp = s match {
-  case Nil => ZERO
-  case c::s => ALT(CHAR(c), RANGE(s))
-} 
-def NMTIMES(r: Rexp, n: Int, m: Int) : Rexp =
-  if (n >= m) NTIMES(r, n) else ALT(NTIMES(r, m), NMTIMES(r, n, m - 1))
-
-
-println("Coursework:")
-val REG1 = PLUS(PLUS("a" ~ "a" ~ "a"))
-val REG2 = PLUS(PLUS("aaaaaaaaaaaaaaaaaaa" ~ OPT("a")))  // 19 as ~ a?
-
-
-//40 * aaa matches
-//43 * aaa + aa does not
-//45 * aaa + a
-
-println("EVIL1:")
-println(matches(REG1, "aaa" * 40))
-println(matches(REG1, "aaa" * 43 + "aa"))
-println(matches(REG1, "aaa" * 45 + "a"))
-println("EVIL2:")
-println(matches(REG2, "aaa" * 40))
-println(matches(REG2, "aaa" * 43 + "aa"))
-println(matches(REG2, "aaa" * 45 + "a"))
-
-println("EMAIL:")
-val LOWERCASE = "abcdefghijklmnopqrstuvwxyz"
-val DIGITS = "0123456789"
-val EMAIL = PLUS(RANGE((LOWERCASE + DIGITS + "_" + "." + "-").toList)) ~ "@" ~ 
-            PLUS(RANGE((LOWERCASE + DIGITS + "." + "-").toList)) ~ "." ~
-            NMTIMES(RANGE((LOWERCASE + ".").toList), 2, 6)
-
-val my_email = "christian.urban@kcl.ac.uk"
-
-println(matches(EMAIL, my_email))
-
-println(matches(NTIMES("a", 2), "a"))
-println(matches(NTIMES("a", 2), "aa"))
-println(matches(NTIMES("a", 2), "aaa"))
-
-println(matches(NMTIMES("a", 2, 3), "a"))
-println(matches(NMTIMES("a", 2, 3), "aa"))
-println(matches(NMTIMES("a", 2, 3), "aaa"))
-println(matches(NMTIMES("a", 2, 3), "aaaa"))