--- a/progs/scala/re2.scala	Sat Mar 19 23:27:29 2016 +0000
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,157 +0,0 @@
-import scala.language.implicitConversions    
-import scala.language.reflectiveCalls
-import scala.annotation.tailrec   
-
-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 RECD(x: String, r: Rexp) extends Rexp
-
-abstract class Val
-case object Empty extends Val
-case class Chr(c: Char) extends Val
-case class Sequ(v1: Val, v2: Val) extends Val
-case class Left(v: Val) extends Val
-case class Right(v: Val) extends Val
-case class Stars(vs: List[Val]) extends Val
-case class Rec(x: String, v: Val) extends Val
-   
-// 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)
-
-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 $ (r: Rexp) = RECD(s, r)
-}
-
-// size of a regular expressions - for testing purposes 
-def size(r: Rexp) : Int = r match {
-  case ZERO => 1
-  case ONE => 1
-  case CHAR(_) => 1
-  case ALT(r1, r2) => 1 + size(r1) + size(r2)
-  case SEQ(r1, r2) => 1 + size(r1) + size(r2)
-  case STAR(r) => 1 + size(r)
-  case RECD(_, r) => 1 + size(r)
-}
-
-
-// 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 RECD(_, r1) => nullable(r1)
-}
-
-// 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 RECD(_, r1) => der(c, r1)
-}
-
-// 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))
-}
-
-// extracts a string from value
-def flatten(v: Val) : String = v match {
-  case Empty => ""
-  case Chr(c) => c.toString
-  case Left(v) => flatten(v)
-  case Right(v) => flatten(v)
-  case Sequ(v1, v2) => flatten(v1) + flatten(v2)
-  case Stars(vs) => vs.map(flatten).mkString
-  case Rec(_, v) => flatten(v)
-}
-
-// extracts an environment from a value
-def env(v: Val) : List[(String, String)] = v match {
-  case Empty => Nil
-  case Chr(c) => Nil
-  case Left(v) => env(v)
-  case Right(v) => env(v)
-  case Sequ(v1, v2) => env(v1) ::: env(v2)
-  case Stars(vs) => vs.flatMap(env)
-  case Rec(x, v) => (x, flatten(v))::env(v)
-}
-
-def inj(r: Rexp, c: Char, v: Val) : Val = (r, v) match {
-  case (STAR(r), Sequ(v1, Stars(vs))) => Stars(inj(r, c, v1)::vs)
-  case (SEQ(r1, r2), Sequ(v1, v2)) => Sequ(inj(r1, c, v1), v2)
-  case (SEQ(r1, r2), Left(Sequ(v1, v2))) => Sequ(inj(r1, c, v1), v2)
-  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 (RECD(x, r1), _) => Rec(x, inj(r1, c, v))
-}
-
-
-// main lexing function (produces a value)
-def lex(r: Rexp, s: List[Char]) : Val = s match {
-  case Nil => if (nullable(r)) mkeps(r) else throw new Exception("Not matched")
-  case c::cs => inj(r, c, lex(der(c, r), cs))
-}
-
-def lexing(r: Rexp, s: String) : Val = lex(r, s.toList)
-
-// Examples
-val K: Rexp = "a" | "b"
-val I: Rexp = "ab" | "ba"  
-
-val R0 = (K | I).%
-
-lexing(R0, "abab")
-
-val K: Rexp = ("key" $ "a" | "b")
-val I: Rexp = ("id" $ ("ab" | "ba"))  
-
-val R0 = (K | I).%
-lexing(R0, "abaa")
-env(lexing(R0, "abaa"))
-
-val r0: Rexp = (K | I).%
-val r1 = der('a', r0)
-val r1_simp = simp2(r1)
-val r2 = der('b', r1)
-val r2_simp = simp2(r2)
-nullable(r2)
-val v2 = mkeps(r2)
-val v1 = inj(r1, 'b', v2)
-val v0 = inj(r0, 'a', v1)
-env(v0)
-env(lexing(r0, "abab"))
-