# HG changeset patch
# User Christian Urban <christian dot urban at kcl dot ac dot uk>
# Date 1411652466 -3600
# Node ID 62fe79ee27264872f7dd9d3fe68aba249a89c526
# Parent  232ea10bed6f15a4b142ded41a85d6be6afb475e
fixed the scala implementation

diff -r 232ea10bed6f -r 62fe79ee2726 progs/scala/re.scala
--- a/progs/scala/re.scala	Mon Sep 22 14:57:02 2014 +0100
+++ b/progs/scala/re.scala	Thu Sep 25 14:41:06 2014 +0100
@@ -15,8 +15,8 @@
 case object Void extends Val
 case class Chr(c: Char) extends Val
 case class Sequ(v1: Val, v2: Val) extends Val
-case class Left(n: Int, v: Val) extends Val
-case class Right(n: Int, v: 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
    
@@ -89,8 +89,8 @@
 def flatten(v: Val) : String = v match {
   case Void => ""
   case Chr(c) => c.toString
-  case Left(n, v) => flatten(v)
-  case Right(n, v) => flatten(v)
+  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)
@@ -100,27 +100,18 @@
 def env(v: Val) : List[(String, String)] = v match {
   case Void => Nil
   case Chr(c) => Nil
-  case Left(n, v) => env(v)
-  case Right(n, v) => env(v)
+  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 left_inc(v: Val) = v match {
-  case Left(v, n) => Left(v, n + 1)
-  case v => Left(v, 1)
-}
-
-def right_inc(v: Val) = v match {
-  case Right(v, n) => Right(v, n + 1)
-  case v => Right(v, 1)
-}
 
 def mkeps(r: Rexp) : Val = r match {
   case EMPTY => Void
   case ALT(r1, r2) => 
-    if (nullable(r1)) left_inc(mkeps(r1)) else right_inc(mkeps(r2))
+    if (nullable(r1)) Left(mkeps(r1)) else Right(mkeps(r2))
   case SEQ(r1, r2) => Sequ(mkeps(r1), mkeps(r2))
   case STAR(r) => Stars(Nil)
   case RECD(x, r) => Rec(x, mkeps(r))
@@ -131,8 +122,7 @@
   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), 1) => Left(inj(r1, c, v1), 1)
-  case (ALT(r1, r2), Left(v1), n) => inc_left(inj(r1, c, Left(v1, n - 1)))
+  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), Void) => Chr(d) 
   case (RECD(x, r1), _) => Rec(x, inj(r1, c, v))
@@ -148,6 +138,12 @@
 def lexing(r: Rexp, s: String) : Val = lex(r, s.toList)
 
 
+val r = (("1" $ "a") | (("2" $ "b") | ("3" $ "ab"))).% 
+env(lexing(r, "ba"))
+
+val r = "a" | "b"
+lexing(r,"a")
+
 // Lexing Rules for a Small While Language
 
 def PLUS(r: Rexp) = r ~ r.%