diff -r 761793cce563 -r c2d36c3cf8ad progs/scala/tests.scala
--- a/progs/scala/tests.scala	Thu Jun 09 12:31:02 2016 +0100
+++ b/progs/scala/tests.scala	Fri Jun 10 23:53:46 2016 +0100
@@ -10,6 +10,9 @@
 case class CHAR(c: Char) extends Rexp {
   override def toString = c.toString 
 }
+case object ANYCHAR extends Rexp {
+  override def toString = "." 
+}
 case class ALT(r1: Rexp, r2: Rexp) extends Rexp {
   override def toString = "(" + r1.toString + "|" + r2.toString + ")" 
 }
@@ -17,7 +20,132 @@
   override def toString = "(" + r1.toString + r2.toString +")"
 } 
 case class STAR(r: Rexp) extends Rexp 
-case class RECD(x: String, r: Rexp) extends Rexp
+case class RECD(x: String, r: Rexp) extends Rexp {
+  override def toString = "[" + r.toString +"]"
+}
+
+
+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
+   
+// 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 ANYCHAR => 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 ANYCHAR => ONE
+  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
+}
+
+// extracts an environment from a value
+def env(v: Val, r: Rexp) : List[(String, String)] = (v, r) match {
+  case (Empty, ONE) => Nil
+  case (Chr(c), CHAR(_)) => Nil
+  case (Chr(c), ANYCHAR) => Nil
+  case (Left(v), ALT(r1, r2)) => env(v, r1)
+  case (Right(v), ALT(r1, r2)) => env(v, r2)
+  case (Sequ(v1, v2), SEQ(r1, r2)) => env(v1, r1) ::: env(v2, r2)
+  case (Stars(vs), STAR(r)) => vs.flatMap(env(_, r))
+  case (v, RECD(x, r)) => (x, flatten(v))::env(v, r)
+}
+
+// extracts indices for the underlying strings
+def env2(v: Val, r: Rexp, n: Int) : (List[(Int, Int)], Int) = (v, r) match {
+  case (Empty, ONE) => (Nil, n)
+  case (Chr(c), CHAR(_)) => (Nil, n + 1)
+  case (Chr(c), ANYCHAR) => (Nil, n + 1)
+  case (Left(v), ALT(r1, r2)) => env2(v, r1, n)
+  case (Right(v), ALT(r1, r2)) => env2(v, r2, n)
+  case (Sequ(v1, v2), SEQ(r1, r2)) => {
+   val (e1, n1) = env2(v1, r1, n) 
+   val (e2, n2) = env2(v2, r2, n1)
+   (e1 ::: e2, n2)
+  }
+  case (Stars(Nil), STAR(r)) => (Nil, n)
+  case (Stars(v :: vs), STAR(r)) => {
+   val (e1, n1) = env2(v, r, n) 
+   val (e2, n2) = env2(Stars(vs), STAR(r), n1)
+   (e1 ::: e2, n2)
+  }
+  case (v, RECD(x, r)) => {
+    val (e1, n1) = env2(v, r, n)
+    ((n, n + flatten(v).length) :: e1, n1)
+  }
+}
+
+// injection part
+def mkeps(r: Rexp) : Val = r match {
+  case ONE => Empty
+  case ALT(r1, 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) => mkeps(r)
+}
+
+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 (ANYCHAR, Empty) => Chr(c) 
+  case (RECD(x, r1), _) => 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)
+
+
+
+// Regular expression parser
 
 case class Parser(s: String) {
   var i = 0
@@ -39,11 +167,10 @@
 
   def Term() : Rexp = {
     var f : Rexp = 
-      if (more() && peek() != ')' && peek() != '|') Factor() else ZERO;
+      if (more() && peek() != ')' && peek() != '|') Factor() else ONE;
     while (more() && peek() != ')' && peek() != '|') {
       f = SEQ(f, Factor()) ;
     }
-
     f
   }
 
@@ -53,13 +180,21 @@
       eat('*') ;
       b = STAR(b) ;
     }
-
+    while (more() && peek() == '?') {
+      eat('?') ;
+      b = ALT(b, ONE) ;
+    }
+    while (more() && peek() == '+') {
+      eat('+') ;
+      b = SEQ(b, STAR(b)) ;
+    }
     b
   }
 
   def Base() : Rexp = {
     peek() match {
-      case '(' => { eat('(') ; val r = Regex(); eat(')') ; r }
+      case '(' => { eat('(') ; val r = Regex(); eat(')') ; RECD("",r) }
+      case '.' => { eat('.'); ANYCHAR }
       case _ => CHAR(next())
     }
   }
@@ -69,14 +204,40 @@
 
 
 def process(line: String) : String = {
-  val s = line.split("\\t+")(1)
-  s + ":   " + Parser(s).Regex().toString
+  if (line.head == '#') "#" else
+    {
+      val line_split = line.split("\\t+")
+      val reg_str = line_split(1)
+      val reg = RECD("", Parser(reg_str).Regex())
+      val in_str = if (line_split(2) == "-") "" else line_split(2)
+      val res_str = line_split(3)
+      val our_val = lexing(reg, in_str)
+      val our_result = env2(our_val, reg, 0)._1.mkString("") 
+      if (our_result != res_str) 
+        { 
+          reg_str + ":   " + 
+          reg.toString + ": " + 
+          in_str + "   \n " + 
+          our_result +  
+          " => \n" + res_str + " ! " +
+          our_val + ":" + reg + "\n" 
+        }
+      else "*"
+    }
 }
 
 
-val filename = "../tests/forced-assoc.txt"
+//val filename = "../tests/forced-assoc.txt"
+//val filename = "../tests/left-assoc.txt"
+//val filename = "../tests/right-assoc.txt"
+//val filename = "../tests/class.txt"
+//val filename = "../tests/basic3.txt"
+//val filename = "../tests/totest.txt"
+//val filename = "../tests/repetition2.txt"
+//val filename = "../tests/osx-bsd-critical.txt"
+val filename = "../tests/nullsub3.txt"
 val filelines : List[String] = Source.fromFile(filename).getLines.toList
 
 
-filelines.foreach((s: String) => println(process(s)))
+filelines.foreach((s: String) => print(process(s)))