--- a/scala/automata1.scala	Sat Jun 15 09:11:11 2013 -0400
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,95 +0,0 @@
-
-// a class for deterministic finite automata,
-// the type of states is kept polymorphic
-
-case class Automaton[A](start: A, states: Set[A], delta: Map[(A, Char), A], fins: Set[A]) {
-
-  // the transition function lifted to list of characters
-  def deltas(q: A, cs: List[Char]) : A = 
-    if (states.contains(q)) cs match {
-      case Nil => q
-      case c::cs => 
-        if (delta.isDefinedAt(q, c)) deltas(delta(q, c), cs)
-        else throw new RuntimeException(q + " does not have a transition for " + c)
-    }
-    else throw new RuntimeException(q + " is not a state of the automaton")
-
-  // wether a string is accepted by the automaton
-  def accepts(s: String) = 
-    try {
-      fins.contains(deltas(start, s.toList))
-    } catch {
-      case e:RuntimeException => false
-    }
-}
-
-
-
-abstract class Rexp
-
-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
-case class SEQ(r1: Rexp, r2: Rexp) extends Rexp 
-case class STAR(r: Rexp) extends Rexp
-
-implicit def string2rexp(s : String) = { 
-  def chars2rexp (cs: List[Char]) : Rexp = cs match {
-    case Nil => EMPTY
-    case c::Nil => CHAR(c)
-    case c::cs => SEQ(CHAR(c), chars2rexp(cs))
-  }
-  chars2rexp(s.toList)
-}
-
-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
-}
-
-def der (r: Rexp, c: Char) : Rexp = r match {
-  case NULL => NULL
-  case EMPTY => NULL
-  case CHAR(d) => if (c == d) EMPTY else NULL
-  case ALT(r1, r2) => ALT(der(r1, c), der(r2, c))
-  case SEQ(r1, r2) => if (nullable(r1)) ALT(SEQ(der(r1, c), r2), der(r2, c))
-                      else SEQ(der(r1, c), r2)
-  case STAR(r) => SEQ(der(r, c), STAR(r))
-}
-
-
-// Here we construct an automaton whose
-// states are regular expressions
-type State = Rexp
-type States = Set[State]
-type Transition =  Map[(State, Char), State]
-
-def goto(q: State, c: Char, qs: States, delta: Transition) : (States, Transition) = {
-  val qc : State = der(q, c)
-  if (qs.contains(qc)) (qs, delta + ((q, c) -> q))
-  else explore(qs + qc, delta + ((q, c) -> qc), qc)
-}
-
-// we use as alphabet all lowercase letters
-val alphabet = "abcdefghijklmnopqrstuvwxyz".toSet
-   
-def explore (qs: States, delta: Transition, q: State) : (States, Transition) =
-  alphabet.foldRight[(States, Transition)] (qs, delta) ((c, qsd) => goto(q, c, qsd._1, qsd._2)) 
-
-
-def mk_automaton (r: Rexp) : Automaton[Rexp] = {
-  val (qs, delta) = explore(Set(r), Map(), r);
-  val fins = for (q <- qs if nullable(q)) yield q;
-  Automaton[Rexp](r, qs, delta, fins)
-}
-
-val A = mk_automaton(ALT("ab","ac"))
-
-println(A.accepts("bd"))
-println(A.accepts("ab"))
-println(A.accepts("ac"))