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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2009, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
// $Id$
package scala.util.automata
import scala.collection.{immutable, mutable, Map}
import scala.util.regexp.WordExp
/** This class turns a regexp into a NondetWordAutom using the
* celebrated position automata construction (also called Berry-Sethi or
* Glushkov)
*
* @author Burak Emir
* @version 1.0
*/
abstract class WordBerrySethi extends BaseBerrySethi {
override val lang: WordExp
type _labelT = this.lang._labelT
import lang.{Alt, Eps, Letter, Meta, RegExp, Sequ, Star}
protected var labels:mutable.HashSet[_labelT] = _
// don't let this fool you, only labelAt is a real, surjective mapping
protected var labelAt: immutable.Map[Int, _labelT] = _ // new alphabet "gamma"
protected var deltaq: Array[mutable.HashMap[_labelT,List[Int]]] = _ // delta
protected var defaultq: Array[List[Int]] = _ // default transitions
protected var initials:immutable.Set[Int] = _
//NondetWordAutom revNfa
// maps a letter to an Integer ( the position )
// is not *really* needed (preorder determines position!)
//protected var posMap: mutable.HashMap[RegExp, Int] = _;
/** Computes <code>first(r)</code> where the word regexp <code>r</code>.
*
* @param r the regular expression
* @return the computed set <code>first(r)</code>
*/
protected override def compFirst(r: RegExp): immutable.Set[Int] = r match {
case x:Letter => emptySet + x.pos //posMap(x); // singleton set
case Eps => emptySet /*ignore*/
case _ => super.compFirst(r)
}
/** Computes <code>last(r)</code> where the word regexp <code>r</code>.
*
* @param r the regular expression
* @return the computed set <code>last(r)</code>
*/
protected override def compLast(r: RegExp): immutable.Set[Int] = r match {
case x:Letter => emptySet + x.pos //posMap(x) // singleton set
case Eps => emptySet /*ignore*/
case _ => super.compLast(r)
}
/** Returns the first set of an expression, setting the follow set along
* the way.
*
* @param fol1 ...
* @param r the regular expression
* @return the computed set
*/
protected override def compFollow1(fol1: immutable.Set[Int], r: RegExp): immutable.Set[Int] =
r match {
case x:Letter =>
//val i = posMap(x)
val i = x.pos
this.follow.update(i, fol1)
emptySet + i
case Eps =>
emptySet /*ignore*/
case _ =>
super.compFollow1(fol1, r)
}
/** returns "Sethi-length" of a pattern, creating the set of position
* along the way
*/
/** called at the leaves of the regexp */
protected def seenLabel(r: RegExp, i: Int, label: _labelT) {
//Console.println("seenLabel (1)");
//this.posMap.add(r, i)
this.labelAt = this.labelAt.updated(i, label)
//@ifdef if( label != Wildcard ) {
this.labels += label
//@ifdef }
}
// overriden in BindingBerrySethi
protected def seenLabel(r: RegExp, label: _labelT): Int = {
//Console.println("seenLabel (2)");
pos = pos + 1
seenLabel(r, pos, label)
pos
}
// todo: replace global variable pos with acc
override def traverse(r: RegExp): Unit = r match {
case a @ Letter(label) => a.pos = seenLabel(r, label)
case Eps => /*ignore*/
case _ => super.traverse(r)
}
protected def makeTransition(src: Int, dest: Int, label: _labelT ) {
//@ifdef compiler if( label == Wildcard )
//@ifdef compiler defaultq.add(src, dest::defaultq( src ))
//@ifdef compiler else
val q = deltaq(src)
q.update(label, dest::(q.get(label) match {
case Some(x) => x
case _ => Nil
}))
}
protected def initialize(subexpr: Seq[RegExp]): Unit = {
//this.posMap = new mutable.HashMap[RegExp,Int]()
this.labelAt = immutable.Map[Int, _labelT]()
this.follow = new mutable.HashMap[Int, immutable.Set[Int]]()
this.labels = new mutable.HashSet[_labelT]()
this.pos = 0
// determine "Sethi-length" of the regexp
//activeBinders = new Vector()
var it = subexpr.elements
while (it.hasNext)
traverse(it.next)
//assert(activeBinders.isEmpty())
this.initials = emptySet + 0
}
protected def initializeAutom() {
finals = immutable.Map.empty[Int, Int] // final states
deltaq = new Array[mutable.HashMap[_labelT, List[Int]]](pos) // delta
defaultq = new Array[List[Int]](pos) // default transitions
var j = 0
while (j < pos) {
deltaq(j) = new mutable.HashMap[_labelT,List[Int]]()
defaultq(j) = Nil
j += 1
}
}
protected def collectTransitions(): Unit = { // make transitions
//Console.println("WBS.collectTrans, this.follow.keys = "+this.follow.keys)
//Console.println("WBS.collectTrans, pos = "+this.follow.keys)
var j = 0; while (j < pos) {
//Console.println("WBS.collectTrans, j = "+j)
val fol = this.follow(j)
val it = fol.elements
while (it.hasNext) {
val k = it.next
if (pos == k)
finals = finals.updated(j, finalTag)
else
makeTransition( j, k, labelAt(k))
}
j += 1
}
}
def automatonFrom(pat: RegExp, finalTag: Int): NondetWordAutom[_labelT] = {
this.finalTag = finalTag
pat match {
case x:Sequ =>
// (1,2) compute follow + first
initialize(x.rs)
pos = pos + 1
globalFirst = compFollow(x.rs)
//System.out.print("someFirst:");debugPrint(someFirst);
// (3) make automaton from follow sets
initializeAutom()
collectTransitions()
if (x.isNullable) // initial state is final
finals = finals.updated(0, finalTag)
var delta1: immutable.Map[Int, Map[_labelT, List[Int]]] =
immutable.Map[Int, Map[_labelT, List[Int]]]()
var i = 0
while (i < deltaq.length) {
delta1 = delta1.updated(i, deltaq(i))
i += 1
}
val finalsArr = new Array[Int](pos)
{
var k = 0; while (k < pos) {
finalsArr(k) = finals.get(k) match {
case Some(z) => z
case None => 0 // 0 == not final
};
k += 1
}
}
val initialsArr = new Array[Int](initials.size)
val it = initials.elements
{
var k = 0; while (k < initials.size) {
initialsArr(k) = it.next
k += 1
}
}
val deltaArr = new Array[Map[_labelT, immutable.BitSet]](pos)
{
var k = 0; while(k < pos) {
val labels = delta1(k).keys
val hmap =
new mutable.HashMap[_labelT, immutable.BitSet]
for (lab <- labels) {
val trans = delta1(k)
val x = new mutable.BitSet(pos)
for (q <- trans(lab))
x += q
hmap.update(lab, x.toImmutable)
}
deltaArr(k) = hmap
k += 1
}
}
val defaultArr = new Array[immutable.BitSet](pos)
{
var k = 0; while(k < pos) {
val x = new mutable.BitSet(pos)
for (q <- defaultq(k))
x += q
defaultArr(k) = x.toImmutable
k += 1
}
}
new NondetWordAutom[_labelT] {
type _labelT = WordBerrySethi.this._labelT
val nstates = pos
val labels = WordBerrySethi.this.labels.toList
val initials = initialsArr
val finals = finalsArr
val delta = deltaArr
val default = defaultArr
}
case z =>
val z1 = z.asInstanceOf[this.lang._regexpT]
automatonFrom(Sequ(z1), finalTag)
}
}
/*
void print1() {
System.out.println("after sethi-style processing");
System.out.println("#positions:" + pos);
System.out.println("posMap:");
for (Iterator it = this.posMap.keySet().iterator();
it.hasNext(); ) {
Tree t = (Tree) it.next();
switch(t) {
case Literal( _ ):
System.out.print( "(" + t.toString() + " -> ");
String s2 = ((Integer) posMap.get(t)).toString();
System.out.print( s2 +") ");
}
}
System.out.println("\nfollow: ");
for (int j = 1; j < pos; j++ ) {
TreeSet fol = (TreeSet) this.follow.get(new Integer(j));
System.out.print("("+j+" -> "+fol.toString()+") ");
//debugPrint( fol );
System.out.println();
}
}
*/
}
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