SAXNonTerminal.java

package edu.hawaii.jmotif.sequitur;

/*
 This class is part of a Java port of Craig Nevill-Manning's Sequitur algorithm.
 Copyright (C) 1997 Eibe Frank

 This program is free software; you can redistribute it and/or
 modify it under the terms of the GNU General Public License
 as published by the Free Software Foundation; either version 2
 of the License, or (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

/**
 * The Non-Terminal symbol - i.e. Rule. Adaption of Eibe Frank code for JMotif API, see
 * {@link sequitur.info} for original version.
 * 
 * @author Manfred Lerner
 * 
 */
public class SAXNonTerminal extends SAXSymbol implements Cloneable {

  protected SAXRule r;

  /**
   * Constructor.
   * 
   * @param theRule the rule.
   */
  public SAXNonTerminal(SAXRule theRule) {
    r = theRule;
    r.count++;
    value = String.valueOf(numTerminals + r.ruleIndex);
    p = null;
    n = null;
  }

  /**
   * Extra cloning method necessary so that count in the corresponding rule is increased.
   */
  protected Object clone() {
    SAXNonTerminal sym = new SAXNonTerminal(r);
    sym.p = p;
    sym.n = n;
    return sym;
  }

  /**
   * {@inheritDoc}
   */
  public void cleanUp() {
    join(p, n);
    deleteDigram();
    r.count--;
    //
    // TODO: here, however, I think I have no need to remove the saved non-terminal position: even
    // if the rule become a part of longer rule, we still need to know that there is the match.
    //
    // However, we might need to "forget", I am not sure
    //
    // r.indexes.remove(this.originalPosition);
  }

  /**
   * {@inheritDoc}
   */
  public boolean isNonTerminal() {
    return true;
  }

  /**
   * This symbol is the last reference to its rule. The contents of the rule are substituted in its
   * place.
   */
  public void expand() {
    join(p, r.first());
    join(r.last(), n);
    // Necessary so that garbage collector
    // can delete rule and guard.
    r.theGuard.r = null;
    r.theGuard = null;
  }
}