assignmentiterator.java

这是一个matlab的java实现。里面有许多内容。请大家慢慢捉摸。

/* Copyright (C) 2003 Univ. of Massachusetts Amherst, Computer Science Dept.
   This file is part of "MALLET" (MAchine Learning for LanguagE Toolkit).
   http://www.cs.umass.edu/~mccallum/mallet
   This software is provided under the terms of the Common Public License,
   version 1.0, as published by http://www.opensource.org.  For further
   information, see the file `LICENSE' included with this distribution. */

package edu.umass.cs.mallet.grmm;

import java.util.Iterator;
import java.util.List;
import edu.umass.cs.mallet.base.types.Matrixn;



/**
 * Iterates over the assignments to a set of variables.
 *  This is never instantiated by user code; instead, use
 *  one of the many assignmentIterator() methods.
 *
 *   DOCTODO: Add note about difference between using this class and iterating
 *    over assignments.
 *   DOCTODO: Explain why advance() is useful instead of next.
 *
 * Created: Sun Nov  9 21:04:03 2003
 *
 * @author <a href="mailto:[e-mail]">Charles Sutton</a>
 * @version $Id: AssignmentIterator.java,v 1.2 2004/08/11 20:07:15 casutton Exp $
 */
public class AssignmentIterator implements Iterator {

	private List vertsList;
		
	private int current = 0;
	private int max = 1;
	private int[] sizes;

	AssignmentIterator (List verts)
	{
		vertsList = verts;
    initSizes ();
  }

  private void initSizes ()
  {
    sizes = new int [vertsList.size()];
    for (int i = 0; i < vertsList.size(); i++) {
      Variable var = (Variable) vertsList.get (i);
      sizes [i] = var.getNumOutcomes ();
      max *= var.getNumOutcomes ();
    }
  }

  public void advance()
	{ 
		current++;
	}

	public Object next() 
	{
		Assignment assn = assignment ();
		advance ();
		return assn;
	}

	int indexOfCurrentAssn () { return current; }

	public Assignment assignment () 
  {
    if (sizes == null) initSizes ();  // Lazily build sizes array
		int[] outcomes = new int [sizes.length];
		Matrixn.singleToIndices (current, outcomes, sizes);
		Variable[] vars = (Variable[]) vertsList.toArray (new Variable [0]);
		return new Assignment (vars, outcomes);
	}

	public boolean hasNext() {
		return current < max;
	}

	public void remove() {
		throw new UnsupportedOperationException 
			("Attempt to remave assignment from Clique.");
	}
		
}