code: //==============================================================================
  //	
  //	Copyright (c) 2002-
  //	Authors:
  //	* Dave Parker <david.parker@comlab.ox.ac.uk> (University of Oxford, formerly University of Birmingham)
  //	
  //------------------------------------------------------------------------------
  //	
  //	This file is part of PRISM.
  //	
  //	PRISM 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.
  //	
  //	PRISM 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 PRISM; if not, write to the Free Software Foundation,
  //	Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  //	
  //==============================================================================
  
  package parser.ast;
  
  import java.util.*;
  
  import parser.*;
  import parser.visitor.*;
  import prism.PrismLangException;
  
  /**
   * Class to store a list of updates with associated probabilities (or rates).
   * e.g. 0.5:(s'=1)&amp;(x'=x+1) + 0.5:(s'=2)&amp;(x'=x-1)
   */
  public class Updates extends ASTElement
  {
  	// Pairs of probabilities/updates
  	private ArrayList<Expression> probs;
  	private ArrayList<Update> updates;
  	// Parent command
  	private Command parent;
  
  	/**
  	 * Construct an empty Updates object.
  	 */
  	public Updates()
  	{
  		probs = new ArrayList<Expression>();
  		updates = new ArrayList<Update>();
  		parent = null;
  	}
  
  	// Set methods
  
  	/**
  	 * Add a probability (or rate) and update pair (probability/rate can be null, which equates to 1.0).
  	 */
  	public void addUpdate(Expression p, Update u)
  	{
  		probs.add(p);
  		updates.add(u);
  		u.setParent(this);
  	}
  
  	/**
  	 * Set the ith update.
  	 */
  	public void setUpdate(int i, Update u)
  	{
  		updates.set(i, u);
  		u.setParent(this);
  	}
  
  	/**
  	 * Set the probability (or rate) of the ith update (can be null; denotes default of 1.0)
  	 */
  	public void setProbability(int i, Expression p)
  	{
  		// Note: probability can be null, which equates to 1.0
  		probs.set(i, p);
  	}
  
  	/**
  	 * Set the parent Command.
  	 */
  	public void setParent(Command c)
  	{
  		parent = c;
  	}
  
  	// Get methods
  
  	/**
  	 * Get the number of updates.
  	 */
  	public int getNumUpdates()
  	{
  		return updates.size();
  	}
  
  	/**
  	 * Get the ith update.
  	 */
  	public Update getUpdate(int i)
  	{
  		return updates.get(i);
  	}
  
  	/**
  	 * Get access to the whole list of the updates
  	 */
  	public List<Update> getUpdates()
  	{
  		return updates;
  	}
  
  	/**
  	 *  Get the probability (or rate) of the ith update (may be null, which should be interpreted as constant 1.0)
  	 */
  	public Expression getProbability(int i)
  	{
  		return probs.get(i);
  	}
  
  	/**
  	 * Evaluate the probability (or rate) of the ith update, in the context of a state
  	 */
  	public double getProbabilityInState(int i, State state) throws PrismLangException
  	{
  		Expression p = probs.get(i);
  		return (p == null) ? 1.0 : p.evaluateDouble(state);
  	}
  			
  	/**
  	 * Get the Command to which this Updates object belongs.
  	 */
  	public Command getParent()
  	{
  		return parent;
  	}
  
  	// Methods required for ASTElement:
  
  	/**
  	 * Visitor method.
  	 */
  	public Object accept(ASTVisitor v) throws PrismLangException
  	{
  		return v.visit(this);
  	}
  
  	/**
  	 * Convert to string.
  	 */
  	public String toString()
  	{
  		String s = "";
  		int i, n;
  
  		n = getNumUpdates();
  		for (i = 0; i < n - 1; i++) {
  			if (getProbability(i) != null)
  				s += getProbability(i) + " : ";
  			s += getUpdate(i) + " + ";
  		}
  		if (getProbability(n - 1) != null)
  			s += getProbability(n - 1) + " : ";
  		s += getUpdate(n - 1);
  
  		return s;
  	}
  
  	/**
  	 * Perform a deep copy.
  	 */
  	public ASTElement deepCopy()
  	{
  		int i, n;
  		Expression p;
  		Updates ret = new Updates();
  		n = getNumUpdates();
  		for (i = 0; i < n; i++) {
  			p = getProbability(i);
  			if (p != null)
  				p = p.deepCopy();
  			ret.addUpdate(p, (Update) getUpdate(i).deepCopy());
  		}
  		ret.setPosition(this);
  		return ret;
  	}
  }
  
  //------------------------------------------------------------------------------
  