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;
  
  /**
   * Information required to evaluate an expression: a State object.
   * This is basically an array of Objects, indexed according to a model file. 
   * Optionally values for constants can also be supplied.
   */
  public class EvaluateContextState implements EvaluateContext
  {
  	private Values constantValues;
  	private Object[] varValues;
  
  	public EvaluateContextState(State state)
  	{
  		this.constantValues = null;
  		this.varValues = state.varValues;
  	}
  
  	public EvaluateContextState(Values constantValues, State state)
  	{
  		this.constantValues = constantValues;
  		this.varValues = state.varValues;
  	}
  
  	public Object getConstantValue(String name)
  	{
  		if (constantValues == null)
  			return null;
  		int i = constantValues.getIndexOf(name);
  		if (i == -1)
  			return null;
  		return constantValues.getValue(i);
  	}
  
  	public Object getVarValue(String name, int index)
  	{
  		// Use index to look up value
  		return index == -1 ? null : varValues[index];
  	}
  }
  