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 param.BigRational;
  import parser.*;
  import parser.visitor.*;
  import prism.PrismLangException;
  
  public class ExpressionLabel extends Expression
  {
  	String name;
  
  	// Constructor
  	
  	public ExpressionLabel(String s)
  	{
  		name = s;
  	}
  
  	// Get Method
  	
  	public String getName()
  	{
  		return name;
  	}
  
  	/**
  	 * Is this the special "init" label?
  	 */
  	public boolean isInitLabel()
  	{
  		return getName().equals("init");
  	}
  
  	/**
  	 * Is this the special "deadlock" label?
  	 */
  	public boolean isDeadlockLabel()
  	{
  		return getName().equals("deadlock");
  	}
  
  	// Methods required for Expression:
  	
  	@Override
  	public boolean isConstant()
  	{
  		// Don't know - err on the side of caution
  		return false;
  	}
  
  	@Override
  	public boolean isProposition()
  	{
  		return true;
  	}
  	
  	@Override
  	public Object evaluate(EvaluateContext ec) throws PrismLangException
  	{
  		throw new PrismLangException("Cannot evaluate labels", this);
  	}
  
  	@Override
  	public BigRational evaluateExact(EvaluateContext ec) throws PrismLangException
  	{
  		throw new PrismLangException("Cannot evaluate labels", this);
  	}
  
  	@Override
  	public boolean returnsSingleValue()
  	{
  		return false;
  	}
  
  	// Methods required for ASTElement:
  	
  	@Override
  	public Object accept(ASTVisitor v) throws PrismLangException
  	{
  		return v.visit(this);
  	}
  	
  	@Override
  	public Expression deepCopy()
  	{
  		ExpressionLabel expr = new ExpressionLabel(name);
  		expr.setType(type);
  		expr.setPosition(this);
  		return expr;
  	}
  
  	// Standard methods
  
  	@Override
  	public String toString()
  	{
  		return "\"" + name + "\"";
  	}
  
  	@Override
  	public int hashCode()
  	{
  		final int prime = 31;
  		int result = 1;
  		result = prime * result + ((name == null) ? 0 : name.hashCode());
  		return result;
  	}
  
  	@Override
  	public boolean equals(Object obj)
  	{
  		if (this == obj)
  			return true;
  		if (obj == null)
  			return false;
  		if (getClass() != obj.getClass())
  			return false;
  		ExpressionLabel other = (ExpressionLabel) obj;
  		if (name == null) {
  			if (other.name != null)
  				return false;
  		} else if (!name.equals(other.name))
  			return false;
  		return true;
  	}
  }
  
  //------------------------------------------------------------------------------
  