//==============================================================================
//	
//	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;
	}
}

//------------------------------------------------------------------------------