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.EvaluateContext;
  import parser.Values;
  import parser.visitor.ASTVisitor;
  import prism.OpRelOpBound;
  import prism.PrismException;
  import prism.PrismLangException;
  
  public class ExpressionSS extends ExpressionQuant
  {
  	// Constructors
  	
  	public ExpressionSS()
  	{
  	}
  	
  	public ExpressionSS(Expression expression, String relOpString, Expression p)
  	{
  		setExpression(expression);
  		setRelOp(relOpString);
  		setBound(p);
  	}
  
  	// Set methods
  	
  	/**
  	 * Set the probability bound. Equivalent to {@code setBound(p)}.
  	 */
  	public void setProb(Expression p)
  	{
  		setBound(p);
  	}
  
  	// Get methods
  	
  	/**
  	 * Get the probability bound. Equivalent to {@code getBound()}.
  	 */
  	public Expression getProb()
  	{
  		return getBound();
  	}
  
  	/**
  	 * Get info about the operator and bound.
  	 * Does some checks, e.g., throws an exception if probability is out of range.
  	 * @param constantValues Values for constants in order to evaluate any bound
  	 */
  	public OpRelOpBound getRelopBoundInfo(Values constantValues) throws PrismException
  	{
  		if (getBound() != null) {
  			double boundValue = getBound().evaluateDouble(constantValues);
  			if (boundValue < 0 || boundValue > 1)
  				throw new PrismException("Invalid probability bound " + boundValue + " in P operator");
  			return new OpRelOpBound("S", getRelOp(), boundValue);
  		} else {
  			return new OpRelOpBound("S", getRelOp(), null);
  		}
  	}
  	
  	// Methods required for Expression:
  	
  	@Override
  	public boolean isConstant()
  	{
  		return false;
  	}
  
  	@Override
  	public boolean isProposition()
  	{
  		return false;
  	}
  	
  	@Override
  	public Object evaluate(EvaluateContext ec) throws PrismLangException
  	{
  		throw new PrismLangException("Cannot evaluate an S operator without a model");
  	}
  
  	@Override
  	public BigRational evaluateExact(EvaluateContext ec) throws PrismLangException
  	{
  		throw new PrismLangException("Cannot evaluate an S operator without a model");
  	}
  
  	@Override
  	public String getResultName()
  	{
  		return (getBound() == null) ? "Probability" : "Result";
  	}
  
  	@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()
  	{
  		ExpressionSS expr = new ExpressionSS();
  		expr.setExpression(getExpression() == null ? null : getExpression().deepCopy());
  		expr.setRelOp(getRelOp());
  		expr.setBound(getBound() == null ? null : getBound().deepCopy());
  		expr.setFilter(getFilter() == null ? null : (Filter)getFilter().deepCopy());
  		expr.setType(type);
  		expr.setPosition(this);
  		return expr;
  	}
  
  	// Standard methods
  	
  	@Override
  	public String toString()
  	{
  		String s = "";
  		
  		s += "S" + getModifierString() + getRelOp();
  		s += (getBound()==null) ? "?" : getBound().toString();
  		s += " [ " + getExpression();
  		if (getFilter() != null) s += " "+getFilter();
  		s += " ]";
  		
  		return s;
  	}
  }
  
  //------------------------------------------------------------------------------
  