code: //==============================================================================
  //	
  //	Copyright (c) 2015-
  //	Authors:
  //	* Joachim Klein <klein@tcs.inf.tu-dresden.de> (TU Dresden)
  //	
  //------------------------------------------------------------------------------
  //	
  //	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.visitor;
  
  import parser.ast.ExpressionProb;
  import parser.ast.ExpressionReward;
  import parser.ast.ExpressionSS;
  import prism.PrismLangException;
  
  /**
   * Base class for recursively traversing an Expression, but not
   * entering nested P/R/SS subexpressions.
   *
   * By default, will not recurse into the P/R/SS elements, but
   * can be configured to allow a certain amount of nested P/R/SS
   * elements before stopping.
   *
   * <br/>
   * Subclasses should not override<br/>
   * <ul>
   *  <li>{@code visit(ExpressionProb)}</li>
   *  <li>{@code visit(ExpressionReward)}</li>
   *  <li>{@code visit(ExpressionSS)}</li>
   * </ul>
   */
  public class ExpressionTraverseNonNested extends ASTTraverse
  {
  	/** the current nesting level */
  	private int currentNesting;
  	/** the maximal nesting level that still allows recursion */
  	private int nestingLimit;
  
  	/** Constructor, defaulting to "no nesting" */
  	public ExpressionTraverseNonNested()
  	{
  		this(0);
  	}
  
  	/** Constructor, with "stop recursion after {@code nestingLimit} nestings" */
  	public ExpressionTraverseNonNested(int nestingLimit)
  	{
  		currentNesting = 0;
  		this.nestingLimit = 0;
  	}
  
  	/** Are we still allowed to recurse? */
  	private boolean inLimit()
  	{
  		return currentNesting <= nestingLimit;
  	}
  
  	@Override
  	public Object visit(ExpressionProb e) throws PrismLangException
  	{
  		currentNesting++;
  		// only visit if we are still in limit
  		if (!inLimit()) {
  			currentNesting--;
  			return null;
  		}
  		Object rv = super.visit(e);
  		currentNesting--;
  		return rv;
  	}
  
  	@Override
  	public Object visit(ExpressionReward e) throws PrismLangException
  	{
  		currentNesting++;
  		// only visit if we are still in limit
  		if (!inLimit()) {
  			currentNesting--;
  			return null;
  		}
  		Object rv = super.visit(e);
  		currentNesting--;
  		return rv;
  	}
  
  	@Override
  	public Object visit(ExpressionSS e) throws PrismLangException
  	{
  		currentNesting++;
  		// only visit if we are still in limit
  		if (!inLimit()) {
  			currentNesting--;
  			return null;
  		}
  		Object rv = super.visit(e);
  		currentNesting--;
  		return rv;
  	}
  }
  