code: //==============================================================================
  //	
  //	Copyright (c) 2002-
  //	Authors:
  //	* Dave Parker <d.a.parker@cs.bham.ac.uk> (University of Birmingham/Oxford)
  //	
  //------------------------------------------------------------------------------
  //	
  //	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 java.util.Vector;
  
  import parser.ast.*;
  import prism.PrismLangException;
  
  /**
   * Perform further  semantic checks on a ModulesFile (or parts of it)
   * that can only be done once values for (at least some) undefined constants have been defined.
   */
  public class ModulesFileSemanticCheckAfterConstants extends ASTTraverse
  {
  	@SuppressWarnings("unused")
  	private ModulesFile modulesFile;
  
  	public ModulesFileSemanticCheckAfterConstants(ModulesFile modulesFile)
  	{
  		setModulesFile(modulesFile);
  	}
  
  	public void setModulesFile(ModulesFile modulesFile)
  	{
  		this.modulesFile = modulesFile;
  	}
  
  	public void visitPost(Update e) throws PrismLangException
  	{
  		int i, n;
  		String var;
  		Vector<String> varsUsed = new Vector<String>();
  
  		// Check that no variables are set twice in the same update
  		// Currently, could do this *before* constants are defined,
  		// but one day we might need to worry about e.g. array indices...
  		n = e.getNumElements();
  		for (i = 0; i < n; i++) {
  			var = e.getVar(i);
  			if (varsUsed.contains(var)) {
  				throw new PrismLangException("Variable \"" + var + "\" is set twice in the same update", e.getVarIdent(i));
  			}
  			varsUsed.add(var);
  		}
  		varsUsed.clear();
  	}
  }
  