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/*
    This file is part of JLog.

    Created by Glendon Holst for Alan Mackworth and the 
    "Computational Intelligence: A Logical Approach" text.
    
    Copyright 1998, 2000, 2002 by University of British Columbia and 
    Alan Mackworth.
    
    This notice must remain in all files which belong to, or are derived 
    from JLog.
    
    Check  or 
     for further information
    about JLog, or to contact the authors.
     
    JLog 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.

    JLog 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 JLog; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    URLs:  or 
*/
//#########################################################################
//	jUserGoal
//#########################################################################

package ubc.cs.JLog.Foundation;

import java.lang.*;
import java.util.*;

/**
 * Goal for getting user queries. jUserGoal is designed as a goal stub so 
 * that user queries have the same behavior as if they were the based off a rule. 
 * Notably, cuts will work, and or predicates containing cuts
 * will also work.  jUserGoal assumes that it is the first goal (it is ok
 * to place it on the empty proved stack first without calling prove, the only goal with 
 * this property).
 * No attempt is made to keep track of unified variables (for cuts), since a retry is
 * guarenteed to fail, and standard behavior is to not display variables if the query fails.
 *
 * @author       Glendon Holst
 * @version      %I%, %G%
 */
public class jUserGoal extends jGoal
{
 public 	jUserGoal()
 {
 };
 
 public boolean 	prove(iGoalStack goals,iGoalStack proved)
 {
  proved.push(this);
  return true;
 };

 public boolean 	retry(iGoalStack goals,iGoalStack proved)
 {
  goals.push(this); // a retry that follows may need a node to remove or retry
  return false;
 }; 

 public String 		getName() 
 {
  return "internal user goal stub";
 };
 
 public int 		getArity() 
 {
  return 0;
 };
 
 public String 		toString()
 {StringBuffer 	sb = new StringBuffer();
   
  sb.append(getName()+"/"+String.valueOf(getArity()));
  
  return sb.toString();
 };
};