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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 
*/
//#########################################################################
//	pPacket
//#########################################################################

package ubc.cs.JLog.Parser;

import java.util.*;
import java.lang.*;
import ubc.cs.JLog.Terms.*;

/**
* Abstract base class representing packets in the parse stream. Each packet is the
* parse stream representation of a prolog term, and is bound to the parse stream via
* its corresponding token. Packets form the nodes in our implicit parse tree.
*  
* @author       Glendon Holst
* @version      %I%, %G%
*/
abstract class pPacket
{
 protected pToken 		token;

 public pPacket(pToken pt)
 {
  token = pt;
 };
 
 public String 		getName()
 {
  return token.getToken();
 };

 public pToken 		getToken()
 {
  return token;
 };

 /**
  * Public interface for generating the real prolog term objects.  May generate syntax errors.
  *
  * @param vars 	A registery of named variables (ensures that variables of the same name
  * 			are the same instance). This should be the variable registry of the
  * 			rule or command containing this operator.
  * @param phash 	A registery of terms and their corresponding parsing tokens.
  *
  * @return 		jTerm representing this packet.
  */
 abstract public jTerm 	getTerm(pVariableRegistry vars,pTermToPacketHashtable phash);

 /**
  * Determine if this packet represents a generic predicate (not builtin).
  * If generic_predicate is true, then only create jPredicate for use as rule 
  * head. This call is for pPredicate class, but others must pass it down to 
  * children packets.
  * Some operators, such as if and command, will pass true to the lhs, and false to rhs. 
  * The initiating call should be with genericpred false for queries, and false when adding
  * terms to the database.
  *
  * @param genericpred 	The value to set generic_predicate to.
  */
 abstract public void 		setGeneric(boolean genericpred);

 public int 		getPosition()
 {
  return token.getPosition();
 };

 public int 		getLine()
 {
  return token.getLine();
 };

 public int 		getCharPos()
 {
  return token.getCharPos();
 };

 public String 		toString()
 {
  return getClass().toString() + ": " + token.toString();
 };
};