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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 
*/
//#########################################################################
//	pOperator
//#########################################################################

package ubc.cs.JLog.Parser;

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

class pOperator extends pPacket
{
 protected pPacket 				lhs = null,rhs = null;
 protected pOperatorEntry 		op;

 public 	pOperator(pOperatorEntry op,pToken pt)
 {
  super(pt);
  this.op = op;
 };
 
 public void 		setLHS(pPacket l)
 {
  lhs = l;
 };
 
 public void 		setRHS(pPacket r)
 {
  rhs = r;
 };
 
 // verifyCompletion and get?HS functions should only be called when there is no possiblity 
 // of any further packets to attach, such as when the operator to the right requires a lhs. 
 public void 		verifyCompletion()
 {
  getLHS();
  getRHS();
 };
 
 public pPacket 	getLHS()
 {
  if (isAtom())
   return lhs;
   
  if (hasLHS() && lhs == null)
   throw new SyntaxErrorException("LHS term required before operator '" + getName() + "' at ",
                                   token.getPosition(),token.getLine(),token.getCharPos()); 
   
  return lhs;
 };
 
 public pPacket 	getRHS()
 {
  if (isAtom())
   return rhs;
   
  if (hasRHS() && rhs == null)
   throw new SyntaxErrorException("RHS term required after operator '" + getName() + "' at ",
                                   token.getPosition(),token.getLine(),token.getCharPos()); 
   
  return rhs;
 };
 
 public boolean 	hasLHS()
 {
  return op.hasLHS();
 };
 
 public boolean 	hasRHS()
 {
  return op.hasRHS();
 };
 
 public boolean 	isAtom()
 {
  return op.isAtomPermitted() && lhs == null && rhs == null;
 };
 
 public int 		getType()
 {
  return op.getType();
 };
 
 public int 		getPriority()
 {
  return op.getPriority();
 };
 
 public int 		getAssociativity()
 {
  return op.getAssociativity();
 };

 public boolean		isNonAssociativeLeft()
 {
  return op.isNonAssociativeLeft();
 };

 public boolean 	isNonAssociativeRight()
 {
  return op.isNonAssociativeRight();
 };

 public boolean 	hasLHSPacket()
 {
  return lhs != null;
 };
 
 public boolean 	hasRHSPacket()
 {
  return rhs != null;
 };

 public jTerm 			getTerm(pVariableRegistry vars,pTermToPacketHashtable phash)
 {jTerm 	term;
  
  term = op.createOperator(token,lhs,rhs,vars,phash);
  phash.putPacket(term,this);
  
  return term;
 };

 // built-in operators can never be generic since they cannot be overridden.  This result
 // happens naturally since non-builtin operators return a jPredicate. rules, which require
 // a jpredicate as the head, will throw an error if a builtin operator appears in the head.
 // the arguments should be non-generic so that they can be called if unified with a variable. 
 public void 		setGeneric(boolean genericpred)
 {pPacket 	l,r;

  l = getLHS();
  r = getRHS();
  
  if (l != null)
   l.setGeneric(false);
  if (r != null)
   r.setGeneric(false);
 };
};