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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 
*/
//#########################################################################
//	TermToList
//#########################################################################
 
package ubc.cs.JLog.Builtins;

import java.lang.*;
import java.util.*;
import ubc.cs.JLog.Terms.*;
import ubc.cs.JLog.Foundation.*;
import ubc.cs.JLog.Parser.*;
import ubc.cs.JLog.Builtins.Goals.*;

public class jTermToList extends jBinaryBuiltinPredicate
{
 public jTermToList(jTerm l,jTerm r)
 {
  super(l,r,TYPE_BUILTINPREDICATE);
 };
  
 public String 		getName()
 {
  return "=..";
 };

 public boolean 	prove(jTermToListGoal tg,pPredicateRegistry pr,
                                pOperatorRegistry or)
 {jTerm 	l,r;
  
  l = tg.lhs.getTerm();
  r = tg.rhs.getTerm();
  
  if (l instanceof iPredicate)
  {jCompoundTerm 	ct = ((iPredicate) l).getArguments();
   Enumeration  	e = ct.enumTerms();
   jListPair 			head,prev;
   
   head = prev = new jListPair(new jAtom(l.getName()),null);
   
   while (e.hasMoreElements())
   {jListPair 		next;
   
    prev.setTail(next = new jListPair((jTerm) e.nextElement(),null));
    prev = next;
   }
   
   prev.setTail(jNullList.NULL_LIST);

   return r.unify(head,tg.unified);
  }
  else if (l instanceof jConjunctTerm)
  {jListPair 			head;
   
   head = new jListPair(new jAtom(l.getName()),
            new jListPair(((jConjunctTerm) l).getLHS(),
            new jListPair(((jConjunctTerm) l).getRHS(),jNullList.NULL_LIST)));

   return r.unify(head,tg.unified);   
  }
  else if (r instanceof jListPair)
  {jListPair 			lst = (jListPair) r;
   jTerm 	 		name = lst.getHead().getTerm();
   jCompoundTerm 		ct;
   jTerm 			next;
   
   if (!(name instanceof iPredicate && ((iPredicate) name).getArity() == 0))
    throw new InvalidTermToListArgumentException();

   ct = new jCompoundTerm();
   next = lst.getTail().getTerm();
   
   while (next instanceof jListPair)
   {
    lst = (jListPair) next;
     
    ct.addTerm(lst.getHead().getTerm());
    next = lst.getTail().getTerm();
   }
   
   if (!(next instanceof jNullList))
    throw new InvalidTermToListArgumentException();
  
   {pPredicateEntry 		pe = pr.getPredicate(name.getName(),ct.size());
    jTerm 			p;
   
    if (pe != null)
    {    
     p = pe.createPredicate(ct);
    }
    else
    {pOperatorEntry 		oe = or.getOperator(name.getName(),true);
     
     if (oe != null)
     {jTerm 			lhs,rhs;

     if (ct.size() != 2)
      throw new InvalidTermToListArgumentException();
      
      lhs = ct.elementAt(0);
      rhs = ct.elementAt(1);
      
      p = oe.createOperator(lhs,rhs);
     }
     else
      p = new jPredicate(name.getName(),ct);
    }
    
    return l.unify(p,tg.unified); 
   }
  }
  else
   throw new InvalidTermToListArgumentException();
 };

 public void 		addGoals(jGoal g,jVariable[] vars,iGoalStack goals)
 {
  goals.push(new jTermToListGoal(this,lhs.duplicate(vars),rhs.duplicate(vars)));
 };

 public void 		addGoals(jGoal g,iGoalStack goals)
 {
  goals.push(new jTermToListGoal(this,lhs,rhs));
 };

 protected jBinaryBuiltinPredicate 		duplicate(jTerm l,jTerm r)
 {
  return new jTermToList(l,r); 
 };
};