ubc.cs.JLog.Terms.Goals.jPredicateGoal Maven / Gradle / Ivy

Go to download
/*
    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 
*/
//#########################################################################
//	jPredicateGoal
//#########################################################################

package ubc.cs.JLog.Terms.Goals;

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

public final class jPredicateGoal extends jGoal
{
 protected final static int 	STARTING_RULE = 0;

 protected jRuleDefinitions 	rules;
 protected int 					rule_number = STARTING_RULE;
 protected jGoal 				end_goal = null;

 // for use by ruledefinitions
 public jCompoundTerm 		input_goal;
 public jCompoundTerm 		rule_goal = null;
 public jUnifiedVector 		unified;
 
 public 	jPredicateGoal(jRuleDefinitions rs,jCompoundTerm in)
 {
  rules = rs;
  input_goal = in;
  unified = new jUnifiedVector();
 };
 
 // endgoal is the previous goal on the goalstack.  if endgoal is null, then goalstack
 // was previously empty.
 public final void 		setEndGoal(jGoal goal)
 {
  end_goal = goal;
 };
 
 public final int 		getNextRuleNumber()
 {
  return rule_number++;
 };
 
 public final int 		getRuleNumber()
 {
  return rule_number;
 };
 
 public final jRuleDefinitions		getRules()
 {
  return rules;
 };
 
 public boolean 	prove(iGoalStack goals,iGoalStack proved)
 {
  if (rules.prove(this,goals))
  {
   proved.push(this);
   return true;
  }
  else
  {
   { // we need to initialize goal to potentially restart
    rule_number = STARTING_RULE; 
    unified.restoreVariables();
   }
   goals.push(this); // a retry that follows may need a node to remove or retry
   return false;
  }
 };

 public boolean 	retry(iGoalStack goals,iGoalStack proved)
 {
  internal_remove(goals);
  unified.restoreVariables();
  
  if (rules.retry(this))
  {
   goals.push(this);
   return true;
  }
  else
  {
   { // we need to initialize goal to potentially restart
    rule_number = STARTING_RULE; 
   }
   goals.push(this); // a retry that follows may need a node to remove or retry
   return false;
  }
 }; 
 
 protected final void 	internal_remove(iGoalStack goals)
 {
  goals.cut(end_goal);
 };
 
 public final void		internal_restore(iGoalStack goals)
 {
  goals.cut(end_goal);

  unified.restoreVariables();
  rule_number = STARTING_RULE;
 };
 
 public String 		getName()
 {
  return rules.getName();
 };
 
 public int 		getArity()
 {
  return rules.getArity();
 };
 
 public String 		toString()
 {StringBuffer 	sb = new StringBuffer();
  int 			rn = rule_number - 1;
   
  sb.append(rules.getName()+"/"+String.valueOf(rules.getArity())+" goal: ");
  sb.append(rules.getName()+input_goal.toString()+" unified: ");
  if (rule_goal != null)
  {
   sb.append(rules.getName() + rule_goal.toString());
  }
  else
   sb.append("not unified");
  
  return sb.toString();
 };
};