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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 
*/
//#########################################################################
//	Rule Definitions
//   set of similar knowledge base rules organized for quick access
//#########################################################################

package ubc.cs.JLog.Foundation;

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

/**
* This class represents an ordered collection of jRules 
* of the same name and arity. This is designed for statically defined
* rules that cannot change during a proof.
*
* @author       Glendon Holst
* @version      %I%, %G%
*/
public class jRuleDefinitions implements iNameArity
{
 protected Vector 		rules = null;
 protected String		rule_name = null;
 protected int          rule_arity = -1;
 protected String		library = null;
 protected boolean 		builtin = false; 			
 
 /**
  * Constructor for use by sub-classes which set up the members themeselves.  
  */
 protected jRuleDefinitions()
 {
 };
 
 public jRuleDefinitions(String name,int arity)
 {
  rules = new Vector();
  rule_name = name;
  rule_arity = arity; 
 };

 public String 		getName()
 {
  return rule_name;
 };

 public int 		getArity()
 {
  return rule_arity;
 };

 /**
  * Determine if rules are builtin predicates.
  *
  * @return  		true if these rules are builtin predicates, 
  * 			false otherwise.
  */
 public boolean 	isBuiltin()
 {
  return builtin;
 };
 
 /**
  * Set the name of the library associated with this rule definition.  Once an association is 
  * made it is an error to change it (throws InvalidLibraryEntryException in this 
  * case).  The default is a null valued library.
  *
  * @param lib		The name of the library.
  */
 public void			setLibrary(String lib)
 {
  if (library == null)
   library = lib;
  else
   throw new InvalidLibraryEntryException();
 };

 /**
  * Get the name of the library associated with this operator.
  *
  * @return		The name of the library. May be null.
  */
 public String			getLibrary()
 {
  return library;
 };

 public boolean			sameLibrary(String lib)
 {
  if (library == null && lib == null)
   return true;
  if (library == null || lib == null)
   return false;
  
   return library.equals(lib); 
 };

 public int 		size()
 {
  return rules.size();
 };
 
 public jRule 		getRuleAt(int n)
 {
  return (jRule) rules.elementAt(n);
 };

 /**
  * Determine if rules match the given name and arity.
  *
  * @param fn 		The given name and arity.
  *
  * @return  		true if these rules have the same name and arity
  * 			as the given argument, false otherwise.
  */
 public final boolean 		match(iNameArity fn)
 {
  return (fn.getName().equals(rule_name) && fn.getArity() == rule_arity);
 };

 /**
  * Add a rule to the definitions. No ordering is specified, and duplicate rules are 
  * permitted.
  *
  * @param fn 		The jRule to add.
  */
 public void 			addRule(jRule fn)
 {
  if (!match(fn))
   throw new UnmatchedRuleException();
  
   rules.addElement(fn); 
 };
 
 /**
  * Add a rule to the begining of the rule definitions. Duplicate rules are 
  * permitted. Rules at the begining are evaluated first during the proof phase.
  *
  * @param fn 		The jRule to add.
  */
 public void 			addRuleFirst(jRule fn)
 {
  if (!match(fn))
   throw new UnmatchedRuleException();
  
   rules.insertElementAt(fn,0); 
 };
 
 /**
  * Add a rule to the end of the rule definitions. Duplicate rules are 
  * permitted. Rules at the end are evaluated last during the proof phase.
  *
  * @param fn 		The jRule to add.
  */
 public void 			addRuleLast(jRule fn)
 {
  if (!match(fn))
   throw new UnmatchedRuleException();
  
   rules.insertElementAt(fn,rules.size()); 
 };
 
 /**
  * Remove a rule from the rule definitions. Removes on one instance of the rule,
  * if duplicate rules exist.
  *
  * @param fn 		The jRule to remove.
  */
 public void 			removeRule(jRule fn)
 {
  rules.removeElement(fn);
 };
 
 public void 			clearRules()
 {
  rules = new Vector();
 };
 
 public Enumeration 	enumRules()
 {
  return rules.elements();
 };

 public jPredicateGoal 	createGoal(jCompoundTerm t)
 {
  return new jPredicateGoal(this,t);
 };
 
 public void 		consult(jKnowledgeBase kb)
 {Enumeration 		e;
  jRule 		r;

  e = enumRules();
  while (e.hasMoreElements())
  {
   r = (jRule) e.nextElement();
   
   // builtin is true if any rule is a builtin.
   if (r instanceof jBuiltinRule)
    builtin = true;
   
   r.consult(kb); 
  }
 };
 
 public final boolean 		prove(jPredicateGoal pg,iGoalStack goals)
 {int 	next_rule;
 
  while ((next_rule = pg.getNextRuleNumber()) < rules.size())
   if (((jRule) rules.elementAt(next_rule)).unify(pg,goals)) 
    return true;

  return false;
 };
 
 public boolean 		retry(jPredicateGoal pg)
 {
  return (pg.getRuleNumber() < rules.size());
 };
 
 public String			toString()
 {StringBuffer			sb = new StringBuffer();

  sb.append(getName() + "/" + Integer.toString(getArity()));
   
  {String   lib = getLibrary();
  
   if (lib != null)
    sb.append(" library:"+lib);
  }
  
  return sb.toString();
 };
};