autofactiterator.java

Mandarax是一个规则引擎的纯Java实现。它支持多类型的事实和基于反映的规则

/*
 * Copyright (C) 1999-2004 <A href="http://www-ist.massey.ac.nz/JBDietrich" target="_top">Jens Dietrich</a>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package org.mandarax.util;

import java.util.Iterator;
import java.util.Vector;

import org.mandarax.kernel.Clause;
import org.mandarax.kernel.Fact;
import org.mandarax.kernel.LogicFactory;
import org.mandarax.kernel.Replacement;
import org.mandarax.kernel.VariableTerm;

/**
 * Clause iterator for auto facts.
 * @author <A href="http://www-ist.massey.ac.nz/JBDietrich" target="_top">Jens Dietrich</A>
 * @version 3.4 <7 March 05>
 * @since 1.2
 */
class AutoFactIterator extends AbstractAutoFactIterator {

    private Iterator       multiIterator = null;
    private Fact           fact          = null;
    private Fact           nextFact      = null;
    private VariableTerm[] variables     = null;
    private Vector         replacements  = null;

    /**
     * Constructor.
     * @param f a fact
     * @param mci an iterator
     * @param vars the variables
     * @param af the client object
     */
    public AutoFactIterator(Fact f, Iterator mci, VariableTerm[] vars,
                            AutoFacts af) {
        super (af);

        fact          = f;
        multiIterator = mci;
        variables     = vars;

        initialize ();
    }

    /**
     * Indicates whether there are more clauses.
     * @return boolean
     */
    public boolean hasMoreClauses() {
        searchNextFact ();

        return(nextFact != null);
    }

    /**
     * Initialize the object.
     */
    private void initialize() {
        replacements = new Vector (variables.length);

        Replacement r;

        for(int i = 0; i < variables.length; i++) {
            r          = new Replacement ();
            r.original = variables[i];

            replacements.add (r);
        }
        ;
    }

    /**
     * Get the next clause.
     * @return the next clause
     */
    public Clause nextClause() {
        return nextFact;
    }

    /**
     * Search the next fact. If there is one,
     * put it into the variable nextFact, otherwise
     * reset this variable to null.
     */
    private void searchNextFact() {
        nextFact = null;

        if(multiIterator == null) {

            // this is the case if there are no variables   
        } else {
            while(multiIterator.hasNext () && (nextFact == null)) {
                Object[] values = (Object[]) multiIterator.next ();

                for(int i = 0; i < variables.length; i++) {
                    ((Replacement) replacements.get (i)).replacement =
                        LogicFactory.getDefaultFactory ().createConstantTerm (
                            values[i]);
                }

                Fact f = fact.applyToFact (replacements);

                if(perform (f,null)) {
                    nextFact = f;

                    nextFact.setContainer (autofacts);
                }
            }
        }
    }
}