not.java

国外的一套开源CRM

package org.ofbiz.rules.engine;


/**
 * <p><b>Title:</b> Not
 * <p><b>Description:</b> None
 * <p>Copyright (c) 1999 Steven J. Metsker.
 * <p>Copyright (c) 2001 The Open For Business Project - www.ofbiz.org
 *
 * <p>Permission is hereby granted, free of charge, to any person obtaining a
 *  copy of this software and associated documentation files (the "Software"),
 *  to deal in the Software without restriction, including without limitation
 *  the rights to use, copy, modify, merge, publish, distribute, sublicense,
 *  and/or sell copies of the Software, and to permit persons to whom the
 *  Software is furnished to do so, subject to the following conditions:
 *
 * <p>The above copyright notice and this permission notice shall be included
 *  in all copies or substantial portions of the Software.
 *
 * <p>THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 *  OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 *  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 *  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 *  CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT
 *  OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR
 *  THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * <br>
 * <p>A Not is a structure that fails if it can prove itself
 * against a program.
 * <p>
 * This simple behavior can have surprising results. For
 * example:
 * <blockquote><pre>
 *     goodBachelor(X) :- male (X), not married(X);
 *     badBachelor(X) :- not married(X), male(X);
 *     married(jim);
 *     male(jeremy);
 *     male(jim);
 * </pre></blockquote>
 *
 * Against this program, a query <code>badBachelor(X)</code>
 * will find no bachelors. This rule negates <code>married(X)
 * </code> which will bind uninstantiated <code>X</code> to
 * <code>jim</code> every time. Thus <code>married(X)</code>
 * will always be true, <code>not married(X)</code> will
 * always be false, and there are no bad bachelors, which is
 * untrue. The good rule instantiates <code>X</code> to a good
 * candidate first, and the negation will prove or disprove
 * itself for that candidate.
 * <p>
 * (A parser of the logic code given above will produce
 * engine calls similar to the following code.)
 *
 * <blockquote><pre>
 *     Program p = new Program();
 *     Variable x = new Variable("X");
 *
 *     p.addAxiom(new Rule(new Structure[]{
 *         new Structure("goodBachelor", new Term[]{x}),
 *         new Structure("male",         new Term[]{x}),
 *         new Not      ("married",      new Term[]{x})}));
 *
 *     p.addAxiom(new Rule(new Structure[]{
 *         new Structure("badBachelor",  new Term[]{x}),
 *         new Not      ("married",      new Term[]{x}),
 *         new Structure("male",         new Term[]{x})}));
 *     p.addAxiom(new Fact("married", "jim"));
 *     p.addAxiom(new Fact("male", "jeremy"));
 *     p.addAxiom(new Fact("male", "jim"));
 *
 *     Query qGood = new Query(
 *         p, new Structure("goodBachelor", new Term[]{x}));
 *     while(qGood.canFindNextProof()) {
 *         System.out.println(
 *             "goodBachelor query finds: " + qGood.lookup("X"));
 *     }
 *
 *     Query qBad = new Query(
 *         p, new Structure("badBachelor", new Term[]{x}));
 *     while(qBad.canFindNextProof()) {
 *         System.out.println(
 *             "badBachelor query finds: " + qBad.lookup("X"));
 *     }
 *
 * </pre></blockquote>
 *
 * Running this code prints out:
 * <blockquote><pre>
 *     goodBachelor query finds: jeremy
 * </pre></blockquote>
 *
 * @author Steven J. Metsker
 * @version 1.0
 */
public class Not extends Structure {

    /**
     * Contructs a Not from the specified object.
     * <p>
     * Such a Not will search a program for a fact that contains
     * just the functor. For example, it might make sense to create a
     * <code>Not("demo")</code> that would look for the fact
     * <code>demo</code> to see if the program is in demo mode.
     *
     * @param   functor   the functor for this structure
     */
    public Not(Object functor) {
        this(functor, new Term[0]);
    }

    /**
     * Constructs a Not with the specified functor and terms.
     *
     * This is the normal way to define a Not. This structure will
     * be true if there is no possible proof of it in a program.
     *
     * @param   functor   the functor of the structure
     *
     * @param   terms   the terms of the structure, which may be either
     *                  variables or other structures
     */
    public Not(Object functor, Term[] terms) {
        super(functor, terms);
    }

    /**
     * Constructs a Not version of the supplied structure.
     *
     * @param   structure   the structure to negate
     */
    public Not(Structure s) {
        this(s.functor, s.terms);
    }

    /**
     * Create a <code>ConsultingNot</code> counterpart that
     * can prove itself.
     *
     * @param AxiomSource where to find axioms to prove
     *        against
     *
     * @param Scope the scope to use for variables in the
     *        <code>ConsultingStructure</code>
     *
     * @return a <code>ConsultingNot</code> counterpart that
     *         can prove itself
     */
    public Term copyForProof(AxiomSource as, Scope scope) {
        Term[] newTerms = new Term[terms.length];

        for (int i = 0; i < terms.length; i++) {
            newTerms[i] = terms[i].copyForProof(as, scope);
        }
        return new ConsultingNot(new ConsultingStructure(as, functor, newTerms));
    }

    /**
     * Returns true if the supplied object is an equivalent
     * not structure.
     *
     * @param   object   the object to compare
     *
     * @return   true, if the supplied object is a Not, and
     *           the two object's sub-structures are equal
     */
    public boolean equals(Object o) {
        if (!(o instanceof Not))
            return false;
        Not n = (Not) o;

        if (!functorAndArityEquals(n)) {
            return false;
        }
        for (int i = 0; i < terms.length; i++) {
            if (!(terms[i].equals(n.terms[i]))) {
                return false;
            }
        }
        return true;
    }

    /**
     * Returns a string description of this Not.
     *
     * @return    a string description of this Not
     */
    public String toString() {
        return "not " + super.toString();
    }
}