/*
 * The contents of this file are subject to the Mozilla Public License
 * Version 1.1 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
 * the License for the specific language governing rights and limitations
 * under the License.
 *
 * The Original Code is the Kowari Metadata Store.
 *
 * The Initial Developer of the Original Code is Plugged In Software Pty
 * Ltd (http://www.pisoftware.com, mailto:info@pisoftware.com). Portions
 * created by Plugged In Software Pty Ltd are Copyright (C) 2001,2002
 * Plugged In Software Pty Ltd. All Rights Reserved.
 *
 * Contributor(s): N/A.
 *
 * [NOTE: The text of this Exhibit A may differ slightly from the text
 * of the notices in the Source Code files of the Original Code. You
 * should use the text of this Exhibit A rather than the text found in the
 * Original Code Source Code for Your Modifications.]
 *
 */

package org.mulgara.query;

import java.util.*;

/**
 * An expression whose leaves are {@link Constraint}s.
 *
 * @created 2001-08-12
 *
 * @author <a href="http://staff.pisoftware.com/raboczi">Simon Raboczi</a>
 *
 * @version $Revision: 1.8 $
 *
 * @modified $Date: 2005/01/05 04:58:20 $
 *
 * @maintenanceAuthor $Author: newmana $
 *
 * @company <A href="mailto:info@PIsoftware.com">Plugged In Software</A>
 *
 * @copyright © 2001-2003 <A href="http://www.PIsoftware.com/">Plugged In
 *      Software Pty Ltd</A>
 *
 * @licence <a href="{@docRoot}/../../LICENCE">Mozilla Public License v1.1</a>
 */
public abstract class AbstractConstraintExpression implements ConstraintExpression {

  /**
   * Allow newer compiled version of the stub to operate when changes
   * have not occurred with the class.
   * NOTE : update this serialVersionUID when a method or a public member is
   * deleted.
   */
  static final long serialVersionUID = -8835851673635062642L;

  /**
   * A set of all variables the compose the constraint.
   */
  protected Set<Variable> variables = null;

  /**
   * The operands.
   */
  protected ArrayList<ConstraintExpression> elements;

  public boolean equals(Object o) {
    if (o == null) return false;
    if (o == this) return true;

    if (o instanceof ConstraintExpression) {
      return (getVariables().equals(((ConstraintExpression)o).getVariables()));
    } else {
      return false;
    }
  }

  /** @see java.lang.Object#hashCode() */
  public int hashCode() {
    return getVariables().hashCode();
  }

  /**
   * Indicates if this operation is associative.
   * @return <code>true</code> iff this operation is associative.
   */
  public boolean isAssociative() {
    return true;
  }

}