001    /*
002     * Copyright (c) 2005 Einar Pehrson <einar@pehrson.nu>.
003     *
004     * This file is part of
005     * CleanSheets - a spreadsheet application for the Java platform.
006     *
007     * CleanSheets is free software; you can redistribute it and/or modify
008     * it under the terms of the GNU General Public License as published by
009     * the Free Software Foundation; either version 2 of the License, or
010     * (at your option) any later version.
011     *
012     * CleanSheets is distributed in the hope that it will be useful,
013     * but WITHOUT ANY WARRANTY; without even the implied warranty of
014     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
015     * GNU General Public License for more details.
016     *
017     * You should have received a copy of the GNU General Public License
018     * along with CleanSheets; if not, write to the Free Software
019     * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
020     */
021    package csheets.core.formula;
022    
023    import java.util.SortedSet;
024    
025    import csheets.core.Cell;
026    import csheets.core.Value;
027    
028    /**
029     * A reference to one or more cells in a spreadsheet.
030     * @author Einar Pehrson
031     */
032    public interface Reference extends Expression, Comparable<Reference> {
033    
034            public Value evaluate();
035    
036            /**
037             * Returns the cell addresses (or address) that the reference points to.
038             * @return a naturally ordered set of the references' addresses
039             */
040            public SortedSet<Cell> getCells();
041    
042            /**
043             * Compares the reference with the given reference for order.
044             * @param reference the reference to be compared
045             * @return a negative integer, zero, or a positive integer as this object is less than, equal to, or greater than the specified object.
046             */
047            public int compareTo(Reference reference);
048    }