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.util;
022    
023    import csheets.core.formula.BinaryOperation;
024    import csheets.core.formula.FunctionCall;
025    import csheets.core.formula.Literal;
026    import csheets.core.formula.Reference;
027    import csheets.core.formula.UnaryOperation;
028    
029    /**
030     * An interface for using the Visitor pattern for traversing expressions.
031     * @author Einar Pehrson
032     */
033    public interface ExpressionVisitor {
034    
035            /**
036             * Visits the given literal.
037             * @param literal the literal to visit
038             * @return an arbitrary object
039             */
040            public Object visitLiteral(Literal literal);
041    
042            /**
043             * Visits the given unary expression.
044             * @param operation the operation to visit
045             * @return an arbitrary object
046             */
047            public Object visitUnaryOperation(UnaryOperation operation);
048    
049            /**
050             * Visits the given binary expression.
051             * @param operation the operation to visit
052             * @return an arbitrary object
053             */
054            public Object visitBinaryOperation(BinaryOperation operation);
055    
056            /**
057             * Visits the given cell reference.
058             * @param reference the reference to visit
059             * @return an arbitrary object
060             */
061            public Object visitReference(Reference reference);
062    
063            /**
064             * Visits the given function call.
065             * @param call the function call to visit
066             * @return an arbitrary object
067             */
068            public Object visitFunctionCall(FunctionCall call);
069    }