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.Expression;
025    import csheets.core.formula.FunctionCall;
026    import csheets.core.formula.Literal;
027    import csheets.core.formula.Reference;
028    import csheets.core.formula.UnaryOperation;
029    
030    /**
031     * A default implementation of an expression visitor, that simply visits all
032     * the nodes in the tree. All methods return the expression that was visited.
033     * @author Einar Pehrson
034     */
035    public abstract class AbstractExpressionVisitor implements ExpressionVisitor {
036    
037            /**
038             * Creates a new expression visitor.
039             */
040            public AbstractExpressionVisitor() {}
041    
042            public Object visitLiteral(Literal literal) {
043                    return literal;
044            }
045    
046            public Object visitUnaryOperation(UnaryOperation operation) {
047                    operation.getOperand().accept(this);
048                    return operation;
049            }
050    
051            public Object visitBinaryOperation(BinaryOperation operation) {
052                    operation.getLeftOperand().accept(this);
053                    operation.getRightOperand().accept(this);
054                    return operation;
055            }
056    
057            public Object visitReference(Reference reference) {
058                    return reference;
059            }
060    
061            public Object visitFunctionCall(FunctionCall call) {
062                    for (Expression argument : call.getArguments())
063                            argument.accept(this);
064                    return call;
065            }
066    }