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 */
021package csheets.core.formula.util;
022        
023import csheets.core.Value;
024import csheets.core.formula.BinaryOperation;
025import csheets.core.formula.FunctionCall;
026import csheets.core.formula.Literal;
027import csheets.core.formula.Reference;
028import csheets.core.formula.UnaryOperation;
029
030/**
031 * A base-class for customized formula interpreters. The interpretation relies
032 * on the Visitor pattern, so a typical invocation would look like
033 * <code>formula.accept(interpreter)</code>.
034 * @author Einar Pehrson
035 */
036public abstract class Interpreter implements ExpressionVisitor {
037
038        /**
039         * Creates a new interpreter.
040         */
041        public Interpreter() {}
042
043        public Value visitLiteral(Literal literal) {
044                return literal.evaluate();
045        }
046
047        public abstract Value visitUnaryOperation(UnaryOperation operation);
048
049        public abstract Value visitBinaryOperation(BinaryOperation operation);
050
051        public Value visitReference(Reference reference) {
052                return reference.evaluate();
053        }
054
055        public abstract Value visitFunctionCall(FunctionCall call);
056}