001 /** 002 * ========================================= 003 * LibFormula : a free Java formula library 004 * ========================================= 005 * 006 * Project Info: http://reporting.pentaho.org/libformula/ 007 * 008 * (C) Copyright 2006-2007, by Pentaho Corporation and Contributors. 009 * 010 * This library is free software; you can redistribute it and/or modify it under the terms 011 * of the GNU Lesser General Public License as published by the Free Software Foundation; 012 * either version 2.1 of the License, or (at your option) any later version. 013 * 014 * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; 015 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 016 * See the GNU Lesser General Public License for more details. 017 * 018 * You should have received a copy of the GNU Lesser General Public License along with this 019 * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, 020 * Boston, MA 02111-1307, USA. 021 * 022 * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 023 * in the United States and other countries.] 024 * 025 * 026 * ------------ 027 * $Id: InfixOperator.java 2887 2007-06-06 17:07:52Z taqua $ 028 * ------------ 029 * (C) Copyright 2006-2007, by Pentaho Corporation. 030 */ 031 package org.jfree.formula.operators; 032 033 import java.io.Serializable; 034 035 import org.jfree.formula.EvaluationException; 036 import org.jfree.formula.FormulaContext; 037 import org.jfree.formula.lvalues.TypeValuePair; 038 039 /** 040 * An operator. An operator always takes two arguments. Prefix and postfix 041 * operators are implemented differently. 042 * 043 * @author Thomas Morgner 044 */ 045 public interface InfixOperator extends Serializable 046 { 047 /** 048 * Evaluates the comptuation for both parameters. This method must never return null. 049 * 050 * @param context 051 * @param value1 052 * @param value2 053 * @return 054 * @throws EvaluationException 055 */ 056 public TypeValuePair evaluate(FormulaContext context, 057 TypeValuePair value1, TypeValuePair value2) 058 throws EvaluationException; 059 060 public int getLevel(); 061 062 /** 063 * Defines the bind-direction of the operator. That direction defines, in 064 * which direction a sequence of equal operators is resolved. 065 * 066 * @return true, if the operation is left-binding, false if right-binding 067 */ 068 public boolean isLeftOperation(); 069 070 /** 071 * Defines, whether the operation is associative. For associative operations, 072 * the evaluation order does not matter, if the operation appears more than 073 * once in an expression, and therefore we can optimize them 074 * a lot better than non-associative operations (ie. merge constant parts 075 * and precompute them once). 076 * 077 * @return true, if the operation is associative, false otherwise 078 */ 079 public boolean isAssociative(); 080 }