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1: /** 2: * ========================================= 3: * LibFormula : a free Java formula library 4: * ========================================= 5: * 6: * Project Info: http://reporting.pentaho.org/libformula/ 7: * 8: * (C) Copyright 2006-2007, by Pentaho Corporation and Contributors. 9: * 10: * This library is free software; you can redistribute it and/or modify it under the terms 11: * of the GNU Lesser General Public License as published by the Free Software Foundation; 12: * either version 2.1 of the License, or (at your option) any later version. 13: * 14: * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; 15: * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 16: * See the GNU Lesser General Public License for more details. 17: * 18: * You should have received a copy of the GNU Lesser General Public License along with this 19: * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, 20: * Boston, MA 02111-1307, USA. 21: * 22: * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 23: * in the United States and other countries.] 24: * 25: * 26: * ------------ 27: * $Id: InfixOperator.java,v 1.5 2007/06/06 17:07:52 taqua Exp $ 28: * ------------ 29: * (C) Copyright 2006-2007, by Pentaho Corporation. 30: */ 31: package org.jfree.formula.operators; 32: 33: import java.io.Serializable; 34: 35: import org.jfree.formula.EvaluationException; 36: import org.jfree.formula.FormulaContext; 37: import org.jfree.formula.lvalues.TypeValuePair; 38: 39: /** 40: * An operator. An operator always takes two arguments. Prefix and postfix 41: * operators are implemented differently. 42: * 43: * @author Thomas Morgner 44: */ 45: public interface InfixOperator extends Serializable 46: { 47: /** 48: * Evaluates the comptuation for both parameters. This method must never return null. 49: * 50: * @param context 51: * @param value1 52: * @param value2 53: * @return 54: * @throws EvaluationException 55: */ 56: public TypeValuePair evaluate(FormulaContext context, 57: TypeValuePair value1, TypeValuePair value2) 58: throws EvaluationException; 59: 60: public int getLevel(); 61: 62: /** 63: * Defines the bind-direction of the operator. That direction defines, in 64: * which direction a sequence of equal operators is resolved. 65: * 66: * @return true, if the operation is left-binding, false if right-binding 67: */ 68: public boolean isLeftOperation(); 69: 70: /** 71: * Defines, whether the operation is associative. For associative operations, 72: * the evaluation order does not matter, if the operation appears more than 73: * once in an expression, and therefore we can optimize them 74: * a lot better than non-associative operations (ie. merge constant parts 75: * and precompute them once). 76: * 77: * @return true, if the operation is associative, false otherwise 78: */ 79: public boolean isAssociative(); 80: }