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 }