Source for org.jfree.formula.operators.InfixOperator

   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: }