Source for org.jfree.formula.lvalues.LValue

   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: LValue.java 2716 2007-04-01 13:51:58Z taqua $
  28:  * ------------
  29:  * (C) Copyright 2006-2007, by Pentaho Corporation.
  30:  */
  31: package org.jfree.formula.lvalues;
  32: 
  33: import java.io.Serializable;
  34: 
  35: import org.jfree.formula.FormulaContext;
  36: import org.jfree.formula.EvaluationException;
  37: import org.jfree.formula.typing.Type;
  38: 
  39: /**
  40:  * A reference is an indirection to hide the details of where the actual
  41:  * value came from.
  42:  *
  43:  * The reference is responsible to report dependencies.
  44:  *
  45:  * @author Thomas Morgner
  46:  */
  47: public interface LValue extends Serializable, Cloneable
  48: {
  49:   public void initialize(FormulaContext context) throws EvaluationException;
  50: 
  51:   public TypeValuePair evaluate() throws EvaluationException;
  52: 
  53:   public Object clone() throws CloneNotSupportedException;
  54: 
  55:   /**
  56:    * Querying the value type is only valid *after* the value has been evaluated.
  57:    * @return
  58:    */
  59:   public Type getValueType();
  60: 
  61:   /**
  62:    * Returns any dependent lvalues (parameters and operands, mostly).
  63:    *
  64:    * @return
  65:    */
  66:   public LValue[] getChildValues();
  67: 
  68:   /**
  69:    * Checks, whether the LValue is constant. Constant lvalues always return
  70:    * the same value.
  71:    *
  72:    * @return
  73:    */
  74:   public boolean isConstant();
  75: }