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: LValue.java 2716 2007-04-01 13:51:58Z taqua $ 028 * ------------ 029 * (C) Copyright 2006-2007, by Pentaho Corporation. 030 */ 031 package org.jfree.formula.lvalues; 032 033 import java.io.Serializable; 034 035 import org.jfree.formula.FormulaContext; 036 import org.jfree.formula.EvaluationException; 037 import org.jfree.formula.typing.Type; 038 039 /** 040 * A reference is an indirection to hide the details of where the actual 041 * value came from. 042 * 043 * The reference is responsible to report dependencies. 044 * 045 * @author Thomas Morgner 046 */ 047 public interface LValue extends Serializable, Cloneable 048 { 049 public void initialize(FormulaContext context) throws EvaluationException; 050 051 public TypeValuePair evaluate() throws EvaluationException; 052 053 public Object clone() throws CloneNotSupportedException; 054 055 /** 056 * Querying the value type is only valid *after* the value has been evaluated. 057 * @return 058 */ 059 public Type getValueType(); 060 061 /** 062 * Returns any dependent lvalues (parameters and operands, mostly). 063 * 064 * @return 065 */ 066 public LValue[] getChildValues(); 067 068 /** 069 * Checks, whether the LValue is constant. Constant lvalues always return 070 * the same value. 071 * 072 * @return 073 */ 074 public boolean isConstant(); 075 }