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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: LValue.java,v 1.4 2007/04/01 13:51:54 taqua Exp $ 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: }