/*
 * JasperReports - Free Java Reporting Library.
 * Copyright (C) 2001 - 2009 Jaspersoft Corporation. All rights reserved.
 * http://www.jaspersoft.com
 *
 * Unless you have purchased a commercial license agreement from Jaspersoft,
 * the following license terms apply:
 *
 * This program is part of JasperReports.
 *
 * JasperReports is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * JasperReports is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with JasperReports. If not, see <http://www.gnu.org/licenses/>.
 */
package net.sf.jasperreports.engine.fill;

/**
 * Interface for objects that can be used by extended incrementers for calculations.
 * 
 * @author Lucian Chirita (lucianc@users.sourceforge.net)
 * @version $Id: JRCalculable.java 3034 2009-08-27 11:58:04Z teodord $
 * @see net.sf.jasperreports.engine.fill.JRExtendedIncrementer
 */
public interface JRCalculable
{
	/**
	 * Constant for the count helper variable.
	 */
	static final byte HELPER_COUNT = 0;
	
	/**
	 * Constant for the sum helper variable.
	 */
	static final byte HELPER_SUM = 1;
	
	/**
	 * Constant for the variance helper variable.
	 */
	static final byte HELPER_VARIANCE = 2;
	
	/**
	 * The number of defined helper variables.
	 */
	static final int HELPER_SIZE = 3;

	
	/**
	 * Returns <code>true</code> if and only if the calculable object was only initialized and not incremented.
	 * 
	 * @return <code>true</code> if and only if the calculable object was only initialized and not incremented
	 */
	boolean isInitialized();
	
	
	/**
	 * Sets the initialized flag for this calculable object.
	 * @param isInitialized the initialized flag
	 * @see #isInitialized()
	 */
	void setInitialized(boolean isInitialized);

	
	/**
	 * Returns the incremented value of the calculable object.
	 * 
	 * @return the incremented value
	 */
	Object getIncrementedValue();

	
	/**
	 * Returns the value of the calculable object.
	 * 
	 * @return the value
	 */
	Object getValue();

	
	/**
	 * Returns a helper variable.
	 * 
	 * @param helperType the desired helper variable type
	 * @return the helper variable
	 */
	JRCalculable getHelperVariable(byte helperType);
}
