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A component of the BIRT runtime

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/***********************************************************************
 * Copyright (c) 2005 Actuate Corporation.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 * Actuate Corporation - initial API and implementation
 ***********************************************************************/

package org.eclipse.birt.chart.factory;

/**
 * This interface provide expression evaluations of any string expression based
 * on a row context. This is usually associated with an underlying resultset.
 * 
 */
public interface IDataRowExpressionEvaluator
{

	/**
	 * Evaluates the expression based on the current row
	 * 
	 * @param A
	 *            String expression
	 * @return An Object representing the evaluated expression. The Object must
	 *         be of a type String, Number, Date, Calendar, or it will be
	 *         evaluated as a String using toString(). If there is any
	 *         BirtException being caught by evaluation, the return value will
	 *         be the caught BirtException.
	 */
	Object evaluate( String expression );

	/**
	 * Evaluates the global expressions which are not associated with the data
	 * rows.
	 * 
	 * @param A
	 *            String expression
	 * @return An Object representing the evaluated expression. The Object must
	 *         be of a type String, Number, Date, Calendar, or it will be
	 *         evaluated as a String using toString().
	 * @deprecated Not used anymore. use {@link #evaluate(String)} instead.
	 */
	Object evaluateGlobal( String expression );

	/**
	 * Moves to the first row. Optional if already positioned on the first row
	 * when passed to Generator.bindData()
	 * 
	 * @return true if the cursor is on a valid row;
	 *         false if there are no rows in the result set
	 */
	boolean first( );

	/**
	 * Moves to the next row.
	 * 
	 * @return False if the last row has been reached. True otherwise.
	 */
	boolean next( );

	/**
	 * Closes the underlying resultset. This is optional (it can be a no-op if
	 * the close is handled externally or not needed).
	 * 
	 */
	void close( );
}