/*
 * This file is part of the LibreOffice project.
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * This file incorporates work covered by the following license notice:
 *
 *   Licensed to the Apache Software Foundation (ASF) under one or more
 *   contributor license agreements. See the NOTICE file distributed
 *   with this work for additional information regarding copyright
 *   ownership. The ASF licenses this file to you under the Apache
 *   License, Version 2.0 (the "License"); you may not use this file
 *   except in compliance with the License. You may obtain a copy of
 *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
 */
package org.libreoffice.report;

/**
 * Functions are statefull computation components.
 *
 * Functions are allowed to have a state, but are considered
 * immutable (the same is true for expressions). Functions are
 * allowed to update their state on every call to 'advance', which
 * signals, that the cursor has been moved.
 *
 * Functions have no way to 'reset' their state, if a reset is needed,
 * the report engine is urged to query a new instance from the ReportAddin.
 */
public interface ReportFunction extends ReportExpression
{

    public ReportFunction advance(DataRow row);
}