001 /*--------------------------------------------------------------------------+ 002 $Id: IAggregator.java 28099 2010-06-09 13:17:22Z hummelb $ 003 | | 004 | Copyright 2005-2010 Technische Universitaet Muenchen | 005 | | 006 | Licensed under the Apache License, Version 2.0 (the "License"); | 007 | you may not use this file except in compliance with the License. | 008 | You may obtain a copy of the License at | 009 | | 010 | http://www.apache.org/licenses/LICENSE-2.0 | 011 | | 012 | Unless required by applicable law or agreed to in writing, software | 013 | distributed under the License is distributed on an "AS IS" BASIS, | 014 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | 015 | See the License for the specific language governing permissions and | 016 | limitations under the License. | 017 +--------------------------------------------------------------------------*/ 018 package edu.tum.cs.commons.math; 019 020 import java.util.Collection; 021 022 /** 023 * Aggregtor interface. 024 * 025 * @author deissenb 026 * @author $Author: hummelb $ 027 * @version $Rev: 28099 $ 028 * @levd.rating GREEN Hash: 07B1BC375A02AAB32E730C81ACD72882 029 */ 030 public interface IAggregator { 031 032 /** 033 * Aggregate collection of values to one value. Implementing classes may 034 * return non-normal numbers, e.g. {@link Double#NaN} for the median of an 035 * empty collections. 036 */ 037 public double aggregate(Collection<? extends Number> values); 038 039 /** 040 * Get the neutral element of this aggregation operator. This may return 041 * non-normal numbers, e.g. {@link Double#NaN} or 042 * {@link Double#POSITIVE_INFINITY} . 043 */ 044 public double getNeutralElement(); 045 046 }