001/*-------------------------------------------------------------------------+
002|                                                                          |
003| Copyright 2005-2011 The ConQAT Project                                   |
004|                                                                          |
005| Licensed under the Apache License, Version 2.0 (the "License");          |
006| you may not use this file except in compliance with the License.         |
007| You may obtain a copy of the License at                                  |
008|                                                                          |
009|    http://www.apache.org/licenses/LICENSE-2.0                            |
010|                                                                          |
011| Unless required by applicable law or agreed to in writing, software      |
012| distributed under the License is distributed on an "AS IS" BASIS,        |
013| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
014| See the License for the specific language governing permissions and      |
015| limitations under the License.                                           |
016+-------------------------------------------------------------------------*/
017package org.conqat.lib.commons.math;
018
019import java.util.Collection;
020
021/**
022 * Aggregtor interface.
023 * 
024 * @author deissenb
025 */
026public interface IAggregator {
027
028        /**
029         * Aggregate collection of values to one value. Implementing classes may
030         * return non-normal numbers, e.g. {@link Double#NaN} for the median of an
031         * empty collections.
032         */
033        public double aggregate(Collection<? extends Number> values);
034
035        /**
036         * Get the neutral element of this aggregation operator. This may return
037         * non-normal numbers, e.g. {@link Double#NaN} or
038         * {@link Double#POSITIVE_INFINITY} .
039         */
040        public double getNeutralElement();
041
042}