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 * This is a base class for aggregators that have a defined neutral element and
023 * operate in pairwise manner.
024 * 
025 * @author Florian Deissenboeck
026 */
027public abstract class PairwiseAggregatorBase implements IAggregator {
028
029        /** {@inheritDoc} */
030        @Override
031        public double aggregate(Collection<? extends Number> values) {
032                double result = getNeutralElement();
033                for (Number value : values) {
034                        result = aggregate(result, value.doubleValue());
035                }
036                return result;
037        }
038
039        /**
040         * Calculate aggregate of two values.
041         * 
042         * @param aggregate
043         *            the value that has been aggregated by previous pairwise
044         *            aggregations
045         * @param value
046         *            the new value
047         */
048        protected abstract double aggregate(double aggregate, double value);
049}