001/*
002 * Copyright (c) 2015-2020, Oracle and/or its affiliates. All rights reserved.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *     http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.tribuo.util;
018
019/**
020 * An interface which can merge double values.
021 * <p>
022 * Provides a few obvious stateless examples.
023 */
024@FunctionalInterface
025public interface Merger {
026
027    /**
028     * Merges first and second.
029     * @param first The first input.
030     * @param second The second input.
031     * @return The merged value.
032     */
033    public double merge(double first, double second);
034
035    /**
036     * A merger which takes the maximum element.
037     * @return The maximum function.
038     */
039    public static Merger max() {
040        return Math::max;
041    }
042
043    /**
044     * A merger which takes the minimum element.
045     * @return The minimum function.
046     */
047    public static Merger min() {
048        return Math::min;
049    }
050
051    /**
052     * A merger which adds the elements.
053     * @return The addition function.
054     */
055    public static Merger add() {
056        return Double::sum;
057    }
058
059}