    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  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.apache.commons.text.similarity;
    018
    019/**
    020 * Interface for the concept of a string similarity score.
    021 *
    022 * <p>
    023 * A string similarity score is intended to have <i>some</i> of the properties of a metric, yet
    024 * allowing for exceptions, namely the Jaro-Winkler similarity score.
    025 * </p>
    026 * <p>
    027 * We Define a SimilarityScore to be a function {@code d: [X * X] -&gt; [0, INFINITY)} with the
    028 * following properties:
    029 * </p>
    030 * <ul>
    031 *     <li>{@code d(x,y) &gt;= 0}, non-negativity or separation axiom</li>
    032 *     <li>{@code d(x,y) == d(y,x)}, symmetry.</li>
    033 * </ul>
    034 *
    035 * <p>
    036 * Notice, these are two of the properties that contribute to d being a metric.
    037 * </p>
    038 *
    039 *
    040 * <p>
    041 * Further, this intended to be BiFunction&lt;CharSequence, CharSequence, R&gt;.
    042 * The {@code apply} method
    043 * accepts a pair of {@link CharSequence} parameters
    044 * and returns an {@code R} type similarity score. We have omitted the explicit
    045 * statement of extending BiFunction due to it only being implemented in Java 1.8, and we
    046 * wish to maintain Java 1.7 compatibility.
    047 * </p>
    048 *
    049 * @param <R> The type of similarity score unit used by this EditDistance.
    050 * @since 1.0
    051 */
    052public interface SimilarityScore<R> {
    053
    054    /**
    055     * Compares two CharSequences.
    056     *
    057     * @param left the first CharSequence
    058     * @param right the second CharSequence
    059     * @return The similarity score between two CharSequences
    060     */
    061    R apply(CharSequence left, CharSequence right);
    062
    063}