    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 *      https://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 * Scores {@link CharSequence} similarity, like a {@link String}.
    021 * <p>
    022 * A string similarity score is intended to have <em>some</em> of the properties of a metric, yet
    023 * allowing for exceptions, like the Jaro-Winkler similarity score.
    024 * </p>
    025 * <p>
    026 * A similarity score is the function {@code d: [X * X] -&gt; [0, INFINITY)} with the
    027 * following properties:
    028 * </p>
    029 * <ul>
    030 *     <li>{@code d(x,y) &gt;= 0}, non-negativity or separation axiom</li>
    031 *     <li>{@code d(x,y) == d(y,x)}, symmetry.</li>
    032 * </ul>
    033 * <p>
    034 * Notice, these are two of the properties that contribute to {@code d} being a metric.
    035 * </p>
    036 * <p>
    037 * Further, this intended to be BiFunction&lt;CharSequence, CharSequence, R&gt;.
    038 * The {@code apply} method accepts a pair of {@link CharSequence} parameters
    039 * and returns an {@code R} type similarity score.
    040 * </p>
    041 *
    042 * @param <R> The type of similarity score unit.
    043 * @since 1.0
    044 */
    045public interface SimilarityScore<R> extends ObjectSimilarityScore<CharSequence, R> {
    046
    047    /**
    048     * Compares two CharSequences.
    049     *
    050     * @param left  the "left" or "first" input.
    051     * @param right the "right" or "second" input.
    052     * @return The similarity score between two CharSequences.
    053     */
    054    @Override
    055    R apply(CharSequence left, CharSequence right);
    056
    057}