    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 * Interface for <a href="https://en.wikipedia.org/wiki/Edit_distance">Edit Distances</a>.
    021 *
    022 * <p>
    023 * An edit distance is a formal metric on the Kleene closure ({@code X<sup>*</sup>}) over an
    024 * alphabet ({@code X}). Note, that a <a href="https://en.wikipedia.org/wiki/Metric_(mathematics)">metric</a>
    025 * on a set {@code S} is a function {@code d: [S * S] -&gt; [0, INFINITY)} such
    026 * that the following hold for {@code x,y,z} in
    027 * the set {@code S}:
    028 * </p>
    029 * <ul>
    030 *     <li>{@code d(x,y) &gt;= 0}, non-negativity or separation axiom</li>
    031 *     <li>{@code d(x,y) == 0}, if and only if, {@code x == y}</li>
    032 *     <li>{@code d(x,y) == d(y,x)}, symmetry, and</li>
    033 *     <li>{@code d(x,z) &lt;=  d(x,y) + d(y,z)}, the triangle inequality</li>
    034 * </ul>
    035 *
    036 *
    037 * <p>
    038 * This is a BiFunction&lt;CharSequence, CharSequence, R&gt;.
    039 * The {@code apply} method
    040 * accepts a pair of {@link CharSequence} parameters
    041 * and returns an {@code R} type similarity score.
    042 * </p>
    043 *
    044 * @param <R> The type of similarity score unit used by this EditDistance.
    045 * @since 1.0
    046 */
    047public interface EditDistance<R> extends SimilarityScore<R> {
    048    // empty
    049}