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Apache Commons Text is a library focused on algorithms working on strings.

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.text.similarity;

/**
 * Interface for Edit Distances.
 *
 * 
 * An edit distance is a formal metric on the Kleene closure ({@code X^*}) over an
 * alphabet ({@code X}). Note, that a metric
 * on a set {@code S} is a function {@code d: [S * S] -> [0, INFINITY)} such
 * that the following hold for {@code x,y,z} in
 * the set {@code S}:
 * 
 * 
 *     {@code d(x,y) >= 0}, non-negativity or separation axiom
 *     {@code d(x,y) == 0}, if and only if, {@code x == y}
 *     {@code d(x,y) == d(y,x)}, symmetry, and
 *     {@code d(x,z) <=  d(x,y) + d(y,z)}, the triangle inequality
 * 
 *
 *
 * 
 * This is a BiFunction<CharSequence, CharSequence, R>.
 * The {@code apply} method
 * accepts a pair of {@link CharSequence} parameters
 * and returns an {@code R} type similarity score.
 * 
 *
 * @param  The type of similarity score unit used by this EditDistance.
 * @since 1.0
 */
public interface EditDistance extends SimilarityScore {

    /**
     * Compares two CharSequences.
     *
     * @param left the first CharSequence
     * @param right the second CharSequence
     * @return The similarity score between two CharSequences
     */
    @Override
    R apply(CharSequence left, CharSequence right);

}