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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 (X^*) over an
 * alphabet (X). Note, that a metric
 * on a set S is a function d: [S * S] -> [0, INFINITY) such
 * that the following hold for x,y,z in
 * the set S:
 * 
 * 
 *     d(x,y) >= 0, non-negativity or separation axiom
 *     d(x,y) == 0, if and only if, x == y
 *     d(x,y) == d(y,x), symmetry, and
 *     d(x,z) <=  d(x,y) + d(y,z), the triangle inequality
 * 
 *
 *
 * 
 * This is a BiFunction<CharSequence, CharSequence, R>.
 * The apply method
 * accepts a pair of {@link CharSequence} parameters
 * and returns an 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);

}