/*
 * 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.lucene.analysis.ru;


/* 
 * This algorithm is updated based on code located at:
 * http://members.unine.ch/jacques.savoy/clef/
 * 
 * Full copyright for that code follows:
 */

/*
 * Copyright (c) 2005, Jacques Savoy
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this 
 * list of conditions and the following disclaimer. Redistributions in binary 
 * form must reproduce the above copyright notice, this list of conditions and
 * the following disclaimer in the documentation and/or other materials 
 * provided with the distribution. Neither the name of the author nor the names 
 * of its contributors may be used to endorse or promote products derived from 
 * this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE 
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

import static org.apache.lucene.analysis.util.StemmerUtil.*;

Light Stemmer for Russian.

This stemmer implements the following algorithm: Indexing and Searching Strategies for the Russian Language. Ljiljana Dolamic and Jacques Savoy.

/** * Light Stemmer for Russian. * <p> * This stemmer implements the following algorithm: * <i>Indexing and Searching Strategies for the Russian Language.</i> * Ljiljana Dolamic and Jacques Savoy. */
public class RussianLightStemmer { public int stem(char s[], int len) { len = removeCase(s, len); return normalize(s, len); } private int normalize(char s[], int len) { if (len > 3) switch(s[len-1]) { case 'ь': case 'и': return len - 1; case 'н': if (s[len-2] == 'н') return len - 1; } return len; } private int removeCase(char s[], int len) { if (len > 6 && (endsWith(s, len, "иями") || endsWith(s, len, "оями"))) return len - 4; if (len > 5 && (endsWith(s, len, "иям") || endsWith(s, len, "иях") || endsWith(s, len, "оях") || endsWith(s, len, "ями") || endsWith(s, len, "оям") || endsWith(s, len, "оьв") || endsWith(s, len, "ами") || endsWith(s, len, "его") || endsWith(s, len, "ему") || endsWith(s, len, "ери") || endsWith(s, len, "ими") || endsWith(s, len, "ого") || endsWith(s, len, "ому") || endsWith(s, len, "ыми") || endsWith(s, len, "оев"))) return len - 3; if (len > 4 && (endsWith(s, len, "ая") || endsWith(s, len, "яя") || endsWith(s, len, "ях") || endsWith(s, len, "юю") || endsWith(s, len, "ах") || endsWith(s, len, "ею") || endsWith(s, len, "их") || endsWith(s, len, "ия") || endsWith(s, len, "ию") || endsWith(s, len, "ьв") || endsWith(s, len, "ою") || endsWith(s, len, "ую") || endsWith(s, len, "ям") || endsWith(s, len, "ых") || endsWith(s, len, "ея") || endsWith(s, len, "ам") || endsWith(s, len, "ем") || endsWith(s, len, "ей") || endsWith(s, len, "ём") || endsWith(s, len, "ев") || endsWith(s, len, "ий") || endsWith(s, len, "им") || endsWith(s, len, "ое") || endsWith(s, len, "ой") || endsWith(s, len, "ом") || endsWith(s, len, "ов") || endsWith(s, len, "ые") || endsWith(s, len, "ый") || endsWith(s, len, "ым") || endsWith(s, len, "ми"))) return len - 2; if (len > 3) switch(s[len-1]) { case 'а': case 'е': case 'и': case 'о': case 'у': case 'й': case 'ы': case 'я': case 'ь': return len - 1; } return len; } }