/*
 * 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.fi;


/* 
 * 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 Finnish.

This stemmer implements the algorithm described in: Report on CLEF-2003 Monolingual Tracks Jacques Savoy

/** * Light Stemmer for Finnish. * <p> * This stemmer implements the algorithm described in: * <i>Report on CLEF-2003 Monolingual Tracks</i> * Jacques Savoy */
public class FinnishLightStemmer { public int stem(char s[], int len) { if (len < 4) return len; for (int i = 0; i < len; i++) switch(s[i]) { case 'ä': case 'å': s[i] = 'a'; break; case 'ö': s[i] = 'o'; break; } len = step1(s, len); len = step2(s, len); len = step3(s, len); len = norm1(s, len); len = norm2(s, len); return len; } private int step1(char s[], int len) { if (len > 8) { if (endsWith(s, len, "kin")) return step1(s, len-3); if (endsWith(s, len, "ko")) return step1(s, len-2); } if (len > 11) { if (endsWith(s, len, "dellinen")) return len-8; if (endsWith(s, len, "dellisuus")) return len-9; } return len; } private int step2(char s[], int len) { if (len > 5) { if (endsWith(s, len, "lla") || endsWith(s, len, "tse") || endsWith(s, len, "sti")) return len-3; if (endsWith(s, len, "ni")) return len-2; if (endsWith(s, len, "aa")) return len-1; // aa -> a } return len; } private int step3(char s[], int len) { if (len > 8) { if (endsWith(s, len, "nnen")) { s[len-4] = 's'; return len-3; } if (endsWith(s, len, "ntena")) { s[len-5] = 's'; return len-4; } if (endsWith(s, len, "tten")) return len-4; if (endsWith(s, len, "eiden")) return len-5; } if (len > 6) { if (endsWith(s, len, "neen") || endsWith(s, len, "niin") || endsWith(s, len, "seen") || endsWith(s, len, "teen") || endsWith(s, len, "inen")) return len-4; if (s[len-3] == 'h' && isVowel(s[len-2]) && s[len-1] == 'n') return len-3; if (endsWith(s, len, "den")) { s[len-3] = 's'; return len-2; } if (endsWith(s, len, "ksen")) { s[len-4] = 's'; return len-3; } if (endsWith(s, len, "ssa") || endsWith(s, len, "sta") || endsWith(s, len, "lla") || endsWith(s, len, "lta") || endsWith(s, len, "tta") || endsWith(s, len, "ksi") || endsWith(s, len, "lle")) return len-3; } if (len > 5) { if (endsWith(s, len, "na") || endsWith(s, len, "ne")) return len-2; if (endsWith(s, len, "nei")) return len-3; } if (len > 4) { if (endsWith(s, len, "ja") || endsWith(s, len, "ta")) return len-2; if (s[len-1] == 'a') return len-1; if (s[len-1] == 'n' && isVowel(s[len-2])) return len-2; if (s[len-1] == 'n') return len-1; } return len; } private int norm1(char s[], int len) { if (len > 5 && endsWith(s, len, "hde")) { s[len-3] = 'k'; s[len-2] = 's'; s[len-1] = 'i'; } if (len > 4) { if (endsWith(s, len, "ei") || endsWith(s, len, "at")) return len-2; } if (len > 3) switch(s[len-1]) { case 't': case 's': case 'j': case 'e': case 'a': case 'i': return len-1; } return len; } private int norm2(char s[], int len) { if (len > 8) { if (s[len-1] == 'e' || s[len-1] == 'o' || s[len-1] == 'u') len--; } if (len > 4) { if (s[len-1] == 'i') len--; if (len > 4) { char ch = s[0]; for (int i = 1; i < len; i++) { if (s[i] == ch && (ch == 'k' || ch == 'p' || ch == 't')) len = delete(s, i--, len); else ch = s[i]; } } } return len; } private boolean isVowel(char ch) { switch(ch) { case 'a': case 'e': case 'i': case 'o': case 'u': case 'y': return true; default: return false; } } }