+++ /dev/null
-package org.apache.lucene.analysis.lv;
-
-import static org.apache.lucene.analysis.util.StemmerUtil.*;
-
-/**
- * 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.
- */
-
-/**
- * Light stemmer for Latvian.
- * <p>
- * This is a light version of the algorithm in Karlis Kreslin's PhD thesis
- * <i>A stemming algorithm for Latvian</i> with the following modifications:
- * <ul>
- * <li>Only explicitly stems noun and adjective morphology
- * <li>Stricter length/vowel checks for the resulting stems (verb etc suffix stripping is removed)
- * <li>Removes only the primary inflectional suffixes: case and number for nouns ;
- * case, number, gender, and definitiveness for adjectives.
- * <li>Palatalization is only handled when a declension II,V,VI noun suffix is removed.
- * </ul>
- */
-public class LatvianStemmer {
- /**
- * Stem a latvian word. returns the new adjusted length.
- */
- public int stem(char s[], int len) {
- int numVowels = numVowels(s, len);
-
- for (int i = 0; i < affixes.length; i++) {
- Affix affix = affixes[i];
- if (numVowels > affix.vc && len >= affix.affix.length + 3 && endsWith(s, len, affix.affix)) {
- len -= affix.affix.length;
- return affix.palatalizes ? unpalatalize(s, len) : len;
- }
- }
-
- return len;
- }
-
- static final Affix affixes[] = {
- new Affix("ajiem", 3, false), new Affix("ajai", 3, false),
- new Affix("ajam", 2, false), new Affix("ajām", 2, false),
- new Affix("ajos", 2, false), new Affix("ajās", 2, false),
- new Affix("iem", 2, true), new Affix("ajā", 2, false),
- new Affix("ais", 2, false), new Affix("ai", 2, false),
- new Affix("ei", 2, false), new Affix("ām", 1, false),
- new Affix("am", 1, false), new Affix("ēm", 1, false),
- new Affix("īm", 1, false), new Affix("im", 1, false),
- new Affix("um", 1, false), new Affix("us", 1, true),
- new Affix("as", 1, false), new Affix("ās", 1, false),
- new Affix("es", 1, false), new Affix("os", 1, true),
- new Affix("ij", 1, false), new Affix("īs", 1, false),
- new Affix("ēs", 1, false), new Affix("is", 1, false),
- new Affix("ie", 1, false), new Affix("u", 1, true),
- new Affix("a", 1, true), new Affix("i", 1, true),
- new Affix("e", 1, false), new Affix("ā", 1, false),
- new Affix("ē", 1, false), new Affix("ī", 1, false),
- new Affix("ū", 1, false), new Affix("o", 1, false),
- new Affix("s", 0, false), new Affix("š", 0, false),
- };
-
- static class Affix {
- char affix[]; // suffix
- int vc; // vowel count of the suffix
- boolean palatalizes; // true if we should fire palatalization rules.
-
- Affix(String affix, int vc, boolean palatalizes) {
- this.affix = affix.toCharArray();
- this.vc = vc;
- this.palatalizes = palatalizes;
- }
- }
-
- /**
- * Most cases are handled except for the ambiguous ones:
- * <ul>
- * <li> s -> š
- * <li> t -> š
- * <li> d -> ž
- * <li> z -> ž
- * </ul>
- */
- private int unpalatalize(char s[], int len) {
- // we check the character removed: if its -u then
- // its 2,5, or 6 gen pl., and these two can only apply then.
- if (s[len] == 'u') {
- // kš -> kst
- if (endsWith(s, len, "kš")) {
- len++;
- s[len-2] = 's';
- s[len-1] = 't';
- return len;
- }
- // ņņ -> nn
- if (endsWith(s, len, "ņņ")) {
- s[len-2] = 'n';
- s[len-1] = 'n';
- return len;
- }
- }
-
- // otherwise all other rules
- if (endsWith(s, len, "pj") || endsWith(s, len, "bj")
- || endsWith(s, len, "mj") || endsWith(s, len, "vj")) {
- // labial consonant
- return len-1;
- } else if (endsWith(s, len, "šņ")) {
- s[len-2] = 's';
- s[len-1] = 'n';
- return len;
- } else if (endsWith(s, len, "žņ")) {
- s[len-2] = 'z';
- s[len-1] = 'n';
- return len;
- } else if (endsWith(s, len, "šļ")) {
- s[len-2] = 's';
- s[len-1] = 'l';
- return len;
- } else if (endsWith(s, len, "žļ")) {
- s[len-2] = 'z';
- s[len-1] = 'l';
- return len;
- } else if (endsWith(s, len, "ļņ")) {
- s[len-2] = 'l';
- s[len-1] = 'n';
- return len;
- } else if (endsWith(s, len, "ļļ")) {
- s[len-2] = 'l';
- s[len-1] = 'l';
- return len;
- } else if (s[len-1] == 'č') {
- s[len-1] = 'c';
- return len;
- } else if (s[len-1] == 'ļ') {
- s[len-1] = 'l';
- return len;
- } else if (s[len-1] == 'ņ') {
- s[len-1] = 'n';
- return len;
- }
-
- return len;
- }
-
- /**
- * Count the vowels in the string, we always require at least
- * one in the remaining stem to accept it.
- */
- private int numVowels(char s[], int len) {
- int n = 0;
- for (int i = 0; i < len; i++) {
- switch(s[i]) {
- case 'a': case 'e': case 'i':
- case 'o': case 'u': case 'ā':
- case 'ī': case 'ē': case 'ū':
- n++;
- }
- }
- return n;
- }
-}
fnp / pylucene.git / blobdiff