pylucene 3.5.0-3

[pylucene.git] / lucene-java-3.5.0 / lucene / contrib / analyzers / common / src / java / org / apache / lucene / analysis / bg / BulgarianStemmer.java

diff --git a/lucene-java-3.5.0/lucene/contrib/analyzers/common/src/java/org/apache/lucene/analysis/bg/BulgarianStemmer.java b/lucene-java-3.5.0/lucene/contrib/analyzers/common/src/java/org/apache/lucene/analysis/bg/BulgarianStemmer.java
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+++ b/lucene-java-3.5.0/lucene/contrib/analyzers/common/src/java/org/apache/lucene/analysis/bg/BulgarianStemmer.java
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+package org.apache.lucene.analysis.bg;
+
+/**
+ * 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.
+ */
+
+import static org.apache.lucene.analysis.util.StemmerUtil.*;
+
+/**
+ * Light Stemmer for Bulgarian.
+ * <p>
+ * Implements the algorithm described in:  
+ * <i>
+ * Searching Strategies for the Bulgarian Language
+ * </i>
+ * http://members.unine.ch/jacques.savoy/Papers/BUIR.pdf
+ */
+public class BulgarianStemmer {
+  
+  /**
+   * Stem an input buffer of Bulgarian text.
+   * 
+   * @param s input buffer
+   * @param len length of input buffer
+   * @return length of input buffer after normalization
+   */
+  public int stem(final char s[], int len) {
+    if (len < 4) // do not stem
+      return len;
+    
+    if (len > 5 && endsWith(s, len, "ища"))
+      return len - 3;
+    
+    len = removeArticle(s, len);
+    len = removePlural(s, len);
+    
+    if (len > 3) {
+      if (endsWith(s, len, "я"))
+        len--;
+      if (endsWith(s, len, "а") ||
+          endsWith(s, len, "о") ||
+          endsWith(s, len, "е"))
+        len--;
+    }
+    
+    // the rule to rewrite ен -> н is duplicated in the paper.
+    // in the perl implementation referenced by the paper, this is fixed.
+    // (it is fixed here as well)
+    if (len > 4 && endsWith(s, len, "ен")) {
+      s[len - 2] = 'н'; // replace with н
+      len--;
+    }
+    
+    if (len > 5 && s[len - 2] == 'ъ') {
+      s[len - 2] = s[len - 1]; // replace ъN with N
+      len--;
+    }
+
+    return len;
+  }
+  
+  /**
+   * Mainly remove the definite article
+   * @param s input buffer
+   * @param len length of input buffer
+   * @return new stemmed length
+   */
+  private int removeArticle(final char s[], final int len) {
+    if (len > 6 && endsWith(s, len, "ият"))
+      return len - 3;
+    
+    if (len > 5) {
+      if (endsWith(s, len, "ът") ||
+          endsWith(s, len, "то") ||
+          endsWith(s, len, "те") ||
+          endsWith(s, len, "та") ||
+          endsWith(s, len, "ия"))
+        return len - 2;
+    }
+    
+    if (len > 4 && endsWith(s, len, "ят"))
+      return len - 2;
+
+    return len;
+  }
+  
+  private int removePlural(final char s[], final int len) {
+    if (len > 6) {
+      if (endsWith(s, len, "овци"))
+        return len - 3; // replace with о
+      if (endsWith(s, len, "ове"))
+        return len - 3;
+      if (endsWith(s, len, "еве")) {
+        s[len - 3] = 'й'; // replace with й
+        return len - 2;
+      }
+    }
+    
+    if (len > 5) {
+      if (endsWith(s, len, "ища"))
+        return len - 3;
+      if (endsWith(s, len, "та"))
+        return len - 2;
+      if (endsWith(s, len, "ци")) {
+        s[len - 2] = 'к'; // replace with к
+        return len - 1;
+      }
+      if (endsWith(s, len, "зи")) {
+        s[len - 2] = 'г'; // replace with г
+        return len - 1;
+      }
+      
+      if (s[len - 3] == 'е' && s[len - 1] == 'и') {
+        s[len - 3] = 'я'; // replace е with я, remove и
+        return len - 1;
+      }
+    }
+    
+    if (len > 4) {
+      if (endsWith(s, len, "си")) {
+        s[len - 2] = 'х'; // replace with х
+        return len - 1;
+      }
+      if (endsWith(s, len, "и"))
+        return len - 1;
+    }
+    
+    return len;
+  }
+}