/*
*
* 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.
*
*/
using System;
using Lucene.Net.Analysis;
namespace Lucene.Net.Analysis.Ru
{
///
/// A filter that stems Russian words. The implementation was inspired by GermanStemFilter.
/// The input should be filtered by RussianLowerCaseFilter before passing it to RussianStemFilter,
/// because RussianStemFilter only works with lowercase part of any "russian" charset.
///
public sealed class RussianStemFilter : TokenFilter
{
///
/// The actual token in the input stream.
///
private Token token = null;
private RussianStemmer stemmer = null;
public RussianStemFilter(TokenStream _in, char[] charset) : base(_in)
{
stemmer = new RussianStemmer(charset);
}
///
///
///
/// Returns the next token in the stream, or null at EOS
public override Token Next()
{
if ((token = input.Next()) == null)
{
return null;
}
else
{
String s = stemmer.Stem(token.TermText());
if (!s.Equals(token.TermText()))
{
return new Token(s, token.StartOffset(), token.EndOffset(),
token.Type());
}
return token;
}
}
///
/// Set a alternative/custom RussianStemmer for this filter.
///
///
public void SetStemmer(RussianStemmer stemmer)
{
if (stemmer != null)
{
this.stemmer = stemmer;
}
}
}
}