src/Lucene.Net.Analysis.Common/Analysis/Sv/SwedishLightStemmer.cs

using Lucene.Net.Analysis.Util;

namespace Lucene.Net.Analysis.Sv
{
    /*
     * 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.
     */

    /* 
     * 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.
     */

    /// <summary>
    /// Light Stemmer for Swedish.
    /// <para>
    /// This stemmer implements the algorithm described in:
    /// <c>Report on CLEF-2003 Monolingual Tracks</c>
    /// Jacques Savoy
    /// </para>
    /// </summary>
    public class SwedishLightStemmer
    {
        public virtual int Stem(char[] s, int len)
        {
            if (len > 4 && s[len - 1] == 's')
            {
                len--;
            }

            if (len > 7 && (StemmerUtil.EndsWith(s, len, "elser") || StemmerUtil.EndsWith(s, len, "heten")))
            {
                return len - 5;
            }

            if (len > 6 && (StemmerUtil.EndsWith(s, len, "arne") || StemmerUtil.EndsWith(s, len, "erna") || StemmerUtil.EndsWith(s, len, "ande") || StemmerUtil.EndsWith(s, len, "else") || StemmerUtil.EndsWith(s, len, "aste") || StemmerUtil.EndsWith(s, len, "orna") || StemmerUtil.EndsWith(s, len, "aren")))
            {
                return len - 4;
            }

            if (len > 5 && (StemmerUtil.EndsWith(s, len, "are") || StemmerUtil.EndsWith(s, len, "ast") || StemmerUtil.EndsWith(s, len, "het")))
            {
                return len - 3;
            }

            if (len > 4 && (StemmerUtil.EndsWith(s, len, "ar") || StemmerUtil.EndsWith(s, len, "er") || StemmerUtil.EndsWith(s, len, "or") || StemmerUtil.EndsWith(s, len, "en") || StemmerUtil.EndsWith(s, len, "at") || StemmerUtil.EndsWith(s, len, "te") || StemmerUtil.EndsWith(s, len, "et")))
            {
                return len - 2;
            }

            if (len > 3)
            {
                switch (s[len - 1])
                {
                    case 't':
                    case 'a':
                    case 'e':
                    case 'n':
                        return len - 1;
                }
            }

            return len;
        }
    }
}