Class PorterStemFilter

Transforms the token stream as per the Porter stemming algorithm.

Note: the input to the stemming filter must already be in lower case, so you will need to use LowerCaseFilter or LowerCaseTokenizer farther down the Tokenizer chain in order for this to work properly!

To use this filter with other analyzers, you'll want to write an Analyzer class that sets up the TokenStream chain as you want it. To use this with LowerCaseTokenizer, for example, you'd write an analyzer like this:

class MyAnalyzer : Analyzer {
            protected override TokenStreamComponents CreateComponents(string fieldName, TextReader reader) {
              Tokenizer source = new LowerCaseTokenizer(version, reader);
              return new TokenStreamComponents(source, new PorterStemFilter(source));
            }
          }

Note: This filter is aware of the Lucene.Net.Analysis.TokenAttributes.IKeywordAttribute. To prevent certain terms from being passed to the stemmer Lucene.Net.Analysis.TokenAttributes.IKeywordAttribute.IsKeyword should be set to

true

in a previous Lucene.Net.Analysis.TokenStream.

Note: For including the original term as well as the stemmed version, see KeywordRepeatFilterFactory

Inheritance

object

AttributeSource

TokenStream

TokenFilter

PorterStemFilter

Implements

IDisposable

Inherited Members

TokenFilter.End()

TokenFilter.Reset()

TokenStream.Dispose()

AttributeSource.GetAttributeFactory()

AttributeSource.GetAttributeClassesEnumerator()

AttributeSource.GetAttributeImplsEnumerator()

AttributeSource.AddAttributeImpl(Attribute)

AttributeSource.AddAttribute<T>()

AttributeSource.HasAttributes

AttributeSource.HasAttribute<T>()

AttributeSource.GetAttribute<T>()

AttributeSource.ClearAttributes()

AttributeSource.CaptureState()

AttributeSource.RestoreState(AttributeSource.State)

AttributeSource.GetHashCode()

AttributeSource.Equals(object)

AttributeSource.ReflectAsString(bool)

AttributeSource.ReflectWith(IAttributeReflector)

AttributeSource.CloneAttributes()

AttributeSource.CopyTo(AttributeSource)

AttributeSource.ToString()

object.Equals(object, object)

object.GetType()

object.ReferenceEquals(object, object)

Namespace: Lucene.Net.Analysis.En

Assembly: Lucene.Net.Analysis.Common.dll

Syntax

public sealed class PorterStemFilter : TokenFilter, IDisposable

Constructors

PorterStemFilter(TokenStream)

Transforms the token stream as per the Porter stemming algorithm.

Note: the input to the stemming filter must already be in lower case, so you will need to use LowerCaseFilter or LowerCaseTokenizer farther down the Tokenizer chain in order for this to work properly!

To use this filter with other analyzers, you'll want to write an Analyzer class that sets up the TokenStream chain as you want it. To use this with LowerCaseTokenizer, for example, you'd write an analyzer like this:

class MyAnalyzer : Analyzer {
            protected override TokenStreamComponents CreateComponents(string fieldName, TextReader reader) {
              Tokenizer source = new LowerCaseTokenizer(version, reader);
              return new TokenStreamComponents(source, new PorterStemFilter(source));
            }
          }

Note: This filter is aware of the Lucene.Net.Analysis.TokenAttributes.IKeywordAttribute. To prevent certain terms from being passed to the stemmer Lucene.Net.Analysis.TokenAttributes.IKeywordAttribute.IsKeyword should be set to

true

in a previous Lucene.Net.Analysis.TokenStream.

Note: For including the original term as well as the stemmed version, see KeywordRepeatFilterFactory

Declaration

public PorterStemFilter(TokenStream @in)

Parameters

Type	Name	Description
TokenStream	in

Methods

IncrementToken()

Consumers (i.e., Lucene.Net.Index.IndexWriter) use this method to advance the stream to the next token. Implementing classes must implement this method and update the appropriate Lucene.Net.Util.IAttributes with the attributes of the next token.

The producer must make no assumptions about the attributes after the method has been returned: the caller may arbitrarily change it. If the producer needs to preserve the state for subsequent calls, it can use Lucene.Net.Util.AttributeSource.CaptureState() to create a copy of the current attribute state.

this method is called for every token of a document, so an efficient implementation is crucial for good performance. To avoid calls to Lucene.Net.Util.AttributeSource.AddAttribute<T>() and Lucene.Net.Util.AttributeSource.GetAttribute<T>(), references to all Lucene.Net.Util.IAttributes that this stream uses should be retrieved during instantiation.

To ensure that filters and consumers know which attributes are available, the attributes must be added during instantiation. Filters and consumers are not required to check for availability of attributes in Lucene.Net.Analysis.TokenStream.IncrementToken().

Declaration

public override bool IncrementToken()

Returns

Type	Description
bool	false for end of stream; true otherwise

Overrides

Lucene.Net.Analysis.TokenStream.IncrementToken()

Implements

IDisposable