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Lucy::Analysis::SnowballStopFilter – Apache Lucy Documentation
Apache Lucy™

NAME

Lucy::Analysis::SnowballStopFilter - Suppress a “stoplist” of common words.

SYNOPSIS

my $stopfilter = Lucy::Analysis::SnowballStopFilter->new(
    language => 'fr',
);
my $polyanalyzer = Lucy::Analysis::PolyAnalyzer->new(
    analyzers => [ $tokenizer, $normalizer, $stopfilter, $stemmer ],
);

DESCRIPTION

A “stoplist” is collection of “stopwords”: words which are common enough to be of little value when determining search results. For example, so many documents in English contain “the”, “if”, and “maybe” that it may improve both performance and relevance to block them.

Before filtering stopwords:

("i", "am", "the", "walrus")

After filtering stopwords:

("walrus")

SnowballStopFilter provides default stoplists for several languages, courtesy of the Snowball project, or you may supply your own.

|-----------------------|
| ISO CODE | LANGUAGE   |
|-----------------------|
| da       | Danish     |
| de       | German     |
| en       | English    |
| es       | Spanish    |
| fi       | Finnish    |
| fr       | French     |
| hu       | Hungarian  |
| it       | Italian    |
| nl       | Dutch      |
| no       | Norwegian  |
| pt       | Portuguese |
| sv       | Swedish    |
| ru       | Russian    |
|-----------------------|

CONSTRUCTORS

new

my $stopfilter = Lucy::Analysis::SnowballStopFilter->new(
    language => 'de',
);

# or...
my $stopfilter = Lucy::Analysis::SnowballStopFilter->new(
    stoplist => \%stoplist,
);

Create a new SnowballStopFilter.

  • stoplist - A hash with stopwords as the keys.
  • language - The ISO code for a supported language.

METHODS

transform

my $inversion = $snowball_stop_filter->transform($inversion);

Take a single Inversion as input and returns an Inversion, either the same one (presumably transformed in some way), or a new one.

  • inversion - An inversion.

INHERITANCE

Lucy::Analysis::SnowballStopFilter isa Lucy::Analysis::Analyzer isa Clownfish::Obj.