/ 
Lingua-Stem-Any-0.02
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/ Lingua::Stem::Any

NAME

Lingua::Stem::Any - Unified interface to any stemmer on CPAN

VERSION

This document describes Lingua::Stem::Any v0.02.

SYNOPSIS

use Lingua::Stem::Any;

# create German stemmer using the default source module
$stemmer = Lingua::Stem::Any->new(language => 'de');

# create German stemmer explicitly using Lingua::Stem::Snowball
$stemmer = Lingua::Stem::Any->new(
    language => 'de',
    source   => 'Lingua::Stem::Snowball',
);

# get stem for word
$stem = $stemmer->stem($word);

# get list of stems for list of words
@stems = $stemmer->stem(@words);

DESCRIPTION

This module aims to provide a simple unified interface to any stemmer on CPAN. It will provide a default available source module when a language is requested but no source is requested.

Attributes

language

The following language codes are currently supported.

┌────────────┬────┐
│ Bulgarian  │ bg │
│ Czech      │ cs │
│ Danish     │ da │
│ Dutch      │ nl │
│ English    │ en │
│ Finnish    │ fi │
│ French     │ fr │
│ Galician   │ gl │
│ German     │ de │
│ Hungarian  │ hu │
│ Italian    │ it │
│ Latin      │ la │
│ Norwegian  │ no │
│ Persian    │ fa │
│ Portuguese │ pt │
│ Romanian   │ ro │
│ Russian    │ ru │
│ Spanish    │ es │
│ Swedish    │ sv │
│ Turkish    │ tr │
└────────────┴────┘

They are in the two-letter ISO 639-1 format and are case-insensitive but are always returned in lowercase when requested.

# instantiate a stemmer object
$stemmer = Lingua::Stem::Any->new(language => $language);

# get current language
$language = $stemmer->language;

# change language
$stemmer->language($language);

Country codes such as cz for the Czech Republic are not supported, nor are IETF language tags such as pt-PT or pt-BR.

source

The following source modules are currently supported.

┌────────────────────────┬──────────────────────────────────────────────┐
│ Module                 │ Languages                                    │
├────────────────────────┼──────────────────────────────────────────────┤
│ Lingua::Stem::Snowball │ da nl en fi fr de hu it no pt ro ru es sv tr │
│ Lingua::Stem::UniNE    │ bg cs fa                                     │
│ Lingua::Stem           │ da de en fr gl it no pt ru sv                │
└────────────────────────┴──────────────────────────────────────────────┘

A module name is used to specify the source. If no source is specified, the first available source in the above list with support for the current language is used.

# get current source
$source = $stemmer->source;

# change source
$stemmer->source('Lingua::Stem::UniNE');
casefold

Boolean value specifying whether to apply Unicode casefolding to words before stemming them. This is enabled by default and is performed before normalization when also enabled.

normalize

Boolean value specifying whether to apply Unicode NFC normalization to words before stemming them. This is enabled by default and is performed after casefolding when also enabled.

Methods

stem

Accepts a list of strings, stems each string, and returns a list of stems. The list returned will always have the same number of elements in the same order as the list provided. When no stemming rules apply to a word, the original word is returned.

@stems = $stemmer->stem(@words);

# get the stem for a single word
$stem = $stemmer->stem($word);

The words should be provided as character strings and the stems are returned as character strings. Byte strings in arbitrary character encodings are not supported.

stem_in_place

Accepts an array reference, stems each element, and replaces them with the resulting stems.

$stemmer->stem_in_place(\@words);

This method is provided for potential optimization when a large array of words is to be stemmed. The return value is not defined.

languages

Returns a list of supported two-letter language codes using lowercase letters.

# all languages
@languages = $stemmer->languages;

# languages supported by Lingua::Stem::Snowball
@languages = $stemmer->languages('Lingua::Stem::Snowball');
sources

Returns a list of supported source module names.

# all sources
@sources = $stemmer->sources;

# sources that support English
@sources = $stemmer->sources('en');

TODO

  • optional stem caching

  • custom stemming exceptions

SEE ALSO

Lingua::Stem::Snowball, Lingua::Stem::UniNE, Lingua::Stem

ACKNOWLEDGEMENTS

This module is brought to you by Shutterstock (@ShutterTech). Additional open source projects from Shutterstock can be found at code.shutterstock.com.

AUTHOR

Nick Patch <patch@cpan.org>

COPYRIGHT AND LICENSE

© 2013 Nick Patch

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.