1Lingua::Stem::Snowball(U3s)er Contributed Perl DocumentatLiionngua::Stem::Snowball(3)
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6 Lingua::Stem::Snowball - Perl interface to Snowball stemmers.
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9 my @words = qw( horse hooves );
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11 # OO interface:
12 my $stemmer = Lingua::Stem::Snowball->new( lang => 'en' );
13 $stemmer->stem_in_place( \@words ); # qw( hors hoov )
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15 # Functional interface:
16 my @stems = stem( 'en', \@words );
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19 Stemming reduces related words to a common root form -- for instance,
20 "horse", "horses", and "horsing" all become "hors". Most commonly,
21 stemming is deployed as part of a search application, allowing searches
22 for a given term to match documents which contain other forms of that
23 term.
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25 This module is very similar to Lingua::Stem -- however, Lingua::Stem is
26 pure Perl, while Lingua::Stem::Snowball is an XS module which provides
27 a Perl interface to the C version of the Snowball stemmers.
28 (<http://snowball.tartarus.org>).
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30 Supported Languages
31 The following stemmers are available (as of Lingua::Stem::Snowball
32 0.95):
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34 |-----------------------------------------------------------|
35 | Language | ISO code | default encoding | also available |
36 |-----------------------------------------------------------|
37 | Danish | da | ISO-8859-1 | UTF-8 |
38 | Dutch | nl | ISO-8859-1 | UTF-8 |
39 | English | en | ISO-8859-1 | UTF-8 |
40 | Finnish | fi | ISO-8859-1 | UTF-8 |
41 | French | fr | ISO-8859-1 | UTF-8 |
42 | German | de | ISO-8859-1 | UTF-8 |
43 | Hungarian | hu | ISO-8859-1 | UTF-8 |
44 | Italian | it | ISO-8859-1 | UTF-8 |
45 | Norwegian | no | ISO-8859-1 | UTF-8 |
46 | Portuguese | pt | ISO-8859-1 | UTF-8 |
47 | Romanian | ro | ISO-8859-2 | UTF-8 |
48 | Russian | ru | KOI8-R | UTF-8 |
49 | Spanish | es | ISO-8859-1 | UTF-8 |
50 | Swedish | sv | ISO-8859-1 | UTF-8 |
51 | Turkish | tr | UTF-8 | |
52 |-----------------------------------------------------------|
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54 Benchmarks
55 Here is a comparison of Lingua::Stem::Snowball and Lingua::Stem, using
56 The Works of Edgar Allen Poe, volumes 1-5 (via Project Gutenberg) as
57 source material. It was produced on a 3.2GHz Pentium 4 running FreeBSD
58 5.3 and Perl 5.8.7. (The benchmarking script is included in this
59 distribution: devel/benchmark_stemmers.plx.)
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61 |--------------------------------------------------------------------|
62 | total words: 454285 | unique words: 22748 |
63 |--------------------------------------------------------------------|
64 | module | config | avg secs | rate |
65 |--------------------------------------------------------------------|
66 | Lingua::Stem 0.81 | no cache | 2.029 | 223881 |
67 | Lingua::Stem 0.81 | cache level 2 | 1.280 | 355025 |
68 | Lingua::Stem::Snowball 0.94 | stem | 1.426 | 318636 |
69 | Lingua::Stem::Snowball 0.94 | stem_in_place | 0.641 | 708495 |
70 |--------------------------------------------------------------------|
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73 new
74 my $stemmer = Lingua::Stem::Snowball->new(
75 lang => 'es',
76 encoding => 'UTF-8',
77 );
78 die $@ if $@;
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80 Create a Lingua::Stem::Snowball object. new() accepts the following
81 hash style parameters:
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83 · lang: An ISO code taken from the table of supported languages,
84 above.
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86 · encoding: A supported character encoding.
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88 Be careful with the values you supply to new(). If "lang" is invalid,
89 Lingua::Stem::Snowball does not throw an exception, but instead sets
90 $@. Also, if you supply an invalid combination of values for "lang"
91 and "encoding", Lingua::Stem::Snowball will not warn you, but the
92 behavior will change: stem() will always return undef, and
93 stem_in_place() will be a no-op.
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95 stem
96 @stemmed = $stemmer->stem( WORDS, [IS_STEMMED] );
97 @stemmed = stem( ISO_CODE, WORDS, [LOCALE], [IS_STEMMED] );
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99 Return lowercased and stemmed output. WORDS may be either an array of
100 words or a single scalar word.
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102 In a scalar context, stem() returns the first item in the array of
103 stems:
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105 $stem = $stemmer->stem($word);
106 $first_stem = $stemmer->stem(\@words); # probably wrong
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108 LOCALE has no effect; it is only there as a placeholder for backwards
109 compatibility (see Changes). IS_STEMMED must be a reference to a
110 scalar; if it is supplied, it will be set to 1 if the output differs
111 from the input in some way, 0 otherwise.
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113 stem_in_place
114 $stemmer->stem_in_place(\@words);
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116 This is a high-performance, streamlined version of stem() (in fact,
117 stem() calls stem_in_place() internally). It has no return value,
118 instead modifying each item in an existing array of words. The words
119 must already be in lower case.
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121 lang
122 my $lang = $stemmer->lang;
123 $stemmer->lang($iso_language_code);
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125 Accessor/mutator for the lang parameter. If there is no stemmer for the
126 supplied ISO code, the language is not changed (but $@ is set).
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128 encoding
129 my $encoding = $stemmer->encoding;
130 $stemmer->encoding($encoding);
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132 Accessor/mutator for the encoding parameter.
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134 stemmers
135 my @iso_codes = stemmers();
136 my @iso_codes = $stemmer->stemmers();
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138 Returns a list of all valid language codes.
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141 Please report any requests, suggestions or bugs via the RT bug-tracking
142 system at http://rt.cpan.org/ or email to
143 bug-Lingua-Stem-Snowball@rt.cpan.org.
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145 http://rt.cpan.org/NoAuth/Bugs.html?Dist=Lingua-Stem-Snowball is the RT
146 queue for Lingua::Stem::Snowball. Please check to see if your bug has
147 already been reported.
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150 Lingua::Stem::Snowball was originally developed to provide access to
151 stemming algorithms for the OpenFTS (full text search engine) project
152 (<http://openfts.sourceforge.net>), by Oleg Bartunov, <oleg at sai dot
153 msu dot su> and Teodor Sigaev, <teodor at stack dot net>.
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155 Currently maintained by Marvin Humphrey <marvin at rectangular dot
156 com>. Previously maintained by Fabien Potencier <fabpot at cpan dot
157 org>.
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160 Perl bindings copyright 2004-2008 by Marvin Humphrey, Fabien Potencier,
161 Oleg Bartunov and Teodor Sigaev.
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163 This software may be freely copied and distributed under the same terms
164 and conditions as Perl.
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166 Snowball files and stemmers are covered by the BSD license.
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169 <http://snowball.tartarus.org>, Lingua::Stem.
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173perl v5.30.0 2019-07-26 Lingua::Stem::Snowball(3)