1package Lingua::Stem::Snowball::Se; 2use strict; 3use bytes; 4# -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 5# Lingua::Stem::Snowball::Se - Swedish stemmer 6# :: based upon the swedish stemmer algorithm at snowball.tartarus.org. 7# by Martin Porter. 8# (c) 2001-2007 Ask Solem Hoel <ask@0x61736b.net> 9# 10# This program is free software; you can redistribute it and/or modify 11# it under the terms of the GNU General Public License version 2, 12# *NOT* "earlier versions", as published by the Free Software Foundation. 13# 14# This program is distributed in the hope that it will be useful, 15# but WITHOUT ANY WARRANTY; without even the implied warranty of 16# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 17# GNU General Public License for more details. 18# 19# You should have received a copy of the GNU General Public License 20# along with this program; if not, write to the Free Software 21# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 22# -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 23##### 24 25 26use vars qw($VERSION); 27$VERSION = 1.2; 28 29# special characters 30my $ae = chr(0xe4); # a" 31my $ao = chr(0xe5); # ao 32my $oe = chr(0xf6); # o" 33 34# delete the s if a "s ending" is preceeded by one 35# of these characters. 36my $s_ending = "bcdfghjklmnoprtvy"; 37 38# swedish vowels. 39my $vowels = "aeiouy$ae$ao$oe"; 40 41# #### 42# the endings in step 1 43# XXX: these must be sorted by length 44# to save time we've done it already, you can do it like this: 45# my $bylength = sub { 46# length $a <=> length $b; 47# } 48# @endings = reverse sort $bylength @endings; 49my @endings = qw/ 50 heterna hetens ornas ernas andet heter arnas arens heten andes 51 anden orna erna erns arna ades aren aste arne ande ast het ens 52 ern ade are er at es ad as en or ar e a s 53/; 54 55# the endings in step 2 56# XXX: these must be sorted by length, like @endings in step 1. 57my @endings2 = ('fullt', "l${oe}st", 'els', 'lig', 'ig'); 58 59my %cache = ( ); 60 61sub new { 62 my $pkg = shift; 63 $pkg = ref $pkg || $pkg; 64 my %arg = @_; 65 my $self = {}; 66 bless $self, $pkg; 67 if($arg{use_cache}) { 68 $self->use_cache(1); 69 } 70 return $self; 71} 72 73sub use_cache { 74 my($self, $use_cache) = @_; 75 if($use_cache) { 76 $self->{USE_CACHE} = 1; 77 } 78 return $self->{USE_CACHE}; 79} 80 81sub stem { 82 my ($self, $word) = @_; 83 no warnings; 84 my $orig_word; 85 86 if($self->use_cache()) { 87 $orig_word = $word; 88 my $cached_word = $cache{$word}; 89 return $cached_word if $cached_word; 90 } 91 92 my ($ls, $rs, $wlen, $lslen, $rslen) = getsides($word); 93 return $word unless $lslen >= 3; 94 95 # ### STEP 1 96 # only need to refresh wlen each time we change the word. 97 foreach my $ending (@endings) { 98 my $endinglen = length $ending; # do this once. 99 100 # only continue if the word has this ending at all. 101 if(substr($rs, $rslen - $endinglen, $rslen) eq $ending) { 102 if($ending eq 's') { # b) 103 # check if it has a valid "s ending"... 104 my $valid_s_ending = 0; 105 if($rslen == 1) { 106 my $wmr1 = substr($word, 0, $wlen - $rslen); 107 if($wmr1 =~ /[$s_ending]$/o) { 108 $valid_s_ending = 1; 109 } 110 } 111 else { 112 if(substr($rs, $rslen - 2, $rslen - 1) =~ /[$s_ending]/o) { 113 $valid_s_ending = 1; 114 } 115 } 116 if($valid_s_ending) { 117 # ...delete the last character (which is a s) 118 $word = substr($word, 0, $wlen - 1); 119 ($ls, $rs, $wlen, $lslen, $rslen) = getsides($word); 120 last; 121 } 122 } 123 else { # a) 124 # delete the ending. 125 $word = substr($word, 0, $wlen - $endinglen); 126 ($ls, $rs, $wlen, $lslen, $rslen) = getsides($word); 127 last; 128 } 129 } 130 } 131 return $word unless $lslen >= 3; 132 133 # ### STEP 2 134 my $ending = substr($rs, $rslen - 2, $rslen); 135 if($ending =~ /dd|gd|nn|dt|gt|kt|tt/) { 136 $word = substr($word, 0, $wlen - 1); 137 ($ls, $rs, $wlen, $lslen, $rslen) = getsides($word); 138 } 139 return $word unless $lslen >= 3; 140 141 # ### STEP 3 142 foreach my $ending (@endings2) { 143 if($rs =~ /\Q$ending\E$/) 144 { 145 if($ending =~ /lig|ig|els/) 146 { 147 my $res = substr($word, 0, $wlen - length($ending)); 148 $word = $res; #if length $res > 2; 149 last 150 } 151 if($ending eq "l${oe}st") 152 { 153 my $res = substr($word, 0, $wlen - 1); 154 $word = $res; #if length $res > 2; 155 last 156 } 157 if($ending eq 'fullt') 158 { 159 my $res = substr($word, 0, $wlen - 1); 160 $word = $res; #if length $res > 2; 161 last 162 } 163 } 164 } 165 166 if($self->use_cache()) { 167 $cache{$orig_word} = $word; 168 } 169 170 return $word; 171} 172 173sub getsides { 174 my $word = shift; 175 no warnings; 176 my $wlen = length $word; 177 178 my($ls, $rs) = (undef, undef); # left side and right side. 179 180 # ### 181 # find the first vowel with a non-vowel after it. 182 my($found_vowel, $nonv_position, $curpos) = (-1, -1, 0); 183 foreach(split//, $word) { 184 if($found_vowel> 0) { 185 if(/[^$vowels]/o) { 186 if($curpos > 0) { 187 $nonv_position = $curpos + 1; 188 last; 189 } 190 } 191 } 192 if(/[$vowels]/o) { 193 $found_vowel = 1; 194 } 195 $curpos++; 196 } 197 198 # got nothing: return false 199 return undef if $nonv_position < 0; 200 201 # ### 202 # length of the left side must be atleast 3 chars. 203 my $leftlen = $wlen - ($wlen - $nonv_position); 204 if($leftlen < 3) { 205 $ls = substr($word, 0, 3); 206 $rs = substr($word, 3, $wlen); 207 } 208 else { 209 $ls = substr($word, 0, $leftlen); 210 $rs = substr($word, $nonv_position, $wlen); 211 } 212 return($ls, $rs, $wlen, length $ls, length $rs); 213} 214 2151; 216 217__END__ 218 219=head1 NAME 220 221Lingua::Stem::Snowball::Se - Porters stemming algorithm for Swedish 222 223=head1 VERSION 224 225This document describes version 1.1. 226 227=head1 SYNOPSIS 228 229 use Lingua::Stem::Snowball::Se 230 my $stemmer = new Lingua::Stem::Snowball::Se (use_cache => 1); 231 232 foreach my $word (@words) { 233 my $stemmed = $stemmer->stem($word); 234 print $stemmed, "\n"; 235 } 236 237=head1 DESCRIPTION 238 239The stem function takes a scalar as a parameter and stems the word 240according to Martin Porters Swedish stemming algorithm, 241which can be found at the Snowball website: L<http://snowball.tartarus.org/>. 242 243It also supports caching if you pass the use_cache option when constructing 244a new L:S:S:S object. 245 246=head2 EXPORT 247 248Lingua::Stem::Snowball::Se has nothing to export. 249 250=head1 AUTHOR 251 252Ask Solem Hoel, E<lt>ask@0x61736b.netE<gt> 253 254=head1 SEE ALSO 255 256L<perl>. L<Lingua::Stem::Snowball>. L<Lingua::Stem>. L<http://snowball.tartarus.org>. 257 258=head1 LICENSE AND COPYRIGHT 259 260Copyright (c), 2007 Ask Solem C<< ask@0x61736b.net >>. 261 262All rights reserved. 263 264This library is free software; you can redistribute it and/or modify 265it under the same terms as Perl itself, either Perl version 5.8.6 or, 266at your option, any later version of Perl 5 you may have available. 267 268=head1 DISCLAIMER OF WARRANTY 269 270BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE 271SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE 272STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE 273SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, 274INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND 275FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND 276PERFORMANCE OF THE SOFTWARE IS WITH YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, 277YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR, OR CORRECTION. 278 279IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY 280COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE 281SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE TO YOU FOR DAMAGES, 282INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING 283OUT OF THE USE OR INABILITY TO USE THE SOFTWARE (INCLUDING BUT NOT LIMITED TO 284LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR 285THIRD PARTIES OR A FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER 286SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE 287POSSIBILITY OF SUCH DAMAGES. 288 289=cut 290