package Lingua::Stem;

# $RCSfile: Stem.pm,v $ $Revision: 1.2 $ $Date: 1999/06/16 17:45:28 $ $Author: snowhare $

#######################################################################
# Initial POD Documentation
#######################################################################

=head1 NAME

Lingua::Stem - Stemming of words

=head1 SYNOPSIS

    use Lingua::Stem qw(stem);
    my $stemmmed_words_anon_array   = stem(@words);

    or for the OO inclined,

    use Lingua::Stem;
    my $stemmer = Lingua::Stem->new(-locale => 'EN-UK');
    $stemmer->stem_caching({ -level => 2 });
    my $stemmmed_words_anon_array   = $stemmer->stem(@words);

=head1 DESCRIPTION

This routine applies stemming algorithms to its parameters,
returning the stemmed words as appropriate to the selected
locale.

You can import some or all of the class methods.

use Lingua::Stem qw (stem clear_stem_cache stem_caching
                     add_exceptions delete_exceptions
                     get_exceptions set_locale get_locale
                     :all :locale :exceptions :stem :caching);

 :all        - imports  stem add_exceptions delete_exceptions get_exceptions
               set_locale get_locale
 :stem       - imports  stem
 :caching    - imports  stem_caching clear_stem_cache
 :locale     - imports  set_locale get_locale
 :exceptions - imports  add_exceptions delete_exceptions get_exceptions

Currently supported locales are:

      DA          - Danish
      DE          - German
      EN          - English (also EN-US and EN-UK)
      FR          - French
      GL          - Galician
      IT          - Italian
      NO          - Norwegian
      PT          - Portuguese
      RU          - Russian (also RU-RU and RU-RU.KOI8-R)
      SV          - Swedish

If you have the memory and lots of stemming to do,
I B<strongly> suggest using cache level 2 and processing
lists in 'big chunks' (long lists) for best performance.

Some benchmarks using Lingua::Stem 0.80 and Lingua::Stem::Snowball 0.7
give an idea of how batching and caching affect performance. The dataset was
3000 randomly selected words from the snowball english voc.txt list repeated
100 times (300000 words total, with 3000 unique words). The tests were performed
on a Linux machine with a 1.7 Ghz Athlon processor running Perl 5.8.5. There
are no tests listed for Lingua::Stem::Snowball using caching because it doesn't have 
a caching mode.

Lingua::Stem::Snowball, one word at a time, no caching:    26741 words/second
Lingua::Stem::Snowball,   3000 word batches, no caching:  169710 words/second
Lingua::Stem::Snowball, one batch, no caching:            155797 words/second

Lingua::Stem, one word at a time, no caching:              13509 words/second
Lingua::Stem,   3000 word batches, no caching:             32765 words/second
Lingua::Stem, one batch, no caching:                       34847 words/second

Lingua::Stem, one word at a time, cache level 2:           25736 words/second
Lingua::Stem,   3000 word batches, cache level 2:         194384 words/second
Lingua::Stem, one batch, cache level 2:                   216602 words/second

=head1 CHANGES

 0.80 2004.07.25 - Added 'RU', 'RU_RU', 'RU_RU.KOI-8' locale.
                   Added support for Lingua::Stem::Ru to
                   Makefile.PL and autoloader.

                   Added documentation stressing use of caching
                   and batches for performance. Added support
                   for '_' as a seperator in the locale strings.
                   Added example benchmark script. Expanded copyright 
                   credits.

 0.70 2004.04.26 - Added FR locale and documentation fixes
                   to Lingua::Stem::Gl

 0.61 2003.09.28 - Documentation fixes. No functional changes.

 0.60 2003.04.05 - Added more locales by wrappering various stemming
                   implementations. Documented currently supported
                   list of locales.

 0.50 2000.09.14 - Fixed major implementation error. Starting with
                   version 0.30 I forgot to include rulesets 2,3 and 4
                   for Porter's algorithm. The resulting stemming results
                   were very poor. Thanks go to <csyap@netfision.com>
                   for bringing the problem to my attention.

                   Unfortunately, the fix inherently generates *different*
                   stemming results than 0.30 and 0.40 did. If you
                   need identically broken output - use locale 'en-broken'.

 0.40 2000.08.25 - Added stem caching support as an option. This
                   can provide a large speedup to the operation
                   of the stemmer. Caching is default turned off
                   to maximize compatibility with previous versions.

 0.30 1999.06.24 - Replaced core of 'En' stemmers with code from
                   Jim Richardson <jimr@maths.usyd.edu.au>
                   Aliased 'en-us' and 'en-uk' to 'en'
                   Fixed 'SYNOPSIS' to correct return value
                   type for stemmed words (SYNOPIS error spotted
                   by <Arved_37@chebucto.ns.ca>)

 0.20 1999.06.15 - Changed to '.pm' module, moved into Lingua:: namespace,
                   added OO interface, optionalized the export of routines
                   into the caller's namespace, added named parameter
                   initialization, stemming exceptions, autoloaded
                   locale support and isolated case flattening to
                   localized stemmers prevent i18n problems later.

                   Input and output text are assumed to be in UTF8
                   encoding (no operational impact right now, but
                   will be important when extending the module to
                   non-English).

=cut

#######################################################################
# Initialization
#######################################################################

use strict;
use Exporter;
use Carp;
use Lingua::Stem::AutoLoader;
use vars qw (@ISA @EXPORT_OK %EXPORT_TAGS @EXPORT $VERSION);

BEGIN {
    $VERSION     = '0.80';
    @ISA         = qw (Exporter);
    @EXPORT      = ();
    @EXPORT_OK   = qw (stem clear_stem_cache stem_caching add_exceptions delete_exceptions get_exceptions set_locale get_locale);
    %EXPORT_TAGS = ( 'all' => [qw (stem stem_caching clear_stem_cache add_exceptions delete_exceptions get_exceptions set_locale get_locale)],
                    'stem' => [qw (stem)],
                 'caching' => [qw (stem_caching clear_stem_cache)],
                  'locale' => [qw (set_locale get_locale)],
              'exceptions' => [qw (add_exceptions delete_exceptions get_exceptions)],
                 );
}

my $defaults = {
            -locale => 'en',
           -stemmer => \&Lingua::Stem::En::stem,
      -stem_caching => \&Lingua::Stem::En::stem_caching,
  -clear_stem_cache => \&Lingua::Stem::En::clear_stem_cache,
        -exceptions => {},
      -known_locales => {
                          'da' => { -stemmer => \&Lingua::Stem::Da::stem,
                               -stem_caching => \&Lingua::Stem::Da::stem_caching,
                           -clear_stem_cache => \&Lingua::Stem::Da::clear_stem_cache,
                           },
                          'de' => { -stemmer => \&Lingua::Stem::De::stem,
                               -stem_caching => \&Lingua::Stem::De::stem_caching,
                           -clear_stem_cache => \&Lingua::Stem::De::clear_stem_cache,
                           },
                          'en' => { -stemmer => \&Lingua::Stem::En::stem,
                               -stem_caching => \&Lingua::Stem::En::stem_caching,
                           -clear_stem_cache => \&Lingua::Stem::En::clear_stem_cache,
                           },
                       'en_us' => { -stemmer => \&Lingua::Stem::En::stem,
                               -stem_caching => \&Lingua::Stem::En::stem_caching,
                           -clear_stem_cache => \&Lingua::Stem::En::clear_stem_cache,
                           },
                       'en-us' => { -stemmer => \&Lingua::Stem::En::stem,
                               -stem_caching => \&Lingua::Stem::En::stem_caching,
                           -clear_stem_cache => \&Lingua::Stem::En::clear_stem_cache,
                           },
                       'en_uk' => { -stemmer => \&Lingua::Stem::En::stem,
                               -stem_caching => \&Lingua::Stem::En::stem_caching,
                           -clear_stem_cache => \&Lingua::Stem::En::clear_stem_cache,
                           },
                       'en-uk' => { -stemmer => \&Lingua::Stem::En::stem,
                               -stem_caching => \&Lingua::Stem::En::stem_caching,
                           -clear_stem_cache => \&Lingua::Stem::En::clear_stem_cache,
                           },
                   'en-broken' => { -stemmer => \&Lingua::Stem::En_Broken::stem,
                               -stem_caching => \&Lingua::Stem::En_Broken::stem_caching,
                           -clear_stem_cache => \&Lingua::Stem::En_Broken::clear_stem_cache,
                           },
                          'fr' => { -stemmer => \&Lingua::Stem::Fr::stem,
                               -stem_caching => \&Lingua::Stem::Fr::stem_caching,
                           -clear_stem_cache => \&Lingua::Stem::Fr::clear_stem_cache,
                           },
                          'gl' => { -stemmer => \&Lingua::Stem::Gl::stem,
                               -stem_caching => \&Lingua::Stem::Gl::stem_caching,
                           -clear_stem_cache => \&Lingua::Stem::Gl::clear_stem_cache,
                           },
                          'it' => { -stemmer => \&Lingua::Stem::It::stem,
                               -stem_caching => \&Lingua::Stem::It::stem_caching,
                           -clear_stem_cache => \&Lingua::Stem::It::clear_stem_cache,
                           },
                          'no' => { -stemmer => \&Lingua::Stem::No::stem,
                               -stem_caching => \&Lingua::Stem::No::stem_caching,
                           -clear_stem_cache => \&Lingua::Stem::No::clear_stem_cache,
                           },
                          'pt' => { -stemmer => \&Lingua::Stem::Pt::stem,
                               -stem_caching => \&Lingua::Stem::Pt::stem_caching,
                           -clear_stem_cache => \&Lingua::Stem::Pt::clear_stem_cache,
                           },
                          'sv' => { -stemmer => \&Lingua::Stem::Sv::stem,
                               -stem_caching => \&Lingua::Stem::Sv::stem_caching,
                           -clear_stem_cache => \&Lingua::Stem::Sv::clear_stem_cache,
                           },
                          'ru' => { -stemmer => \&Lingua::Stem::Ru::stem,
                               -stem_caching => \&Lingua::Stem::Ru::stem_caching,
                           -clear_stem_cache => \&Lingua::Stem::Ru::clear_stem_cache,
                           },
                          'ru_ru' => {
                                    -stemmer => \&Lingua::Stem::Ru::stem,
                               -stem_caching => \&Lingua::Stem::Ru::stem_caching,
                           -clear_stem_cache => \&Lingua::Stem::Ru::clear_stem_cache,
                           },
                          'ru-ru' => {
                                    -stemmer => \&Lingua::Stem::Ru::stem,
                               -stem_caching => \&Lingua::Stem::Ru::stem_caching,
                           -clear_stem_cache => \&Lingua::Stem::Ru::clear_stem_cache,
                           },
                          'ru-ru.koi8-r' => {
                                    -stemmer => \&Lingua::Stem::Ru::stem,
                               -stem_caching => \&Lingua::Stem::Ru::stem_caching,
                           -clear_stem_cache => \&Lingua::Stem::Ru::clear_stem_cache,
                           },
                          'ru_ru.koi8-r' => {
                                    -stemmer => \&Lingua::Stem::Ru::stem,
                               -stem_caching => \&Lingua::Stem::Ru::stem_caching,
                           -clear_stem_cache => \&Lingua::Stem::Ru::clear_stem_cache,
                           },
                   },
    };

#######################################################################
# Methods
#######################################################################

=head1 METHODS

=cut

#######################################################################

=over 4

=item new(...);

Returns a new instance of a Lingua::Stem object and, optionally, selection
of the locale to be used for stemming.

Examples:

  # By default the locale is en
  $us_stemmer = Lingua::Stem->new;

  # Turn on the cache
  $us_stemmer->stem_caching({ -level => 2 });

  # Overriding the default for a specific instance
  $uk_stemmer = Lingua::Stem->new({ -locale => 'en-uk' });

  # Overriding the default for a specific instance and changing the default
  $uk_stemmer = Lingua::Stem->new({ -default_locale => 'en-uk' });

=back

=cut

sub new {
    my $proto = shift;
    my $class = ref ($proto) || $proto || __PACKAGE__;
    my $self = bless {},$class;

    # Set the defaults
    %{$self->{'Lingua::Stem'}->{-exceptions}}     = %{$defaults->{-exceptions}};
    $self->{'Lingua::Stem'}->{-locale}            = $defaults->{-locale};
    $self->{'Lingua::Stem'}->{-stemmer}           = $defaults->{-stemmer};
    $self->{'Lingua::Stem'}->{-stem_caching}      = $defaults->{-stem_caching};
    $self->{'Lingua::Stem'}->{-clear_stem_cache}  = $defaults->{-clear_stem_cache};

    # Handle any passed parms
    my @errors = ();
    if ($#_ > -1) {
        my $parm_ref = $_[0];
        if (not ref $parm_ref) {
            $parm_ref = {@_};
        }
        foreach my $key (keys %$parm_ref) {
            my $lc_key = lc ($key);
            if    ($lc_key eq '-locale')         { $self->set_locale($parm_ref->{$key});  }
            elsif ($lc_key eq '-default_locale') { set_locale($parm_ref->{$key});         }
            else { push (@errors," '$key' => '$parm_ref->{$key}'"); }
        }
    }
    if ($#errors > -1) {
        croak (__PACKAGE__ . "::new() - unrecognized parameters passed:" . join(', ',@errors));
    }

    $self;
}

#######################################################################

=over 4

=item set_locale($locale);

Sets the locale to one of the recognized locales.
locale identifiers are converted to lowercase.

Called as a class method, it changes the default locale for all
subseqently generated object instances.

Called as an instance method, it only changes the locale for
that particular instance.

'croaks' if passed an unknown locale.

Examples:

 # Change default locale
 Lingua::Stem::set_locale('en-uk'); # UK's spellings

 # Change instance locale
 $self->set_locale('en-us');  # US's spellings

=back

=cut

sub set_locale {
    my ($self)   = shift;

    my ($locale);
    if (ref $self) {
        ($locale) = @_;
        $locale   = lc $locale;
        if (not exists $defaults->{-known_locales}->{$locale}) {
            croak (__PACKAGE__ . "::set_locale() - Unknown locale '$locale'");
        }
        $self->{'Lingua::Stem'}->{-locale}           = $locale;
        $self->{'Lingua::Stem'}->{-stemmer}          = $defaults->{-known_locales}->{$locale}->{-stemmer};
        $self->{'Lingua::Stem'}->{-stem_caching}     = $defaults->{-known_locales}->{$locale}->{-stem_caching};
        $self->{'Lingua::Stem'}->{-clear_stem_cache} = $defaults->{-known_locales}->{$locale}->{-clear_stem_cache};
    } else {
        $locale = lc $self;
        if (not exists $defaults->{-known_locales}->{$locale}) {
            croak (__PACKAGE__ . "::set_locale() - Unknown locale '$locale'");
        }
        $defaults->{-locale}           = $locale;
        $defaults->{-stemmer}          = $defaults->{-known_locales}->{$locale}->{-stemmer};
        $defaults->{-stem_caching}     = $defaults->{-known_locales}->{$locale}->{-stem_caching};
        $defaults->{-clear_stem_cache} = $defaults->{-known_locales}->{$locale}->{-clear_stem_cache};
    }
}

#######################################################################

=over 4

=item get_locale;

Called as a class method, returns the current default locale.

Example:

 $default_locale = Lingua::Stem::get_locale;

Called as an instance method, returns the locale for the instance

 $instance_locale = $stemmer->get_locale;

=back

=cut

sub get_locale {
    my ($self) = shift;

    if (ref $self) {
        return $self->{'Lingua::Stem'}->{-locale};
    } else {
        return $defaults->{-locale};
    }
}

#######################################################################

=over 4

=item add_exceptions($exceptions_hash_ref);

Exceptions allow overriding the stemming algorithm on a case by case
basis. It is done on an exact match and substitution basis: If a passed
word is identical to the exception it will be replaced by the specified
value. No case adjustments are performed.

Called as a class method, adds exceptions to the default exceptions list
used for subsequently instantations of Lingua::Stem objects.

Example:

 # adding default exceptions
 Lingua::Stem::add_exceptions({ 'emily' => 'emily',
                                'driven' => 'driven',
                            });

Called as an instance method, adds exceptions only to the specific
instance.

 # adding instance exceptions
 $stemmer->add_exceptions({ 'steely' => 'steely' });

The exceptions shortcut the normal stemming - if an exception matches
no further stemming is performed after the substitution.

Adding an exception with the same key value as an already defined
exception replaces the pre-existing exception with the new value.

=back

=cut

sub add_exceptions {
    my ($self);

    my ($exceptions,$exception_list);
    my $reference =ref $_[0];
    if ($reference eq 'HASH') {
        ($exceptions) =  @_;
        $exception_list = $defaults->{-exceptions};
    } elsif (not $reference) {
        $exceptions = { @_ };
        $exception_list = $defaults->{-exceptions};
    } else {
        $self = shift;
        ($exceptions) = @_;
        $exception_list = $self->{'Lingua::Stem'}->{-exceptions};
    }
    while (my ($exception,$replace_with) = each %$exceptions) {
            $exception_list->{$exception} = $replace_with;
    }
}

#######################################################################

=over 4

=item delete_exceptions(@exceptions_list);

The mirror of add_exceptions, this allows the _removal_ of exceptions
from either the defaults for the class or from the instance.

 # Deletion of exceptions from class default exceptions
 Lingua::Stem::delete_exceptions('aragorn','frodo','samwise');

 # Deletion of exceptions from instance
 $stemmer->delete_exceptions('smaug','sauron','gollum');

 # Deletion of all class default exceptions
 delete_exceptions;

 # Deletion of all exceptions from instance
 $stemmer->delete_exceptions;

=back

=cut

sub delete_exceptions {
    my $self;

    my ($exception_list,$exceptions);
    if ($#_ == -1) {
        $defaults->{-exceptions} = {};
        return;
    }
    my $reference =ref $_[0];
    if ($reference eq 'ARRAY') {
        ($exceptions) =  @_;
        $exception_list = $defaults->{-exceptions};
    } elsif (not $reference) {
        $exceptions = [@_];
        $exception_list = $defaults->{-exceptions};
    } else {
        $self = shift;
        if ($#_ == -1) {
            $self->{'Lingua::Stem'}->{-exceptions} = {};
        } else {
            $reference = ref $_[0];
            if ($reference eq 'ARRAY') {
                ($exceptions) =  @_;
                $exception_list = $self->{'Lingua::Stem'}->{-exceptions};
            } else {
                ($exceptions) = [@_];
                $exception_list = $self->{'Lingua::Stem'}->{-exceptions};
            }
        }
    }

    foreach (@$exceptions) { delete $exception_list->{$_}; }
}

#######################################################################

=over 4

=item get_exceptions;

As a class method with no parameters it returns all the default exceptions
as an anonymous hash of 'exception' => 'replace with' pairs.

Example:

 # Returns all class default exceptions
 $exceptions = Lingua::Stem::get_exceptions;

As a class method with parameters, it returns the default exceptions listed
in the parameters as an anonymous hash of 'exception' => 'replace with' pairs.
If a parameter specifies an undefined 'exception', the value is set to undef.

 # Returns class default exceptions for 'emily' and 'george'
 $exceptions = Lingua::Stem::get_exceptions('emily','george');

As an instance method, with no parameters it returns the currently active
exceptions for the instance.

 # Returns all instance exceptions
 $exceptions = $stemmer->get_exceptions;

As an instance method with parameters, it returns the instance exceptions listed
in the parameters as an anonymous hash of 'exception' => 'replace with' pairs.
If a parameter specifies an undefined 'exception', the value is set to undef.

 # Returns instance exceptions for 'lisa' and 'bart'
 $exceptions = $stemmer->get_exceptions('lisa','bart');

=back

=cut

sub get_exceptions {

    my $exception_list = {};
    if ($#_ == -1) {
        %$exception_list = %{$defaults->{-exceptions}};
        return $exception_list;
    }
    my $reference = ref $_[0];
    if ($reference eq 'ARRAY') {
        %$exception_list = %{$defaults->{-exceptions}};
    } elsif ($reference) {
        my $self = shift;
        if ($#_ > -1) {
            foreach (@_) {
                $exception_list->{$_} = $self->{'Lingua::Stem'}->{-exceptions}->{$_};
            }
        } else {
            %$exception_list = %{$self->{'Lingua::Stem'}->{-exceptions}};
        }
    } else {
        foreach (@_) {
            $exception_list->{$_} = $_;
        }
    }
    $exception_list;
}

#######################################################################

=over 4

=item stem(@list);

Called as a class method, it applies the default settings
and stems the list of passed words, returning an anonymous
array with the stemmed words in the same order as the passed
list of words.

Example:

    # Default settings applied
    my $anon_array_of_stemmed_words = Lingua::Stem::stem(@words);

Called as an instance method, it applies the instance's settings
and stems the list of passed words, returning an anonymous
array with the stemmed words in the same order as the passed
list of words.

   # Instance's settings applied
   my $stemmed_words = $stemmer->stem(@words);

The stemmer performs best when handed long lists of words
rather than one word at a time. The cache also provides
a huge speed up if you are processing lots of text.

=back

=cut

sub stem {
    my $self;
    return [] if ($#_ == -1);
    my ($exceptions,$locale,$stemmer);
    if (ref $_[0]) {
        my $self = shift;
        $exceptions = $self->{'Lingua::Stem'}->{-exceptions};
        $stemmer    = $self->{'Lingua::Stem'}->{-stemmer};
        $locale     = $self->{'Lingua::Stem'}->{-locale};
    } else {
        $exceptions = $defaults->{-exceptions};
        $stemmer    = $defaults->{-stemmer};
        $locale     = $defaults->{-locale};
    }
    &$stemmer({ -words => \@_,
               -locale => $locale,
           -exceptions => $exceptions });
}

#######################################################################

=over 4

=item clear_stem_cache;

Clears the stemming cache for the current locale. Can be called as either
a class method or an instance method.

    $stemmer->clear_stem_cache;

    clear_stem_cache;

=back

=cut

sub clear_stem_cache {
    my $clear_stem_cache_sub;
    if (ref $_[0]) {
        my $self = shift;
        $clear_stem_cache_sub = $self->{'Lingua::Stem'}->{-clear_stem_cache};
    } else {
        $clear_stem_cache_sub = $defaults->{-clear_stem_cache};
    }
    &$clear_stem_cache_sub;
}

#######################################################################

=over 4

=item stem_caching ({ -level => 0|1|2 });

Sets stemming cache level for the current locale. Can be called as either
a class method or an instance method.

    $stemmer->stem_caching({ -level => 1 });

    stem_caching({ -level => 1 });

For the sake of maximum compatibility with previous versions,
stem caching is set to '-level => 0' by default.

'-level' definitions

 '0' means 'no caching'. This is the default level.

 '1' means 'cache per run'. This caches stemming results during each
    call to 'stem'.

 '2' means 'cache indefinitely'. This caches stemming results until
    either the process exits or the 'clear_stem_cache' method is called.

stem caching is global to the locale. If you turn on stem caching for one
instance of a locale stemmer, all instances using the same locale will have it
turned on as well.

I B<STRONGLY> suggest turning caching on if you have enough memory and
are processing a lot of data.

=back

=cut

sub stem_caching {
    my $stem_caching_sub;
    my $first_parm_ref = ref $_[0];
    if ($first_parm_ref && ($first_parm_ref ne 'HASH')) {
        my $self = shift;
        $stem_caching_sub = $self->{'Lingua::Stem'}->{-stem_caching};
    } else {
        $stem_caching_sub = $defaults->{-stem_caching};
    }
    &$stem_caching_sub(@_);
}

#######################################################################
# Terminal POD Documentation
#######################################################################

=head1 VERSION

 0.80 2004.07.25

=head1 NOTES

It started with the 'Text::Stem' module which has been adapted into
a more general framework and moved into the more
language oriented 'Lingua' namespace and re-organized to support a OOP
interface as well as switch core 'En' locale stemmers.

Version 0.40 added a cache for stemmed words. This can provide up
to a several fold performance improvement.

Organization is such that extending this module to any number
of languages should be direct and simple.

Case flattening is a function of the language, so the 'exceptions'
methods have to be used appropriately to the language. For 'En'
family stemming, use lower case words, only, for exceptions.

=head1 AUTHORS

 Benjamin Franz <snowhare@nihongo.org>
 Jim Richardson  <imr@maths.usyd.edu.au>

=head1 CREDITS

 Jim Richardson             <imr@maths.usyd.edu.au>
 Ulrich Pfeifer             <pfeifer@ls6.informatik.uni-dortmund.de>
 Aldo Calpini               <dada@perl.it>
 xern                       <xern@cpan.org>
 Ask Solem Hoel             <ask@unixmonks.net>
 Dennis Haney               <davh@davh.dk>
 Sébastien Darribere-Pleyt  <sebastien.darribere@lefute.com>
 Aleksandr Guidrevitch      <pillgrim@mail.ru>

=head1 SEE ALSO

 Lingua::Stem::En            Lingua::Stem::En            Lingua::Stem::Da
 Lingua::Stem::De            Lingua::Stem::Gl            Lingua::Stem::No
 Lingua::Stem::Pt            Lingua::Stem::Sv            Lingua::Stem::It
 Lingua::Stem::Fr            Lingua::Stem::Ru            Text::German
 Lingua::PT::Stemmer         Lingua::GL::Stemmer         Lingua::Stem::Snowball::No
 Lingua::Stem::Snowball::Se  Lingua::Stem::Snowball::Da  Lingua::Stem::Snowball::Sv
 Lingua::Stemmer::GL         Lingua::Stem::Snowball

 http://snowball.tartarus.org

=head1 COPYRIGHT

Copyright 1999-2004

Freerun Technologies, Inc (Freerun),
Jim Richardson, University of Sydney <imr@maths.usyd.edu.au>
and Benjamin Franz <snowhare@nihongo.org>. All rights reserved.

Text::German was written and is copyrighted by Ulrich Pfeifer.

Lingua::Stem::Snowball::Da was written and is copyrighted by
Dennis Haney and Ask Solem Hoel.

Lingua::Stem::It was written and is copyrighted by Aldo Calpini.

Lingua::Stem::Snowball::No, Lingua::Stem::Snowball::Se, Lingua::Stem::Snowball::Sv were
written and are copyrighted by Ask Solem Hoel.

Lingua::Stemmer::GL and Lingua::PT::Stemmer were written and are copyrighted by Xern.

Lingua::Stem::Fr was written and is copyrighted by  Aldo Calpini and SĂ©bastien Darribere-Pley.

Lingua::Stem::Ru was written and is copyrighted by Aleksandr Guidrevitch.

This software may be freely copied and distributed under the same
terms and conditions as Perl.

=head1 BUGS

None known.

=head1 TODO

Add more languages. Extend regression tests. Add support for the
Lingua::Stem::Snowball family of stemmers as an alternative core stemming
engine.

=cut

1;
