Lingua::Stem::En(3pm)					User Contributed Perl Documentation				     Lingua::Stem::En(3pm)

NAME

       Lingua::Stem::En - Porter's stemming algorithm for 'generic' English

SYNOPSIS

	   use Lingua::Stem::En;
	   my $stems   = Lingua::Stem::En::stem({ -words => $word_list_reference,
					       -locale => 'en',
					   -exceptions => $exceptions_hash,
					    });

DESCRIPTION

       This routine applies the Porter Stemming Algorithm to its parameters, returning the stemmed words.

       It is derived from the C program "stemmer.c" as found in freewais and elsewhere, which contains these notes:

	  Purpose:    Implementation of the Porter stemming algorithm documented
		      in: Porter, M.F., "An Algorithm For Suffix Stripping,"
		      Program 14(3), July 1980, pp. 130-137.
	  Provenance: Written by B. Frakes and C. Cox, 1986.

       I have re-interpreted areas that use Frakes and Cox's "WordSize" function. My version may misbehave on short words starting with "y", but I
       can't think of any examples.

       The step numbers correspond to Frakes and Cox, and are probably in Porter's article (which I've not seen).  Porter's algorithm still has
       rough spots (e.g current/currency, -ings words), which I've not attempted to cure, although I have added support for the British -ise
       suffix.

CHANGES

	1999.06.15 - Changed to '.pm' module, moved into Lingua::Stem namespace,
		     optionalized the export of the 'stem' routine
		     into the caller's namespace, added named parameters

	1999.06.24 - Switch core implementation of the Porter stemmer to
		     the one written by Jim Richardson <jimr@maths.usyd.edu.au>

	2000.08.25 - 2.11 Added stemming cache

	2000.09.14 - 2.12 Fixed *major* :( implementation error of Porter's algorithm
		     Error was entirely my fault - I completely forgot to include
		     rule sets 2,3, and 4 starting with Lingua::Stem 0.30.
		     -- Benjamin Franz

	2003.09.28 - 2.13 Corrected documentation error pointed out by Simon Cozens.

	2005.11.20 - 2.14 Changed rule declarations to conform to Perl style convention
		     for 'private' subroutines. Changed Exporter invokation to more
		     portable 'require' vice 'use'.

	2006.02.14 - 2.15 Added ability to pass word list by 'handle' for in-place stemming.

	2009.07.27   2.16 Documentation Fix

METHODS

       stem({ -words => @words, -locale => 'en', -exceptions => \%exceptions });
	   Stems a list of passed words using the rules of US English. Returns an anonymous array reference to the stemmed words.

	   Example:

	     my @words	       = ( 'wordy', 'another' );
	     my $stemmed_words = Lingua::Stem::En::stem({ -words => @words,
							 -locale => 'en',
						     -exceptions => \%exceptions,
				     });

	   If the first element of @words is a list reference, then the stemming is performed 'in place' on that list (modifying the passed list
	   directly instead of copying it to a new array).

	   This is only useful if you do not need to keep the original list. If you do need to keep the original list, use the normal semantic of
	   having 'stem' return a new list instead - that is faster than making your own copy and using the 'in place' semantics since the primary
	   difference between 'in place' and 'by value' stemming is the creation of a copy of the original list.  If you don't need the original
	   list, then the 'in place' stemming is about 60% faster.

	   Example of 'in place' stemming:

	     my $words	       = [ 'wordy', 'another' ];
	     my $stemmed_words = Lingua::Stem::En::stem({ -words => [$words],
				     -locale => 'en',
				 -exceptions => \%exceptions,
				 });

	   The 'in place' mode returns a reference to the original list with the words stemmed.

       stem_caching({ -level => 0|1|2 });
	   Sets the level of stem caching.

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

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

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

       clear_stem_cache;
	   Clears the cache of stemmed words

NOTES

       This code is almost entirely derived from the Porter 2.1 module written by Jim Richardson.

SEE ALSO

	Lingua::Stem

AUTHOR

	 Jim Richardson, University of Sydney
	 jimr@maths.usyd.edu.au or http://www.maths.usyd.edu.au:8000/jimr.html

	 Integration in Lingua::Stem by
	 Benjamin Franz, FreeRun Technologies,
	 snowhare@nihongo.org or http://www.nihongo.org/snowhare/

COPYRIGHT

       Jim Richardson, University of Sydney Benjamin Franz, FreeRun Technologies

       This code is freely available under the same terms as Perl.

BUGS

TODO

perl v5.10.1							    2010-06-13						     Lingua::Stem::En(3pm)