Text::Soundex(3pm)                              Perl Programmers Reference Guide                              Text::Soundex(3pm)



NAME
       Text::Soundex - Implementation of the soundex algorithm.

SYNOPSIS
         use Text::Soundex;

         # Original algorithm.
         $code = soundex($name);    # Get the soundex code for a name.
         @codes = soundex(@names);  # Get the list of codes for a list of names.

         # American Soundex variant (NARA) - Used for US census data.
         $code = soundex_nara($name);    # Get the soundex code for a name.
         @codes = soundex_nara(@names);  # Get the list of codes for a list of names.

         # Redefine the value that soundex() will return if the input string
         # contains no identifiable sounds within it.
         $Text::Soundex::nocode = 'Z000';

DESCRIPTION
       Soundex is a phonetic algorithm for indexing names by sound, as pronounced in English. The goal is for names with the
       same pronunciation to be encoded to the same representation so that they can be matched despite minor differences in
       spelling. Soundex is the most widely known of all phonetic algorithms and is often used (incorrectly) as a synonym for
       "phonetic algorithm". Improvements to Soundex are the basis for many modern phonetic algorithms. (Wikipedia, 2007)

       This module implements the original soundex algorithm developed by Robert Russell and Margaret Odell, patented in 1918
       and 1922, as well as a variation called "American Soundex" used for US census data, and current maintained by the
       National Archives and Records Administration (NARA).

       The soundex algorithm may be recognized from Donald Knuth's The Art of Computer Programming. The algorithm described by
       Knuth is the NARA algorithm.

       The value returned for strings which have no soundex encoding is defined using $Text::Soundex::nocode. The default value
       is "undef", however values such as 'Z000' are commonly used alternatives.

       For backward compatibility with older versions of this module the $Text::Soundex::nocode is exported into the caller's
       namespace as $soundex_nocode.

       In scalar context, "soundex()" returns the soundex code of its first argument. In list context, a list is returned in
       which each element is the soundex code for the corresponding argument passed to "soundex()". For example, the following
       code assigns @codes the value "('M200', 'S320')":

          @codes = soundex qw(Mike Stok);

       To use "Text::Soundex" to generate codes that can be used to search one of the publically available US Censuses, a
       variant of the soundex algorithm must be used:

           use Text::Soundex;
           $code = soundex_nara($name);

       An example of where these algorithm differ follows:

           use Text::Soundex;
           print soundex("Ashcraft"), "\n";       # prints: A226
           print soundex_nara("Ashcraft"), "\n";  # prints: A261

EXAMPLES
       Donald Knuth's examples of names and the soundex codes they map to are listed below:

         Euler, Ellery -> E460
         Gauss, Ghosh -> G200
         Hilbert, Heilbronn -> H416
         Knuth, Kant -> K530
         Lloyd, Ladd -> L300
         Lukasiewicz, Lissajous -> L222

       so:

         $code = soundex 'Knuth';         # $code contains 'K530'
         @list = soundex qw(Lloyd Gauss); # @list contains 'L300', 'G200'

LIMITATIONS
       As the soundex algorithm was originally used a long time ago in the US it considers only the English alphabet and
       pronunciation. In particular, non-ASCII characters will be ignored. The recommended method of dealing with characters
       that have accents, or other unicode characters, is to use the Text::Unidecode module available from CPAN. Either use the
       module explicitly:

           use Text::Soundex;
           use Text::Unidecode;

           print soundex(unidecode("Fran\xE7ais")), "\n"; # Prints "F652\n"

       Or use the convenient wrapper routine:

           use Text::Soundex 'soundex_unicode';

           print soundex_unicode("Fran\xE7ais"), "\n";    # Prints "F652\n"

       Since the soundex algorithm maps a large space (strings of arbitrary length) onto a small space (single letter plus 3
       digits) no inference can be made about the similarity of two strings which end up with the same soundex code.  For
       example, both "Hilbert" and "Heilbronn" end up with a soundex code of "H416".

MAINTAINER
       This module is currently maintain by Mark Mielke ("markATmielke.cc").

HISTORY
       Version 3 is a significant update to provide support for versions of Perl later than Perl 5.004. Specifically, the XS
       version of the soundex() subroutine understands strings that are encoded using UTF-8 (unicode strings).

       Version 2 of this module was a re-write by Mark Mielke ("markATmielke.cc") to improve the speed of the subroutines. The XS
       version of the soundex() subroutine was introduced in 2.00.

       Version 1 of this module was written by Mike Stok ("mikeATstok.uk") and was included into the Perl core library set.

       Dave Carlsen ("dcarlsenATcsranet.com") made the request for the NARA algorithm to be included. The NARA soundex page can
       be viewed at: "http://www.nara.gov/genealogy/soundex/soundex.html"

       Ian Phillips ("ianATpipex.net") and Rich Pinder ("rpinderAThsc.edu") supplied ideas and spotted mistakes for v1.x.



perl v5.12.4                                               2011-06-01                                         Text::Soundex(3pm)