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Soundex(3) User Contributed Perl Documentation Soundex(3)
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 ("mark AT mielke.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 ("mark AT mielke.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 ("mike AT stok.uk") and was included
into the Perl core library set.
Dave Carlsen ("dcarlsen AT csranet.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 ("ian AT pipex.net") and Rich Pinder ("rpinder AT hsc.edu") supplied ideas and
spotted mistakes for v1.x.
perl v5.16.3 2013-01-18 Soundex(3)
Generated by $Id: phpMan.php,v 4.55 2007/09/05 04:42:51 chedong Exp $ Author: Che Dong
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