Manual Reference Pages - TEXT::SOUNDEX (3)
Text::Soundex - Implementation of the soundex algorithm.
# 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;
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,
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
The soundex algorithm may be recognized from Donald Knuths
<B>The Art of Computer ProgrammingB>. 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 callers namespace as
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:
$code = soundex_nara($name);
An example of where these algorithm differ follows:
print soundex("Ashcraft"), "\n"; # prints: A226
print soundex_nara("Ashcraft"), "\n"; # prints: A261
Donald Knuths 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
$code = soundex Knuth; # $code contains K530
@list = soundex qw(Lloyd Gauss); # @list contains L300, G200
As the soundex algorithm was originally used a <B>longB> 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
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.
COPYRIGHT AND LICENSE
This software is copyright (c) 1998-2003 by Mark Mielke.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
This module is currently maintain by Mark Mielke (firstname.lastname@example.org).
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
Version 2 of this module was a re-write by Mark Mielke (email@example.com)
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 (firstname.lastname@example.org)
and was included into the Perl core library set.
Dave Carlsen (email@example.com) made the request for the NARA
algorithm to be included. The NARA soundex page can be viewed at:
Ian Phillips (firstname.lastname@example.org) and Rich Pinder (email@example.com)
supplied ideas and spotted mistakes for v1.x.
|perl v5.20.3 ||SOUNDEX (3) ||2015-11-10 |
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