Text::Soundex(3) Perl Programmers Reference GuideText::Soundex(3)NAMEText::Soundex - Implementation of the Soundex Algorithm as
Described by Knuth
SYNOPSIS
use Text::Soundex;
$code = soundex $string; # get soundex code for a string
@codes = soundex @list; # get list of codes for list of strings
# set value to be returned for strings without soundex code
$soundex_nocode = 'Z000';
DESCRIPTION
This module implements the soundex algorithm as described
by Donald Knuth in Volume 3 of The Art of Computer
Programming. The algorithm is intended to hash words (in
particular surnames) into a small space using a simple
model which approximates the sound of the word when spoken
by an English speaker. Each word is reduced to a four
character string, the first character being an upper case
letter and the remaining three being digits.
If there is no soundex code representation for a string
then the value of $soundex_nocode is returned. This is
initially set to undef, but many people seem to prefer an
unlikely value like Z000 (how unlikely this is depends on
the data set being dealt with.) Any value can be assigned
to $soundex_nocode.
In scalar context soundex returns the soundex code of its
first argument, and in array context a list is returned in
which each element is the soundex code for the
corresponding argument passed to soundex e.g.
@codes = soundex qw(Mike Stok);
leaves @codes containing ('M200', 'S320').
EXAMPLES
Knuth's examples of various 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:
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Text::Soundex(3) Perl Programmers Reference GuideText::Soundex(3)
$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.
As it is mapping a large space (arbitrary length strings)
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.
AUTHOR
This code was implemented by Mike Stok (stok@cybercom.net)
from the description given by Knuth. Ian Phillips
(ian@pipex.net) and Rich Pinder (rpinder@hsc.usc.edu)
supplied ideas and spotted mistakes.
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