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
$soundex_nocode = 'Z000';
DESCRIPTION
This module implements the soundex algorithm as described
by Donald Knuth in Volume 3 of The Art of Computer Pro
gramming. The algorithm is intended to hash words (in
particular surnames) into a small space using a simple
model which approximates the sound of the word when spoken
by an English speaker. Each word is reduced to a four
character string, the first character being an upper case
letter and the remaining three being digits.
If there is no soundex code representation for a string
then the value of "$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 list context a list is returned
in which each element is the soundex code for the corre
sponding 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:
$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 infer
ence 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@cyber
com.net") from the description given by Knuth. Ian
Phillips ("ian@pipex.net") and Rich Pinder ("rpin
der@hsc.usc.edu") supplied ideas and spotted mistakes.
2001-02-22 perl v5.6.1 Text::Soundex(3)
