Text::Soundex(3p)Perl Programmers Reference GuidText::Soundex(3p)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 sur-
names) into a small space using a simple model which approx-
imates 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 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
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Text::Soundex(3p)Perl Programmers Reference GuidText::Soundex(3p)
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 pronun-
ciation.
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 "Hil-
bert" 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 Phillipps
("ian@pipex.net") and Rich Pinder ("rpinder@hsc.usc.edu")
supplied ideas and spotted mistakes.
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