text::soundex(3pm)
NAME
Text::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 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 - 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 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 Phillipps ("ian@pipex.net") and Rich
Pinder ("rpinder@hsc.usc.edu") supplied ideas and spotted mistakes.