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Text::Soundex

Section: Perl Programmers Reference Guide (3)
Updated: perl 5.004, patch 04
Index

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 Knuthin Volume 3 of The Art of Computer Programming. The algorithm isintended to hash words (in particular surnames) into a small space using asimple model which approximates the sound of the word when spoken by an Englishspeaker. Each word is reduced to a four character string, the firstcharacter 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, butmany people seem to prefer an unlikely value like Z000(how unlikely this is depends on the data set being dealt with.) Any valuecan be assigned to $soundex_nocode.

In scalar context soundex returns the soundex code of its firstargument, 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 toare 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 USit considers only the English alphabet and pronunciation.

As it is mapping a large space (arbitrary length strings) onto a smallspace (single letter plus 3 digits) no inference can be made about thesimilarity of two strings which end up with the same soundex code. For example, both Hilbert and Heilbronn end up with a soundex codeof H416.

AUTHOR

This code was implemented by Mike Stok (stokAATTcybercom.net) from the description given by Knuth. Ian Phillips (ianAATTpipex.net) and Rich Pinder (rpinderAATThsc.usc.edu) supplied ideas and spotted mistakes.

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