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151 lines
4.2 KiB
Perl
151 lines
4.2 KiB
Perl
package Text::Soundex;
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require 5.000;
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require Exporter;
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@ISA = qw(Exporter);
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@EXPORT = qw(&soundex $soundex_nocode);
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$VERSION = '1.01';
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# $Id: soundex.pl,v 1.2 1994/03/24 00:30:27 mike Exp $
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#
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# Implementation of soundex algorithm as described by Knuth in volume
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# 3 of The Art of Computer Programming, with ideas stolen from Ian
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# Phillipps <ian@pipex.net>.
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#
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# Mike Stok <Mike.Stok@meiko.concord.ma.us>, 2 March 1994.
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#
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# Knuth's test cases are:
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#
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# Euler, Ellery -> E460
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# Gauss, Ghosh -> G200
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# Hilbert, Heilbronn -> H416
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# Knuth, Kant -> K530
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# Lloyd, Ladd -> L300
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# Lukasiewicz, Lissajous -> L222
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#
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# $Log: soundex.pl,v $
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# Revision 1.2 1994/03/24 00:30:27 mike
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# Subtle bug (any excuse :-) spotted by Rich Pinder <rpinder@hsc.usc.edu>
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# in the way I handles leasing characters which were different but had
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# the same soundex code. This showed up comparing it with Oracle's
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# soundex output.
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#
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# Revision 1.1 1994/03/02 13:01:30 mike
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# Initial revision
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#
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#
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##############################################################################
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# $soundex_nocode is used to indicate a string doesn't have a soundex
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# code, I like undef other people may want to set it to 'Z000'.
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$soundex_nocode = undef;
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sub soundex
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{
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local (@s, $f, $fc, $_) = @_;
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push @s, '' unless @s; # handle no args as a single empty string
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foreach (@s)
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{
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$_ = uc $_;
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tr/A-Z//cd;
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if ($_ eq '')
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{
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$_ = $soundex_nocode;
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}
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else
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{
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($f) = /^(.)/;
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tr/AEHIOUWYBFPVCGJKQSXZDTLMNR/00000000111122222222334556/;
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($fc) = /^(.)/;
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s/^$fc+//;
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tr///cs;
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tr/0//d;
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$_ = $f . $_ . '000';
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s/^(.{4}).*/$1/;
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}
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}
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wantarray ? @s : shift @s;
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}
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1;
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__END__
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=head1 NAME
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Text::Soundex - Implementation of the Soundex Algorithm as Described by Knuth
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=head1 SYNOPSIS
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use Text::Soundex;
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$code = soundex $string; # get soundex code for a string
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@codes = soundex @list; # get list of codes for list of strings
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# set value to be returned for strings without soundex code
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$soundex_nocode = 'Z000';
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=head1 DESCRIPTION
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This module implements the soundex algorithm as described by Donald Knuth
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in Volume 3 of B<The Art of Computer Programming>. The algorithm is
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intended to hash words (in particular surnames) into a small space using a
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simple model which approximates the sound of the word when spoken by an English
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speaker. Each word is reduced to a four character string, the first
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character being an upper case letter and the remaining three being digits.
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If there is no soundex code representation for a string then the value of
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C<$soundex_nocode> is returned. This is initially set to C<undef>, but
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many people seem to prefer an I<unlikely> value like C<Z000>
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(how unlikely this is depends on the data set being dealt with.) Any value
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can be assigned to C<$soundex_nocode>.
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In scalar context C<soundex> returns the soundex code of its first
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argument, and in list context a list is returned in which each element is the
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soundex code for the corresponding argument passed to C<soundex> e.g.
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@codes = soundex qw(Mike Stok);
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leaves C<@codes> containing C<('M200', 'S320')>.
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=head1 EXAMPLES
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Knuth's examples of various names and the soundex codes they map to
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are listed below:
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Euler, Ellery -> E460
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Gauss, Ghosh -> G200
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Hilbert, Heilbronn -> H416
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Knuth, Kant -> K530
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Lloyd, Ladd -> L300
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Lukasiewicz, Lissajous -> L222
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so:
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$code = soundex 'Knuth'; # $code contains 'K530'
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@list = soundex qw(Lloyd Gauss); # @list contains 'L300', 'G200'
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=head1 LIMITATIONS
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As the soundex algorithm was originally used a B<long> time ago in the US
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it considers only the English alphabet and pronunciation.
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As it is mapping a large space (arbitrary length strings) onto a small
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space (single letter plus 3 digits) no inference can be made about the
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similarity of two strings which end up with the same soundex code. For
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example, both C<Hilbert> and C<Heilbronn> end up with a soundex code
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of C<H416>.
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=head1 AUTHOR
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This code was implemented by Mike Stok (C<stok@cybercom.net>) from the
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description given by Knuth. Ian Phillipps (C<ian@pipex.net>) and Rich Pinder
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(C<rpinder@hsc.usc.edu>) supplied ideas and spotted mistakes.
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