mingw/html/lib/Text/Soundex.html

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   5 <title>Text::Soundex - Implementation of the Soundex Algorithm as Described by Knuth</title>
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  13 <big><strong><span class="block">&nbsp;Text::Soundex - Implementation of the Soundex Algorithm as Described by Knuth</span></strong></big>
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  20 <ul>
  21
  22         <li><a href="#name">NAME</a></li>
  23         <li><a href="#synopsis">SYNOPSIS</a></li>
  24         <li><a href="#description">DESCRIPTION</a></li>
  25         <li><a href="#examples">EXAMPLES</a></li>
  26         <li><a href="#limitations">LIMITATIONS</a></li>
  27         <li><a href="#author">AUTHOR</a></li>
  28 </ul>
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  32 <p>
  33 </p>
  34 <h1><a name="name">NAME</a></h1>
  35 <p>Text::Soundex - Implementation of the Soundex Algorithm as Described by Knuth</p>
  36 <p>
  37 </p>
  38 <hr />
  39 <h1><a name="synopsis">SYNOPSIS</a></h1>
  40 <pre>
  41   use Text::Soundex;</pre>
  42 <pre>
  43   $code = soundex $string;            # get soundex code for a string
  44   @codes = soundex @list;             # get list of codes for list of strings</pre>
  45 <pre>
  46   # set value to be returned for strings without soundex code</pre>
  47 <pre>
  48   $soundex_nocode = 'Z000';</pre>
  49 <p>
  50 </p>
  51 <hr />
  52 <h1><a name="description">DESCRIPTION</a></h1>
  53 <p>This module implements the soundex algorithm as described by Donald Knuth
  54 in Volume 3 of <strong>The Art of Computer Programming</strong>.  The algorithm is
  55 intended to hash words (in particular surnames) into a small space using a
  56 simple model which approximates the sound of the word when spoken by an English
  57 speaker.  Each word is reduced to a four character string, the first
  58 character being an upper case letter and the remaining three being digits.</p>
  59 <p>If there is no soundex code representation for a string then the value of
  60 <code>$soundex_nocode</code> is returned.  This is initially set to <a href="file://C|\msysgit\mingw\html/pod/perlfunc.html#item_undef"><code>undef</code></a>, but
  61 many people seem to prefer an <em>unlikely</em> value like <code>Z000</code>
  62 (how unlikely this is depends on the data set being dealt with.)  Any value
  63 can be assigned to <code>$soundex_nocode</code>.</p>
  64 <p>In scalar context <code>soundex</code> returns the soundex code of its first
  65 argument, and in list context a list is returned in which each element is the
  66 soundex code for the corresponding argument passed to <code>soundex</code> e.g.</p>
  67 <pre>
  68   @codes = soundex qw(Mike Stok);</pre>
  69 <p>leaves <code>@codes</code> containing <code>('M200', 'S320')</code>.</p>
  70 <p>
  71 </p>
  72 <hr />
  73 <h1><a name="examples">EXAMPLES</a></h1>
  74 <p>Knuth's examples of various names and the soundex codes they map to
  75 are listed below:</p>
  76 <pre>
  77   Euler, Ellery -&gt; E460
  78   Gauss, Ghosh -&gt; G200
  79   Hilbert, Heilbronn -&gt; H416
  80   Knuth, Kant -&gt; K530
  81   Lloyd, Ladd -&gt; L300
  82   Lukasiewicz, Lissajous -&gt; L222</pre>
  83 <p>so:</p>
  84 <pre>
  85   $code = soundex 'Knuth';              # $code contains 'K530'
  86   @list = soundex qw(Lloyd Gauss);      # @list contains 'L300', 'G200'</pre>
  87 <p>
  88 </p>
  89 <hr />
  90 <h1><a name="limitations">LIMITATIONS</a></h1>
  91 <p>As the soundex algorithm was originally used a <strong>long</strong> time ago in the US
  92 it considers only the English alphabet and pronunciation.</p>
  93 <p>As it is mapping a large space (arbitrary length strings) onto a small
  94 space (single letter plus 3 digits) no inference can be made about the
  95 similarity of two strings which end up with the same soundex code.  For
  96 example, both <code>Hilbert</code> and <code>Heilbronn</code> end up with a soundex code
  97 of <code>H416</code>.</p>
  98 <p>
  99 </p>
 100 <hr />
 101 <h1><a name="author">AUTHOR</a></h1>
 102 <p>This code was implemented by Mike Stok (<code>stok@cybercom.net</code>) from the
 103 description given by Knuth.  Ian Phillipps (<code>ian@pipex.net</code>) and Rich Pinder
 104 (<code>rpinder@hsc.usc.edu</code>) supplied ideas and spotted mistakes.</p>
 105 <table border="0" width="100%" cellspacing="0" cellpadding="3">
 106 <tr><td class="block" style="background-color: #cccccc" valign="middle">
 107 <big><strong><span class="block">&nbsp;Text::Soundex - Implementation of the Soundex Algorithm as Described by Knuth</span></strong></big>
 108 </td></tr>
 109 </table>
 110
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