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  <title>TokenizerFunction Concept</title>
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  <h1 align="center">TokenizerFunction Concept</h1>

  <p>A TokenizerFunction is a functor whose purpose is to parse a given
  sequence until exactly 1 token has been found or the end is reached. It
  then updates the token, and informs the caller of the location in the
  sequence of the next element immediately after the last element of the
  sequence that was parsed for the current token.</p>

  <h2>Refinement of</h2>

  <p>Assignable, CopyConstructable</p>

  <h2>Notation</h2>

  <table border="1" summary="">
    <tr>
      <td valign="top"><tt>X</tt></td>

      <td valign="top">A type that is a model of TokenizerFunction</td>
    </tr>

    <tr>
      <td valign="top"><tt>func</tt></td>

      <td valign="top">Object of type <tt>X</tt></td>
    </tr>

    <tr>
      <td valign="top"><tt>tok</tt></td>

      <td valign="top">Object of Token</td>
    </tr>

    <tr>
      <td>next</td>

      <td>iterator that points to the first unparsed element of the sequence
      being parsed</td>
    </tr>

    <tr>
      <td>end</td>

      <td>iterator that points to the past the end of the sequence being
      parsed</td>
    </tr>
  </table>

  <h2>Definitions</h2>

  <p>A token is the result of parsing a sequence.</p>

  <h2>Valid expressions</h2>

  <p>In addition to the expression in Assignable and CopyConstructable the
  following expressions are valid</p>

  <table border="1" summary="">
    <tr>
      <th>Name</th>

      <th>Expression</th>

      <th>Return type</th>
    </tr>

    <tr>
      <td valign="top">Functor</td>

      <td valign="top"><tt>func(next, end, tok)</tt></td>

      <td valign="top"><tt>bool</tt></td>
    </tr>

    <tr>
      <td valign="top">reset</td>

      <td valign="top"><tt>reset()</tt></td>

      <td valign="top"><tt>void</tt></td>
    </tr>
  </table>

  <h2>Expression semantics</h2>

  <p>In addition to the expression semantics in Assignable and
  CopyConstructable, TokenizerFunction has the following expression
  semantcs</p>

  <table border="1" summary="">
    <tr>
      <th>Name</th>

      <th>Expression</th>

      <th>Precondition</th>

      <th>Semantics</th>

      <th>Postcondition</th>
    </tr>

    <tr>
      <td>operator()</td>

      <td><tt>func(next, end, tok)</tt></td>

      <td><tt>next</tt> and <tt>end</tt> are valid iterators to the same
      sequence. next is a reference the function is free to modify. tok is
      constructed.</td>

      <td>The return value indicates whether a new token was found in the
      sequence [next,end)</td>

      <td>If the return value is true, the new token is assigned to tok. next
      is always updated to the position where parsing should start on the
      subsequent call.</td>
    </tr>

    <tr>
      <td>reset</td>

      <td><tt>reset()</tt></td>

      <td><tt>None</tt></td>

      <td>Clears out all state variables that are used by the object in
      parsing the current sequence.</td>

      <td>A new sequence to parse can be given.</td>
    </tr>
  </table>

  <h2>Complexity guarantees</h2>

  <p>No guarantees. Models of TokenizerFunction are free to define their own
  complexity</p>

  <h2>Models</h2>

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  <p>Revised 
  <!--webbot bot="Timestamp" s-type="EDITED" s-format="%d %B, %Y" startspan -->25
  December, 2006<!--webbot bot="Timestamp" endspan i-checksum="38518" --></p>

  <p><i>Copyright &copy; 2001 John R. Bandela</i></p>

  <p><i>Distributed under the Boost Software License, Version 1.0. (See
  accompanying file <a href="../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or
  copy at <a href=
  "http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</a>)</i></p>
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