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<div class="titlepage"><div><div><h3 class="title">
<a name="variadic_macro_data.vmd_specific.vmd_number"></a><a class="link" href="vmd_number.html" title="Numbers">Numbers</a>
</h3></div></div></div>
<p>
        A number in VMD is a preprocessing 'pp-number', limited to a Boost PP number.
        This is an integral literal between 0 and 256. The form of the number does
        not contain leading zeros. Acceptable as numbers are:
      </p>
<pre class="programlisting"><span class="number">0</span>
<span class="number">127</span>
<span class="number">33</span>
<span class="number">254</span>
<span class="number">18</span>
</pre>
<p>
        but not:
      </p>
<pre class="programlisting"><span class="number">033</span>
<span class="number">06</span>
<span class="number">00</span><span class="number">9</span>
<span class="number">00</span>
</pre>
<h5>
<a name="variadic_macro_data.vmd_specific.vmd_number.h0"></a>
        <span class="phrase"><a name="variadic_macro_data.vmd_specific.vmd_number.problem_testing_any_number"></a></span><a class="link" href="vmd_number.html#variadic_macro_data.vmd_specific.vmd_number.problem_testing_any_number">Problem
        testing any number</a>
      </h5>
<p>
        As can be seen from the explanation of an identifier, a number is merely
        a small subset of all possible identifiers, for which VMD internally provides
        registration macros for its use and pre-detection macros for its use. Therefore
        the particular constraint on the input to test is exactly the same as for
        identifiers.
      </p>
<p>
        The constraint is that the beginning input character, ignoring any whitespace,
        passed as the input to test must be either:
      </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
            an identifier character, ie. an alphanumeric or an underscore
          </li>
<li class="listitem">
            the left parenthesis of a tuple
          </li>
</ul></div>
<p>
        and if the first character is not the left parenthesis of a tuple the remaining
        characters must be alphanumeric or an underscore until a space character
        or end of input occurs.
      </p>
<p>
        If this is not the case the behavior is undefined, and most likely a preprocessing
        error will occur.
      </p>
<h5>
<a name="variadic_macro_data.vmd_specific.vmd_number.h1"></a>
        <span class="phrase"><a name="variadic_macro_data.vmd_specific.vmd_number.testing_for_a_number_macro"></a></span><a class="link" href="vmd_number.html#variadic_macro_data.vmd_specific.vmd_number.testing_for_a_number_macro">Testing
        for a number macro</a>
      </h5>
<p>
        The macro used to test for any number in VMD is called BOOST_VMD_IS_NUMBER.
        The macro takes a single parameter, the input to test against.
      </p>
<p>
        The macro returns 1 if the parameter is a Boost PP number, otherwise the
        macro returns 0.
      </p>
<p>
        The Boost PP library has a great amount of functionality for working with
        numbers, so once you use VMD to parse/test for a number you can use Boost
        PP to work with that number in various ways. The VMD makes no attempt to
        duplicate the functionality of numbers that in the Boost PP library.
      </p>
<p>
        Any number is also an identifier, which has been registered and pre-detected,
        so you can also use the VMD functionality which works with identifiers to
        work with a number as an identifier if you like.
      </p>
<h5>
<a name="variadic_macro_data.vmd_specific.vmd_number.h2"></a>
        <span class="phrase"><a name="variadic_macro_data.vmd_specific.vmd_number.example"></a></span><a class="link" href="vmd_number.html#variadic_macro_data.vmd_specific.vmd_number.example">Example</a>
      </h5>
<p>
        Let us look at an example of how to use BOOST_VMD_IS_NUMBER.
      </p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">vmd</span><span class="special">/</span><span class="identifier">is_number</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>

<span class="identifier">BOOST_VMD_IS_NUMBER</span><span class="special">(</span><span class="identifier">input</span><span class="special">)</span>

<span class="identifier">returns</span><span class="special">:</span>

<span class="keyword">if</span> <span class="identifier">input</span> <span class="special">=</span> <span class="number">0</span><span class="special">,</span> <span class="number">1</span>
<span class="keyword">if</span> <span class="identifier">input</span> <span class="special">=</span> <span class="number">44</span><span class="special">,</span> <span class="number">1</span>
<span class="keyword">if</span> <span class="identifier">input</span> <span class="special">=</span> <span class="identifier">SQUARE</span><span class="special">,</span> <span class="number">0</span>
<span class="keyword">if</span> <span class="identifier">input</span> <span class="special">=</span> <span class="number">44</span> <span class="identifier">DATA</span><span class="special">,</span> <span class="number">0</span> <span class="identifier">since</span> <span class="identifier">there</span> <span class="identifier">are</span> <span class="identifier">tokens</span> <span class="identifier">after</span> <span class="identifier">the</span> <span class="identifier">number</span>
<span class="keyword">if</span> <span class="identifier">input</span> <span class="special">=</span> <span class="number">044</span><span class="special">,</span> <span class="number">0</span> <span class="identifier">since</span> <span class="identifier">no</span> <span class="identifier">leading</span> <span class="identifier">zeros</span> <span class="identifier">are</span> <span class="identifier">allowed</span> <span class="keyword">for</span> <span class="identifier">our</span> <span class="identifier">Boost</span> <span class="identifier">PP</span> <span class="identifier">numbers</span>
<span class="keyword">if</span> <span class="identifier">input</span> <span class="special">=</span> <span class="number">256</span><span class="special">,</span> <span class="number">1</span>
<span class="keyword">if</span> <span class="identifier">input</span> <span class="special">=</span> <span class="number">257</span><span class="special">,</span> <span class="number">0</span> <span class="identifier">since</span> <span class="identifier">it</span> <span class="identifier">falls</span> <span class="identifier">outside</span> <span class="identifier">the</span> <span class="identifier">Boost</span> <span class="identifier">PP</span> <span class="identifier">number</span> <span class="identifier">range</span> <span class="identifier">of</span> <span class="number">0</span><span class="special">-</span><span class="number">256</span>
<span class="keyword">if</span> <span class="identifier">input</span> <span class="special">=</span> <span class="special">%</span><span class="number">44</span><span class="special">,</span> <span class="identifier">does</span> <span class="keyword">not</span> <span class="identifier">meet</span> <span class="identifier">the</span> <span class="identifier">constraint</span> <span class="identifier">therefore</span> <span class="identifier">undefined</span> <span class="identifier">behavior</span>
<span class="keyword">if</span> <span class="identifier">input</span> <span class="special">=</span> <span class="number">44.0</span><span class="special">,</span> <span class="identifier">does</span> <span class="keyword">not</span> <span class="identifier">meet</span> <span class="identifier">the</span> <span class="identifier">constraint</span> <span class="identifier">therefore</span> <span class="identifier">undefined</span> <span class="identifier">behavior</span>
<span class="keyword">if</span> <span class="identifier">input</span> <span class="special">=</span> <span class="special">(</span> <span class="number">44</span> <span class="special">),</span> <span class="number">0</span> <span class="identifier">since</span> <span class="identifier">the</span> <span class="identifier">macro</span> <span class="identifier">begins</span> <span class="identifier">with</span> <span class="identifier">a</span> <span class="identifier">tuple</span> <span class="keyword">and</span> <span class="keyword">this</span> <span class="identifier">can</span> <span class="identifier">be</span> <span class="identifier">tested</span> <span class="keyword">for</span>
</pre>
<h5>
<a name="variadic_macro_data.vmd_specific.vmd_number.h3"></a>
        <span class="phrase"><a name="variadic_macro_data.vmd_specific.vmd_number.usage"></a></span><a class="link" href="vmd_number.html#variadic_macro_data.vmd_specific.vmd_number.usage">Usage</a>
      </h5>
<p>
        To use the BOOST_VMD_IS_NUMBER macro either include the general header:
      </p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">vmd</span><span class="special">/</span><span class="identifier">vmd</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
</pre>
<p>
        or include the specific header:
      </p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">vmd</span><span class="special">/</span><span class="identifier">is_number</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
</pre>
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