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  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="variadic_macro_data.vmd_generic.vmd_convert_sequence"></a><a class="link" href="vmd_convert_sequence.html" title="Getting the type of data">Getting
  28       the type of data</a>
  29 </h3></div></div></div>
  30 <p>
  31         VMD has the ability to retrieve the type of any data which it can parse,
  32         which means any VMD sequence. The macro to do this is called BOOST_VMD_GET_TYPE
  33         and it takes a single required parameter, which is a VMD sequence.
  34       </p>
  35 <p>
  36         It returns one of the types previously discussed when introducing v-types
  37         as an identifier subset. As explained previously in that topic a v-type is
  38         fully recognized by VMD macros and can be part of a sequence and passed as
  39         VMD data just like all the other data types VMD recognizes.
  40       </p>
  41 <p>
  42         When BOOST_VMD_GET_TYPE returns the type of data it returns by default the
  43         most specific type that the data can be. This means that non-empty lists
  44         and arrays are returned as such, not as tuples, and numbers and types and
  45         empty lists are returned as such, not as identifiers.
  46       </p>
  47 <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">get_type</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
  48
  49 <span class="preprocessor">#define</span> <span class="identifier">BOOST_VMD_REGISTER_ANID</span> <span class="special">(</span><span class="identifier">ANID</span><span class="special">)</span>
  50 <span class="preprocessor">#define</span> <span class="identifier">SEQUENCE_EMPTY</span>
  51 <span class="preprocessor">#define</span> <span class="identifier">SEQUENCE_MULTI</span> <span class="special">(</span><span class="number">1</span><span class="special">,</span><span class="number">2</span><span class="special">,</span><span class="number">3</span><span class="special">)</span> <span class="number">88</span>
  52 <span class="preprocessor">#define</span> <span class="identifier">SEQUENCE1</span> <span class="special">(</span><span class="number">3</span><span class="special">,(</span><span class="number">1</span><span class="special">,</span><span class="number">2</span><span class="special">,</span><span class="number">3</span><span class="special">))</span>
  53 <span class="preprocessor">#define</span> <span class="identifier">SEQUENCE2</span> <span class="identifier">ANID</span>
  54 <span class="preprocessor">#define</span> <span class="identifier">SEQUENCE3</span> <span class="special">(</span><span class="number">1</span><span class="special">,(</span><span class="number">2</span><span class="special">,(</span><span class="number">3</span><span class="special">,</span><span class="identifier">BOOST_PP_NIL</span><span class="special">)))</span>
  55 <span class="preprocessor">#define</span> <span class="identifier">SEQUENCE4</span> <span class="number">1</span>
  56 <span class="preprocessor">#define</span> <span class="identifier">SEQUENCE5</span> <span class="special">(</span><span class="number">1</span><span class="special">)(</span><span class="number">2</span><span class="special">)(</span><span class="number">3</span><span class="special">)</span>
  57 <span class="preprocessor">#define</span> <span class="identifier">SEQUENCE6</span> <span class="special">(</span><span class="number">1</span><span class="special">,</span><span class="number">2</span><span class="special">,</span><span class="number">3</span><span class="special">)</span>
  58 <span class="preprocessor">#define</span> <span class="identifier">SEQUENCE7</span> <span class="identifier">BOOST_VMD_TYPE_NUMBER</span>
  59
  60 <span class="identifier">BOOST_VMD_GET_TYPE</span><span class="special">(</span><span class="identifier">SEQUENCE_EMPTY</span><span class="special">)</span> <span class="identifier">will</span> <span class="keyword">return</span> <span class="identifier">BOOST_VMD_TYPE_EMPTY</span>
  61 <span class="identifier">BOOST_VMD_GET_TYPE</span><span class="special">(</span><span class="identifier">SEQUENCE_MULTI</span><span class="special">)</span> <span class="identifier">will</span> <span class="keyword">return</span> <span class="identifier">BOOST_VMD_TYPE_SEQUENCE</span>
  62 <span class="identifier">BOOST_VMD_GET_TYPE</span><span class="special">(</span><span class="identifier">SEQUENCE1</span><span class="special">)</span> <span class="identifier">will</span> <span class="keyword">return</span> <span class="identifier">BOOST_VMD_TYPE_ARRAY</span>
  63 <span class="identifier">BOOST_VMD_GET_TYPE</span><span class="special">(</span><span class="identifier">SEQUENCE2</span><span class="special">)</span> <span class="identifier">will</span> <span class="keyword">return</span> <span class="identifier">BOOST_VMD_TYPE_IDENTIFIER</span>
  64 <span class="identifier">BOOST_VMD_GET_TYPE</span><span class="special">(</span><span class="identifier">SEQUENCE3</span><span class="special">)</span> <span class="identifier">will</span> <span class="keyword">return</span> <span class="identifier">BOOST_VMD_TYPE_LIST</span>
  65 <span class="identifier">BOOST_VMD_GET_TYPE</span><span class="special">(</span><span class="identifier">SEQUENCE4</span><span class="special">)</span> <span class="identifier">will</span> <span class="keyword">return</span> <span class="identifier">BOOST_VMD_TYPE_NUMBER</span>
  66 <span class="identifier">BOOST_VMD_GET_TYPE</span><span class="special">(</span><span class="identifier">SEQUENCE5</span><span class="special">)</span> <span class="identifier">will</span> <span class="keyword">return</span> <span class="identifier">BOOST_VMD_TYPE_SEQ</span>
  67 <span class="identifier">BOOST_VMD_GET_TYPE</span><span class="special">(</span><span class="identifier">SEQUENCE6</span><span class="special">)</span> <span class="identifier">will</span> <span class="keyword">return</span> <span class="identifier">BOOST_VMD_TYPE_TUPLE</span>
  68 <span class="identifier">BOOST_VMD_GET_TYPE</span><span class="special">(</span><span class="identifier">SEQUENCE7</span><span class="special">)</span> <span class="identifier">will</span> <span class="keyword">return</span> <span class="identifier">BOOST_VMD_TYPE_TYPE</span>
  69 </pre>
  70 <h5>
  71 <a name="variadic_macro_data.vmd_generic.vmd_convert_sequence.h0"></a>
  72         <span class="phrase"><a name="variadic_macro_data.vmd_generic.vmd_convert_sequence.usage"></a></span><a class="link" href="vmd_convert_sequence.html#variadic_macro_data.vmd_generic.vmd_convert_sequence.usage">Usage</a>
  73       </h5>
  74 <p>
  75         You can use the general header file:
  76       </p>
  77 <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>
  78 </pre>
  79 <p>
  80         or you can use the individual header file:
  81       </p>
  82 <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">get_type</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
  83 </pre>
  84 <p>
  85         for the BOOST_VMD_GET_TYPE macro.
  86       </p>
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