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- <title>Getting the type of data</title>
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- <div class="titlepage"><div><div><h3 class="title">
- <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
- the type of data</a>
- </h3></div></div></div>
- <p>
- VMD has the ability to retrieve the type of any data which it can parse,
- which means any VMD sequence. The macro to do this is called BOOST_VMD_GET_TYPE
- and it takes a single required parameter, which is a VMD sequence.
- </p>
- <p>
- It returns one of the types previously discussed when introducing v-types
- as an identifier subset. As explained previously in that topic a v-type is
- fully recognized by VMD macros and can be part of a sequence and passed as
- VMD data just like all the other data types VMD recognizes.
- </p>
- <p>
- When BOOST_VMD_GET_TYPE returns the type of data it returns by default the
- most specific type that the data can be. This means that non-empty lists
- and arrays are returned as such, not as tuples, and numbers and types and
- empty lists are returned as such, not as identifiers.
- </p>
- <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</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">></span>
- <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>
- <span class="preprocessor">#define</span> <span class="identifier">SEQUENCE_EMPTY</span>
- <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>
- <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>
- <span class="preprocessor">#define</span> <span class="identifier">SEQUENCE2</span> <span class="identifier">ANID</span>
- <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>
- <span class="preprocessor">#define</span> <span class="identifier">SEQUENCE4</span> <span class="number">1</span>
- <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>
- <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>
- <span class="preprocessor">#define</span> <span class="identifier">SEQUENCE7</span> <span class="identifier">BOOST_VMD_TYPE_NUMBER</span>
- <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>
- <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>
- <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>
- <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>
- <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>
- <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>
- <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>
- <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>
- <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>
- </pre>
- <h5>
- <a name="variadic_macro_data.vmd_generic.vmd_convert_sequence.h0"></a>
- <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>
- </h5>
- <p>
- You can use the general header file:
- </p>
- <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</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">></span>
- </pre>
- <p>
- or you can use the individual header file:
- </p>
- <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</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">></span>
- </pre>
- <p>
- for the BOOST_VMD_GET_TYPE macro.
- </p>
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