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  28 <h2><span class="refentrytitle">Macro BOOST_TTI_TRAIT_HAS_MEMBER_DATA</span></h2>
  29 <p>BOOST_TTI_TRAIT_HAS_MEMBER_DATA &#8212; Expands to a metafunction which tests whether a member data with a particular name and type exists. </p>
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  31 <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
  32 <div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="header/boost/tti/has_member_data_hpp.html" title="Header &lt;boost/tti/has_member_data.hpp&gt;">boost/tti/has_member_data.hpp</a>&gt;
  33
  34 </span>BOOST_TTI_TRAIT_HAS_MEMBER_DATA(trait, name)</pre></div>
  35 <div class="refsect1">
  36 <a name="idm45944205567408"></a><h2>Description</h2>
  37 <p>trait = the name of the metafunction.</p>
  38 <p>name = the name of the inner member to introspect.</p>
  39 <p>generates a metafunction called "trait" where 'trait' is the macro parameter.       template&lt;class BOOST_TTI_TP_ET,class BOOST_TTI_TP_TYPE&gt;
  40       struct trait
  41         {
  42         static const value = unspecified;
  43         typedef mpl::bool_&lt;true-or-false&gt; type;
  44         };
  45
  46       The metafunction types and return:
  47
  48         BOOST_TTI_TP_ET   = the enclosing type in which to look for our 'name'
  49                                                  OR
  50                             The type of the member data in the form of a pointer
  51                             to member data.
  52
  53         BOOST_TTI_TP_TYPE = (optional) The type of the member data if the first
  54                             parameter is the enclosing type.
  55
  56         returns  = 'value' is true if the 'name' exists, with the correct data type,
  57                    otherwise 'value' is false.
  58  </p>
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