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## Macro BOOST_TTI_TRAIT_HAS_MEMBER_DATA

BOOST_TTI_TRAIT_HAS_MEMBER_DATA — A macro which expands to a metafunction which tests whether member data with a particular name and type exists.

## Synopsis

    // In header: <boost/tti/has_member_data.hpp>

    BOOST_TTI_TRAIT_HAS_MEMBER_DATA(trait, name)

## Description

BOOST_TTI_TRAIT_HAS_MEMBER_DATA is a macro which expands to a metafunction. The metafunction tests whether member data with a particular name and type exists. The macro takes the form of BOOST_TTI_TRAIT_HAS_MEMBER_DATA(trait,name) where

trait = the name of the metafunction.
name = the name of the inner member data.

BOOST_TTI_TRAIT_HAS_MEMBER_DATA generates a metafunction called "trait" where 'trait' is the macro parameter.

    template<class BOOST_TTI_TP_ET,class BOOST_TTI_TP_TYPE>
    struct trait
      {
      static const value = unspecified;
      typedef mpl::bool_<true-or-false> type;
      };

    The metafunction types and return:

      BOOST_TTI_TP_ET   = the enclosing type in which to look for our 'name'
                          The enclosing type can be a class, struct, or union.
                                               OR
                          The type of the member data in the form of a pointer
                          to member data.

      BOOST_TTI_TP_TYPE = (optional) The type of the member data if the first
                          parameter is the enclosing type.

      returns  = 'value' is true if the 'name' exists, with the correct data type,
                 otherwise 'value' is false.