Description

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

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

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

template<class BOOST_TTI_TP_T,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_T    = the enclosing type in which to look for our 'name'
                      The enclosing type can be a class, struct, or union.
                      If the type is a union, static member data can only
                      be found if the C++11 unrestricted union is implemented
                      by the compiler being used, since prior to C++11 a union
                      could not have static data members.
  
  BOOST_TTI_TP_TYPE = The type of the member data or static member.
  
  returns  = 'value' is true if the 'name' exists, with the correct data type,
             otherwise 'value' is false.