\verbatim BOOST_PREPROCESSOR_IDENTITY(X)() // ^^ NOTE! \endverbatimThe above expands to:
\verbatim X \endverbatimNOTE: If BOOST_PREPROCESSOR_IDENTITY() is not invoked, the expansion will not be usable. */ #define BOOST_PREPROCESSOR_IDENTITY(X) X BOOST_PREPROCESSOR_EMPTY #endif