T_VMD_ELEM. Together these facilities
      provide a rich set of functionality for handling identifiers in macros.
    </p>
<p>
      Both numbers and v-types are subtypes of identifiers, and can both be individually
      recognized as data types of their own or worked with as identifiers using the
      identifier facilities already mentioned. Numbers, in particular, also have
      a rich set of functionality within the Boost PP library. As subtypes numbers
      and v-types can be used as filter modifi