[#metaprogramming_value]
[section Template metaprogramming value]

A ['template metaprogramming value] is a
[link nullary_metafunction nullary template metafunction] returning itself.
For example:

  struct void_
  {
    using type = void_;
  };

This template metaprogramming value is called `void_`. It is a nullary
metafunction returning itself as its result. Because of this, it can be treated
as a nullary metafunction and evaluated any number of times. For example 
`void_::type::type::type` is still `void_`.

[endsect]