ceph/src/boost/libs/metaparse/doc/boxed_value.qbk

   1 [#boxed_value]
   2 [section Boxed value]
   3
   4 A ['boxed value] is a type representing a constant value. It has a public static
   5 `const` or `constexpr` member called `value`. The class represents that value as
   6 a type, so it can be manipulated by [link metafunction template metafunction]s.
   7 It has to be a [link metaprogramming_value template metaprogramming value].
   8
   9 For example the following `struct` represents the `true` value of type `bool`:
  10
  11   struct true_type
  12   {
  13     static constexpr bool value = true;
  14     using type = true_type;
  15   };
  16
  17 The `value` member is the wrapped value. `true_type::type` is an alias of
  18 `true_type` which makes it a template metaprogramming value.
  19
  20 [endsect]
  21