...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
using lowest_layer_type = typename get_lowest_layer< next_layer_type >::type;
This will contain a nested type
equal to T::lowest_layer_type
if it exists, else
type
will be equal to
T
.
Declaring a wrapper:
template<class Stream> struct stream_wrapper { using next_layer_type = typename std::remove_reference<Stream>::type; using lowest_layer_type = typename get_lowest_layer<stream_type>::type; };
Defining a metafunction:
template<class T> using is_stream_wrapper : std::integral_constant<bool, ! std::is_same<T, typename get_lowest_layer<T>::type>::value> {};