Boost
C++ Libraries
...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
This is an older version of Boost and was released in 2016. The current version is 1.90.0.
boost::accumulators::feature_of<tag::droppable< Feature >>
// In header: <boost/accumulators/framework/accumulators/droppable_accumulator.hpp> template<typename Feature> struct feature_of<tag::droppable< Feature >> : public boost::accumulators::feature_of< Feature > { };