...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
boost::log::result_of::extract — A metafunction that allows to acquire the result of the value extraction.
// In header: <boost/log/attributes/value_extraction.hpp> template<typename T, typename TagT> struct extract { // types typedef value_ref< T, TagT > type; };