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 2018. The current version is 1.89.0.
boost::numeric::functional::left_ref
// In header: <boost/accumulators/numeric/functional.hpp> template<typename Left, typename Right> struct left_ref { // types typedef Left & type; };