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 2019. The current version is 1.90.0.
boost::units::length_base_dimension — base dimension of length
// In header: <boost/units/physical_dimensions/length.hpp> struct length_base_dimension : public boost::units::base_dimension< length_base_dimension, -9 > { };