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 1.89.0.
boost::units::information::hartleys
// In header: <boost/units/systems/information/hartley.hpp> static const hu::hartley::info hartleys;