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::hash<std::type_index>
// In header: <boost/container_hash/hash.hpp> struct hash<std::type_index> { std::size_t operator()(std::type_index) const; };