[jcelerier]

are there fundamental differences with https://github.com/serge-sans-paille/frozen ?

[Jyaif]

The map is not frozen.

[hogliux]

Yup. The frozen map cannot be updated once it is initialized:

<<Once initialized, the containers cannot be updated, and in exchange, lookups are faster. And initialization is free when constexpr is used :-).>>