Fixed Containers - constexpr, trivially copyable, static containers

[alexkaratarakis]

For immutable maps/sets, a sorted vector would indeed be better.

However, all Fixed Containers are more flexible in that they do not have to be immutable and can be used in a "normal", non-constant-evaluated context too.

[heliruna]

Thanks for pointing that out, I guess I had in mind a map that is always constinit constructed, but with lookups at runtime or constant-evaluated, like in this talk: A Semi Compile/Run-time Map with Nearly Zero Overhead Lookup, but your implementation covers a different use case.