if this is a C++17 library why couldn't you use `constexpr` evaluation and not murder your compilation time?

Template metaprogramming isn't really suited for this task, the prime sieve here serves only as a proof of concept, meant to show the capabilities of this style. But there are cases where `constexpr` is not applicable, especially when involving type manipulations.

On the other hand, C++ template metaprogramming, as an esolang, is fun to tame and experiment with.

I imagine because some of the cool constexpr improvements are only available in C++20 and C++23.