Practicing C++ Templates

[Sermil]

I want to get better at C++ templates. I can do the basics:

template<typename T>
T& min(T& t1, T& t2) {
  return t1 < t2 ? t1 : t2;
}

but I'm not great at parameter packs and <concepts>.

Does anyone know a good place to get practice? What I'd really love is something like leetcode, but focused on C++ templates instead of algorithms.

[kyoryu]

What's your overall knowledge of c++?