> I mean C++ templates are a compile-time language, but they are a language that has only one type - types and no real iterations over collection types. Wait, they have no collection types. The one and only type is types.

There is Boost.Hana and the older Boost MPL and brigand.

C++20 will have more constexpr improvements.

Although I do conceed they require a C++ Wizard hat, and aren't not even close of Lisp's macros friendliness.