Non Type Template Arguments

[TheFloatingBrain]

I looked at this answer #3662

Wanted to ask

0: Are non-type template arguments to my C++ class, type, or function supported? It seems like I have to put in every possible value? I saw something about it in a change log. This would be difficult if it were, say, a floating-point. Even a range of integers would be a lot.

Cython seems to support it [0, 1] though I am thinking is may be because it comes bundled with a compiler?

1: Regarding the code

    m.def("mysum_with_args", [](py::args args)
          {
              int sum = 0;
              for (auto it : args)
              {
                  sum += it.cast<int>();
              }
              return sum;
          });

Does py::args contain type information, so potentially I could have a switch statement for different types and use a recursive template to implement the call?

2: Is Python typing supported in this way, suppose I had

2.0

template<typename T> class MyClass { /* ... */ };

Can one do from the Python side?

x: MyClass[int]
y: MyClass[float]

(wrapping each type of course)

2.1
If non type

template<int X> class MyClass2 { /* ... */ };

x: MyClass2[33]
y: MyClass2[123]

Probably using std::make_index_sequence to generate each version and wrap it.

2.2

Could one use a custom enum here?

enum class MyEnum { A, B, C, /*...*/ };
template<MyEnum X> class MyClass2 { /* ... */ };

x: MyClass2[MyEnum.A]
y: MyClass2[MyEnum.C]