vectors of vectors of vectors -> HOW ?

[petrasvestartas]

Context

I need to pass from python to C++ a list of Polylines:

• a list has two polylines
• 1st Polyline has 2 points e.g. 6 coordinates
• 2nd Polyline has 1 point e.g. 3 coordinates

Question

Is there any way to this efficiently?
I was doing this similarly on pybind11 and it was slow for big collections...
Is there a way to represent this in array or eigen matrices for a better efficiency when you have hundreds of polylines?

Example

C++

nb::bind_vector<std::vector<unsigned int>>(m, "VectorInt");
nb::bind_vector<std::vector<bool>>(m, "VectorBool");
nb::bind_vector<std::vector<double>>(m, "VectorDouble1D");
nb::bind_vector<std::vector<std::vector<double>>>(m, "VectorDouble2D");
nb::bind_vector<std::vector<std::vector<std::vector<double>>>>(m, "VectorDouble3D");

Python

vector_double_1d_0 = m.VectorDouble1D([1,2,3,4,5,8])
vector_double_1d_1 = m.VectorDouble1D([8,9,10])
vector_double_1d_2 = m.VectorDouble1D([1,2,3,4,5,8,1,2,3,4,5,8])

vector_double_2d_0 = m.VectorDouble2D([vector_double_1d_0,vector_double_1d_1])
vector_double_2d_1 = m.VectorDouble2D([vector_double_1d_2])

vector_double_3d = m.VectorDouble3D([vector_double_2d_0, vector_double_2d_1])

I also did this and I see the code becomes very repetitive, why there is no way to use templates inside the main NB_Module method?

    nb::class_<std::vector<int>>(m, "IntVector")
        .def(nb::init<>())
        .def("reserve", &std::vector<int>::reserve)
        .def("emplace_back", [](std::vector<int>& v, int x) {
            v.emplace_back(x);
        });

    nb::class_<std::vector<std::vector<int>>>(m, "IntVector2D")
        .def(nb::init<>())
        .def("reserve", &std::vector<std::vector<int>>::reserve)
        .def("emplace_back", [](std::vector<std::vector<int>>& v, const std::vector<int>& p) {
            v.emplace_back(p);
        });

    nb::class_<std::vector<std::vector<std::vector<int>>>>(m, "IntVector3D")
        .def(nb::init<>())
        .def("reserve", &std::vector<std::vector<std::vector<int>>>::reserve)
        .def("emplace_back", [](std::vector<std::vector<std::vector<int>>>& v, const std::vector<std::vector<int>>& p) {
            v.emplace_back(p);
        });

    nb::class_<std::vector<std::vector<std::vector<std::vector<int>>>>>(m, "IntVector4D")
        .def(nb::init<>())
        .def("reserve", &std::vector<std::vector<std::vector<std::vector<int>>>>::reserve)
        .def("emplace_back", [](std::vector<std::vector<std::vector<std::vector<int>>>>& v, const std::vector<std::vector<std::vector<int>>>& p) {
            v.emplace_back(p);
        });