Passing vector<complex<float>> to function argument

[gillesdegottex]

Hi,

I struggle in passing a vector of complex values to a function.

For example, the following works as expected for float type:

#include <nanobind/nanobind.h>
#include <nanobind/stl/vector.h>
#include <iostream>

namespace nb = nanobind;

NB_MODULE(pybar, m) {
    m.def("foo", [](std::vector<float>& x){
        std::cout << "x[0]=" << x[0] << std::endl;
    });
}

leads to:

> python3 -c 'import pybar; import numpy as np; x = np.array([1],dtype=np.single); pybar.foo(x)'
x[0]=1

However, if using std::complex<float> type instead of float:

#include <nanobind/nanobind.h>
#include <nanobind/stl/vector.h>
#include <iostream>

namespace nb = nanobind;

NB_MODULE(pybar, m) {
    m.def("foo", [](std::vector<std::complex<float>>& x){
        std::cout << "x[0]=" << x[0] << std::endl;
    });
}

leads to:

> python3 -c 'import pybar; import numpy as np; x = np.array([1+1j],dtype=np.csingle); pybar.foo(x)'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
TypeError: foo(): incompatible function arguments. The following argument types are supported:
    1. foo(arg: list[std::complex<float>], /) -> None

Invoked with types: ndarray

I did try to add an explicit type_caster in stl/vector.h (defined before the generic typecaster<Type>):

template <typename Type, typename Alloc> struct type_caster<std::vector<std::complex<Type>, Alloc>>
 : list_caster<std::vector<std::complex<Type>, Alloc>, std::complex<Type>> { };

which leads to the exact same error as above.

Any idea how this should be done in nanobind?

(thanks to this new C++/Python binder!)

[wjakob]

Nanobind currently lacks a type caster for `std::complex``. Help on this front is appreciated. This is not an issue but a feature request, so I am closing the ticket.

[gillesdegottex]

Ok!

A few questions:

• Where can I open a feature request? For follow up on this subject.
• To add support for std::complex, I guess I should add a stl/complex.h, and maybe dig into bn_cast.h, right? Am I in the proper direction?

[wjakob]

This project does not accept feature requests, though you are welcome to submit a PR. And yes, that's right, the type caster would go to stl/complex.h