pybind_example.cpp

// pybind_example.cpp
// Compiled with pybind11
#include <pybind11/pybind11.h>
#include <pybind11/stl.h>
#include <pybind11/numpy.h>
#include <vector>
#include <cmath>
#include <string>

namespace py = pybind11;

// A simple function
double add(double a, double b) {
    return a + b;
}

// A function that takes and returns a numpy array
py::array_t<double> scale_array(py::array_t<double> input, double factor) {
    auto buf = input.request();
    auto *ptr = static_cast<double *>(buf.ptr);
    
    auto result = py::array_t<double>(buf.size);
    auto res_buf = result.request();
    auto *res_ptr = static_cast<double *>(res_buf.ptr);
    
    for (ssize_t i = 0; i < buf.size; i++) {
        res_ptr[i] = ptr[i] * factor;
    }
    
    return result;
}

// A simple class
class Integrator {
    double a_, b_;
    int n_;
public:
    Integrator(double a, double b, int n) : a_(a), b_(b), n_(n) {}
    
    double trapezoid(py::object func) {
        double h = (b_ - a_) / n_;
        double sum = 0.5 * (func(a_).cast<double>() + func(b_).cast<double>());
        for (int i = 1; i < n_; i++) {
            sum += func(a_ + i * h).cast<double>();
        }
        return sum * h;
    }
    
    std::string describe() const {
        return "Integrator(a=" + std::to_string(a_) + ", b=" + std::to_string(b_) 
               + ", n=" + std::to_string(n_) + ")";
    }
    
    double get_a() const { return a_; }
    double get_b() const { return b_; }
    int get_n() const { return n_; }
};

PYBIND11_MODULE(pybind_example, m) {
    m.doc() = "pybind11 example module";
    
    m.def("add", &add, "Add two numbers", py::arg("a"), py::arg("b"));
    
    m.def("scale_array", &scale_array, "Scale a numpy array",
          py::arg("input"), py::arg("factor"));
    
    py::class_<Integrator>(m, "Integrator")
        .def(py::init<double, double, int>(),
             py::arg("a"), py::arg("b"), py::arg("n") = 1000)
        .def("trapezoid", &Integrator::trapezoid, py::arg("func"))
        .def("describe", &Integrator::describe)
        .def_property_readonly("a", &Integrator::get_a)
        .def_property_readonly("b", &Integrator::get_b)
        .def_property_readonly("n", &Integrator::get_n)
        .def("__repr__", &Integrator::describe);
}