basic_mod.cpp

#include <pybind11/pybind11.h>
#include <pybind11/stl.h>
#include <iostream>

namespace py = pybind11;


void print_arg(int arg)
{
    std::cout << "Integer arg: " << arg << std::endl;
}


void print_arg(double arg)
{
    std::cout << "Double arg: " << arg << std::endl;
}


void print_arg(const std::vector<int> & v)
{
    std::cout << "Integer vector of length " << v.size() << " : ";
    for(const auto & it : v)
        std::cout << it << " ";
    std::cout << std::endl;
}


long factorial(long n)
{
    if(n < 0)
        throw std::runtime_error("factorial(n) with n < 0 is undefined!");

    long fac = 1;
    for(long i = n; i > 0; i--)
        fac *= i;

    return fac;
}


long binomial_coefficient(long n, long k)
{
    if(n < k)
        throw std::runtime_error("n must be >= k for binomial coefficient");
    if(n < 0) 
        throw std::runtime_error("n must be >= 0 for binomial coefficient");
    if(k < 0) 
        throw std::runtime_error("k must be >= 0 for binomial coefficient");

    return factorial(n)/(factorial(k)*factorial(n-k));
}


long double_factorial(long n)
{
    if(n < -1)
        throw std::runtime_error("n must be >= -1 for double factorial");

    long fac = 1;
    for(long i = n; i > 0; i -= 2)
        fac *= i;
    return fac;
}


double dot_product(const std::vector<double> & v1,
                   const std::vector<double> & v2)
{
    double dot = 0.0;

    if(v1.size() != v2.size())
        throw std::runtime_error("Cannot perform dot product of vectors with different sizes");

    for(size_t i = 0; i < v1.size(); i++)
        dot += v1[i] * v2[i];

    return dot;
}


PYBIND11_PLUGIN(basic_mod)
{
    py::module m("basic_mod", "Ben's basic pybind11 module");

    m.def("print_arg", static_cast<void(*)(int)>(&print_arg));
    m.def("print_arg", static_cast<void(*)(double)>(&print_arg));
    m.def("print_arg", static_cast<void(*)(const std::vector<int> &)>(&print_arg));
    m.def("print_arg", [](const std::string & s) { std::cout << "String arg: " << s << std::endl; });

    m.def("factorial", &factorial, "Compute the factorial of an integer");
    m.def("double_factorial", &double_factorial, "Compute the double factorial of an integer");
    m.def("binomial_coefficient", &binomial_coefficient, "Compute the binomial coefficient of two integers");
    m.def("dot_product", &dot_product, "Compute the dot product of two vectors");

    return m.ptr();
}