In the below C++ code, even though the type std::tuple<int> is registered,
boost::python fails to find that out when the tuple is within an
std::vector exposed through the vector_indexing suite. At the same time, it
is possible to reference and use the type normally as long as it's not in
the vector.
For example, this happens:
>>> print makeMyTuple()
(0,)
>>> print makeTuples()[0]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: No Python class registered for C++ class std::tuple<int>
>>>
Is there any way to make this work?
Best,
Eugenio
MVE:
#include <tuple>
#include <vector>
#include <boost/python.hpp>
#include <boost/python/suite/indexing/vector_indexing_suite.hpp>
template <typename T>
struct TupleToPython {
TupleToPython() {
boost::python::to_python_converter<T, TupleToPython<T>>();
}
template<int...>
struct sequence {};
template<int N, int... S>
struct generator : generator<N-1, N-1, S...> { };
template<int... S>
struct generator<0, S...> {
using type = sequence<S...>;
};
template <int... I>
static boost::python::tuple boostConvertImpl(const T& t,
sequence<I...>) {
return boost::python::make_tuple(std::get<I>(t)...);
}
template <typename... Args>
static boost::python::tuple boostConvert(const std::tuple<Args...> & t)
{
return boostConvertImpl(t, typename
generator<sizeof...(Args)>::type());
}
static PyObject* convert(const T& t) {
return boost::python::incref(boostConvert(t).ptr());
}
};
using MyTuple = std::tuple<int>;
using Tuples = std::vector<MyTuple>;
MyTuple makeMyTuple() {
return MyTuple();
}
Tuples makeTuples() {
return Tuples{MyTuple()};
}
BOOST_PYTHON_MODULE(h)
{
using namespace boost::python;
TupleToPython<MyTuple>();
def("makeMyTuple", makeMyTuple);
class_<std::vector<MyTuple>>{"Tuples"}
.def(vector_indexing_suite<std::vector<MyTuple>>());
def("makeTuples", makeTuples);
}
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