Function vector_accessor

include/pybind11/stl_bind.h:316–349

// The usual case: access and iterate by reference
template <typename Vector, typename Class_>
void vector_accessor(enable_if_t<!vector_needs_copy<Vector>::value, Class_> &cl) {
    using T = typename Vector::value_type;
    using SizeType = typename Vector::size_type;
    using DiffType = typename Vector::difference_type;
    using ItType = typename Vector::iterator;

    auto wrap_i = [](DiffType i, SizeType n) {
        if (i < 0) {
            i += n;
        }
        if (i < 0 || (SizeType) i >= n) {
            throw index_error();
        }
        return i;
    };

    cl.def(
        "__getitem__",
        [wrap_i](Vector &v, DiffType i) -> T & {
            i = wrap_i(i, v.size());
            return v[(SizeType) i];
        },
        return_value_policy::reference_internal // ref + keepalive
    );

    cl.def(
        "__iter__",
        [](Vector &v) {
            return make_iterator<return_value_policy::reference_internal, ItType, ItType, T &>(
                v.begin(), v.end());
        },
        keep_alive<0, 1>() /* Essential: keep list alive while iterator exists */
    );
}

// The case for special objects, like std::vector<bool>, that have to be returned-by-copy:
template <typename Vector, typename Class_>