Function vectorize

include/pybind11/numpy.h:2291–2293

// Vanilla pointer vectorizer:
template <typename Return, typename... Args>
detail::vectorize_helper<Return (*)(Args...), Return, Args...> vectorize(Return (*f)(Args...)) {
    return detail::vectorize_helper<Return (*)(Args...), Return, Args...>(f);
}

// lambda vectorizer:
template <typename Func, detail::enable_if_t<detail::is_lambda<Func>::value, int> = 0>