Bootstrapping in C++ using variadic templates for parallel estimators application

bootstrap.hpp

template <typename T>
struct estimate { T mean, lbound, ubound, stdev; }

template <typename T, typename... Rs>
std::tuple<estimate<Rs>...> bootstrap(std::vector<T> &sample, size_t resamples,
                                      std::function<Rs(std::vector<T>)>... estimators)
{
    const size_t n = sample.size();

    // re-sample and estimate our sample

    std::default_random_engine rng;
    std::uniform_int_distribution<size_t> index_dist(0, n - 1);

    std::vector<std::tuple<Rs...>> esample;
    esample.reserve(resamples);
    for (size_t i = 0; i < resamples; ++i)
    {
        std::vector<T> bsample;
        bsample.reserve(n);
        for (size_t j = 0; j < n; ++j)
        {
            bsample.emplace_back(sample[index_dist(rng)]);
        }
        esample.empalce_back(estimators(bsample)...);
    }

    // lets calculate mean
    std::tuple<Rs...> emean = {Rs(0)...};
    for (const auto &evalue : esample)
    {
        // XXX: what to put here?
        // emean += evalue; <-- element-by-element
    }

    return {}; // TODO:
}