Function random_pick

random.hh:25–32

template<typename I>
I random_pick(I beg, I end) {
    if (beg == end)
      throw std::runtime_error("No candidates available");

    std::uniform_int_distribution<> pick(0, std::distance(beg, end) - 1);
    std::advance(beg, pick(smith::rng));
    return beg;
}

template<typename I>
I random_pick(std::pair<I,I> iters) {