BEFORE
==================================
template <typename T>
std::string join(T const &v, const std::string& s = ",")
{
        std::stringstream str;
        for(typename T::const_iterator i = v.begin(); i != v.end(); ++i) {
                str << *i;
                if (std::next(i) != v.end())
                        str << s;
        }

        return str.str();
}

AFTER
==================================
template <typename T>
std::string join(T const &v, const std::string& s = ",")
{
    using move_iter = std::move_iterator<typename T::const_iterator>;

    return std::accumulate(move_iter(v.begin()), move_iter(v.end()), s);
}