Pushing multiple items into a vector

It's also possible to write a helper that does not reduce any results but processes multiple actions of the same kind. Like inserting items into an std::vector, which does not return any results (std::vector::insert() signalizes error by throwing exceptions):

template <typename T, typename ... Ts>
void insert_all(std::vector<T> &vec, Ts ... ts)
{
    (vec.push_back(ts), ...);
}

int main()
{
    std::vector<int> v {1, 2, 3};
    insert_all(v, 4, 5, 6);
}

Note that we use the comma (,) operator in order to expand the parameter pack into individual vec.push_back(...) calls without folding the actual result. This function also works nicely with an empty parameter pack because the comma operator has an implicit identity element, void(), which translates to do nothing.