Is ostream_iterator efficient?

Question

I just learned how to use ostream_iterator today, but I don't know if this is efficient comparing to the normal for-loop way.

Here is the code:

//The first one
vector<int> v = {1, 2, 3, 4, 5};
ostream_iterator<int> osit(cout, " ");
copy(v.begin(), v.end(), osit);

And

//The second one
vector<int> v = {1, 2, 3, 4, 5};
for (int i : v) cout << i << " ";

Which one is more efficient?

Thank you in advance!

Answer 1

std::copy is using operator= from the iterator. It looks something like this

ostream_iterator& operator=(const _Ty& _Val)
{   // insert value into output stream, followed by delimiter
    *_Myostr << _Val;
    if (_Mydelim != 0)
    {
        *_Myostr << _Mydelim;
    }

    return (*this);
}

Looks very similar to the code you have in your for-loop, except for the conditional output of the separator (which takes zero time compared to formatting the integer and outputting it).