Delete element using iterator, without knowing vector

Question

I have a situation. I have used a templated function for one of my task. To this function, I pass iterator by reference. Now, I have to delete few elements from a vector. How do I do this using only iterators? Pl find the respective code:

template <class BidirectionalIterator, class Iterator> bool

SomeFunc( BidirectionalIterator& first, BidirectionalIterator& last, Iterator anotherVecBegin )
{
    while((first+1) != last)
    {
        if(some_condition)
            // delete (first); HOW?
        else if(some_other_condition)
            // delete (first + 1); HOW?
    }

    // add something to another vector using anotherVecBegin

    return true;
}

There are many already asked questions, but they all have a vector in context. so myVec.erase(*first) is easy..

I am also aware that its not a very good way that I pass iterator by reference. But I am following simple rules: use references when something is expected to be changed or to avoid heavy copy. My scenario is fitting first condition.

So How do I delete?

Answer 1

You cannot modify a container if all you have are iterators for the container elements. The whole point of iterators is separating the concept of a container from the concept of range of elements, so that algorithms can be expressed universally in terms of the latter without caring about the former. That's also why we have a remove algorithm that permutes a range and returns an iterator that's suitable for erasing elements from a container, but the erasing needs to be done by someone who knows the container.