Iterator newbie question

Hi everyone!
How can I index a list with an integer? I can´t add integers to iterators :(
Thanks any help!

A linked list?
Linked lists generally don't support random accessing, i.e. indexing, as it's horribly slow. Generally iterators override the increment and de-increment operators (++, --), in order to walk through the list.

If you really needed to, you could overload the arithmetic operators (+, -), with code like this:

Code:

---

iterator List::operator+(iterator pos, int index)
{
        for(size_t count = 0; count < index; count++)
        {
                pos++
        }
        return pos;
}

---

With that you could write the operator[] function fairly easily by starting with the beginning element of the list and adding the index. However I don't remember the syntax for that particular operator, so I'll leave that to you or someone else to look up.

Why not use a vector instead of a list?

I'm going to feel really silly if that was the answer he was looking for. I've been working on implementing a linked-list for the last month in my data structs class, so I just assumed people randomly rewrite basic containers for no reason.
/me heads off for a very long nap

Well, anyways if you do need some list-exclusive functionality, you can do the operator+ overloading if you're indexing only rarely, or you can use a vector and use a STL copy algorithm to transfer the vector to a list, use the list functionality and convert back to vector, if the list functionality is rarely needed (by rarely I mean 'once every half hour or more'). Of course, most of the time option (a) will be the better choice, especially if you have a lot of elements in the container, but if you don't need that list stuff, you might as well use a vector.

Actually, the thought just occurred to me that you might want to use a std::deque, since it's got indexing and still has most of the std::list stuff that you might want.

Thanks for the help!
I was thinking in something like:

Code:

---

int returnElement(list<int>& l, int index){
  return *(l.begin() + index);
}

---

But I'll use vectors.

>>I'm going to feel really silly if that was the answer he was looking for.
Has it started yet? :)