Reverse Iterator not working as expected

Question

I am using a reverse iterator on a std::vector and according to the following link:

http://www.cplusplus.com/reference/stl/vector/rbegin/

myVector.rbegin() is the last element of the vector. In my case, I am actually getting the past the end iterator on rbegin() and the fist element from rend() . I would have expected rend() to give me past the end iterator and rbegin() to give me the last element in the container. Did I understand the whole thing wrong?

The following is my code, nothing special. I put a break point just after the assignments, and the above is the result I am getting in the debugger ( VecDebugCubes is a type define for a std::vector<myStructure> )

VecDebugCubes::reverse_iterator itr    = pActiveDebugCubes.rbegin();
VecDebugCubes::reverse_iterator itrEnd = pActiveDebugCubes.rend();
while (itr != itrEnd)
{
  (*itr)->printDebugValues();
  ++itr;
}

Answer 1

See http://www.cplusplus.com/reference/std/iterator/reverse_iterator/base/ .

Dereferencing a reverse iterator will return a different value than the one that you see it pointing to in your debugger.

Answer 2

past the end for rbegin() and the first element for rend() is how the iterator is supposed to work. That's why it's called a reverse iterator. It's designed such that you can use it in a for loop without having to bother about making a mistake about the start and end points of the range. You'll notice that a simple i++ can be used for the iterator, and the iterator actually iterates backward on the range. I guess all you need to know is, that that's how it is supposed to work. There's nothing wrong. It just makes your life easier since you're less likely to make a mistake while writing for(i=beginAtTheEnd to finishAtTheStart and decrement-i-in-the-same-way-as-i++) rather than having for(i=10;i>0;i--) , where you might make the mistake of putting i<0 or i>1 in the condition. This is a simplified example. You'll appreciate it more when you want to reverse iterate on a container.