Why does pushing an element on one of the ends of a std::deque invalidate all the existing iterators (All references remain valid though)?
I understand that deque is implemented as an array of arrays and that pushing an element on either end won't cause any reallocation of existing elements. And this is why references remain valid. But so should the iterators.
I also understand that the iterator of a deque is of type RandomAccessIterator and that this iterator should support some operations like adding/subtracting a constant number, ++, -- etc.
What I don't understand is that which of the operations that should be supported by RandomAccessIterator cannot be implemented by the underlying structure of std::deque.