Is end() required to be constant in an STL map/set?

Question

§23.1.2.8 in the standard states that insertion/deletion operations on a set/map will not invalidate any iterators to those objects (except iterators pointing to a deleted eleme

Answer 1

I believe that this depends entirely on what type of iterator is being used.

In a vector, end() is the one past the end pointer and it will obviously change as elements are inserted and removed.

In another kind of container, the end() iterator might be a special value like NULL or a default constructed element. In this case it doesn't change because it doesn't point at anything. Instead of being a pointer-like thing, end() is just a value to compare against.

I believe that set and map iterators are the second kind, but I don't know of anything that requires them to be implemented in that way.