How is STL iterator equality established?

Question

I was wondering, how is equality (==) established for STL iterators? Is it a simple pointer comparison (and thus based on addresses) or something more fancy?

If I have t

Answer 1

The equality test is specific to the type of iterator you are using, or may not exist at all. If you really want to know, you can always check the source code of the implementation of STL you are using, look for operator==() in the iterator class.

Iterators are NOT always pointers, and indeed in some "safe" versions of the STL, are never pointers. Iterators for vectors and strings are commonly implemented as pointers because they can be. Iterators for deques, lists, sets and maps cannot be pointers in any half efficient implementation.

What iterators are is a type of smart pointer. They follow the generic principle that if they look and behave like a pointer, then they are a pointer as far as the user is concerned.