Paul Elliott writes:

I am trying to figure out iterators and I have a dumb question: I have an iterator A_iter, that can traverse in both directions ( A_iter++ and A_iter-- ) and can do input (operator*()). Value_type = type of *A_iter is A;

and A is static_cast able to B:

A start; B fish = static_cast<B>(start); // OK

How do I use adapters to create B_iter, which is the same as A_iter, but whose value_type= typeof *B_iter is B?

I am sorry if this is a dumb question.

Your question isn't dumb, but it's incomplete. It's not clear how you want the B_iter to produce Bs from the As that A_iter yields. The message subject indicates you intend to use dynamic_cast. I assume if you care about dynamic_cast that B must be derived from A, but if the type of *A_iter is A (and not A&), you won't be able to dynamic_cast down to B. Same goes for static_cast, which might compile but will produce undefined behavior from downcasting if you start with an A. Aside from those considerations, you should be able to simply use transform_iterator with a function or function object that does the desired cast. -- Dave Abrahams Boost Consulting www.boost-consulting.com