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What is a good way to create both an iterator and a const iterator while only having to specify all my custom behavior once?

Maybe template your iterator on the base iterator, and dispatching when necessary depending on whether that base iterator is the const iterator or the mutable iterator? E.g.,

template< class Base > struct my_iterator   : boost::iterator_adaptor< Base > { };

typedef my_iterator< base_iterator > iterator;

typedef my_iterator< base_const_iterator > const_iterator;

More generally, template your iterator on whatever types will be different between the mutable and const versions (value type, reference type, etc.) The libstdc++ implementation of std::deque::iterator is an instructive example for doing this sort of thing. Regards, Nate