Obtaining const_iterator from iterator

Question

Is there a metafunction f that maps an iterator to its corresponding const_iterator?

I.e. f::ite

Answer 1

I don't think this is possible since there is often no well-defined mapping between iterator types. E.g., two containers could share the non-const iterator type, but have different const iterators. In general you can only map from container types to iterator types, but not between iterator types or from an iterator type to a container type.