derive from STL's set::iterator

[corcor]

Hi !

deriving from list::iterator and vector::iterator is no problem, but how can I derive from set::iterator ?

I've tried

template < class T, class Pred = less<T>, class A = allocator< T > > 
class MySetIt : public set< T, Pred, A >::iterator
{
};

set< CString* > s;
MySetIt< CString* > it;
it = s.begin(); // <= Compile error C2440

and always get the compile error C2440 (cannot convert from ... to ...)

How can I derive the iterator ?
which constructor do I have to provide ?

Thanks !!