How to restrict an iterator to being a forward iterator?

Question

I have a function that needs to enumerate an iterator multiple times, but according to MSDN, \"Once you increment any copy of an input iterator, none of the other copies can

Answer 1

Not tested but you could try something along the lines of:

template
bool EnumerateTwice_Interal(const It &begin, const It &end, TCallback callback, 
      std::forward_iterator_tag)
{
     //do your things
}

template
bool EnumerateTwice(const It &begin, const It &end, TCallback callback)
{
    EnumerateTwice_Internal(begin, end, callback,
        typename std::iterator_traits::iterator_category());
}