Why doesn't my custom iterator work with the STL copy?

Question

I wrote an OutputIterator for an answer to another question. Here it is:

#include 

using namespace std;

template< typename T, typename U &g         


        

Answer 1

Your iterator doesn't meet the requirement for an 'assignable' type which is a requirement for an output iterator because it contains a reference and assignable types need to ensure that after t = u that t is equivalent to u.

You can provide a suitable specialization for iterator_traits for your iterator either by deriving from a specialization of std::iterator or by providing one explicitly.

namespace std
{
    template<> struct iterator_traits
    {
        typedef std::output_iterator_tag iterator_category;
        typedef void value_type;
        typedef void difference_type;
    };
}