#include <iostream>
    #include <iterator>
    #include <limits>
    #include <vector>


    template <typename T>
    struct iterator_extractor { typedef typename T::iterator type; };

    template <typename T>
    struct iterator_extractor<T const> { typedef typename T::const_iterator type; };


    template <typename T>
    class Indexer {
    public:
        class iterator {
            typedef typename iterator_extractor<T>::type inner_iterator;

            typedef typename std::iterator_traits<inner_iterator>::reference inner_reference;
        public:
            typedef std::pair<size_t, inner_reference> reference;

            iterator(inner_iterator it): _pos(0), _it(it) {}

            reference operator*() const { return reference(_pos, *_it); }

            iterator& operator++() { ++_pos; ++_it; return *this; }
            iterator operator++(int) { iterator tmp(*this); ++*this; return tmp; }

            bool operator==(iterator const& it) const { return _it == it._it; }
            bool operator!=(iterator const& it) const { return !(*this == it); }

        private:
            size_t _pos;
            inner_iterator _it;
        };

        Indexer(T& t): _container(t) {}

        iterator begin() const { return iterator(_container.begin()); }
        iterator end() const { return iterator(_container.end()); }

    private:
        T& _container;
    }; // class Indexer

    template <typename T>
    Indexer<T> index(T& t) { return Indexer<T>(t); }

    int main() {
        std::vector<int> v{1, 2, 3, 4, 5, 6, 7, 8, 9};

        auto in = index(v);

        for (auto it = in.begin(), end = in.end(); it != end; ++it) {
            auto p = *it;
            std::cout << p.first << ": " << p.second << "\n";
        }
    }