//The following copied from:
/*
From: "Robert Ramey" <ramey@rrsd.com>
Newsgroups: gmane.comp.lib.boost.user
Subject: Re: challange to MPL gurus
Date: Mon, 12 Dec 2011 20:49:37 -0800
 */
#include <boost/mpl/list.hpp>
#include <boost/mpl/deref.hpp>
#include <boost/mpl/next.hpp>
#include <boost/mpl/begin_end.hpp>
#include <boost/mpl/print.hpp>
#include <boost/mpl/assert.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/type_traits/is_convertible.hpp>
#include <boost/concept/assert.hpp>

namespace boost{namespace mpl{
template<typename I>
struct ForwardIterator {
    template<typename, typename>
    struct is_end {};

    template<typename I2>
    struct is_end<I2, false_> {
        typedef typename deref<I2>::type t1;
        typedef typename next<I2>::type t2;
        BOOST_CONCEPT_ASSERT(( ForwardIterator<t2> ));
    };

    typedef typename is_end<
        I,
        typename boost::is_same<
            boost::mpl::l_iter<boost::mpl::l_end>,
            I
        >
    > type;
    typedef typename boost::mpl::print<
        I
    >::type t1;

    BOOST_MPL_ASSERT((
        is_convertible<
            typename I::category,
            forward_iterator_tag
        >
    ));
};

}}