//Following copied then maybe modifed from:
/*
From: Jeremiah Willcock <jewillco@osl.iu.edu>
Newsgroups: gmane.comp.lib.boost.user
Subject: Re: challange to MPL gurus
Date: Mon, 12 Dec 2011 17:39:44 -0500 (EST)
 */
#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 I, typename B>
struct check_unless_end {};

template <typename I>
struct check_unless_end<I, boost::mpl::false_> {
  typedef typename boost::mpl::deref<I>::type t1;
  typedef typename boost::mpl::next<I>::type t2;
  BOOST_CONCEPT_ASSERT(( ForwardIterator<t2> ));
};

template<typename I>
struct ForwardIterator {
  #if 1
    typedef typename boost::mpl::print<
        I
    >::type t1;
  #endif
    typedef check_unless_end<
        I,
        boost::is_same<
            boost::mpl::l_iter<boost::mpl::l_end>,
            I
        >
    > t2;
    BOOST_MPL_ASSERT((
            boost::is_convertible<
                typename I::category,
                boost::mpl::forward_iterator_tag
            >
    ));
};

template<typename S>
struct ForwardSequence {
  typedef typename boost::mpl::end<S>::type t2;
  BOOST_CONCEPT_ASSERT(( ForwardIterator<t2> ));
};

#include <boost/mpl/list.hpp>
void test_list_sequence(){
    BOOST_CONCEPT_ASSERT(( ForwardSequence<
            boost::mpl::list<int, char>
        >
    ));
}

}}