#ifndef BOOST_MPL_AUX_SINGLE_ELEMENT_ITER_HPP_INCLUDED

#define BOOST_MPL_AUX_SINGLE_ELEMENT_ITER_HPP_INCLUDED

// Copyright Aleksey Gurtovoy 2000-2004

//

// Distributed under the Boost Software License, Version 1.0. 

// (See accompanying file LICENSE_1_0.txt or copy at 

// http://www.boost.org/LICENSE_1_0.txt)

//

// See http://www.boost.org/libs/mpl for documentation.

// $Id: single_element_iter.hpp 49267 2008-10-11 06:19:02Z agurtovoy $

// $Date: 2008-10-11 02:19:02 -0400 (Sat, 11 Oct 2008) $

// $Revision: 49267 $

#include <boost/mpl/iterator_tags.hpp>

#include <boost/mpl/advance_fwd.hpp>

#include <boost/mpl/distance_fwd.hpp>

#include <boost/mpl/next_prior.hpp>

#include <boost/mpl/deref.hpp>

#include <boost/mpl/int.hpp>

#include <boost/mpl/aux_/nttp_decl.hpp>

#include <boost/mpl/aux_/value_wknd.hpp>

#include <boost/mpl/aux_/config/ctps.hpp>

namespace boost { namespace mpl { 

#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)

namespace aux {

template< typename T, BOOST_MPL_AUX_NTTP_DECL(int, is_last_) >

struct sel_iter;

template< typename T >

struct sel_iter<T,0>

{

    typedef random_access_iterator_tag category;

    typedef sel_iter<T,1> next;

    typedef T type;

};

template< typename T >

struct sel_iter<T,1>

{

    typedef random_access_iterator_tag category;

    typedef sel_iter<T,0> prior;

};

} // namespace aux

template< typename T, BOOST_MPL_AUX_NTTP_DECL(int, is_last_), typename Distance >

struct advance< aux::sel_iter<T,is_last_>,Distance>

{

    typedef aux::sel_iter<

          T

        , ( is_last_ + BOOST_MPL_AUX_NESTED_VALUE_WKND(int, Distance) )

        > type;

};

template< 

      typename T

    , BOOST_MPL_AUX_NTTP_DECL(int, l1)

    , BOOST_MPL_AUX_NTTP_DECL(int, l2) 

    >

struct distance< aux::sel_iter<T,l1>, aux::sel_iter<T,l2> >

    : int_<( l2 - l1 )>

{

};

#else

namespace aux {

struct sel_iter_tag;

template< typename T, BOOST_MPL_AUX_NTTP_DECL(int, is_last_) >

struct sel_iter

{

    enum { pos_ = is_last_ };

    typedef aux::sel_iter_tag tag;

    typedef random_access_iterator_tag category;

    typedef sel_iter<T,(is_last_ + 1)> next;

    typedef sel_iter<T,(is_last_ - 1)> prior;

    typedef T type;

};

} // namespace aux

template<> struct advance_impl<aux::sel_iter_tag>

{

    template< typename Iterator, typename N > struct apply

    {

        enum { pos_ = Iterator::pos_, n_ = N::value };

        typedef aux::sel_iter<

              typename Iterator::type

            , (pos_ + n_)

            > type;

    };

};

template<> struct distance_impl<aux::sel_iter_tag>

{

    template< typename Iter1, typename Iter2 > struct apply

    {

        enum { pos1_ = Iter1::pos_, pos2_ = Iter2::pos_ };

        typedef int_<( pos2_ - pos1_ )> type;

        BOOST_STATIC_CONSTANT(int, value = ( pos2_ - pos1_ ));

    };

};

#endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION

}}

#endif // BOOST_MPL_AUX_SINGLE_ELEMENT_ITER_HPP_INCLUDED