#ifndef BOOST_MPL_INDEX_IF_HPP_INCLUDED

#define BOOST_MPL_INDEX_IF_HPP_INCLUDED

// Copyright Eric Friedman 2003

//

// 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.

// $Id$

// $Date$

// $Revision$

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

#include <boost/mpl/begin_end.hpp>

#include <boost/mpl/if.hpp>

#include <boost/mpl/int.hpp>

#include <boost/mpl/iter_fold_if.hpp>

#include <boost/mpl/next.hpp>

#include <boost/mpl/void.hpp>

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

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

#include <boost/type_traits/is_same.hpp>

namespace boost { namespace mpl {

template<

      typename BOOST_MPL_AUX_NA_PARAM(Sequence)

    , typename BOOST_MPL_AUX_NA_PARAM(Predicate)

    >

struct index_if

{

    typedef typename iter_fold_if<

          Sequence

        , int_<0>

        , next<>

        , aux::find_if_pred<Predicate>

        >::type result_;

    typedef typename end<Sequence>::type not_found_;

    typedef typename first<result_>::type result_index_;

    typedef typename second<result_>::type result_iterator_;

    typedef typename if_<

          is_same< result_iterator_,not_found_ >

        , void_

        , result_index_

        >::type type;

    BOOST_MPL_AUX_LAMBDA_SUPPORT(2,index_if,(Sequence,Predicate))

};

BOOST_MPL_AUX_NA_SPEC(2, index_if)

}}

#endif // BOOST_MPL_INDEX_IF_HPP_INCLUDED