//-----------------------------------------------------------------------------
// boost mpl/is_placeholder.hpp header file
// See http://www.boost.org for updates, documentation, and revision history.
//-----------------------------------------------------------------------------
//
// Copyright (c) 2001-02
// Aleksey Gurtovoy
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee, 
// provided that the above copyright notice appears in all copies and 
// that both the copyright notice and this permission notice appear in 
// supporting documentation. No representations are made about the 
// suitability of this software for any purpose. It is provided "as is" 
// without express or implied warranty.

#ifndef BOOST_MPL_IS_PLACEHOLDER_HPP_INCLUDED
#define BOOST_MPL_IS_PLACEHOLDER_HPP_INCLUDED

#include "boost/mpl/arg_fwd.hpp"
#include "boost/mpl/bool.hpp"
#include "boost/mpl/aux_/yes_no.hpp"
#include "boost/mpl/aux_/config/ctps.hpp"
#include "boost/mpl/aux_/config/nttp.hpp"

namespace boost { namespace mpl {

#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)

template< typename T >
struct is_placeholder
    : bool_<false>
{
};

template< BOOST_MPL_AUX_NTTP_DECL(int, N) >
struct is_placeholder< arg<N> >
    : bool_<true>
{
};

#else

namespace aux {

aux::no_tag is_placeholder_helper(...);

template< BOOST_MPL_AUX_NTTP_DECL(int, N) >
aux::yes_tag is_placeholder_helper(arg<N>*);

} // namespace aux

template< typename T >
struct is_placeholder
{
    BOOST_STATIC_CONSTANT(bool, value = 
        sizeof(aux::is_placeholder_helper(static_cast<T*>(0))) == sizeof(aux::yes_tag)
    );
};

#endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION

}} // namespace boost::mpl

#endif // BOOST_MPL_IS_PLACEHOLDER_HPP_INCLUDED