//-----------------------------------------------------------------------------

// boost blank.hpp header file

// See http://www.boost.org for updates, documentation, and revision history.

//-----------------------------------------------------------------------------

//

// Copyright (c) 2003

// Eric Friedman

//

// 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)

#ifndef BOOST_BLANK_HPP

#define BOOST_BLANK_HPP

#include "boost/blank_fwd.hpp"

#include <iosfwd> // for std::basic_ostream forward declare

#include "boost/detail/templated_streams.hpp"

#include "boost/mpl/bool.hpp"

#include "boost/type_traits/is_empty.hpp"

#include "boost/type_traits/is_pod.hpp"

#include "boost/type_traits/is_stateless.hpp"

namespace boost {

struct blank

{

};

// type traits specializations

//

template <>

struct is_pod< blank >

    : mpl::true_

{

};

template <>

struct is_empty< blank >

    : mpl::true_

{

};

template <>

struct is_stateless< blank >

    : mpl::true_

{

};

// relational operators

//

inline bool operator==(const blank&, const blank&)

{

    return true;

}

inline bool operator<=(const blank&, const blank&)

{

    return true;

}

inline bool operator>=(const blank&, const blank&)

{

    return true;

}

inline bool operator!=(const blank&, const blank&)

{

    return false;

}

inline bool operator<(const blank&, const blank&)

{

    return false;

}

inline bool operator>(const blank&, const blank&)

{

    return false;

}

// streaming support

//

BOOST_TEMPLATED_STREAM_TEMPLATE(E,T)

inline BOOST_TEMPLATED_STREAM(ostream, E,T)& operator<<(

      BOOST_TEMPLATED_STREAM(ostream, E,T)& out

    , const blank&

    )

{

    // (output nothing)

    return out;

}

} // namespace boost

#endif // BOOST_BLANK_HPP