//-----------------------------------------------------------------------------
 // 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"
 
 #if !defined(BOOST_NO_IOSTREAM)
 #include <iosfwd> // for std::basic_ostream forward declare
 #include "boost/detail/templated_streams.hpp"
 #endif // BOOST_NO_IOSTREAM
 
 #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
 //
 #if !defined(BOOST_NO_IOSTREAM)
 
 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;
 }
 
 #endif // BOOST_NO_IOSTREAM
 
 } // namespace boost
 
 #endif // BOOST_BLANK_HPP