#ifndef BOOST_MPL_VOID_HPP_INCLUDED

 #define BOOST_MPL_VOID_HPP_INCLUDED

 // Copyright Aleksey Gurtovoy 2001-2004

 //

 // 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.

 // $Source: /cvsroot/boost/boost/boost/mpl/void.hpp,v $

 // $Date: 2004/09/02 15:40:42 $

 // $Revision: 1.9 $

 #include <boost/mpl/void_fwd.hpp>

 #include <boost/mpl/bool.hpp>

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

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

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

 BOOST_MPL_AUX_ADL_BARRIER_NAMESPACE_OPEN

 //  [JDG Feb-4-2003] made void_ a complete type to allow it to be

 //  instantiated so that it can be passed in as an object that can be

 //  used to select an overloaded function. Possible use includes signaling

 //  a zero arity functor evaluation call.

 struct void_ { typedef void_ type; };

 BOOST_MPL_AUX_ADL_BARRIER_NAMESPACE_CLOSE

 namespace boost { namespace mpl {

 template< typename T >

 struct is_void_

     : false_

 {

 #if BOOST_WORKAROUND(BOOST_MSVC, < 1300)

     using false_::value;

 #endif

 };

 template<>

 struct is_void_<void_>

     : true_

 {

 #if BOOST_WORKAROUND(BOOST_MSVC, < 1300)

     using true_::value;

 #endif

 };

 template< typename T >

 struct is_not_void_

     : true_

 {

 #if BOOST_WORKAROUND(BOOST_MSVC, < 1300)

     using true_::value;

 #endif

 };

 template<>

 struct is_not_void_<void_>

     : false_

 {

 #if BOOST_WORKAROUND(BOOST_MSVC, < 1300)

     using false_::value;

 #endif

 };

 BOOST_MPL_AUX_NA_SPEC(1, is_void_)

 BOOST_MPL_AUX_NA_SPEC(1, is_not_void_)

 }}

 #endif // BOOST_MPL_VOID_HPP_INCLUDED