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

// boost variant/static_visitor.hpp header file

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

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

//

// Copyright (c) 2002-2003

// 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_VARIANT_STATIC_VISITOR_HPP

#define BOOST_VARIANT_STATIC_VISITOR_HPP



#include "boost/config.hpp"

#include "boost/detail/workaround.hpp"



#include "boost/mpl/if.hpp"

#include "boost/type_traits/is_base_and_derived.hpp"



#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)

#   include "boost/type_traits/is_same.hpp"

#endif



// should be the last #include

#include "boost/type_traits/detail/bool_trait_def.hpp"



namespace boost {



//////////////////////////////////////////////////////////////////////////

// class template static_visitor

//

// An empty base class that typedefs the return type of a deriving static

// visitor. The class is analogous to std::unary_function in this role.

//



namespace detail {



    struct is_static_visitor_tag { };



    typedef void static_visitor_default_return;



} // namespace detail



template <typename R = ::boost::detail::static_visitor_default_return>

class static_visitor

    : public detail::is_static_visitor_tag

{

public: // typedefs



    typedef R result_type;



protected: // for use as base class only



    static_visitor() { }

    ~static_visitor() { }



};



//////////////////////////////////////////////////////////////////////////

// metafunction is_static_visitor

//

// Value metafunction indicates whether the specified type derives from

// static_visitor<...>.

//

// NOTE #1: This metafunction does NOT check whether the specified type

//  fulfills the requirements of the StaticVisitor concept.

//

// NOTE #2: This template never needs to be specialized!

//



namespace detail {



template <typename T>

struct is_static_visitor_impl

{

    BOOST_STATIC_CONSTANT(bool, value = 

        (::boost::is_base_and_derived< 

            detail::is_static_visitor_tag,

            T

        >::value));

};



} // namespace detail



BOOST_TT_AUX_BOOL_TRAIT_DEF1(

      is_static_visitor

    , T

    , (::boost::detail::is_static_visitor_impl<T>::value)

    )



} // namespace boost



#include "boost/type_traits/detail/bool_trait_undef.hpp"



#endif // BOOST_VARIANT_STATIC_VISITOR_HPP

