williamr@2: //-----------------------------------------------------------------------------
williamr@2: // boost variant/static_visitor.hpp header file
williamr@2: // See http://www.boost.org for updates, documentation, and revision history.
williamr@2: //-----------------------------------------------------------------------------
williamr@2: //
williamr@2: // Copyright (c) 2002-2003
williamr@2: // Eric Friedman
williamr@2: //
williamr@2: // Distributed under the Boost Software License, Version 1.0. (See
williamr@2: // accompanying file LICENSE_1_0.txt or copy at
williamr@2: // http://www.boost.org/LICENSE_1_0.txt)
williamr@2: 
williamr@2: #ifndef BOOST_VARIANT_STATIC_VISITOR_HPP
williamr@2: #define BOOST_VARIANT_STATIC_VISITOR_HPP
williamr@2: 
williamr@2: #include "boost/config.hpp"
williamr@2: #include "boost/detail/workaround.hpp"
williamr@2: 
williamr@2: #include "boost/mpl/if.hpp"
williamr@2: #include "boost/type_traits/is_base_and_derived.hpp"
williamr@2: 
williamr@2: #if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
williamr@2: #   include "boost/type_traits/is_same.hpp"
williamr@2: #endif
williamr@2: 
williamr@2: // should be the last #include
williamr@2: #include "boost/type_traits/detail/bool_trait_def.hpp"
williamr@2: 
williamr@2: namespace boost {
williamr@2: 
williamr@2: //////////////////////////////////////////////////////////////////////////
williamr@2: // class template static_visitor
williamr@2: //
williamr@2: // An empty base class that typedefs the return type of a deriving static
williamr@2: // visitor. The class is analogous to std::unary_function in this role.
williamr@2: //
williamr@2: 
williamr@2: namespace detail {
williamr@2: 
williamr@2:     struct is_static_visitor_tag { };
williamr@2: 
williamr@2:     typedef void static_visitor_default_return;
williamr@2: 
williamr@2: } // namespace detail
williamr@2: 
williamr@2: template <typename R = ::boost::detail::static_visitor_default_return>
williamr@2: class static_visitor
williamr@2:     : public detail::is_static_visitor_tag
williamr@2: {
williamr@2: public: // typedefs
williamr@2: 
williamr@2:     typedef R result_type;
williamr@2: 
williamr@2: protected: // for use as base class only
williamr@2: 
williamr@2:     static_visitor() { }
williamr@2:     ~static_visitor() { }
williamr@2: 
williamr@2: };
williamr@2: 
williamr@2: //////////////////////////////////////////////////////////////////////////
williamr@2: // metafunction is_static_visitor
williamr@2: //
williamr@2: // Value metafunction indicates whether the specified type derives from
williamr@2: // static_visitor<...>.
williamr@2: //
williamr@2: // NOTE #1: This metafunction does NOT check whether the specified type
williamr@2: //  fulfills the requirements of the StaticVisitor concept.
williamr@2: //
williamr@2: // NOTE #2: This template never needs to be specialized!
williamr@2: //
williamr@2: 
williamr@2: namespace detail {
williamr@2: 
williamr@2: template <typename T>
williamr@2: struct is_static_visitor_impl
williamr@2: {
williamr@2:     BOOST_STATIC_CONSTANT(bool, value = 
williamr@2:         (::boost::is_base_and_derived< 
williamr@2:             detail::is_static_visitor_tag,
williamr@2:             T
williamr@2:         >::value));
williamr@2: };
williamr@2: 
williamr@2: } // namespace detail
williamr@2: 
williamr@2: BOOST_TT_AUX_BOOL_TRAIT_DEF1(
williamr@2:       is_static_visitor
williamr@2:     , T
williamr@2:     , (::boost::detail::is_static_visitor_impl<T>::value)
williamr@2:     )
williamr@2: 
williamr@2: } // namespace boost
williamr@2: 
williamr@2: #include "boost/type_traits/detail/bool_trait_undef.hpp"
williamr@2: 
williamr@2: #endif // BOOST_VARIANT_STATIC_VISITOR_HPP