williamr@2: //-----------------------------------------------------------------------------
williamr@2: // boost variant/detail/enable_recursive_fwd.hpp header file
williamr@2: // See http://www.boost.org for updates, documentation, and revision history.
williamr@2: //-----------------------------------------------------------------------------
williamr@2: //
williamr@2: // Copyright (c) 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_DETAIL_ENABLE_RECURSIVE_FWD_HPP
williamr@2: #define BOOST_VARIANT_DETAIL_ENABLE_RECURSIVE_FWD_HPP
williamr@2: 
williamr@2: #include "boost/mpl/aux_/config/ctps.hpp"
williamr@2: 
williamr@2: #include "boost/mpl/bool_fwd.hpp"
williamr@2: 
williamr@2: #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
williamr@2: #   include "boost/mpl/bool.hpp"
williamr@2: #else
williamr@2: #   include "boost/type_traits/is_base_and_derived.hpp"
williamr@2: #endif
williamr@2: 
williamr@2: namespace boost {
williamr@2: namespace detail { namespace variant {
williamr@2: 
williamr@2: ///////////////////////////////////////////////////////////////////////////////
williamr@2: // (detail) tag recursive_flag
williamr@2: //
williamr@2: // Signifies that the variant should perform recursive substituion.
williamr@2: //
williamr@2: 
williamr@2: #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
williamr@2: 
williamr@2: template <typename T>
williamr@2: struct recursive_flag
williamr@2: {
williamr@2:     typedef T type;
williamr@2: };
williamr@2: 
williamr@2: #else // defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
williamr@2: 
williamr@2: struct recursive_flag_tag
williamr@2: {
williamr@2: };
williamr@2: 
williamr@2: template <typename T>
williamr@2: struct recursive_flag
williamr@2:     : recursive_flag_tag
williamr@2: {
williamr@2:     typedef T type;
williamr@2: };
williamr@2: 
williamr@2: #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION workaround
williamr@2: 
williamr@2: ///////////////////////////////////////////////////////////////////////////////
williamr@2: // (detail) metafunction is_recursive_flag
williamr@2: //
williamr@2: // Signifies that the variant should perform recursive substituion.
williamr@2: //
williamr@2: 
williamr@2: #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
williamr@2: 
williamr@2: template <typename T>
williamr@2: struct is_recursive_flag
williamr@2:     : mpl::false_
williamr@2: {
williamr@2: };
williamr@2: 
williamr@2: template <typename T>
williamr@2: struct is_recursive_flag< recursive_flag<T> >
williamr@2:     : mpl::true_
williamr@2: {
williamr@2: };
williamr@2: 
williamr@2: #else // defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
williamr@2: 
williamr@2: template <typename T>
williamr@2: struct is_recursive_flag
williamr@2:     : is_base_and_derived< recursive_flag_tag,T >
williamr@2: {
williamr@2: };
williamr@2: 
williamr@2: #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION workaround
williamr@2: 
williamr@2: ///////////////////////////////////////////////////////////////////////////////
williamr@2: // (detail) metafunction enable_recursive
williamr@2: //
williamr@2: // Attempts recursive_variant_ tag substitution, wrapping with
williamr@2: // boost::recursive_wrapper if substituion occurs w/ non-indirect result
williamr@2: // (i.e., not a reference or pointer) *and* NoWrapper is false_.
williamr@2: //
williamr@2: template <
williamr@2:       typename T
williamr@2:     , typename RecursiveVariant
williamr@2:     , typename NoWrapper = mpl::false_
williamr@2:     >
williamr@2: struct enable_recursive;
williamr@2: 
williamr@2: ///////////////////////////////////////////////////////////////////////////////
williamr@2: // (detail) metafunction class quoted_enable_recursive
williamr@2: //
williamr@2: // Same behavior as enable_recursive metafunction (see above).
williamr@2: //
williamr@2: template <
williamr@2:       typename RecursiveVariant
williamr@2:     , typename NoWrapper = mpl::false_
williamr@2:     >
williamr@2: struct quoted_enable_recursive;
williamr@2: 
williamr@2: }} // namespace detail::variant
williamr@2: } // namespace boost
williamr@2: 
williamr@2: #endif // BOOST_VARIANT_DETAIL_ENABLE_RECURSIVE_FWD_HPP