Chris@16: //-----------------------------------------------------------------------------
Chris@16: // boost variant/recursive_wrapper_fwd.hpp header file
Chris@16: // See http://www.boost.org for updates, documentation, and revision history.
Chris@16: //-----------------------------------------------------------------------------
Chris@16: //
Chris@16: // Copyright (c) 2002
Chris@16: // Eric Friedman, Itay Maman
Chris@16: //
Chris@16: // Portions Copyright (C) 2002 David Abrahams
Chris@16: //
Chris@16: // Distributed under the Boost Software License, Version 1.0. (See
Chris@16: // accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: #ifndef BOOST_VARIANT_RECURSIVE_WRAPPER_FWD_HPP
Chris@16: #define BOOST_VARIANT_RECURSIVE_WRAPPER_FWD_HPP
Chris@16: 
Chris@16: #include "boost/mpl/aux_/config/ctps.hpp"
Chris@16: 
Chris@16: #include "boost/mpl/aux_/lambda_support.hpp"
Chris@16: 
Chris@16: // should be the last #include
Chris@16: #include "boost/type_traits/detail/bool_trait_def.hpp"
Chris@16: 
Chris@16: namespace boost {
Chris@16: 
Chris@16: //////////////////////////////////////////////////////////////////////////
Chris@16: // class template recursive_wrapper
Chris@16: //
Chris@16: // Enables recursive types in templates by breaking cyclic dependencies.
Chris@16: //
Chris@16: // For example:
Chris@16: //
Chris@16: //   class my;
Chris@16: //
Chris@16: //   typedef variant< int, recursive_wrapper<my> > var;
Chris@16: //
Chris@16: //   class my {
Chris@16: //     var var_;
Chris@16: //     ...
Chris@16: //   };
Chris@16: //
Chris@16: template <typename T> class recursive_wrapper;
Chris@16: 
Chris@16: ///////////////////////////////////////////////////////////////////////////////
Chris@16: // metafunction is_recursive_wrapper (modeled on code by David Abrahams)
Chris@16: //
Chris@16: // True iff specified type matches recursive_wrapper<T>.
Chris@16: //
Chris@16: 
Chris@16: namespace detail {
Chris@16: 
Chris@16: 
Chris@16: template <typename T>
Chris@16: struct is_recursive_wrapper_impl
Chris@16:     : mpl::false_
Chris@16: {
Chris@16: };
Chris@16: 
Chris@16: template <typename T>
Chris@16: struct is_recursive_wrapper_impl< recursive_wrapper<T> >
Chris@16:     : mpl::true_
Chris@16: {
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: } // namespace detail
Chris@16: 
Chris@16: BOOST_TT_AUX_BOOL_TRAIT_DEF1(
Chris@16:       is_recursive_wrapper
Chris@16:     , T
Chris@16:     , (::boost::detail::is_recursive_wrapper_impl<T>::value)
Chris@16:     )
Chris@16: 
Chris@16: ///////////////////////////////////////////////////////////////////////////////
Chris@16: // metafunction unwrap_recursive
Chris@16: //
Chris@16: // If specified type T matches recursive_wrapper<U>, then U; else T.
Chris@16: //
Chris@16: 
Chris@16: 
Chris@16: template <typename T>
Chris@16: struct unwrap_recursive
Chris@16: {
Chris@16:     typedef T type;
Chris@16: 
Chris@16:     BOOST_MPL_AUX_LAMBDA_SUPPORT(1,unwrap_recursive,(T))
Chris@16: };
Chris@16: 
Chris@16: template <typename T>
Chris@16: struct unwrap_recursive< recursive_wrapper<T> >
Chris@16: {
Chris@16:     typedef T type;
Chris@16: 
Chris@16:     BOOST_MPL_AUX_LAMBDA_SUPPORT_SPEC(1,unwrap_recursive,(T))
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #include "boost/type_traits/detail/bool_trait_undef.hpp"
Chris@16: 
Chris@16: #endif // BOOST_VARIANT_RECURSIVE_WRAPPER_FWD_HPP