| //----------------------------------------------------------------------------- |
| // boost variant/recursive_wrapper_fwd.hpp header file |
| // See http://www.boost.org for updates, documentation, and revision history. |
| //----------------------------------------------------------------------------- |
| // |
| // Copyright (c) 2002 |
| // Eric Friedman, Itay Maman |
| // |
| // Portions Copyright (C) 2002 David Abrahams |
| // |
| // 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_RECURSIVE_WRAPPER_FWD_HPP |
| #define BOOST_VARIANT_RECURSIVE_WRAPPER_FWD_HPP |
| |
| #include "boost/mpl/aux_/config/ctps.hpp" |
| #if defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) |
| # include "boost/mpl/eval_if.hpp" |
| # include "boost/mpl/bool.hpp" |
| # include "boost/mpl/identity.hpp" |
| # include "boost/type.hpp" |
| #endif |
| |
| #include "boost/mpl/aux_/lambda_support.hpp" |
| |
| // should be the last #include |
| #include "boost/type_traits/detail/bool_trait_def.hpp" |
| |
| namespace boost { |
| |
| ////////////////////////////////////////////////////////////////////////// |
| // class template recursive_wrapper |
| // |
| // Enables recursive types in templates by breaking cyclic dependencies. |
| // |
| // For example: |
| // |
| // class my; |
| // |
| // typedef variant< int, recursive_wrapper<my> > var; |
| // |
| // class my { |
| // var var_; |
| // ... |
| // }; |
| // |
| template <typename T> class recursive_wrapper; |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| // metafunction is_recursive_wrapper (modeled on code by David Abrahams) |
| // |
| // True iff specified type matches recursive_wrapper<T>. |
| // |
| |
| namespace detail { |
| |
| #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) |
| |
| template <typename T> |
| struct is_recursive_wrapper_impl |
| : mpl::false_ |
| { |
| }; |
| |
| template <typename T> |
| struct is_recursive_wrapper_impl< recursive_wrapper<T> > |
| : mpl::true_ |
| { |
| }; |
| |
| #else // defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) |
| |
| typedef char (&yes_recursive_wrapper_t)[1]; |
| typedef char (&no_recursive_wrapper_t)[2]; |
| |
| no_recursive_wrapper_t is_recursive_wrapper_test(...); |
| |
| template<typename T> |
| yes_recursive_wrapper_t is_recursive_wrapper_test( |
| type< ::boost::recursive_wrapper<T> > |
| ); |
| |
| template<typename T> |
| struct is_recursive_wrapper_impl |
| { |
| BOOST_STATIC_CONSTANT(bool, value = ( |
| sizeof(is_recursive_wrapper_test(type<T>())) |
| == sizeof(yes_recursive_wrapper_t) |
| )); |
| }; |
| |
| #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION workaround |
| |
| } // namespace detail |
| |
| BOOST_TT_AUX_BOOL_TRAIT_DEF1( |
| is_recursive_wrapper |
| , T |
| , (::boost::detail::is_recursive_wrapper_impl<T>::value) |
| ) |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| // metafunction unwrap_recursive |
| // |
| // If specified type T matches recursive_wrapper<U>, then U; else T. |
| // |
| |
| #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) |
| |
| template <typename T> |
| struct unwrap_recursive |
| { |
| typedef T type; |
| |
| BOOST_MPL_AUX_LAMBDA_SUPPORT(1,unwrap_recursive,(T)) |
| }; |
| |
| template <typename T> |
| struct unwrap_recursive< recursive_wrapper<T> > |
| { |
| typedef T type; |
| |
| BOOST_MPL_AUX_LAMBDA_SUPPORT_SPEC(1,unwrap_recursive,(T)) |
| }; |
| |
| #else // defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) |
| |
| template <typename T> |
| struct unwrap_recursive |
| : mpl::eval_if< |
| is_recursive_wrapper<T> |
| , T |
| , mpl::identity< T > |
| > |
| { |
| BOOST_MPL_AUX_LAMBDA_SUPPORT(1,unwrap_recursive,(T)) |
| }; |
| |
| #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION workaround |
| |
| } // namespace boost |
| |
| #include "boost/type_traits/detail/bool_trait_undef.hpp" |
| |
| #endif // BOOST_VARIANT_RECURSIVE_WRAPPER_FWD_HPP |