//----------------------------------------------------------------------------- | |
// 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 |