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//-----------------------------------------------------------------------------
// 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
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