148 lines
3.6 KiB
C++
148 lines
3.6 KiB
C++
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//-----------------------------------------------------------------------------
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// boost variant/recursive_wrapper_fwd.hpp header file
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// See http://www.boost.org for updates, documentation, and revision history.
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//-----------------------------------------------------------------------------
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//
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// Copyright (c) 2002
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// Eric Friedman, Itay Maman
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//
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// Portions Copyright (C) 2002 David Abrahams
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//
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_VARIANT_RECURSIVE_WRAPPER_FWD_HPP
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#define BOOST_VARIANT_RECURSIVE_WRAPPER_FWD_HPP
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#include "boost/mpl/aux_/config/ctps.hpp"
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#if defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
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# include "boost/mpl/eval_if.hpp"
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# include "boost/mpl/bool.hpp"
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# include "boost/mpl/identity.hpp"
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# include "boost/type.hpp"
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#endif
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#include "boost/mpl/aux_/lambda_support.hpp"
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// should be the last #include
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#include "boost/type_traits/detail/bool_trait_def.hpp"
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namespace boost {
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//////////////////////////////////////////////////////////////////////////
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// class template recursive_wrapper
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//
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// Enables recursive types in templates by breaking cyclic dependencies.
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//
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// For example:
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//
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// class my;
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//
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// typedef variant< int, recursive_wrapper<my> > var;
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//
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// class my {
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// var var_;
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// ...
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// };
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//
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template <typename T> class recursive_wrapper;
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///////////////////////////////////////////////////////////////////////////////
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// metafunction is_recursive_wrapper (modeled on code by David Abrahams)
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//
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// True iff specified type matches recursive_wrapper<T>.
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//
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namespace detail {
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#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
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template <typename T>
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struct is_recursive_wrapper_impl
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: mpl::false_
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{
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};
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template <typename T>
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struct is_recursive_wrapper_impl< recursive_wrapper<T> >
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: mpl::true_
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{
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};
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#else // defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
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typedef char (&yes_recursive_wrapper_t)[1];
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typedef char (&no_recursive_wrapper_t)[2];
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no_recursive_wrapper_t is_recursive_wrapper_test(...);
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template<typename T>
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yes_recursive_wrapper_t is_recursive_wrapper_test(
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type< ::boost::recursive_wrapper<T> >
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);
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template<typename T>
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struct is_recursive_wrapper_impl
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{
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BOOST_STATIC_CONSTANT(bool, value = (
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sizeof(is_recursive_wrapper_test(type<T>()))
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== sizeof(yes_recursive_wrapper_t)
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));
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};
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#endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION workaround
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} // namespace detail
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BOOST_TT_AUX_BOOL_TRAIT_DEF1(
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is_recursive_wrapper
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, T
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, (::boost::detail::is_recursive_wrapper_impl<T>::value)
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)
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///////////////////////////////////////////////////////////////////////////////
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// metafunction unwrap_recursive
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//
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// If specified type T matches recursive_wrapper<U>, then U; else T.
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//
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#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
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template <typename T>
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struct unwrap_recursive
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{
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typedef T type;
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BOOST_MPL_AUX_LAMBDA_SUPPORT(1,unwrap_recursive,(T))
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};
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template <typename T>
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struct unwrap_recursive< recursive_wrapper<T> >
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{
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typedef T type;
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BOOST_MPL_AUX_LAMBDA_SUPPORT_SPEC(1,unwrap_recursive,(T))
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};
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#else // defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
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template <typename T>
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struct unwrap_recursive
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: mpl::eval_if<
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is_recursive_wrapper<T>
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, T
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, mpl::identity< T >
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>
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{
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BOOST_MPL_AUX_LAMBDA_SUPPORT(1,unwrap_recursive,(T))
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};
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#endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION workaround
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} // namespace boost
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#include "boost/type_traits/detail/bool_trait_undef.hpp"
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#endif // BOOST_VARIANT_RECURSIVE_WRAPPER_FWD_HPP
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