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147 lines
3.6 KiB
147 lines
3.6 KiB
//----------------------------------------------------------------------------- |
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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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