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116 lines
2.9 KiB
116 lines
2.9 KiB
//----------------------------------------------------------------------------- |
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// boost variant/detail/enable_recursive_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) 2003 |
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// Eric Friedman |
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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_DETAIL_ENABLE_RECURSIVE_FWD_HPP |
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#define BOOST_VARIANT_DETAIL_ENABLE_RECURSIVE_FWD_HPP |
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#include "boost/mpl/aux_/config/ctps.hpp" |
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#include "boost/mpl/bool_fwd.hpp" |
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#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) |
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# include "boost/mpl/bool.hpp" |
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#else |
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# include "boost/type_traits/is_base_and_derived.hpp" |
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#endif |
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namespace boost { |
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namespace detail { namespace variant { |
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/////////////////////////////////////////////////////////////////////////////// |
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// (detail) tag recursive_flag |
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// |
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// Signifies that the variant should perform recursive substituion. |
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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 recursive_flag |
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{ |
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typedef T type; |
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}; |
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#else // defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) |
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struct recursive_flag_tag |
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{ |
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}; |
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template <typename T> |
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struct recursive_flag |
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: recursive_flag_tag |
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{ |
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typedef T type; |
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}; |
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#endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION workaround |
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/////////////////////////////////////////////////////////////////////////////// |
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// (detail) metafunction is_recursive_flag |
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// |
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// Signifies that the variant should perform recursive substituion. |
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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 is_recursive_flag |
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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_flag< recursive_flag<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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template <typename T> |
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struct is_recursive_flag |
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: is_base_and_derived< recursive_flag_tag,T > |
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{ |
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}; |
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#endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION workaround |
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/////////////////////////////////////////////////////////////////////////////// |
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// (detail) metafunction enable_recursive |
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// |
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// Attempts recursive_variant_ tag substitution, wrapping with |
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// boost::recursive_wrapper if substituion occurs w/ non-indirect result |
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// (i.e., not a reference or pointer) *and* NoWrapper is false_. |
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// |
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template < |
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typename T |
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, typename RecursiveVariant |
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, typename NoWrapper = mpl::false_ |
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> |
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struct enable_recursive; |
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/////////////////////////////////////////////////////////////////////////////// |
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// (detail) metafunction class quoted_enable_recursive |
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// |
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// Same behavior as enable_recursive metafunction (see above). |
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// |
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template < |
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typename RecursiveVariant |
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, typename NoWrapper = mpl::false_ |
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> |
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struct quoted_enable_recursive; |
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}} // namespace detail::variant |
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} // namespace boost |
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#endif // BOOST_VARIANT_DETAIL_ENABLE_RECURSIVE_FWD_HPP
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