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/*=============================================================================
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Copyright (c) 2002-2003 Joel de Guzman
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Copyright (c) 2002-2003 Hartmut Kaiser
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http://spirit.sourceforge.net/
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Use, modification and distribution is subject to the Boost Software
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License, Version 1.0. (See 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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=============================================================================*/
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#if !defined(BOOST_SPIRIT_TRAVERSE_HPP)
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#define BOOST_SPIRIT_TRAVERSE_HPP
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#include <boost/spirit/meta/impl/traverse.ipp>
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namespace boost { namespace spirit
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{
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///////////////////////////////////////////////////////////////////////////
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//
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// Post-order traversal of auxilliary parsers.
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//
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///////////////////////////////////////////////////////////////////////////
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struct post_order
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{
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// Return the parser type, which is generated as the result of the
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// traverse function below.
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template <typename MetaT, typename ParserT>
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struct result
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{
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typedef typename
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traverse_post_order_return<
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MetaT
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, ParserT
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, traverse_post_order_env<0, 0, 0, 0>
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>::type
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type;
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};
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// Traverse a given parser and refactor it with the help of the given
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// MetaT metafunction template.
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template <typename MetaT, typename ParserT>
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static typename result<MetaT, ParserT>::type
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traverse(MetaT const &meta_, ParserT const &parser_)
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{
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typedef typename ParserT::parser_category_t parser_category_t;
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return impl::traverse_post_order<parser_category_t>::generate(
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meta_, parser_, traverse_post_order_env<0, 0, 0, 0>());
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}
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};
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///////////////////////////////////////////////////////////////////////////
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//
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// Transform policies
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//
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// The following policy classes could be used to assemble some new
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// transformation metafunction which uses identity transformations
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// for some parser_category type parsers.
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//
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///////////////////////////////////////////////////////////////////////////
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///////////////////////////////////////////////////////////////////////////
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// transform plain parsers
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template <typename TransformT>
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struct plain_identity_policy
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{
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template <typename ParserT, typename EnvT>
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struct plain_result
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{
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// plain parsers should be embedded and returned correctly
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typedef typename ParserT::embed_t type;
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};
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template <typename ParserT, typename EnvT>
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typename parser_traversal_plain_result<TransformT, ParserT, EnvT>::type
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generate_plain(ParserT const &parser_, EnvT const& /*env*/) const
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{
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return parser_;
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}
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};
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//////////////////////////////////
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// transform unary parsers
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template <typename UnaryT, typename SubjectT>
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struct unary_identity_policy_return
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{
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typedef typename UnaryT::parser_generator_t parser_generator_t;
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typedef typename parser_generator_t
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::template result<SubjectT>::type type;
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};
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template <typename TransformT>
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struct unary_identity_policy
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{
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template <typename UnaryT, typename SubjectT, typename EnvT>
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struct unary_result
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{
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typedef
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typename unary_identity_policy_return<UnaryT, SubjectT>::type
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type;
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};
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template <typename UnaryT, typename SubjectT, typename EnvT>
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typename parser_traversal_unary_result<
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TransformT, UnaryT, SubjectT, EnvT>::type
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generate_unary(
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UnaryT const &, SubjectT const &subject_, EnvT const& /*env*/) const
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{
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typedef typename UnaryT::parser_generator_t parser_generator_t;
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return parser_generator_t::template generate<SubjectT>(subject_);
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}
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};
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//////////////////////////////////
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// transform action parsers
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template <typename TransformT>
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struct action_identity_policy
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{
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template <typename ActionT, typename SubjectT, typename EnvT>
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struct action_result
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{
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typedef action<SubjectT, typename ActionT::predicate_t> type;
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};
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template <typename ActionT, typename SubjectT, typename EnvT>
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typename parser_traversal_action_result<
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TransformT, ActionT, SubjectT, EnvT
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>::type
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generate_action(ActionT const &action_, SubjectT const &subject_,
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EnvT const& /*env*/) const
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{
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return subject_[action_.predicate()];
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}
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};
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//////////////////////////////////
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// transform binary parsers
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template <typename BinaryT, typename LeftT, typename RightT>
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struct binary_identity_policy_return
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{
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typedef typename BinaryT::parser_generator_t parser_generator_t;
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typedef typename parser_generator_t
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::template result<LeftT, RightT>::type type;
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};
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template <typename TransformT>
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struct binary_identity_policy
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{
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template <typename BinaryT, typename LeftT
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, typename RightT, typename EnvT>
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struct binary_result {
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typedef typename
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binary_identity_policy_return<BinaryT, LeftT, RightT>::type
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type;
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};
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template <typename BinaryT, typename LeftT
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, typename RightT, typename EnvT>
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typename parser_traversal_binary_result<
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TransformT, BinaryT, LeftT, RightT, EnvT
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>::type
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generate_binary(
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BinaryT const &, LeftT const& left_
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, RightT const& right_, EnvT const& /*env*/) const
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{
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typedef typename BinaryT::parser_generator_t parser_generator_t;
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return parser_generator_t::
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template generate<LeftT, RightT>(left_, right_);
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}
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};
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///////////////////////////////////////////////////////////////////////////
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//
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// transform_policies template
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//
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// The transform_policies template metafunction could serve as a
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// base class for new metafunctions to be passed to the traverse meta
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// template (see above), where only minimal parts have to be
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// overwritten.
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//
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///////////////////////////////////////////////////////////////////////////
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template <
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typename TransformT,
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typename PlainPolicyT = plain_identity_policy<TransformT>,
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typename UnaryPolicyT = unary_identity_policy<TransformT>,
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typename ActionPolicyT = action_identity_policy<TransformT>,
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typename BinaryPolicyT = binary_identity_policy<TransformT>
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>
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struct transform_policies :
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public PlainPolicyT,
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public UnaryPolicyT,
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public ActionPolicyT,
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public BinaryPolicyT
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{
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};
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///////////////////////////////////////////////////////////////////////////
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//
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// Identity transformation
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//
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// The identity_transform metafunction supplied to the traverse
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// template will generate a new parser, which will be exactly
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// identical to the parser given as the parameter to the traverse
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// metafunction. I.e. the following conceptual 'equation' will be
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// always true:
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//
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// some_parser ==
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// post_order::traverse(identity_transform(), some_parser)
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//
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///////////////////////////////////////////////////////////////////////////
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struct identity_transform : transform_policies<identity_transform> {};
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}} // namespace boost::spirit
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#endif // !defined(BOOST_SPIRIT_TRAVERSE_HPP)
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