// Copyright (c) 2001-2011 Hartmut Kaiser
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// Copyright (c) 2001-2011 Joel de Guzman
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_SPIRIT_QI_DETAIL_ATTRIBUTES_HPP
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#define BOOST_SPIRIT_QI_DETAIL_ATTRIBUTES_HPP
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#include <boost/spirit/home/qi/domain.hpp>
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#include <boost/spirit/home/support/attributes_fwd.hpp>
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#include <boost/spirit/home/support/attributes.hpp>
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#include <boost/spirit/home/support/utree/utree_traits_fwd.hpp>
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///////////////////////////////////////////////////////////////////////////////
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namespace boost { namespace spirit { namespace qi
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{
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template <typename Exposed, typename Transformed>
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struct default_transform_attribute
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{
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typedef Transformed type;
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static Transformed pre(Exposed&) { return Transformed(); }
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static void post(Exposed& val, Transformed const& attr)
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{
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traits::assign_to(attr, val);
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}
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// fail() will be called by Qi rule's if the rhs failed parsing
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static void fail(Exposed&) {}
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};
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// handle case where no transformation is required as the types are the same
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template <typename Attribute>
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struct default_transform_attribute<Attribute, Attribute>
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{
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typedef Attribute& type;
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static Attribute& pre(Attribute& val) { return val; }
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static void post(Attribute&, Attribute const&) {}
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static void fail(Attribute&) {}
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};
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template <typename Exposed, typename Transformed>
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struct proxy_transform_attribute
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{
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typedef Transformed type;
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static Transformed pre(Exposed& val) { return Transformed(val); }
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static void post(Exposed&, Transformed const&) { /* no-op */ }
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// fail() will be called by Qi rule's if the rhs failed parsing
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static void fail(Exposed&) {}
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};
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// handle case where no transformation is required as the types are the same
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template <typename Attribute>
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struct proxy_transform_attribute<Attribute, Attribute>
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{
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typedef Attribute& type;
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static Attribute& pre(Attribute& val) { return val; }
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static void post(Attribute&, Attribute const&) {}
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static void fail(Attribute&) {}
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};
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// main specialization for Qi
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template <typename Exposed, typename Transformed, typename Enable = void>
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struct transform_attribute
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: mpl::if_<
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mpl::and_<
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mpl::not_<is_const<Exposed> >
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, mpl::not_<is_reference<Exposed> >
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, traits::is_proxy<Transformed> >
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, proxy_transform_attribute<Exposed, Transformed>
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, default_transform_attribute<Exposed, Transformed>
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>::type
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{};
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template <typename Exposed, typename Transformed>
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struct transform_attribute<boost::optional<Exposed>, Transformed
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, typename disable_if<is_same<boost::optional<Exposed>, Transformed> >::type>
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{
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typedef Transformed& type;
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static Transformed& pre(boost::optional<Exposed>& val)
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{
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if (!val)
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val = Transformed();
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return boost::get<Transformed>(val);
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}
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static void post(boost::optional<Exposed>&, Transformed const&) {}
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static void fail(boost::optional<Exposed>& val)
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{
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val = none; // leave optional uninitialized if rhs failed
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}
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};
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// unused_type needs some special handling as well
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template <>
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struct transform_attribute<unused_type, unused_type>
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{
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typedef unused_type type;
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static unused_type pre(unused_type) { return unused; }
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static void post(unused_type, unused_type) {}
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static void fail(unused_type) {}
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};
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template <>
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struct transform_attribute<unused_type const, unused_type>
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: transform_attribute<unused_type, unused_type>
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{};
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template <typename Attribute>
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struct transform_attribute<Attribute, unused_type>
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: transform_attribute<unused_type, unused_type>
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{};
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template <typename Attribute>
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struct transform_attribute<Attribute const, unused_type>
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: transform_attribute<unused_type, unused_type>
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{};
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}}}
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///////////////////////////////////////////////////////////////////////////////
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namespace boost { namespace spirit { namespace traits
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{
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namespace detail {
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template <typename Exposed, typename Transformed>
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struct transform_attribute_base<Exposed, Transformed, qi::domain>
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: qi::transform_attribute<Exposed, Transformed>
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{};
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}
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}}}
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#endif
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