84 lines
3.0 KiB
C++
84 lines
3.0 KiB
C++
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/*=============================================================================
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Copyright (c) 2001-2014 Joel de Guzman
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Copyright (c) 2001-2011 Hartmut Kaiser
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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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=============================================================================*/
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#if !defined(BOOST_SPIRIT_X3_OPTIONAL_MARCH_23_2007_1117PM)
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#define BOOST_SPIRIT_X3_OPTIONAL_MARCH_23_2007_1117PM
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#include <boost/spirit/home/x3/core/proxy.hpp>
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#include <boost/spirit/home/x3/core/detail/parse_into_container.hpp>
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#include <boost/spirit/home/x3/support/traits/attribute_of.hpp>
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#include <boost/spirit/home/x3/support/traits/move_to.hpp>
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#include <boost/spirit/home/x3/support/traits/optional_traits.hpp>
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#include <boost/spirit/home/x3/support/traits/attribute_category.hpp>
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namespace boost { namespace spirit { namespace x3
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{
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template <typename Subject>
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struct optional : proxy<Subject, optional<Subject>>
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{
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typedef proxy<Subject, optional<Subject>> base_type;
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static bool const is_pass_through_unary = false;
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static bool const handles_container = true;
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constexpr optional(Subject const& subject)
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: base_type(subject) {}
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using base_type::parse_subject;
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// Attribute is a container
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template <typename Iterator, typename Context
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, typename RContext, typename Attribute>
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bool parse_subject(Iterator& first, Iterator const& last
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, Context const& context, RContext& rcontext, Attribute& attr
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, traits::container_attribute) const
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{
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detail::parse_into_container(
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this->subject, first, last, context, rcontext, attr);
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return true;
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}
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// Attribute is an optional
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template <typename Iterator, typename Context
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, typename RContext, typename Attribute>
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bool parse_subject(Iterator& first, Iterator const& last
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, Context const& context, RContext& rcontext, Attribute& attr
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, traits::optional_attribute) const
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{
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typedef typename
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x3::traits::optional_value<Attribute>::type
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value_type;
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// create a local value
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value_type val{};
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if (this->subject.parse(first, last, context, rcontext, val))
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{
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// assign the parsed value into our attribute
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x3::traits::move_to(val, attr);
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}
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return true;
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}
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};
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template <typename Subject>
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constexpr optional<typename extension::as_parser<Subject>::value_type>
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operator-(Subject const& subject)
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{
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return { as_parser(subject) };
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}
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}}}
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namespace boost { namespace spirit { namespace x3 { namespace traits
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{
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template <typename Subject, typename Context>
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struct attribute_of<x3::optional<Subject>, Context>
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: build_optional<
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typename attribute_of<Subject, Context>::type> {};
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}}}}
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#endif
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